Ard: I don't think it is good way to define GCC_VISIBILITY_PROTECTED and apply it in EntryPointLib. We only need to expose _ModuleEntryPoint. It has been specified in LINK_FLAGS in tools_def.txt. Could we also specify its attribute in CC_FLAGS or LINK_FLAGS in tools_def.txt?
Thanks Liming > -----Original Message----- > From: edk2-devel [mailto:[email protected]] On Behalf Of > Ard Biesheuvel > Sent: Monday, August 01, 2016 4:02 PM > To: Shi, Steven ; Zhu, Yonghong > ; Gao, Liming ; Justen, > Jordan L ; [email protected] > Cc: [email protected]; [email protected]; Ard Biesheuvel > > Subject: [edk2] [PATCH v5 7/8] MdePkg GCC/X64: avoid 'hidden' visibility for > module entry points > > When building with LTO enabled, the LTO routines infer from the 'hidden' > visibility of the _ModuleEntryPoint symbol that its code only needs to be > retained if it is referenced internally, and disregards the fact that > it is referenced by the entry point field in the ELF metadata. > > This is arguably a bug in LTO, but we can work around it by ensuring that > the _ModuleEntryPoint symbol is emitted with protected visibility instead. > > Contributed-under: TianoCore Contribution Agreement 1.0 > Signed-off-by: Ard Biesheuvel > --- > MdePkg/Include/X64/ProcessorBind.h | 9 ++++++++- > MdePkg/Library/DxeCoreEntryPoint/DxeCoreEntryPoint.inf | 2 ++ > MdePkg/Library/PeiCoreEntryPoint/PeiCoreEntryPoint.inf | 2 ++ > MdePkg/Library/PeimEntryPoint/PeimEntryPoint.inf | 2 ++ > MdePkg/Library/UefiApplicationEntryPoint/UefiApplicationEntryPoint.inf | 2 > ++ > MdePkg/Library/UefiDriverEntryPoint/UefiDriverEntryPoint.inf | 2 ++ > 6 files changed, 18 insertions(+), 1 deletion(-) > > diff --git a/MdePkg/Include/X64/ProcessorBind.h > b/MdePkg/Include/X64/ProcessorBind.h > index 666cc8e8bd16..e45b9cba2bb3 100644 > --- a/MdePkg/Include/X64/ProcessorBind.h > +++ b/MdePkg/Include/X64/ProcessorBind.h > @@ -29,13 +29,20 @@ > > #if defined(__GNUC__) && defined(__pic__) > // > -// Mark all symbol declarations and references as hidden, 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. > // > +// * Under LTO, the entry point of a module must have protected or default > +// visibility to prevent it from being pruned. > +// > +#ifdef GCC_VISIBILITY_PROTECTED > +#pragma GCC visibility push (protected) > +#else > #pragma GCC visibility push (hidden) > #endif > +#endif > > #if defined(__INTEL_COMPILER) > // > diff --git a/MdePkg/Library/DxeCoreEntryPoint/DxeCoreEntryPoint.inf > b/MdePkg/Library/DxeCoreEntryPoint/DxeCoreEntryPoint.inf > index 01f64c34c7a1..2d6f87ed062e 100644 > --- a/MdePkg/Library/DxeCoreEntryPoint/DxeCoreEntryPoint.inf > +++ b/MdePkg/Library/DxeCoreEntryPoint/DxeCoreEntryPoint.inf > @@ -39,3 +39,5 @@ [LibraryClasses] > BaseLib > DebugLib > > +[BuildOptions] > + GCC:*_*_X64_CC_FLAGS = -DGCC_VISIBILITY_PROTECTED > diff --git a/MdePkg/Library/PeiCoreEntryPoint/PeiCoreEntryPoint.inf > b/MdePkg/Library/PeiCoreEntryPoint/PeiCoreEntryPoint.inf > index d920306713c5..4e61783b3bd5 100644 > --- a/MdePkg/Library/PeiCoreEntryPoint/PeiCoreEntryPoint.inf > +++ b/MdePkg/Library/PeiCoreEntryPoint/PeiCoreEntryPoint.inf > @@ -37,3 +37,5 @@ [LibraryClasses] > BaseLib > DebugLib > > +[BuildOptions] > + GCC:*_*_X64_CC_FLAGS = -DGCC_VISIBILITY_PROTECTED > diff --git a/MdePkg/Library/PeimEntryPoint/PeimEntryPoint.inf > b/MdePkg/Library/PeimEntryPoint/PeimEntryPoint.inf > index a2db9e058bbe..adfd91bdc57e 100644 > --- a/MdePkg/Library/PeimEntryPoint/PeimEntryPoint.inf > +++ b/MdePkg/Library/PeimEntryPoint/PeimEntryPoint.inf > @@ -37,3 +37,5 @@ [Packages] > [LibraryClasses] > DebugLib > > +[BuildOptions] > + GCC:*_*_X64_CC_FLAGS = -DGCC_VISIBILITY_PROTECTED > diff --git > a/MdePkg/Library/UefiApplicationEntryPoint/UefiApplicationEntryPoint.inf > b/MdePkg/Library/UefiApplicationEntryPoint/UefiApplicationEntryPoint.inf > index be92b3dc0760..9525c55c2051 100644 > --- > a/MdePkg/Library/UefiApplicationEntryPoint/UefiApplicationEntryPoint.inf > +++ > b/MdePkg/Library/UefiApplicationEntryPoint/UefiApplicationEntryPoint.inf > @@ -38,3 +38,5 @@ [LibraryClasses] > DebugLib > BaseLib > > +[BuildOptions] > + GCC:*_*_X64_CC_FLAGS = -DGCC_VISIBILITY_PROTECTED > diff --git a/MdePkg/Library/UefiDriverEntryPoint/UefiDriverEntryPoint.inf > b/MdePkg/Library/UefiDriverEntryPoint/UefiDriverEntryPoint.inf > index 7a9dcbcd4df2..8d30b1197850 100644 > --- a/MdePkg/Library/UefiDriverEntryPoint/UefiDriverEntryPoint.inf > +++ b/MdePkg/Library/UefiDriverEntryPoint/UefiDriverEntryPoint.inf > @@ -65,3 +65,5 @@ [Depex.common.UEFI_DRIVER] > gEfiVariableArchProtocolGuid AND > gEfiWatchdogTimerArchProtocolGuid > > +[BuildOptions] > + GCC:*_*_X64_CC_FLAGS = -DGCC_VISIBILITY_PROTECTED > -- > 2.7.4 > > _______________________________________________ > edk2-devel mailing list > [email protected] > https://lists.01.org/mailman/listinfo/edk2-devel _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel

