glibc/glibc-fini-unwind.diff

61 lines
2.1 KiB
Diff

Index: glibc-2.15/sysdeps/x86_64/elf/initfini.c
===================================================================
--- glibc-2.15.orig/sysdeps/x86_64/elf/initfini.c
+++ glibc-2.15/sysdeps/x86_64/elf/initfini.c
@@ -44,6 +44,25 @@
* crtn.s puts the corresponding function epilogues
in the .init and .fini sections. */
+/* The unwind annotation for _fini is peculiar for good reasons:
+ (a) We need a real function that isn't constructed separately
+ (i.e. one which has a .size directive) in order to attach unwind
+ info to it. Hence _fini is a wrapper around _real_fini, the
+ former being a normal function, the latter being the first
+ instruction of the traditional _fini.
+ (b) We must not fiddle with the stack pointer in _real_fini,
+ as we wouldn't be able to describe the effects in unwind info
+ (c) some versions of GCC have no correct unwind info for
+ __do_global_dtors_aux, meaning they can't properly restore %rbp
+ (unwinding through it is possible but later up when we next
+ need %rbp we can't access it anymore)
+ Therefore we save/restore it in _fini for uses later up the call chain.
+ But we don't make the CFA use that register (that would lead to
+ the above problem)
+ (d) We want an 16-aligned stack pointer at _real_fini. Because of (a)
+ we can't align it in _real_fini, hence we do it in the caller by
+ subtracting 8, making in 8mod16 which the call then make 0mod16
+ again. */
__asm__ ("\n\
#include \"defs.h\"\n\
\n\
@@ -88,16 +107,28 @@ _init:\n\
.globl _fini\n\
.type _fini,@function\n\
_fini:\n\
+ .cfi_startproc\n\
+ push %rbp\n\
+ .cfi_def_cfa_offset 16\n\
+ .cfi_offset 6,-16\n\
subq $8, %rsp\n\
+ .cfi_def_cfa_offset 24\n\
+ call _real_fini\n\
+ addq $8, %rsp\n\
+ .cfi_def_cfa_offset 16\n\
+ pop %rbp\n\
+ ret\n\
+ .cfi_endproc\n\
ALIGN\n\
END_FINI\n\
+.size _fini, .-_fini\n\
+_real_fini:\n\
\n\
/*@_fini_PROLOG_ENDS*/\n\
call i_am_not_a_leaf@PLT\n\
\n\
/*@_fini_EPILOG_BEGINS*/\n\
.section .fini\n\
- addq $8, %rsp\n\
ret\n\
END_FINI\n\
\n\