From fd8c06e7b56baab37ce6154cca6c518a76d54a78 Mon Sep 17 00:00:00 2001 From: Mark Rowe Date: Tue, 22 Oct 2013 02:50:52 -0700 Subject: [PATCH] Fix unwinding on OS X 10.9. OS X 10.9's linker has a bug that results in it failing to preserve DWARF unwind information when passed the -no_compact_unwind flag. This flag is passed on OS X because the unwind information for __morestack cannot be represented by the compact unwind format. We can work around this problem by using a more targeted approach to disabling compact unwind information. The OS X linker looks for a particular pattern in the DWARF unwind information and will not attempt to convert the unwind information to the compact format. The pattern in question is the return address register being saved twice to the same location. Fixes #6849. --- mk/platform.mk | 4 ++-- src/librustc/back/link.rs | 8 -------- src/rt/arch/i386/morestack.S | 15 ++++++++++++--- src/rt/arch/x86_64/morestack.S | 9 +++++++++ 4 files changed, 23 insertions(+), 13 deletions(-) diff --git a/mk/platform.mk b/mk/platform.mk index 7ba8f77ef980e..27fe373b761ea 100644 --- a/mk/platform.mk +++ b/mk/platform.mk @@ -204,7 +204,7 @@ CFG_LIB_GLOB_x86_64-apple-darwin=lib$(1)-*.dylib CFG_LIB_DSYM_GLOB_x86_64-apple-darwin=lib$(1)-*.dylib.dSYM CFG_GCCISH_CFLAGS_x86_64-apple-darwin := -Wall -Werror -g -fPIC -m64 -arch x86_64 CFG_GCCISH_CXXFLAGS_x86_64-apple-darwin := -fno-rtti -CFG_GCCISH_LINK_FLAGS_x86_64-apple-darwin := -dynamiclib -pthread -framework CoreServices -Wl,-no_compact_unwind -m64 +CFG_GCCISH_LINK_FLAGS_x86_64-apple-darwin := -dynamiclib -pthread -framework CoreServices -m64 CFG_GCCISH_DEF_FLAG_x86_64-apple-darwin := -Wl,-exported_symbols_list, CFG_GCCISH_PRE_LIB_FLAGS_x86_64-apple-darwin := CFG_GCCISH_POST_LIB_FLAGS_x86_64-apple-darwin := @@ -230,7 +230,7 @@ CFG_LIB_GLOB_i686-apple-darwin=lib$(1)-*.dylib CFG_LIB_DSYM_GLOB_i686-apple-darwin=lib$(1)-*.dylib.dSYM CFG_GCCISH_CFLAGS_i686-apple-darwin := -Wall -Werror -g -fPIC -m32 -arch i386 CFG_GCCISH_CXXFLAGS_i686-apple-darwin := -fno-rtti -CFG_GCCISH_LINK_FLAGS_i686-apple-darwin := -dynamiclib -pthread -framework CoreServices -Wl,-no_compact_unwind -m32 +CFG_GCCISH_LINK_FLAGS_i686-apple-darwin := -dynamiclib -pthread -framework CoreServices -m32 CFG_GCCISH_DEF_FLAG_i686-apple-darwin := -Wl,-exported_symbols_list, CFG_GCCISH_PRE_LIB_FLAGS_i686-apple-darwin := CFG_GCCISH_POST_LIB_FLAGS_i686-apple-darwin := diff --git a/src/librustc/back/link.rs b/src/librustc/back/link.rs index 7c2856b75776a..ad74aa68dd3e4 100644 --- a/src/librustc/back/link.rs +++ b/src/librustc/back/link.rs @@ -1112,14 +1112,6 @@ pub fn link_args(sess: Session, ~"-Wl,-rpath,/usr/local/lib/gcc44"]); } - // OS X 10.6 introduced 'compact unwind info', which is produced by the - // linker from the dwarf unwind info. Unfortunately, it does not seem to - // understand how to unwind our __morestack frame, so we have to turn it - // off. This has impacted some other projects like GHC. - if sess.targ_cfg.os == session::OsMacos { - args.push(~"-Wl,-no_compact_unwind"); - } - // Stack growth requires statically linking a __morestack function args.push(~"-lmorestack"); diff --git a/src/rt/arch/i386/morestack.S b/src/rt/arch/i386/morestack.S index 25f907f479caa..2f03251e54ae5 100644 --- a/src/rt/arch/i386/morestack.S +++ b/src/rt/arch/i386/morestack.S @@ -62,9 +62,9 @@ is that OS X 10.6+ uses its own 'compact unwind info', an undocumented format generated by the linker from the DWARF CFI. This compact unwind info doesn't correctly - capture the nuance of the __morestack frame, and as a - result all of our linking on OS X uses the -no_compact_unwind - flag. + capture the nuance of the __morestack frame, so we need to + prevent the linker from attempting to convert its DWARF unwind + information. */ .text @@ -118,6 +118,15 @@ MORESTACK: // FIXME(#9854) these cfi directives don't work on windows. pushl %ebp + +#if defined(__APPLE__) + // The pattern of the return address being saved twice to the same location + // tells the OS X linker that it should not attempt to convert the DWARF + // unwind information to the compact format. + .cfi_offset %eip, -4 + .cfi_offset %eip, -4 +#endif + // The CFA is 20 bytes above the register that it is // associated with for this frame (which will be %ebp) .cfi_def_cfa_offset 20 diff --git a/src/rt/arch/x86_64/morestack.S b/src/rt/arch/x86_64/morestack.S index d248d79d12147..6ccabbf5994d5 100644 --- a/src/rt/arch/x86_64/morestack.S +++ b/src/rt/arch/x86_64/morestack.S @@ -43,6 +43,15 @@ MORESTACK: // bytes greater than a normal frame, to allow the unwinder // to skip the partial frame of the original function. .cfi_def_cfa_offset 24 + +#if defined(__APPLE__) + // The pattern of the return address being saved twice to the same location + // tells the OS X linker that it should not attempt to convert the DWARF + // unwind information to the compact format. + .cfi_offset %rip, -8 + .cfi_offset %rip, -8 +#endif + // %rbp is -24 bytes from the CFA .cfi_offset %rbp, -24 movq %rsp, %rbp