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authorWilly Tarreau <w@1wt.eu>2021-10-24 20:28:15 +0300
committerPaul E. McKenney <paulmck@kernel.org>2021-12-01 04:26:42 +0300
commitebbe0d8a449d183fa43b42d84fcb248e25303985 (patch)
tree5ca7fe5659f80a4f97f274e6e34d282e068a5ba6 /tools/include
parent937ed91c712273131de6d2a02caafd3ee84e0c72 (diff)
downloadlinux-ebbe0d8a449d183fa43b42d84fcb248e25303985.tar.xz
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.h10
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"