| Message ID | 1470034640-3912-1-git-send-email-ard.biesheuvel@linaro.org |
|---|---|
| State | Accepted |
| Commit | 28ade7b802e0732cf9839017ee6e9cf78b842582 |
| Headers | show |
On 2 August 2016 at 04:49, Gao, Liming <liming.gao@intel.com> wrote: > Reviewed-by: Liming Gao <liming.gao@intel.com> > Thanks Pushed as 28ade7b802e0 -- Ard. >> -----Original Message----- >> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org] >> Sent: Monday, August 01, 2016 2:57 PM >> To: Shi, Steven <steven.shi@intel.com>; Zhu, Yonghong >> <yonghong.zhu@intel.com>; Gao, Liming <liming.gao@intel.com>; Justen, >> Jordan L <jordan.l.justen@intel.com>; edk2-devel@lists.01.org >> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> >> Subject: [PATCH] MdePkg: move to 'hidden' visibility for all symbols under >> GCC/X64 >> >> When using GCC to build for X64, we switched to the position independent >> small code model, which is much more efficient in terms of code generation >> and runtime relocation footprint, and produces binaries that can execute >> correctly from any offset. >> >> However, the PIC routines are by default geared towards hosted binaries >> containing symbol references that may resolve to definitions in other >> dynamic objects, and for this reason, external symbol references are >> indirected via a GOT entry by default (which also results in a .reloc fixup >> entry) unless we annotate them. >> >> For this reason, we introduced the 'protected' visibility annotation for >> all symbol definitions and references, by setting the GCC visibility >> pragma. However, as it turns out, this is not sufficient for all versions >> of GCC, and in some cases (GCC 5.x using the GCC49 toolchain tag), may >> still result in GOT based relocations. >> >> So switch to 'hidden' visibility instead, which is slightly stronger, and >> fixes this issue for the versions of GCC that exhibit the problem. >> >> Contributed-under: TianoCore Contribution Agreement 1.0 >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> >> --- >> MdePkg/Include/X64/ProcessorBind.h | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/MdePkg/Include/X64/ProcessorBind.h >> b/MdePkg/Include/X64/ProcessorBind.h >> index a4aad3e524e8..666cc8e8bd16 100644 >> --- a/MdePkg/Include/X64/ProcessorBind.h >> +++ b/MdePkg/Include/X64/ProcessorBind.h >> @@ -29,12 +29,12 @@ >> >> #if defined(__GNUC__) && defined(__pic__) >> // >> -// Mark all symbol declarations and references as protected, meaning they >> will >> +// Mark all symbol declarations and references as hidden, meaning they will >> // not be subject to symbol preemption. This allows the compiler to refer to >> // symbols directly using relative references rather than via the GOT, which >> // contains absolute symbol addresses that are subject to runtime relocation. >> // >> -#pragma GCC visibility push (protected) >> +#pragma GCC visibility push (hidden) >> #endif >> >> #if defined(__INTEL_COMPILER) >> -- >> 2.7.4 > _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
diff --git a/MdePkg/Include/X64/ProcessorBind.h b/MdePkg/Include/X64/ProcessorBind.h index a4aad3e524e8..666cc8e8bd16 100644 --- a/MdePkg/Include/X64/ProcessorBind.h +++ b/MdePkg/Include/X64/ProcessorBind.h @@ -29,12 +29,12 @@ #if defined(__GNUC__) && defined(__pic__) // -// Mark all symbol declarations and references as protected, meaning they will +// Mark all symbol declarations and references as hidden, meaning they will // not be subject to symbol preemption. This allows the compiler to refer to // symbols directly using relative references rather than via the GOT, which // contains absolute symbol addresses that are subject to runtime relocation. // -#pragma GCC visibility push (protected) +#pragma GCC visibility push (hidden) #endif #if defined(__INTEL_COMPILER)
When using GCC to build for X64, we switched to the position independent small code model, which is much more efficient in terms of code generation and runtime relocation footprint, and produces binaries that can execute correctly from any offset. However, the PIC routines are by default geared towards hosted binaries containing symbol references that may resolve to definitions in other dynamic objects, and for this reason, external symbol references are indirected via a GOT entry by default (which also results in a .reloc fixup entry) unless we annotate them. For this reason, we introduced the 'protected' visibility annotation for all symbol definitions and references, by setting the GCC visibility pragma. However, as it turns out, this is not sufficient for all versions of GCC, and in some cases (GCC 5.x using the GCC49 toolchain tag), may still result in GOT based relocations. So switch to 'hidden' visibility instead, which is slightly stronger, and fixes this issue for the versions of GCC that exhibit the problem. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- MdePkg/Include/X64/ProcessorBind.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) -- 2.7.4 _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel