| Message ID | 3785c2b6-4d2b-e1ac-4276-8a6231db7c56@redhat.com |
|---|---|
| State | New |
| Headers | show |
On 16 Dec 2016, Florian Weimer outgrape: > On 12/15/2016 09:22 PM, Florian Weimer wrote: >> I think this attempt at PLT avoidance within libc.so itself is subtly >> wrong. We need to mirror more closely what >> libc_hidden_proto/libc_hidden_def does, and perhaps disentangle this >> from the __stack_chk_fail_local definition used in other DSOs. >> >> I think this means removing any definition of a C function definition >> called __stack_chk_fail_local from libc.so, and instead use a strong >> alias from __stack_chk_fail to __stack_chk_fail_local to define the >> symbol. The alias will not incorporate a PLT reference. If you look at >> include/libc-symbols.h, strong_alias and hidden_def are quite similar. > > With this patch on top of the series you posted (without any other changes), I get both MIPS and ia64 to build, and I don't see a > PLT failure on SPARC. I'll give this a spin, then post a new series. It'll be a few hours, as usual for a full test cycle :( -- NULL && (void)
diff --git a/debug/Makefile b/debug/Makefile index 27da081..cfcf392 100644 --- a/debug/Makefile +++ b/debug/Makefile @@ -48,14 +48,10 @@ routines = backtrace backtracesyms backtracesymsfd noophooks \ vdprintf_chk obprintf_chk \ longjmp_chk ____longjmp_chk \ fdelt_chk poll_chk ppoll_chk \ - stack_chk_fail fortify_fail libc-stack_chk_fail_local \ + stack_chk_fail fortify_fail \ $(static-only-routines) -# stack_chk_fail_local must be non-PIC, thus static-only, but we also -# want an identical thunk hidden in libc.so to avoid going via the PLT. - static-only-routines := warning-nop stack_chk_fail_local -shared-only-routines += libc-stack_chk_fail_local # Building the stack-protector failure routines with stack protection # makes no sense. diff --git a/debug/libc-stack_chk_fail_local.c b/debug/libc-stack_chk_fail_local.c deleted file mode 100644 index 73da970..0000000 --- a/debug/libc-stack_chk_fail_local.c +++ /dev/null @@ -1,3 +0,0 @@ -/* This goes into the shared libc. */ - -#include <stack_chk_fail_local.c> diff --git a/debug/stack_chk_fail.c b/debug/stack_chk_fail.c index 4d0796f..a545239 100644 --- a/debug/stack_chk_fail.c +++ b/debug/stack_chk_fail.c @@ -27,3 +27,11 @@ __stack_chk_fail (void) { __fortify_fail ("stack smashing detected"); } + +#ifdef SHARED +/* The compiler generates hidden references to __stack_chk_fail for + PLT avoidance. Outside of libc.so, a definition provided by + libc_nonshared.a, but within libc.so, a local definition is + needed. */ +strong_alias (__stack_chk_fail, __stack_chk_fail_local) +#endif diff --git a/sysdeps/generic/symbol-hacks.h b/sysdeps/generic/symbol-hacks.h index 36908b5..ce576c9 100644 --- a/sysdeps/generic/symbol-hacks.h +++ b/sysdeps/generic/symbol-hacks.h @@ -4,8 +4,4 @@ asm ("memmove = __GI_memmove"); asm ("memset = __GI_memset"); asm ("memcpy = __GI_memcpy"); - -/* -fstack-protector generates calls to __stack_chk_fail, which need - similar adjustments to avoid going through the PLT. */ -asm ("__stack_chk_fail = __stack_chk_fail_local"); #endif