From: "Ard Biesheuvel" <ard.biesheuvel@linaro.org>
To: "Gao, Liming" <liming.gao@intel.com>
Cc: "devel@edk2.groups.io" <devel@edk2.groups.io>,
"eugene@hp.com" <eugene@hp.com>
Subject: Re: [edk2-devel] [PATCH 1/1] BaseTools/GenFw AARCH64: disregard ADRP instructions that are patched already
Date: Fri, 8 Nov 2019 09:00:18 +0100 [thread overview]
Message-ID: <CAKv+Gu9gPhdPBxrNmW0YVCaYK+Mv6AkrAghV-MnScVd6pPU3Vg@mail.gmail.com> (raw)
In-Reply-To: <4A89E2EF3DFEDB4C8BFDE51014F606A14E539892@SHSMSX104.ccr.corp.intel.com>
On Fri, 8 Nov 2019 at 01:39, Gao, Liming <liming.gao@intel.com> wrote:
>
> Acked-by: Liming Gao <liming.gao@intel.com>
>
Thanks all
Pushed as 9e9f0be353d4..f55c76b301f1
> >-----Original Message-----
> >From: devel@edk2.groups.io [mailto:devel@edk2.groups.io] On Behalf Of Ard
> >Biesheuvel
> >Sent: Thursday, November 07, 2019 5:06 PM
> >To: devel@edk2.groups.io
> >Cc: eugene@hp.com; Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >Subject: [edk2-devel] [PATCH 1/1] BaseTools/GenFw AARCH64: disregard
> >ADRP instructions that are patched already
> >
> >In order to permit the use of compilers that only implement the small
> >code model [which involves the use of ADRP instructions that require
> >4 KB segment alignment] for generating PE/COFF binaries with a small
> >footprint, we patch ADRP instructions into ADR instructions while doing
> >the ELF to PE/COFF conversion.
> >
> >As it turns out, the linker may be doing the same, but for different
> >reasons: there is a silicon erratum #843419 for ARM Cortex-A53 which
> >affects ADRP instructions appearing at a certain offset in memory, and
> >one of the mitigations for this erratum is to patch them into ADR
> >instructions at link time if the symbol reference is within -/+ 1 MB.
> >However, the LD linker fails to update the static relocation tables, and
> >so we end up with an ADR instruction in the fully linked binary, but
> >with a relocation entry in the RELA section identifying it as an ADRP
> >instruction.
> >
> >Since the linker has already updated the symbol reference, there is no
> >handling needed in GenFw for such instructions, and we can simply treat
> >it as an ordinary ADR. However, since it is guaranteed to be accompanied
> >by an add or load instruction with a LO12 relocation referencing the same
> >symbol, the section offset check we apply to ADR instructions is going to
> >take place anyway, so we can just disregard the ADR instruction entirely.
> >
> >Reported-by: Eugene Cohen <eugene@hp.com>
> >Suggested-by: Eugene Cohen <eugene@hp.com>
> >Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >---
> > BaseTools/Source/C/GenFw/Elf64Convert.c | 13 +++++++++++++
> > 1 file changed, 13 insertions(+)
> >
> >diff --git a/BaseTools/Source/C/GenFw/Elf64Convert.c
> >b/BaseTools/Source/C/GenFw/Elf64Convert.c
> >index d574300ac4fe..d623dce1f9da 100644
> >--- a/BaseTools/Source/C/GenFw/Elf64Convert.c
> >+++ b/BaseTools/Source/C/GenFw/Elf64Convert.c
> >@@ -1044,6 +1044,19 @@ WriteSections64 (
> > /* fall through */
> >
> > case R_AARCH64_ADR_PREL_PG_HI21:
> >+ //
> >+ // In order to handle Cortex-A53 erratum #843419, the LD linker may
> >+ // convert ADRP instructions into ADR instructions, but without
> >+ // updating the static relocation type, and so we may end up here
> >+ // while the instruction in question is actually ADR. So let's
> >+ // just disregard it: the section offset check we apply below to
> >+ // ADR instructions will trigger for its R_AARCH64_xxx_ABS_LO12_NC
> >+ // companion instruction as well, so it is safe to omit it here.
> >+ //
> >+ if ((*(UINT32 *)Targ & BIT31) == 0) {
> >+ break;
> >+ }
> >+
> > //
> > // AArch64 PG_H21 relocations are typically paired with ABS_LO12
> > // relocations, where a PC-relative reference with +/- 4 GB range is
> >--
> >2.17.1
> >
> >
> >
>
prev parent reply other threads:[~2019-11-08 8:00 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-07 9:06 [PATCH 1/1] BaseTools/GenFw AARCH64: disregard ADRP instructions that are patched already Ard Biesheuvel
2019-11-07 9:09 ` Ard Biesheuvel
2019-11-07 12:17 ` Cohen, Eugene
2019-11-07 16:14 ` Leif Lindholm
2019-11-08 0:39 ` [edk2-devel] " Liming Gao
2019-11-08 8:00 ` Ard Biesheuvel [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-list from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAKv+Gu9gPhdPBxrNmW0YVCaYK+Mv6AkrAghV-MnScVd6pPU3Vg@mail.gmail.com \
--to=devel@edk2.groups.io \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox