This is a note to let you know that I've just added the patch titled
tools/nolibc: x86-64: Use `mov $60,%eax` instead of `mov $60,%rax`
to the 5.15-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-x86-64-use-mov-60-eax-instead-of-mov-60.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit d74510b4743015fc50c3cda41dc632340f1905d7
Author: Ammar Faizi <ammar.faizi@xxxxxxxxxxxxxxxxxxxxx>
Date: Sun Oct 24 19:43:22 2021 +0200
tools/nolibc: x86-64: Use `mov $60,%eax` instead of `mov $60,%rax`
[ Upstream commit 7bdc0e7a390511cd3df8194003b908f15a6170a5 ]
Note that mov to 32-bit register will zero extend to 64-bit register.
Thus `mov $60,%eax` has the same effect with `mov $60,%rax`. Use the
shorter opcode to achieve the same thing.
```
b8 3c 00 00 00 mov $60,%eax (5 bytes) [1]
48 c7 c0 3c 00 00 00 mov $60,%rax (7 bytes) [2]
```
Currently, we use [2]. Change it to [1] for shorter code.
Signed-off-by: Ammar Faizi <ammar.faizi@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Stable-dep-of: 184177c3d6e0 ("tools/nolibc: restore mips branch ordering in the _start block")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/tools/include/nolibc/nolibc.h b/tools/include/nolibc/nolibc.h
index ece7a70d8b39..676fe5d92875 100644
--- a/tools/include/nolibc/nolibc.h
+++ b/tools/include/nolibc/nolibc.h
@@ -420,7 +420,7 @@ asm(".section .text\n"
"and $-16, %rsp\n" // x86 ABI : esp must be 16-byte aligned before call
"call main\n" // main() returns the status code, we'll exit with it.
"mov %eax, %edi\n" // retrieve exit code (32 bit)
- "mov $60, %rax\n" // NR_exit == 60
+ "mov $60, %eax\n" // NR_exit == 60
"syscall\n" // really exit
"hlt\n" // ensure it does not return
"");
