This is a note to let you know that I've just added the patch titled
tools/nolibc: i386: fix initial stack alignment
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tools-nolibc-i386-fix-initial-stack-alignment.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ebbe0d8a449d183fa43b42d84fcb248e25303985 Mon Sep 17 00:00:00 2001
From: Willy Tarreau <w@xxxxxx>
Date: Sun, 24 Oct 2021 19:28:15 +0200
Subject: tools/nolibc: i386: fix initial stack alignment
From: Willy Tarreau <w@xxxxxx>
commit ebbe0d8a449d183fa43b42d84fcb248e25303985 upstream.
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@xxxxxxxxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Willy Tarreau <w@xxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
tools/include/nolibc/nolibc.h | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
--- a/tools/include/nolibc/nolibc.h
+++ b/tools/include/nolibc/nolibc.h
@@ -606,13 +606,21 @@ 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"
Patches currently in stable-queue which might be from w@xxxxxx are
queue-5.10/tools-nolibc-fix-incorrect-truncation-of-exit-code.patch
queue-5.10/tools-nolibc-i386-fix-initial-stack-alignment.patch
queue-5.10/tools-nolibc-x86-64-fix-startup-code-bug.patch
