* [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS @ 2018-05-18 18:23 Laszlo Ersek 2018-05-19 8:21 ` Ard Biesheuvel 2018-05-21 10:30 ` Leif Lindholm 0 siblings, 2 replies; 9+ messages in thread From: Laszlo Ersek @ 2018-05-18 18:23 UTC (permalink / raw) To: edk2-devel-01 Cc: Danilo C. L. de Paula, Ard Biesheuvel, Cole Robinson, Gerd Hoffmann, Leif Lindholm, Liming Gao, Paolo Bonzini, Yonghong Zhu The ElfConvert routines in GenFw don't handle the ".eh_frame" ELF section emitted by gcc. For this reason, Leif disabled the generation of that section for AARCH64 with "-fno-asynchronous-unwind-tables" in commit 28e80befa4fe [1], and Ard did the same for IA32 and X64 in commit 26ecc55c027d [2]. (The CLANG38 toolchain received the same flag at its inception, in commit 6f756db5ea05 [3].) However, ".eh_frame" is back now; in upstream gcc commit 9cbee213b579 [4] (part of tag "gcc-8_1_0-release"), both "-fasynchronous-unwind-tables" and "-funwind-tables" were made the default for AARCH64. (The patch author described the effects on the gcc mailing list [5].) We have to counter the latter flag with "-fno-unwind-tables", otherwise GenFw chokes on ".eh_frame" again (triggered for example on Fedora 28). "-f[no-]unwind-tables" goes back to at least gcc-4.4 [6], so it's safe to add to GCC_AARCH64_CC_FLAGS. [1] https://github.com/tianocore/edk2/commit/28e80befa4fe [2] https://github.com/tianocore/edk2/commit/26ecc55c027d [3] https://github.com/tianocore/edk2/commit/6f756db5ea05 [4] https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=9cbee213b579 [5] http://mid.mail-archive.com/7b28c03a-c032-6cec-c127-1c12cbe98eeb@foss.arm.com [6] https://gcc.gnu.org/onlinedocs/gcc-4.4.7/gcc/Code-Gen-Options.html Cc: "Danilo C. L. de Paula" <ddepaula@redhat.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Cole Robinson <crobinso@redhat.com> Cc: Gerd Hoffmann <kraxel@redhat.com> Cc: Leif Lindholm <leif.lindholm@linaro.org> Cc: Liming Gao <liming.gao@intel.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Yonghong Zhu <yonghong.zhu@intel.com> Reported-by: "Danilo C. L. de Paula" <ddepaula@redhat.com> Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Laszlo Ersek <lersek@redhat.com> --- Notes: Repo: https://github.com/lersek/edk2.git Branch: aarch64_no_unwind_tables BaseTools/Conf/tools_def.template | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template index 03d700018550..9429033fe2e3 100755 --- a/BaseTools/Conf/tools_def.template +++ b/BaseTools/Conf/tools_def.template @@ -4537,7 +4537,7 @@ DEFINE GCC_X64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mno-red-zone -Wno-ad DEFINE GCC_IPF_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -minline-int-divide-min-latency DEFINE GCC_ARM_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -mabi=aapcs -fno-short-enums -funsigned-char -ffunction-sections -fdata-sections -fomit-frame-pointer -Wno-address -mthumb -mfloat-abi=soft -fno-pic -fno-pie DEFINE GCC_ARM_CC_XIPFLAGS = -mno-unaligned-access -DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm -funsigned-char -ffunction-sections -fdata-sections -Wno-address -fno-asynchronous-unwind-tables -fno-pic -fno-pie -ffixed-x18 +DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm -funsigned-char -ffunction-sections -fdata-sections -Wno-address -fno-asynchronous-unwind-tables -fno-unwind-tables -fno-pic -fno-pie -ffixed-x18 DEFINE GCC_AARCH64_CC_XIPFLAGS = -mstrict-align -mgeneral-regs-only DEFINE GCC_DLINK_FLAGS_COMMON = -nostdlib --pie DEFINE GCC_DLINK2_FLAGS_COMMON = -Wl,--script=$(EDK_TOOLS_PATH)/Scripts/GccBase.lds -- 2.14.1.3.gb7cf6e02401b ^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS 2018-05-18 18:23 [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS Laszlo Ersek @ 2018-05-19 8:21 ` Ard Biesheuvel 2018-05-21 0:37 ` Gao, Liming 2018-05-21 10:30 ` Leif Lindholm 1 sibling, 1 reply; 9+ messages in thread From: Ard Biesheuvel @ 2018-05-19 8:21 UTC (permalink / raw) To: Laszlo Ersek Cc: edk2-devel-01, Danilo C. L. de Paula, Cole Robinson, Gerd Hoffmann, Leif Lindholm, Liming Gao, Paolo Bonzini, Yonghong Zhu On 18 May 2018 at 20:23, Laszlo Ersek <lersek@redhat.com> wrote: > The ElfConvert routines in GenFw don't handle the ".eh_frame" ELF section > emitted by gcc. For this reason, Leif disabled the generation of that > section for AARCH64 with "-fno-asynchronous-unwind-tables" in commit > 28e80befa4fe [1], and Ard did the same for IA32 and X64 in commit > 26ecc55c027d [2]. (The CLANG38 toolchain received the same flag at its > inception, in commit 6f756db5ea05 [3].) > > However, ".eh_frame" is back now; in upstream gcc commit 9cbee213b579 [4] > (part of tag "gcc-8_1_0-release"), both "-fasynchronous-unwind-tables" and > "-funwind-tables" were made the default for AARCH64. (The patch author > described the effects on the gcc mailing list [5].) We have to counter the > latter flag with "-fno-unwind-tables", otherwise GenFw chokes on > ".eh_frame" again (triggered for example on Fedora 28). > > "-f[no-]unwind-tables" goes back to at least gcc-4.4 [6], so it's safe to > add to GCC_AARCH64_CC_FLAGS. > > [1] https://github.com/tianocore/edk2/commit/28e80befa4fe > [2] https://github.com/tianocore/edk2/commit/26ecc55c027d > [3] https://github.com/tianocore/edk2/commit/6f756db5ea05 > [4] https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=9cbee213b579 > [5] http://mid.mail-archive.com/7b28c03a-c032-6cec-c127-1c12cbe98eeb@foss.arm.com > [6] https://gcc.gnu.org/onlinedocs/gcc-4.4.7/gcc/Code-Gen-Options.html > > Cc: "Danilo C. L. de Paula" <ddepaula@redhat.com> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> > Cc: Cole Robinson <crobinso@redhat.com> > Cc: Gerd Hoffmann <kraxel@redhat.com> > Cc: Leif Lindholm <leif.lindholm@linaro.org> > Cc: Liming Gao <liming.gao@intel.com> > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Yonghong Zhu <yonghong.zhu@intel.com> > Reported-by: "Danilo C. L. de Paula" <ddepaula@redhat.com> > Contributed-under: TianoCore Contribution Agreement 1.1 > Signed-off-by: Laszlo Ersek <lersek@redhat.com> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > --- > > Notes: > Repo: https://github.com/lersek/edk2.git > Branch: aarch64_no_unwind_tables > > BaseTools/Conf/tools_def.template | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template > index 03d700018550..9429033fe2e3 100755 > --- a/BaseTools/Conf/tools_def.template > +++ b/BaseTools/Conf/tools_def.template > @@ -4537,7 +4537,7 @@ DEFINE GCC_X64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mno-red-zone -Wno-ad > DEFINE GCC_IPF_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -minline-int-divide-min-latency > DEFINE GCC_ARM_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -mabi=aapcs -fno-short-enums -funsigned-char -ffunction-sections -fdata-sections -fomit-frame-pointer -Wno-address -mthumb -mfloat-abi=soft -fno-pic -fno-pie > DEFINE GCC_ARM_CC_XIPFLAGS = -mno-unaligned-access > -DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm -funsigned-char -ffunction-sections -fdata-sections -Wno-address -fno-asynchronous-unwind-tables -fno-pic -fno-pie -ffixed-x18 > +DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm -funsigned-char -ffunction-sections -fdata-sections -Wno-address -fno-asynchronous-unwind-tables -fno-unwind-tables -fno-pic -fno-pie -ffixed-x18 > DEFINE GCC_AARCH64_CC_XIPFLAGS = -mstrict-align -mgeneral-regs-only > DEFINE GCC_DLINK_FLAGS_COMMON = -nostdlib --pie > DEFINE GCC_DLINK2_FLAGS_COMMON = -Wl,--script=$(EDK_TOOLS_PATH)/Scripts/GccBase.lds > -- > 2.14.1.3.gb7cf6e02401b > ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS 2018-05-19 8:21 ` Ard Biesheuvel @ 2018-05-21 0:37 ` Gao, Liming 2018-05-21 9:32 ` Ard Biesheuvel 0 siblings, 1 reply; 9+ messages in thread From: Gao, Liming @ 2018-05-21 0:37 UTC (permalink / raw) To: Ard Biesheuvel, Laszlo Ersek Cc: edk2-devel-01, Danilo C. L. de Paula, Cole Robinson, Gerd Hoffmann, Leif Lindholm, Paolo Bonzini, Zhu, Yonghong Laszlo: Is this change required for IA32 and X64 arch? Thanks Liming > -----Original Message----- > From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org] > Sent: Saturday, May 19, 2018 4:21 PM > To: Laszlo Ersek <lersek@redhat.com> > Cc: edk2-devel-01 <edk2-devel@lists.01.org>; Danilo C. L. de Paula <ddepaula@redhat.com>; Cole Robinson <crobinso@redhat.com>; > Gerd Hoffmann <kraxel@redhat.com>; Leif Lindholm <leif.lindholm@linaro.org>; Gao, Liming <liming.gao@intel.com>; Paolo Bonzini > <pbonzini@redhat.com>; Zhu, Yonghong <yonghong.zhu@intel.com> > Subject: Re: [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS > > On 18 May 2018 at 20:23, Laszlo Ersek <lersek@redhat.com> wrote: > > The ElfConvert routines in GenFw don't handle the ".eh_frame" ELF section > > emitted by gcc. For this reason, Leif disabled the generation of that > > section for AARCH64 with "-fno-asynchronous-unwind-tables" in commit > > 28e80befa4fe [1], and Ard did the same for IA32 and X64 in commit > > 26ecc55c027d [2]. (The CLANG38 toolchain received the same flag at its > > inception, in commit 6f756db5ea05 [3].) > > > > However, ".eh_frame" is back now; in upstream gcc commit 9cbee213b579 [4] > > (part of tag "gcc-8_1_0-release"), both "-fasynchronous-unwind-tables" and > > "-funwind-tables" were made the default for AARCH64. (The patch author > > described the effects on the gcc mailing list [5].) We have to counter the > > latter flag with "-fno-unwind-tables", otherwise GenFw chokes on > > ".eh_frame" again (triggered for example on Fedora 28). > > > > "-f[no-]unwind-tables" goes back to at least gcc-4.4 [6], so it's safe to > > add to GCC_AARCH64_CC_FLAGS. > > > > [1] https://github.com/tianocore/edk2/commit/28e80befa4fe > > [2] https://github.com/tianocore/edk2/commit/26ecc55c027d > > [3] https://github.com/tianocore/edk2/commit/6f756db5ea05 > > [4] https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=9cbee213b579 > > [5] http://mid.mail-archive.com/7b28c03a-c032-6cec-c127-1c12cbe98eeb@foss.arm.com > > [6] https://gcc.gnu.org/onlinedocs/gcc-4.4.7/gcc/Code-Gen-Options.html > > > > Cc: "Danilo C. L. de Paula" <ddepaula@redhat.com> > > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> > > Cc: Cole Robinson <crobinso@redhat.com> > > Cc: Gerd Hoffmann <kraxel@redhat.com> > > Cc: Leif Lindholm <leif.lindholm@linaro.org> > > Cc: Liming Gao <liming.gao@intel.com> > > Cc: Paolo Bonzini <pbonzini@redhat.com> > > Cc: Yonghong Zhu <yonghong.zhu@intel.com> > > Reported-by: "Danilo C. L. de Paula" <ddepaula@redhat.com> > > Contributed-under: TianoCore Contribution Agreement 1.1 > > Signed-off-by: Laszlo Ersek <lersek@redhat.com> > > Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > > > --- > > > > Notes: > > Repo: https://github.com/lersek/edk2.git > > Branch: aarch64_no_unwind_tables > > > > BaseTools/Conf/tools_def.template | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template > > index 03d700018550..9429033fe2e3 100755 > > --- a/BaseTools/Conf/tools_def.template > > +++ b/BaseTools/Conf/tools_def.template > > @@ -4537,7 +4537,7 @@ DEFINE GCC_X64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mno-red-zone -Wno-ad > > DEFINE GCC_IPF_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -minline-int-divide-min-latency > > DEFINE GCC_ARM_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -mabi=aapcs -fno-short-enums > -funsigned-char -ffunction-sections -fdata-sections -fomit-frame-pointer -Wno-address -mthumb -mfloat-abi=soft -fno-pic -fno-pie > > DEFINE GCC_ARM_CC_XIPFLAGS = -mno-unaligned-access > > -DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm > -funsigned-char -ffunction-sections -fdata-sections -Wno-address -fno-asynchronous-unwind-tables -fno-pic -fno-pie -ffixed-x18 > > +DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm > -funsigned-char -ffunction-sections -fdata-sections -Wno-address -fno-asynchronous-unwind-tables -fno-unwind-tables -fno-pic > -fno-pie -ffixed-x18 > > DEFINE GCC_AARCH64_CC_XIPFLAGS = -mstrict-align -mgeneral-regs-only > > DEFINE GCC_DLINK_FLAGS_COMMON = -nostdlib --pie > > DEFINE GCC_DLINK2_FLAGS_COMMON = -Wl,--script=$(EDK_TOOLS_PATH)/Scripts/GccBase.lds > > -- > > 2.14.1.3.gb7cf6e02401b > > ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS 2018-05-21 0:37 ` Gao, Liming @ 2018-05-21 9:32 ` Ard Biesheuvel 2018-05-22 9:05 ` Laszlo Ersek 0 siblings, 1 reply; 9+ messages in thread From: Ard Biesheuvel @ 2018-05-21 9:32 UTC (permalink / raw) To: Gao, Liming Cc: Laszlo Ersek, edk2-devel-01, Danilo C. L. de Paula, Cole Robinson, Gerd Hoffmann, Leif Lindholm, Paolo Bonzini, Zhu, Yonghong On 21 May 2018 at 02:37, Gao, Liming <liming.gao@intel.com> wrote: > Laszlo: > Is this change required for IA32 and X64 arch? > The upstream GCC change is limited to AArch64, but I suppose it wouldn't hurt to add this to IA32/X64 as well, given that it currently only reaffirms the default, and will do the right thing if that default ever changes for IA32/X64 as well. >> -----Original Message----- >> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org] >> Sent: Saturday, May 19, 2018 4:21 PM >> To: Laszlo Ersek <lersek@redhat.com> >> Cc: edk2-devel-01 <edk2-devel@lists.01.org>; Danilo C. L. de Paula <ddepaula@redhat.com>; Cole Robinson <crobinso@redhat.com>; >> Gerd Hoffmann <kraxel@redhat.com>; Leif Lindholm <leif.lindholm@linaro.org>; Gao, Liming <liming.gao@intel.com>; Paolo Bonzini >> <pbonzini@redhat.com>; Zhu, Yonghong <yonghong.zhu@intel.com> >> Subject: Re: [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS >> >> On 18 May 2018 at 20:23, Laszlo Ersek <lersek@redhat.com> wrote: >> > The ElfConvert routines in GenFw don't handle the ".eh_frame" ELF section >> > emitted by gcc. For this reason, Leif disabled the generation of that >> > section for AARCH64 with "-fno-asynchronous-unwind-tables" in commit >> > 28e80befa4fe [1], and Ard did the same for IA32 and X64 in commit >> > 26ecc55c027d [2]. (The CLANG38 toolchain received the same flag at its >> > inception, in commit 6f756db5ea05 [3].) >> > >> > However, ".eh_frame" is back now; in upstream gcc commit 9cbee213b579 [4] >> > (part of tag "gcc-8_1_0-release"), both "-fasynchronous-unwind-tables" and >> > "-funwind-tables" were made the default for AARCH64. (The patch author >> > described the effects on the gcc mailing list [5].) We have to counter the >> > latter flag with "-fno-unwind-tables", otherwise GenFw chokes on >> > ".eh_frame" again (triggered for example on Fedora 28). >> > >> > "-f[no-]unwind-tables" goes back to at least gcc-4.4 [6], so it's safe to >> > add to GCC_AARCH64_CC_FLAGS. >> > >> > [1] https://github.com/tianocore/edk2/commit/28e80befa4fe >> > [2] https://github.com/tianocore/edk2/commit/26ecc55c027d >> > [3] https://github.com/tianocore/edk2/commit/6f756db5ea05 >> > [4] https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=9cbee213b579 >> > [5] http://mid.mail-archive.com/7b28c03a-c032-6cec-c127-1c12cbe98eeb@foss.arm.com >> > [6] https://gcc.gnu.org/onlinedocs/gcc-4.4.7/gcc/Code-Gen-Options.html >> > >> > Cc: "Danilo C. L. de Paula" <ddepaula@redhat.com> >> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> >> > Cc: Cole Robinson <crobinso@redhat.com> >> > Cc: Gerd Hoffmann <kraxel@redhat.com> >> > Cc: Leif Lindholm <leif.lindholm@linaro.org> >> > Cc: Liming Gao <liming.gao@intel.com> >> > Cc: Paolo Bonzini <pbonzini@redhat.com> >> > Cc: Yonghong Zhu <yonghong.zhu@intel.com> >> > Reported-by: "Danilo C. L. de Paula" <ddepaula@redhat.com> >> > Contributed-under: TianoCore Contribution Agreement 1.1 >> > Signed-off-by: Laszlo Ersek <lersek@redhat.com> >> >> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> >> >> > --- >> > >> > Notes: >> > Repo: https://github.com/lersek/edk2.git >> > Branch: aarch64_no_unwind_tables >> > >> > BaseTools/Conf/tools_def.template | 2 +- >> > 1 file changed, 1 insertion(+), 1 deletion(-) >> > >> > diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template >> > index 03d700018550..9429033fe2e3 100755 >> > --- a/BaseTools/Conf/tools_def.template >> > +++ b/BaseTools/Conf/tools_def.template >> > @@ -4537,7 +4537,7 @@ DEFINE GCC_X64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mno-red-zone -Wno-ad >> > DEFINE GCC_IPF_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -minline-int-divide-min-latency >> > DEFINE GCC_ARM_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -mabi=aapcs -fno-short-enums >> -funsigned-char -ffunction-sections -fdata-sections -fomit-frame-pointer -Wno-address -mthumb -mfloat-abi=soft -fno-pic -fno-pie >> > DEFINE GCC_ARM_CC_XIPFLAGS = -mno-unaligned-access >> > -DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm >> -funsigned-char -ffunction-sections -fdata-sections -Wno-address -fno-asynchronous-unwind-tables -fno-pic -fno-pie -ffixed-x18 >> > +DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm >> -funsigned-char -ffunction-sections -fdata-sections -Wno-address -fno-asynchronous-unwind-tables -fno-unwind-tables -fno-pic >> -fno-pie -ffixed-x18 >> > DEFINE GCC_AARCH64_CC_XIPFLAGS = -mstrict-align -mgeneral-regs-only >> > DEFINE GCC_DLINK_FLAGS_COMMON = -nostdlib --pie >> > DEFINE GCC_DLINK2_FLAGS_COMMON = -Wl,--script=$(EDK_TOOLS_PATH)/Scripts/GccBase.lds >> > -- >> > 2.14.1.3.gb7cf6e02401b >> > ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS 2018-05-21 9:32 ` Ard Biesheuvel @ 2018-05-22 9:05 ` Laszlo Ersek 0 siblings, 0 replies; 9+ messages in thread From: Laszlo Ersek @ 2018-05-22 9:05 UTC (permalink / raw) To: Ard Biesheuvel, Gao, Liming Cc: edk2-devel-01, Danilo C. L. de Paula, Cole Robinson, Gerd Hoffmann, Leif Lindholm, Paolo Bonzini, Zhu, Yonghong On 05/21/18 11:32, Ard Biesheuvel wrote: > On 21 May 2018 at 02:37, Gao, Liming <liming.gao@intel.com> wrote: >> Laszlo: >> Is this change required for IA32 and X64 arch? >> > > The upstream GCC change is limited to AArch64, but I suppose it > wouldn't hurt to add this to IA32/X64 as well, given that it currently > only reaffirms the default, and will do the right thing if that > default ever changes for IA32/X64 as well. Right; I wanted to keep the patch surgical. I don't really understand why it makes sense for gcc to use different "unwind-tables" defaults for AARCH64 vs. IA32/X64; however, I did think the gcc developers must have made a conscious decision, to restrict the change to AARCH64. I can submit a followup patch for IA32/X64, but I'll first respond under Leif's suggestion too (that subthread will likely take more discussion). Thanks! Laszlo > > >>> -----Original Message----- >>> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org] >>> Sent: Saturday, May 19, 2018 4:21 PM >>> To: Laszlo Ersek <lersek@redhat.com> >>> Cc: edk2-devel-01 <edk2-devel@lists.01.org>; Danilo C. L. de Paula <ddepaula@redhat.com>; Cole Robinson <crobinso@redhat.com>; >>> Gerd Hoffmann <kraxel@redhat.com>; Leif Lindholm <leif.lindholm@linaro.org>; Gao, Liming <liming.gao@intel.com>; Paolo Bonzini >>> <pbonzini@redhat.com>; Zhu, Yonghong <yonghong.zhu@intel.com> >>> Subject: Re: [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS >>> >>> On 18 May 2018 at 20:23, Laszlo Ersek <lersek@redhat.com> wrote: >>>> The ElfConvert routines in GenFw don't handle the ".eh_frame" ELF section >>>> emitted by gcc. For this reason, Leif disabled the generation of that >>>> section for AARCH64 with "-fno-asynchronous-unwind-tables" in commit >>>> 28e80befa4fe [1], and Ard did the same for IA32 and X64 in commit >>>> 26ecc55c027d [2]. (The CLANG38 toolchain received the same flag at its >>>> inception, in commit 6f756db5ea05 [3].) >>>> >>>> However, ".eh_frame" is back now; in upstream gcc commit 9cbee213b579 [4] >>>> (part of tag "gcc-8_1_0-release"), both "-fasynchronous-unwind-tables" and >>>> "-funwind-tables" were made the default for AARCH64. (The patch author >>>> described the effects on the gcc mailing list [5].) We have to counter the >>>> latter flag with "-fno-unwind-tables", otherwise GenFw chokes on >>>> ".eh_frame" again (triggered for example on Fedora 28). >>>> >>>> "-f[no-]unwind-tables" goes back to at least gcc-4.4 [6], so it's safe to >>>> add to GCC_AARCH64_CC_FLAGS. >>>> >>>> [1] https://github.com/tianocore/edk2/commit/28e80befa4fe >>>> [2] https://github.com/tianocore/edk2/commit/26ecc55c027d >>>> [3] https://github.com/tianocore/edk2/commit/6f756db5ea05 >>>> [4] https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=9cbee213b579 >>>> [5] http://mid.mail-archive.com/7b28c03a-c032-6cec-c127-1c12cbe98eeb@foss.arm.com >>>> [6] https://gcc.gnu.org/onlinedocs/gcc-4.4.7/gcc/Code-Gen-Options.html >>>> >>>> Cc: "Danilo C. L. de Paula" <ddepaula@redhat.com> >>>> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> >>>> Cc: Cole Robinson <crobinso@redhat.com> >>>> Cc: Gerd Hoffmann <kraxel@redhat.com> >>>> Cc: Leif Lindholm <leif.lindholm@linaro.org> >>>> Cc: Liming Gao <liming.gao@intel.com> >>>> Cc: Paolo Bonzini <pbonzini@redhat.com> >>>> Cc: Yonghong Zhu <yonghong.zhu@intel.com> >>>> Reported-by: "Danilo C. L. de Paula" <ddepaula@redhat.com> >>>> Contributed-under: TianoCore Contribution Agreement 1.1 >>>> Signed-off-by: Laszlo Ersek <lersek@redhat.com> >>> >>> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> >>> >>>> --- >>>> >>>> Notes: >>>> Repo: https://github.com/lersek/edk2.git >>>> Branch: aarch64_no_unwind_tables >>>> >>>> BaseTools/Conf/tools_def.template | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template >>>> index 03d700018550..9429033fe2e3 100755 >>>> --- a/BaseTools/Conf/tools_def.template >>>> +++ b/BaseTools/Conf/tools_def.template >>>> @@ -4537,7 +4537,7 @@ DEFINE GCC_X64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mno-red-zone -Wno-ad >>>> DEFINE GCC_IPF_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -minline-int-divide-min-latency >>>> DEFINE GCC_ARM_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -mabi=aapcs -fno-short-enums >>> -funsigned-char -ffunction-sections -fdata-sections -fomit-frame-pointer -Wno-address -mthumb -mfloat-abi=soft -fno-pic -fno-pie >>>> DEFINE GCC_ARM_CC_XIPFLAGS = -mno-unaligned-access >>>> -DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm >>> -funsigned-char -ffunction-sections -fdata-sections -Wno-address -fno-asynchronous-unwind-tables -fno-pic -fno-pie -ffixed-x18 >>>> +DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm >>> -funsigned-char -ffunction-sections -fdata-sections -Wno-address -fno-asynchronous-unwind-tables -fno-unwind-tables -fno-pic >>> -fno-pie -ffixed-x18 >>>> DEFINE GCC_AARCH64_CC_XIPFLAGS = -mstrict-align -mgeneral-regs-only >>>> DEFINE GCC_DLINK_FLAGS_COMMON = -nostdlib --pie >>>> DEFINE GCC_DLINK2_FLAGS_COMMON = -Wl,--script=$(EDK_TOOLS_PATH)/Scripts/GccBase.lds >>>> -- >>>> 2.14.1.3.gb7cf6e02401b >>>> ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS 2018-05-18 18:23 [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS Laszlo Ersek 2018-05-19 8:21 ` Ard Biesheuvel @ 2018-05-21 10:30 ` Leif Lindholm 2018-05-22 9:29 ` Laszlo Ersek 1 sibling, 1 reply; 9+ messages in thread From: Leif Lindholm @ 2018-05-21 10:30 UTC (permalink / raw) To: Laszlo Ersek Cc: edk2-devel-01, Danilo C. L. de Paula, Ard Biesheuvel, Cole Robinson, Gerd Hoffmann, Liming Gao, Paolo Bonzini, Yonghong Zhu, pjones On Fri, May 18, 2018 at 08:23:01PM +0200, Laszlo Ersek wrote: > The ElfConvert routines in GenFw don't handle the ".eh_frame" ELF section > emitted by gcc. For this reason, Leif disabled the generation of that > section for AARCH64 with "-fno-asynchronous-unwind-tables" in commit > 28e80befa4fe [1], and Ard did the same for IA32 and X64 in commit > 26ecc55c027d [2]. (The CLANG38 toolchain received the same flag at its > inception, in commit 6f756db5ea05 [3].) > > However, ".eh_frame" is back now; in upstream gcc commit 9cbee213b579 [4] > (part of tag "gcc-8_1_0-release"), both "-fasynchronous-unwind-tables" and > "-funwind-tables" were made the default for AARCH64. (The patch author > described the effects on the gcc mailing list [5].) We have to counter the > latter flag with "-fno-unwind-tables", otherwise GenFw chokes on > ".eh_frame" again (triggered for example on Fedora 28). > > "-f[no-]unwind-tables" goes back to at least gcc-4.4 [6], so it's safe to > add to GCC_AARCH64_CC_FLAGS. I'm not against this patch (which fixes a real problem), but would it be possible to take the opposite approach, as Peter Jones did for GRUB when the same issue hit there?: http://lists.gnu.org/archive/html/grub-devel/2018-02/msg00095.html I.e., rather than keep adding flags when new "special" sections are added by toolchains, explicitly filter those out as part of the link step. / Leif > [1] https://github.com/tianocore/edk2/commit/28e80befa4fe > [2] https://github.com/tianocore/edk2/commit/26ecc55c027d > [3] https://github.com/tianocore/edk2/commit/6f756db5ea05 > [4] https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=9cbee213b579 > [5] http://mid.mail-archive.com/7b28c03a-c032-6cec-c127-1c12cbe98eeb@foss.arm.com > [6] https://gcc.gnu.org/onlinedocs/gcc-4.4.7/gcc/Code-Gen-Options.html > > Cc: "Danilo C. L. de Paula" <ddepaula@redhat.com> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> > Cc: Cole Robinson <crobinso@redhat.com> > Cc: Gerd Hoffmann <kraxel@redhat.com> > Cc: Leif Lindholm <leif.lindholm@linaro.org> > Cc: Liming Gao <liming.gao@intel.com> > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Yonghong Zhu <yonghong.zhu@intel.com> > Reported-by: "Danilo C. L. de Paula" <ddepaula@redhat.com> > Contributed-under: TianoCore Contribution Agreement 1.1 > Signed-off-by: Laszlo Ersek <lersek@redhat.com> > --- > > Notes: > Repo: https://github.com/lersek/edk2.git > Branch: aarch64_no_unwind_tables > > BaseTools/Conf/tools_def.template | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template > index 03d700018550..9429033fe2e3 100755 > --- a/BaseTools/Conf/tools_def.template > +++ b/BaseTools/Conf/tools_def.template > @@ -4537,7 +4537,7 @@ DEFINE GCC_X64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mno-red-zone -Wno-ad > DEFINE GCC_IPF_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -minline-int-divide-min-latency > DEFINE GCC_ARM_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -mabi=aapcs -fno-short-enums -funsigned-char -ffunction-sections -fdata-sections -fomit-frame-pointer -Wno-address -mthumb -mfloat-abi=soft -fno-pic -fno-pie > DEFINE GCC_ARM_CC_XIPFLAGS = -mno-unaligned-access > -DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm -funsigned-char -ffunction-sections -fdata-sections -Wno-address -fno-asynchronous-unwind-tables -fno-pic -fno-pie -ffixed-x18 > +DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm -funsigned-char -ffunction-sections -fdata-sections -Wno-address -fno-asynchronous-unwind-tables -fno-unwind-tables -fno-pic -fno-pie -ffixed-x18 > DEFINE GCC_AARCH64_CC_XIPFLAGS = -mstrict-align -mgeneral-regs-only > DEFINE GCC_DLINK_FLAGS_COMMON = -nostdlib --pie > DEFINE GCC_DLINK2_FLAGS_COMMON = -Wl,--script=$(EDK_TOOLS_PATH)/Scripts/GccBase.lds > -- > 2.14.1.3.gb7cf6e02401b > ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS 2018-05-21 10:30 ` Leif Lindholm @ 2018-05-22 9:29 ` Laszlo Ersek 2018-05-23 14:21 ` Gao, Liming 0 siblings, 1 reply; 9+ messages in thread From: Laszlo Ersek @ 2018-05-22 9:29 UTC (permalink / raw) To: Leif Lindholm Cc: edk2-devel-01, Danilo C. L. de Paula, Ard Biesheuvel, Cole Robinson, Gerd Hoffmann, Liming Gao, Paolo Bonzini, Yonghong Zhu, pjones On 05/21/18 12:30, Leif Lindholm wrote: > On Fri, May 18, 2018 at 08:23:01PM +0200, Laszlo Ersek wrote: >> The ElfConvert routines in GenFw don't handle the ".eh_frame" ELF section >> emitted by gcc. For this reason, Leif disabled the generation of that >> section for AARCH64 with "-fno-asynchronous-unwind-tables" in commit >> 28e80befa4fe [1], and Ard did the same for IA32 and X64 in commit >> 26ecc55c027d [2]. (The CLANG38 toolchain received the same flag at its >> inception, in commit 6f756db5ea05 [3].) >> >> However, ".eh_frame" is back now; in upstream gcc commit 9cbee213b579 [4] >> (part of tag "gcc-8_1_0-release"), both "-fasynchronous-unwind-tables" and >> "-funwind-tables" were made the default for AARCH64. (The patch author >> described the effects on the gcc mailing list [5].) We have to counter the >> latter flag with "-fno-unwind-tables", otherwise GenFw chokes on >> ".eh_frame" again (triggered for example on Fedora 28). >> >> "-f[no-]unwind-tables" goes back to at least gcc-4.4 [6], so it's safe to >> add to GCC_AARCH64_CC_FLAGS. > > I'm not against this patch (which fixes a real problem), but would > it be possible to take the opposite approach, as Peter Jones did for > GRUB when the same issue hit there?: > > http://lists.gnu.org/archive/html/grub-devel/2018-02/msg00095.html > > I.e., rather than keep adding flags when new "special" sections are > added by toolchains, explicitly filter those out as part of the link > step. I guess this could be implemented in two places in BaseTools: (1) In GenFw / ElfConvert. I'm afraid that's beyond my binutils-fu at the moment. (2) In "BaseTools/Scripts/GccBase.lds". This is similarly beyond my binutils-fu, but at least I can make more comments on it: We already discard a good number of sections, but we keep (and realign) "eh_frame". From Ard's commit message 26ecc55c027d, I believe the idea here was to "retain the .eh_frame data for external debugging", and then strip it with "objcopy -R .eh_frame" finally (see [Dynamic-Library-File], <Command.GCC, Command.GCCLD> in "BaseTools/Conf/build_rule.template"). However, in practice we stub out objcopy (see under "GCC Common" in "BaseTools/Conf/tools_def.template"), and then we must prevent the generation of .eh_frame in the first place. Rather than adding "-fno-unwind-tables", I considered moving .eh_frame to /DISCARD/, or else turning $(OBJCOPY) into the real thing. However, that would affect more targets than just AARCH64/GCC, and I really didn't (don't) remember why we have this redundancy with "objcopy -R .eh_frame" vs. "-no-fasynchronous-unwind-tables". The latest practice seemed to be "add more -fno-..." (see the commits I referenced above), so I went with that. I suggest we push this patch now, plus I could: - submit a followup for IA32/X64, if that's deemed best, - file a BZ for GenFw / ElfConvert about the programmatic relocation filtering, - file a BZ for GccBase.lds / tools_def.template, to discard or strip .eh_frame under GCC. Thanks Laszlo ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS 2018-05-22 9:29 ` Laszlo Ersek @ 2018-05-23 14:21 ` Gao, Liming 2018-05-23 15:18 ` Laszlo Ersek 0 siblings, 1 reply; 9+ messages in thread From: Gao, Liming @ 2018-05-23 14:21 UTC (permalink / raw) To: Laszlo Ersek, Leif Lindholm Cc: Ard Biesheuvel, edk2-devel-01, pjones@redhat.com, Cole Robinson, Paolo Bonzini, Danilo C. L. de Paula Laszlo: I agree to add this change first in tools_def.txt. Then, update IA32/X64 arch when there is a real request. For long term, I prefer to file a BZ for GccBase.lds / tools_def.template, to discard or strip .eh_frame under GCC. Reviewed-by: Liming Gao <liming.gao@intel.com> Thanks Liming > -----Original Message----- > From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Laszlo Ersek > Sent: Tuesday, May 22, 2018 5:30 PM > To: Leif Lindholm <leif.lindholm@linaro.org> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>; edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming <liming.gao@intel.com>; > pjones@redhat.com; Cole Robinson <crobinso@redhat.com>; Paolo Bonzini <pbonzini@redhat.com>; Danilo C. L. de Paula > <ddepaula@redhat.com> > Subject: Re: [edk2] [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS > > On 05/21/18 12:30, Leif Lindholm wrote: > > On Fri, May 18, 2018 at 08:23:01PM +0200, Laszlo Ersek wrote: > >> The ElfConvert routines in GenFw don't handle the ".eh_frame" ELF section > >> emitted by gcc. For this reason, Leif disabled the generation of that > >> section for AARCH64 with "-fno-asynchronous-unwind-tables" in commit > >> 28e80befa4fe [1], and Ard did the same for IA32 and X64 in commit > >> 26ecc55c027d [2]. (The CLANG38 toolchain received the same flag at its > >> inception, in commit 6f756db5ea05 [3].) > >> > >> However, ".eh_frame" is back now; in upstream gcc commit 9cbee213b579 [4] > >> (part of tag "gcc-8_1_0-release"), both "-fasynchronous-unwind-tables" and > >> "-funwind-tables" were made the default for AARCH64. (The patch author > >> described the effects on the gcc mailing list [5].) We have to counter the > >> latter flag with "-fno-unwind-tables", otherwise GenFw chokes on > >> ".eh_frame" again (triggered for example on Fedora 28). > >> > >> "-f[no-]unwind-tables" goes back to at least gcc-4.4 [6], so it's safe to > >> add to GCC_AARCH64_CC_FLAGS. > > > > I'm not against this patch (which fixes a real problem), but would > > it be possible to take the opposite approach, as Peter Jones did for > > GRUB when the same issue hit there?: > > > > http://lists.gnu.org/archive/html/grub-devel/2018-02/msg00095.html > > > > I.e., rather than keep adding flags when new "special" sections are > > added by toolchains, explicitly filter those out as part of the link > > step. > > I guess this could be implemented in two places in BaseTools: > > (1) In GenFw / ElfConvert. I'm afraid that's beyond my binutils-fu at > the moment. > > (2) In "BaseTools/Scripts/GccBase.lds". This is similarly beyond my > binutils-fu, but at least I can make more comments on it: > > We already discard a good number of sections, but we keep (and realign) > "eh_frame". From Ard's commit message 26ecc55c027d, I believe the idea > here was to "retain the .eh_frame data for external debugging", and then > strip it with "objcopy -R .eh_frame" finally (see > [Dynamic-Library-File], <Command.GCC, Command.GCCLD> in > "BaseTools/Conf/build_rule.template"). > > However, in practice we stub out objcopy (see under "GCC Common" in > "BaseTools/Conf/tools_def.template"), and then we must prevent the > generation of .eh_frame in the first place. > > Rather than adding "-fno-unwind-tables", I considered moving .eh_frame > to /DISCARD/, or else turning $(OBJCOPY) into the real thing. However, > that would affect more targets than just AARCH64/GCC, and I really > didn't (don't) remember why we have this redundancy with "objcopy -R > .eh_frame" vs. "-no-fasynchronous-unwind-tables". The latest practice > seemed to be "add more -fno-..." (see the commits I referenced above), > so I went with that. > > > I suggest we push this patch now, plus I could: > > - submit a followup for IA32/X64, if that's deemed best, > - file a BZ for GenFw / ElfConvert about the programmatic relocation > filtering, > - file a BZ for GccBase.lds / tools_def.template, to discard or strip > .eh_frame under GCC. > > Thanks > Laszlo > _______________________________________________ > edk2-devel mailing list > edk2-devel@lists.01.org > https://lists.01.org/mailman/listinfo/edk2-devel ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS 2018-05-23 14:21 ` Gao, Liming @ 2018-05-23 15:18 ` Laszlo Ersek 0 siblings, 0 replies; 9+ messages in thread From: Laszlo Ersek @ 2018-05-23 15:18 UTC (permalink / raw) To: Gao, Liming, Leif Lindholm Cc: Ard Biesheuvel, edk2-devel-01, pjones@redhat.com, Cole Robinson, Paolo Bonzini, Danilo C. L. de Paula On 05/23/18 16:21, Gao, Liming wrote: > Laszlo: > I agree to add this change first in tools_def.txt. Then, update IA32/X64 arch when there is a real request. For long term, I prefer to file a BZ for GccBase.lds / tools_def.template, to discard or strip .eh_frame under GCC. > > Reviewed-by: Liming Gao <liming.gao@intel.com> Thanks! I've pushed this patch now as commit cbf00651eda6, and filed <https://bugzilla.tianocore.org/show_bug.cgi?id=955>. Cheers, Laszlo >> -----Original Message----- >> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Laszlo Ersek >> Sent: Tuesday, May 22, 2018 5:30 PM >> To: Leif Lindholm <leif.lindholm@linaro.org> >> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>; edk2-devel-01 <edk2-devel@lists.01.org>; Gao, Liming <liming.gao@intel.com>; >> pjones@redhat.com; Cole Robinson <crobinso@redhat.com>; Paolo Bonzini <pbonzini@redhat.com>; Danilo C. L. de Paula >> <ddepaula@redhat.com> >> Subject: Re: [edk2] [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS >> >> On 05/21/18 12:30, Leif Lindholm wrote: >>> On Fri, May 18, 2018 at 08:23:01PM +0200, Laszlo Ersek wrote: >>>> The ElfConvert routines in GenFw don't handle the ".eh_frame" ELF section >>>> emitted by gcc. For this reason, Leif disabled the generation of that >>>> section for AARCH64 with "-fno-asynchronous-unwind-tables" in commit >>>> 28e80befa4fe [1], and Ard did the same for IA32 and X64 in commit >>>> 26ecc55c027d [2]. (The CLANG38 toolchain received the same flag at its >>>> inception, in commit 6f756db5ea05 [3].) >>>> >>>> However, ".eh_frame" is back now; in upstream gcc commit 9cbee213b579 [4] >>>> (part of tag "gcc-8_1_0-release"), both "-fasynchronous-unwind-tables" and >>>> "-funwind-tables" were made the default for AARCH64. (The patch author >>>> described the effects on the gcc mailing list [5].) We have to counter the >>>> latter flag with "-fno-unwind-tables", otherwise GenFw chokes on >>>> ".eh_frame" again (triggered for example on Fedora 28). >>>> >>>> "-f[no-]unwind-tables" goes back to at least gcc-4.4 [6], so it's safe to >>>> add to GCC_AARCH64_CC_FLAGS. >>> >>> I'm not against this patch (which fixes a real problem), but would >>> it be possible to take the opposite approach, as Peter Jones did for >>> GRUB when the same issue hit there?: >>> >>> http://lists.gnu.org/archive/html/grub-devel/2018-02/msg00095.html >>> >>> I.e., rather than keep adding flags when new "special" sections are >>> added by toolchains, explicitly filter those out as part of the link >>> step. >> >> I guess this could be implemented in two places in BaseTools: >> >> (1) In GenFw / ElfConvert. I'm afraid that's beyond my binutils-fu at >> the moment. >> >> (2) In "BaseTools/Scripts/GccBase.lds". This is similarly beyond my >> binutils-fu, but at least I can make more comments on it: >> >> We already discard a good number of sections, but we keep (and realign) >> "eh_frame". From Ard's commit message 26ecc55c027d, I believe the idea >> here was to "retain the .eh_frame data for external debugging", and then >> strip it with "objcopy -R .eh_frame" finally (see >> [Dynamic-Library-File], <Command.GCC, Command.GCCLD> in >> "BaseTools/Conf/build_rule.template"). >> >> However, in practice we stub out objcopy (see under "GCC Common" in >> "BaseTools/Conf/tools_def.template"), and then we must prevent the >> generation of .eh_frame in the first place. >> >> Rather than adding "-fno-unwind-tables", I considered moving .eh_frame >> to /DISCARD/, or else turning $(OBJCOPY) into the real thing. However, >> that would affect more targets than just AARCH64/GCC, and I really >> didn't (don't) remember why we have this redundancy with "objcopy -R >> .eh_frame" vs. "-no-fasynchronous-unwind-tables". The latest practice >> seemed to be "add more -fno-..." (see the commits I referenced above), >> so I went with that. >> >> >> I suggest we push this patch now, plus I could: >> >> - submit a followup for IA32/X64, if that's deemed best, >> - file a BZ for GenFw / ElfConvert about the programmatic relocation >> filtering, >> - file a BZ for GccBase.lds / tools_def.template, to discard or strip >> .eh_frame under GCC. >> >> Thanks >> Laszlo >> _______________________________________________ >> edk2-devel mailing list >> edk2-devel@lists.01.org >> https://lists.01.org/mailman/listinfo/edk2-devel > _______________________________________________ > edk2-devel mailing list > edk2-devel@lists.01.org > https://lists.01.org/mailman/listinfo/edk2-devel > ^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2018-05-23 15:18 UTC | newest] Thread overview: 9+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2018-05-18 18:23 [PATCH] BaseTools/tools_def: add "-fno-unwind-tables" to GCC_AARCH64_CC_FLAGS Laszlo Ersek 2018-05-19 8:21 ` Ard Biesheuvel 2018-05-21 0:37 ` Gao, Liming 2018-05-21 9:32 ` Ard Biesheuvel 2018-05-22 9:05 ` Laszlo Ersek 2018-05-21 10:30 ` Leif Lindholm 2018-05-22 9:29 ` Laszlo Ersek 2018-05-23 14:21 ` Gao, Liming 2018-05-23 15:18 ` Laszlo Ersek
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