diff options
| author | Willy Tarreau <w@1wt.eu> | 2021-10-24 19:28:15 +0200 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2021-11-30 17:26:42 -0800 |
| commit | ebbe0d8a449d183fa43b42d84fcb248e25303985 (patch) | |
| tree | 5ca7fe5659f80a4f97f274e6e34d282e068a5ba6 /tools/include | |
| parent | 937ed91c712273131de6d2a02caafd3ee84e0c72 (diff) | |
| download | linux-ebbe0d8a449d183fa43b42d84fcb248e25303985.tar.bz2 | |
tools/nolibc: i386: fix initial stack alignment
After re-checking in the spec and comparing stack offsets with glibc,
The last pushed argument must be 16-byte aligned (i.e. aligned before the
call) so that in the callee esp+4 is multiple of 16, so the principle is
the 32-bit equivalent to what Ammar fixed for x86_64. It's possible that
32-bit code using SSE2 or MMX could have been affected. In addition the
frame pointer ought to be zero at the deepest level.
Link: https://gitlab.com/x86-psABIs/i386-ABI/-/wikis/Intel386-psABI
Cc: Ammar Faizi <ammar.faizi@students.amikom.ac.id>
Cc: stable@vger.kernel.org
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'tools/include')
| -rw-r--r-- | tools/include/nolibc/nolibc.h | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/tools/include/nolibc/nolibc.h b/tools/include/nolibc/nolibc.h index 96b6d56acb57..7f300dc379e7 100644 --- a/tools/include/nolibc/nolibc.h +++ b/tools/include/nolibc/nolibc.h @@ -583,13 +583,21 @@ struct sys_stat_struct { }) /* startup code */ +/* + * i386 System V ABI mandates: + * 1) last pushed argument must be 16-byte aligned. + * 2) The deepest stack frame should be set to zero + * + */ asm(".section .text\n" ".global _start\n" "_start:\n" "pop %eax\n" // argc (first arg, %eax) "mov %esp, %ebx\n" // argv[] (second arg, %ebx) "lea 4(%ebx,%eax,4),%ecx\n" // then a NULL then envp (third arg, %ecx) - "and $-16, %esp\n" // x86 ABI : esp must be 16-byte aligned when + "xor %ebp, %ebp\n" // zero the stack frame + "and $-16, %esp\n" // x86 ABI : esp must be 16-byte aligned before + "sub $4, %esp\n" // the call instruction (args are aligned) "push %ecx\n" // push all registers on the stack so that we "push %ebx\n" // support both regparm and plain stack modes "push %eax\n" |