* [PATCH] BaseTools/GccBase.lds: don't copy RELA section to PE/COFF
@ 2016-08-10 8:55 Ard Biesheuvel
2016-08-22 7:10 ` Ard Biesheuvel
0 siblings, 1 reply; 6+ messages in thread
From: Ard Biesheuvel @ 2016-08-10 8:55 UTC (permalink / raw)
To: steven.shi, yonghong.zhu, liming.gao, edk2-devel; +Cc: Ard Biesheuvel
The CLANG38 toolchain creates a PIE binary at link time. This is
necessary since the LTO code generation may otherwise result in
code that cannot execute correctly when loaded above 2 GB.
PIE executables contain a RELA section consisting of dynamic
relocation entries that are intended for consumption by the loader
at runtime. For this reason, it has the SHF_ALLOC attribute set by
default, and will be identified by GenFw as a section that needs to
be copied into the PE/COFF binary, resulting in waste of space since
the PE/COFF loader does not use this data at all.
So mark the RELA section as informational: this will prevent the
linker from setting the SHF_ALLOC attribute, causing GenFw to
ignore it.
DxeCore.efi before:
Detected 'X64' type PE/COFF image consisting of 3 sections
Section alignment: 0x40
File alignment: 0x40
Section '.text' @ 0x00000240
File offset: 0x240
Virtual size: 0x21000
Raw size: 0x21000
Section '.data' @ 0x00021240
File offset: 0x21240
Virtual size: 0x3640
Raw size: 0x3640
Section '.reloc' @ 0x00024880
File offset: 0x24880
Virtual size: 0x280
Raw size: 0x280
DxeCore.efi after:
Detected 'X64' type PE/COFF image consisting of 3 sections
Section alignment: 0x40
File alignment: 0x40
Section '.text' @ 0x00000240
File offset: 0x240
Virtual size: 0x1f440
Raw size: 0x1f440
Section '.data' @ 0x0001f680
File offset: 0x1f680
Virtual size: 0x3640
Raw size: 0x3640
Section '.reloc' @ 0x00022cc0
File offset: 0x22cc0
Virtual size: 0x280
Raw size: 0x280
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
BaseTools/Scripts/GccBase.lds | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/BaseTools/Scripts/GccBase.lds b/BaseTools/Scripts/GccBase.lds
index 281af8a9bd33..900848747144 100644
--- a/BaseTools/Scripts/GccBase.lds
+++ b/BaseTools/Scripts/GccBase.lds
@@ -54,7 +54,7 @@ SECTIONS {
KEEP (*(.eh_frame))
}
- .rela ALIGN(CONSTANT(COMMONPAGESIZE)) : {
+ .rela (INFO) : {
*(.rela .rela.*)
}
--
2.7.4
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] BaseTools/GccBase.lds: don't copy RELA section to PE/COFF
2016-08-10 8:55 [PATCH] BaseTools/GccBase.lds: don't copy RELA section to PE/COFF Ard Biesheuvel
@ 2016-08-22 7:10 ` Ard Biesheuvel
2016-08-22 7:22 ` Gao, Liming
0 siblings, 1 reply; 6+ messages in thread
From: Ard Biesheuvel @ 2016-08-22 7:10 UTC (permalink / raw)
To: Shi, Steven, Zhu, Yonghong, Gao, Liming, edk2-devel-01; +Cc: Ard Biesheuvel
On 10 August 2016 at 10:55, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> The CLANG38 toolchain creates a PIE binary at link time. This is
> necessary since the LTO code generation may otherwise result in
> code that cannot execute correctly when loaded above 2 GB.
>
> PIE executables contain a RELA section consisting of dynamic
> relocation entries that are intended for consumption by the loader
> at runtime. For this reason, it has the SHF_ALLOC attribute set by
> default, and will be identified by GenFw as a section that needs to
> be copied into the PE/COFF binary, resulting in waste of space since
> the PE/COFF loader does not use this data at all.
>
> So mark the RELA section as informational: this will prevent the
> linker from setting the SHF_ALLOC attribute, causing GenFw to
> ignore it.
>
> DxeCore.efi before:
>
> Detected 'X64' type PE/COFF image consisting of 3 sections
> Section alignment: 0x40
> File alignment: 0x40
> Section '.text' @ 0x00000240
> File offset: 0x240
> Virtual size: 0x21000
> Raw size: 0x21000
> Section '.data' @ 0x00021240
> File offset: 0x21240
> Virtual size: 0x3640
> Raw size: 0x3640
> Section '.reloc' @ 0x00024880
> File offset: 0x24880
> Virtual size: 0x280
> Raw size: 0x280
>
> DxeCore.efi after:
>
> Detected 'X64' type PE/COFF image consisting of 3 sections
> Section alignment: 0x40
> File alignment: 0x40
> Section '.text' @ 0x00000240
> File offset: 0x240
> Virtual size: 0x1f440
> Raw size: 0x1f440
> Section '.data' @ 0x0001f680
> File offset: 0x1f680
> Virtual size: 0x3640
> Raw size: 0x3640
> Section '.reloc' @ 0x00022cc0
> File offset: 0x22cc0
> Virtual size: 0x280
> Raw size: 0x280
>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Steven, Liming: any comments?
> ---
> BaseTools/Scripts/GccBase.lds | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/BaseTools/Scripts/GccBase.lds b/BaseTools/Scripts/GccBase.lds
> index 281af8a9bd33..900848747144 100644
> --- a/BaseTools/Scripts/GccBase.lds
> +++ b/BaseTools/Scripts/GccBase.lds
> @@ -54,7 +54,7 @@ SECTIONS {
> KEEP (*(.eh_frame))
> }
>
> - .rela ALIGN(CONSTANT(COMMONPAGESIZE)) : {
> + .rela (INFO) : {
> *(.rela .rela.*)
> }
>
> --
> 2.7.4
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] BaseTools/GccBase.lds: don't copy RELA section to PE/COFF
2016-08-22 7:10 ` Ard Biesheuvel
@ 2016-08-22 7:22 ` Gao, Liming
2016-08-22 7:25 ` Ard Biesheuvel
0 siblings, 1 reply; 6+ messages in thread
From: Gao, Liming @ 2016-08-22 7:22 UTC (permalink / raw)
To: Ard Biesheuvel, Shi, Steven, Zhu, Yonghong, edk2-devel-01
Ard:
Sorry. I miss this patch. GccBase.lds is used by GCC44~GCC5. GCC44~GCC49 doesn't enable LTO, GCC5 enables LTO. That means RELA section is not used with LTO or without LTO. Right?
Thanks
Liming
> -----Original Message-----
> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
> Sent: Monday, August 22, 2016 3:11 PM
> To: Shi, Steven <steven.shi@intel.com>; Zhu, Yonghong
> <yonghong.zhu@intel.com>; Gao, Liming <liming.gao@intel.com>; edk2-
> devel-01 <edk2-devel@lists.01.org>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Subject: Re: [PATCH] BaseTools/GccBase.lds: don't copy RELA section to
> PE/COFF
>
> On 10 August 2016 at 10:55, Ard Biesheuvel <ard.biesheuvel@linaro.org>
> wrote:
> > The CLANG38 toolchain creates a PIE binary at link time. This is
> > necessary since the LTO code generation may otherwise result in
> > code that cannot execute correctly when loaded above 2 GB.
> >
> > PIE executables contain a RELA section consisting of dynamic
> > relocation entries that are intended for consumption by the loader
> > at runtime. For this reason, it has the SHF_ALLOC attribute set by
> > default, and will be identified by GenFw as a section that needs to
> > be copied into the PE/COFF binary, resulting in waste of space since
> > the PE/COFF loader does not use this data at all.
> >
> > So mark the RELA section as informational: this will prevent the
> > linker from setting the SHF_ALLOC attribute, causing GenFw to
> > ignore it.
> >
> > DxeCore.efi before:
> >
> > Detected 'X64' type PE/COFF image consisting of 3 sections
> > Section alignment: 0x40
> > File alignment: 0x40
> > Section '.text' @ 0x00000240
> > File offset: 0x240
> > Virtual size: 0x21000
> > Raw size: 0x21000
> > Section '.data' @ 0x00021240
> > File offset: 0x21240
> > Virtual size: 0x3640
> > Raw size: 0x3640
> > Section '.reloc' @ 0x00024880
> > File offset: 0x24880
> > Virtual size: 0x280
> > Raw size: 0x280
> >
> > DxeCore.efi after:
> >
> > Detected 'X64' type PE/COFF image consisting of 3 sections
> > Section alignment: 0x40
> > File alignment: 0x40
> > Section '.text' @ 0x00000240
> > File offset: 0x240
> > Virtual size: 0x1f440
> > Raw size: 0x1f440
> > Section '.data' @ 0x0001f680
> > File offset: 0x1f680
> > Virtual size: 0x3640
> > Raw size: 0x3640
> > Section '.reloc' @ 0x00022cc0
> > File offset: 0x22cc0
> > Virtual size: 0x280
> > Raw size: 0x280
> >
> > Contributed-under: TianoCore Contribution Agreement 1.0
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>
> Steven, Liming: any comments?
>
> > ---
> > BaseTools/Scripts/GccBase.lds | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/BaseTools/Scripts/GccBase.lds b/BaseTools/Scripts/GccBase.lds
> > index 281af8a9bd33..900848747144 100644
> > --- a/BaseTools/Scripts/GccBase.lds
> > +++ b/BaseTools/Scripts/GccBase.lds
> > @@ -54,7 +54,7 @@ SECTIONS {
> > KEEP (*(.eh_frame))
> > }
> >
> > - .rela ALIGN(CONSTANT(COMMONPAGESIZE)) : {
> > + .rela (INFO) : {
> > *(.rela .rela.*)
> > }
> >
> > --
> > 2.7.4
> >
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] BaseTools/GccBase.lds: don't copy RELA section to PE/COFF
2016-08-22 7:22 ` Gao, Liming
@ 2016-08-22 7:25 ` Ard Biesheuvel
2016-08-22 8:47 ` Gao, Liming
0 siblings, 1 reply; 6+ messages in thread
From: Ard Biesheuvel @ 2016-08-22 7:25 UTC (permalink / raw)
To: Gao, Liming; +Cc: Shi, Steven, Zhu, Yonghong, edk2-devel-01
On 22 August 2016 at 09:22, Gao, Liming <liming.gao@intel.com> wrote:
> Ard:
> Sorry. I miss this patch. GccBase.lds is used by GCC44~GCC5. GCC44~GCC49 doesn't enable LTO, GCC5 enables LTO. That means RELA section is not used with LTO or without LTO. Right?
The allocatable RELA section is only emitted when linking a PIE binary
(i.e., the -pie linker switch, not the -fpie compiler switch). It
contains ELF relocations that the PE/COFF loader does not understand.
CLANG38LTO is the first toolchain to use the -pie linker switch, GCC5
does use PIE objects but does not create a PIE binary at link time.
In some cases, (i.e., when we add support for GOT based relocations),
the contents of this RELA section must be taken into account by GenFw,
but currently, it can only contain relocations that are duplicates of
the relocations we encounter in the non-allocatable RELA sections
(.rela.text, .rela.data etc etc)
So it never makes sense to copy it into the PE/COFF binary, regardless
of whether we inspect its contents or not.
--
Ard.
>
> Thanks
> Liming
>> -----Original Message-----
>> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
>> Sent: Monday, August 22, 2016 3:11 PM
>> To: Shi, Steven <steven.shi@intel.com>; Zhu, Yonghong
>> <yonghong.zhu@intel.com>; Gao, Liming <liming.gao@intel.com>; edk2-
>> devel-01 <edk2-devel@lists.01.org>
>> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> Subject: Re: [PATCH] BaseTools/GccBase.lds: don't copy RELA section to
>> PE/COFF
>>
>> On 10 August 2016 at 10:55, Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> wrote:
>> > The CLANG38 toolchain creates a PIE binary at link time. This is
>> > necessary since the LTO code generation may otherwise result in
>> > code that cannot execute correctly when loaded above 2 GB.
>> >
>> > PIE executables contain a RELA section consisting of dynamic
>> > relocation entries that are intended for consumption by the loader
>> > at runtime. For this reason, it has the SHF_ALLOC attribute set by
>> > default, and will be identified by GenFw as a section that needs to
>> > be copied into the PE/COFF binary, resulting in waste of space since
>> > the PE/COFF loader does not use this data at all.
>> >
>> > So mark the RELA section as informational: this will prevent the
>> > linker from setting the SHF_ALLOC attribute, causing GenFw to
>> > ignore it.
>> >
>> > DxeCore.efi before:
>> >
>> > Detected 'X64' type PE/COFF image consisting of 3 sections
>> > Section alignment: 0x40
>> > File alignment: 0x40
>> > Section '.text' @ 0x00000240
>> > File offset: 0x240
>> > Virtual size: 0x21000
>> > Raw size: 0x21000
>> > Section '.data' @ 0x00021240
>> > File offset: 0x21240
>> > Virtual size: 0x3640
>> > Raw size: 0x3640
>> > Section '.reloc' @ 0x00024880
>> > File offset: 0x24880
>> > Virtual size: 0x280
>> > Raw size: 0x280
>> >
>> > DxeCore.efi after:
>> >
>> > Detected 'X64' type PE/COFF image consisting of 3 sections
>> > Section alignment: 0x40
>> > File alignment: 0x40
>> > Section '.text' @ 0x00000240
>> > File offset: 0x240
>> > Virtual size: 0x1f440
>> > Raw size: 0x1f440
>> > Section '.data' @ 0x0001f680
>> > File offset: 0x1f680
>> > Virtual size: 0x3640
>> > Raw size: 0x3640
>> > Section '.reloc' @ 0x00022cc0
>> > File offset: 0x22cc0
>> > Virtual size: 0x280
>> > Raw size: 0x280
>> >
>> > Contributed-under: TianoCore Contribution Agreement 1.0
>> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>>
>> Steven, Liming: any comments?
>>
>> > ---
>> > BaseTools/Scripts/GccBase.lds | 2 +-
>> > 1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/BaseTools/Scripts/GccBase.lds b/BaseTools/Scripts/GccBase.lds
>> > index 281af8a9bd33..900848747144 100644
>> > --- a/BaseTools/Scripts/GccBase.lds
>> > +++ b/BaseTools/Scripts/GccBase.lds
>> > @@ -54,7 +54,7 @@ SECTIONS {
>> > KEEP (*(.eh_frame))
>> > }
>> >
>> > - .rela ALIGN(CONSTANT(COMMONPAGESIZE)) : {
>> > + .rela (INFO) : {
>> > *(.rela .rela.*)
>> > }
>> >
>> > --
>> > 2.7.4
>> >
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] BaseTools/GccBase.lds: don't copy RELA section to PE/COFF
2016-08-22 7:25 ` Ard Biesheuvel
@ 2016-08-22 8:47 ` Gao, Liming
2016-08-22 8:56 ` Shi, Steven
0 siblings, 1 reply; 6+ messages in thread
From: Gao, Liming @ 2016-08-22 8:47 UTC (permalink / raw)
To: Ard Biesheuvel; +Cc: edk2-devel-01
Ard:
Thanks for the detail information. Your patch makes sense. Reviewed-by: Liming Gao <liming.gao@intel.com>
> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
> Ard Biesheuvel
> Sent: Monday, August 22, 2016 3:26 PM
> To: Gao, Liming <liming.gao@intel.com>
> Cc: edk2-devel-01 <edk2-devel@lists.01.org>
> Subject: Re: [edk2] [PATCH] BaseTools/GccBase.lds: don't copy RELA section
> to PE/COFF
>
> On 22 August 2016 at 09:22, Gao, Liming <liming.gao@intel.com> wrote:
> > Ard:
> > Sorry. I miss this patch. GccBase.lds is used by GCC44~GCC5.
> GCC44~GCC49 doesn't enable LTO, GCC5 enables LTO. That means RELA
> section is not used with LTO or without LTO. Right?
>
> The allocatable RELA section is only emitted when linking a PIE binary
> (i.e., the -pie linker switch, not the -fpie compiler switch). It
> contains ELF relocations that the PE/COFF loader does not understand.
> CLANG38LTO is the first toolchain to use the -pie linker switch, GCC5
> does use PIE objects but does not create a PIE binary at link time.
>
> In some cases, (i.e., when we add support for GOT based relocations),
> the contents of this RELA section must be taken into account by GenFw,
> but currently, it can only contain relocations that are duplicates of
> the relocations we encounter in the non-allocatable RELA sections
> (.rela.text, .rela.data etc etc)
>
> So it never makes sense to copy it into the PE/COFF binary, regardless
> of whether we inspect its contents or not.
>
> --
> Ard.
>
> >
> > Thanks
> > Liming
> >> -----Original Message-----
> >> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
> >> Sent: Monday, August 22, 2016 3:11 PM
> >> To: Shi, Steven <steven.shi@intel.com>; Zhu, Yonghong
> >> <yonghong.zhu@intel.com>; Gao, Liming <liming.gao@intel.com>; edk2-
> >> devel-01 <edk2-devel@lists.01.org>
> >> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >> Subject: Re: [PATCH] BaseTools/GccBase.lds: don't copy RELA section to
> >> PE/COFF
> >>
> >> On 10 August 2016 at 10:55, Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >> wrote:
> >> > The CLANG38 toolchain creates a PIE binary at link time. This is
> >> > necessary since the LTO code generation may otherwise result in
> >> > code that cannot execute correctly when loaded above 2 GB.
> >> >
> >> > PIE executables contain a RELA section consisting of dynamic
> >> > relocation entries that are intended for consumption by the loader
> >> > at runtime. For this reason, it has the SHF_ALLOC attribute set by
> >> > default, and will be identified by GenFw as a section that needs to
> >> > be copied into the PE/COFF binary, resulting in waste of space since
> >> > the PE/COFF loader does not use this data at all.
> >> >
> >> > So mark the RELA section as informational: this will prevent the
> >> > linker from setting the SHF_ALLOC attribute, causing GenFw to
> >> > ignore it.
> >> >
> >> > DxeCore.efi before:
> >> >
> >> > Detected 'X64' type PE/COFF image consisting of 3 sections
> >> > Section alignment: 0x40
> >> > File alignment: 0x40
> >> > Section '.text' @ 0x00000240
> >> > File offset: 0x240
> >> > Virtual size: 0x21000
> >> > Raw size: 0x21000
> >> > Section '.data' @ 0x00021240
> >> > File offset: 0x21240
> >> > Virtual size: 0x3640
> >> > Raw size: 0x3640
> >> > Section '.reloc' @ 0x00024880
> >> > File offset: 0x24880
> >> > Virtual size: 0x280
> >> > Raw size: 0x280
> >> >
> >> > DxeCore.efi after:
> >> >
> >> > Detected 'X64' type PE/COFF image consisting of 3 sections
> >> > Section alignment: 0x40
> >> > File alignment: 0x40
> >> > Section '.text' @ 0x00000240
> >> > File offset: 0x240
> >> > Virtual size: 0x1f440
> >> > Raw size: 0x1f440
> >> > Section '.data' @ 0x0001f680
> >> > File offset: 0x1f680
> >> > Virtual size: 0x3640
> >> > Raw size: 0x3640
> >> > Section '.reloc' @ 0x00022cc0
> >> > File offset: 0x22cc0
> >> > Virtual size: 0x280
> >> > Raw size: 0x280
> >> >
> >> > Contributed-under: TianoCore Contribution Agreement 1.0
> >> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >>
> >> Steven, Liming: any comments?
> >>
> >> > ---
> >> > BaseTools/Scripts/GccBase.lds | 2 +-
> >> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >> >
> >> > diff --git a/BaseTools/Scripts/GccBase.lds
> b/BaseTools/Scripts/GccBase.lds
> >> > index 281af8a9bd33..900848747144 100644
> >> > --- a/BaseTools/Scripts/GccBase.lds
> >> > +++ b/BaseTools/Scripts/GccBase.lds
> >> > @@ -54,7 +54,7 @@ SECTIONS {
> >> > KEEP (*(.eh_frame))
> >> > }
> >> >
> >> > - .rela ALIGN(CONSTANT(COMMONPAGESIZE)) : {
> >> > + .rela (INFO) : {
> >> > *(.rela .rela.*)
> >> > }
> >> >
> >> > --
> >> > 2.7.4
> >> >
> _______________________________________________
> edk2-devel mailing list
> edk2-devel@lists.01.org
> https://lists.01.org/mailman/listinfo/edk2-devel
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] BaseTools/GccBase.lds: don't copy RELA section to PE/COFF
2016-08-22 8:47 ` Gao, Liming
@ 2016-08-22 8:56 ` Shi, Steven
0 siblings, 0 replies; 6+ messages in thread
From: Shi, Steven @ 2016-08-22 8:56 UTC (permalink / raw)
To: Gao, Liming, Ard Biesheuvel; +Cc: edk2-devel-01
Ard,
Your patch rock! Thank you let us know and contribute this optimization.
Steven Shi
Intel\SSG\STO\UEFI Firmware
Tel: +86 021-61166522
iNet: 821-6522
> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
> Gao, Liming
> Sent: Monday, August 22, 2016 4:47 PM
> To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: edk2-devel-01 <edk2-devel@lists.01.org>
> Subject: Re: [edk2] [PATCH] BaseTools/GccBase.lds: don't copy RELA section
> to PE/COFF
>
> Ard:
> Thanks for the detail information. Your patch makes sense. Reviewed-by:
> Liming Gao <liming.gao@intel.com>
>
> > -----Original Message-----
> > From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
> > Ard Biesheuvel
> > Sent: Monday, August 22, 2016 3:26 PM
> > To: Gao, Liming <liming.gao@intel.com>
> > Cc: edk2-devel-01 <edk2-devel@lists.01.org>
> > Subject: Re: [edk2] [PATCH] BaseTools/GccBase.lds: don't copy RELA
> section
> > to PE/COFF
> >
> > On 22 August 2016 at 09:22, Gao, Liming <liming.gao@intel.com> wrote:
> > > Ard:
> > > Sorry. I miss this patch. GccBase.lds is used by GCC44~GCC5.
> > GCC44~GCC49 doesn't enable LTO, GCC5 enables LTO. That means RELA
> > section is not used with LTO or without LTO. Right?
> >
> > The allocatable RELA section is only emitted when linking a PIE binary
> > (i.e., the -pie linker switch, not the -fpie compiler switch). It
> > contains ELF relocations that the PE/COFF loader does not understand.
> > CLANG38LTO is the first toolchain to use the -pie linker switch, GCC5
> > does use PIE objects but does not create a PIE binary at link time.
> >
> > In some cases, (i.e., when we add support for GOT based relocations),
> > the contents of this RELA section must be taken into account by GenFw,
> > but currently, it can only contain relocations that are duplicates of
> > the relocations we encounter in the non-allocatable RELA sections
> > (.rela.text, .rela.data etc etc)
> >
> > So it never makes sense to copy it into the PE/COFF binary, regardless
> > of whether we inspect its contents or not.
> >
> > --
> > Ard.
> >
> > >
> > > Thanks
> > > Liming
> > >> -----Original Message-----
> > >> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
> > >> Sent: Monday, August 22, 2016 3:11 PM
> > >> To: Shi, Steven <steven.shi@intel.com>; Zhu, Yonghong
> > >> <yonghong.zhu@intel.com>; Gao, Liming <liming.gao@intel.com>;
> edk2-
> > >> devel-01 <edk2-devel@lists.01.org>
> > >> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > >> Subject: Re: [PATCH] BaseTools/GccBase.lds: don't copy RELA section to
> > >> PE/COFF
> > >>
> > >> On 10 August 2016 at 10:55, Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > >> wrote:
> > >> > The CLANG38 toolchain creates a PIE binary at link time. This is
> > >> > necessary since the LTO code generation may otherwise result in
> > >> > code that cannot execute correctly when loaded above 2 GB.
> > >> >
> > >> > PIE executables contain a RELA section consisting of dynamic
> > >> > relocation entries that are intended for consumption by the loader
> > >> > at runtime. For this reason, it has the SHF_ALLOC attribute set by
> > >> > default, and will be identified by GenFw as a section that needs to
> > >> > be copied into the PE/COFF binary, resulting in waste of space since
> > >> > the PE/COFF loader does not use this data at all.
> > >> >
> > >> > So mark the RELA section as informational: this will prevent the
> > >> > linker from setting the SHF_ALLOC attribute, causing GenFw to
> > >> > ignore it.
> > >> >
> > >> > DxeCore.efi before:
> > >> >
> > >> > Detected 'X64' type PE/COFF image consisting of 3 sections
> > >> > Section alignment: 0x40
> > >> > File alignment: 0x40
> > >> > Section '.text' @ 0x00000240
> > >> > File offset: 0x240
> > >> > Virtual size: 0x21000
> > >> > Raw size: 0x21000
> > >> > Section '.data' @ 0x00021240
> > >> > File offset: 0x21240
> > >> > Virtual size: 0x3640
> > >> > Raw size: 0x3640
> > >> > Section '.reloc' @ 0x00024880
> > >> > File offset: 0x24880
> > >> > Virtual size: 0x280
> > >> > Raw size: 0x280
> > >> >
> > >> > DxeCore.efi after:
> > >> >
> > >> > Detected 'X64' type PE/COFF image consisting of 3 sections
> > >> > Section alignment: 0x40
> > >> > File alignment: 0x40
> > >> > Section '.text' @ 0x00000240
> > >> > File offset: 0x240
> > >> > Virtual size: 0x1f440
> > >> > Raw size: 0x1f440
> > >> > Section '.data' @ 0x0001f680
> > >> > File offset: 0x1f680
> > >> > Virtual size: 0x3640
> > >> > Raw size: 0x3640
> > >> > Section '.reloc' @ 0x00022cc0
> > >> > File offset: 0x22cc0
> > >> > Virtual size: 0x280
> > >> > Raw size: 0x280
> > >> >
> > >> > Contributed-under: TianoCore Contribution Agreement 1.0
> > >> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > >>
> > >> Steven, Liming: any comments?
> > >>
> > >> > ---
> > >> > BaseTools/Scripts/GccBase.lds | 2 +-
> > >> > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >> >
> > >> > diff --git a/BaseTools/Scripts/GccBase.lds
> > b/BaseTools/Scripts/GccBase.lds
> > >> > index 281af8a9bd33..900848747144 100644
> > >> > --- a/BaseTools/Scripts/GccBase.lds
> > >> > +++ b/BaseTools/Scripts/GccBase.lds
> > >> > @@ -54,7 +54,7 @@ SECTIONS {
> > >> > KEEP (*(.eh_frame))
> > >> > }
> > >> >
> > >> > - .rela ALIGN(CONSTANT(COMMONPAGESIZE)) : {
> > >> > + .rela (INFO) : {
> > >> > *(.rela .rela.*)
> > >> > }
> > >> >
> > >> > --
> > >> > 2.7.4
> > >> >
> > _______________________________________________
> > 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] 6+ messages in thread
end of thread, other threads:[~2016-08-22 8:56 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2016-08-10 8:55 [PATCH] BaseTools/GccBase.lds: don't copy RELA section to PE/COFF Ard Biesheuvel
2016-08-22 7:10 ` Ard Biesheuvel
2016-08-22 7:22 ` Gao, Liming
2016-08-22 7:25 ` Ard Biesheuvel
2016-08-22 8:47 ` Gao, Liming
2016-08-22 8:56 ` Shi, Steven
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