2012-04-19 13:14:21 +02:00
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Index: glibc-2.15/sysdeps/x86_64/elf/initfini.c
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2011-02-04 05:30:37 +01:00
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===================================================================
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2012-04-19 13:14:21 +02:00
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--- glibc-2.15.orig/sysdeps/x86_64/elf/initfini.c
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+++ glibc-2.15/sysdeps/x86_64/elf/initfini.c
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2011-02-04 05:30:37 +01:00
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@@ -44,6 +44,25 @@
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* crtn.s puts the corresponding function epilogues
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in the .init and .fini sections. */
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+/* The unwind annotation for _fini is peculiar for good reasons:
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+ (a) We need a real function that isn't constructed separately
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+ (i.e. one which has a .size directive) in order to attach unwind
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+ info to it. Hence _fini is a wrapper around _real_fini, the
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+ former being a normal function, the latter being the first
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+ instruction of the traditional _fini.
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+ (b) We must not fiddle with the stack pointer in _real_fini,
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+ as we wouldn't be able to describe the effects in unwind info
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+ (c) some versions of GCC have no correct unwind info for
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+ __do_global_dtors_aux, meaning they can't properly restore %rbp
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+ (unwinding through it is possible but later up when we next
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+ need %rbp we can't access it anymore)
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+ Therefore we save/restore it in _fini for uses later up the call chain.
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+ But we don't make the CFA use that register (that would lead to
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+ the above problem)
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+ (d) We want an 16-aligned stack pointer at _real_fini. Because of (a)
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+ we can't align it in _real_fini, hence we do it in the caller by
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+ subtracting 8, making in 8mod16 which the call then make 0mod16
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+ again. */
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__asm__ ("\n\
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#include \"defs.h\"\n\
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\n\
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@@ -88,16 +107,28 @@ _init:\n\
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.globl _fini\n\
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.type _fini,@function\n\
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_fini:\n\
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+ .cfi_startproc\n\
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+ push %rbp\n\
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+ .cfi_def_cfa_offset 16\n\
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+ .cfi_offset 6,-16\n\
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subq $8, %rsp\n\
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+ .cfi_def_cfa_offset 24\n\
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+ call _real_fini\n\
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+ addq $8, %rsp\n\
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+ .cfi_def_cfa_offset 16\n\
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+ pop %rbp\n\
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+ ret\n\
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+ .cfi_endproc\n\
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ALIGN\n\
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END_FINI\n\
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+.size _fini, .-_fini\n\
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+_real_fini:\n\
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\n\
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/*@_fini_PROLOG_ENDS*/\n\
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call i_am_not_a_leaf@PLT\n\
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\n\
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/*@_fini_EPILOG_BEGINS*/\n\
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.section .fini\n\
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- addq $8, %rsp\n\
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ret\n\
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END_FINI\n\
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\n\
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