Ammar Faizi reported that our exit code handling is wrong. We truncate it to the lowest 8 bits but the syscall itself is expected to take a regular 32-bit signed integer, not an unsigned char. It's the kernel that later truncates it to the lowest 8 bits. The difference is visible in strace, where the program below used to show exit(255) instead of exit(-1):
int main(void) { return -1; }
This patch applies the fix to all archs. x86_64, i386, arm64, armv7 and mips were all tested and confirmed to work fine now. Risc-v was not tested but the change is trivial and exactly the same as for other archs.
Reported-by: Ammar Faizi ammar.faizi@students.amikom.ac.id Cc: stable@vger.kernel.org Signed-off-by: Willy Tarreau w@1wt.eu --- tools/include/nolibc/nolibc.h | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-)
diff --git a/tools/include/nolibc/nolibc.h b/tools/include/nolibc/nolibc.h index 7f300dc379e7..3e2c6f2ed587 100644 --- a/tools/include/nolibc/nolibc.h +++ b/tools/include/nolibc/nolibc.h @@ -414,7 +414,7 @@ asm(".section .text\n" "xor %ebp, %ebp\n" // zero the stack frame "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. - "movzb %al, %rdi\n" // retrieve exit code from 8 lower bits + "mov %eax, %edi\n" // retrieve exit code (32 bit) "mov $60, %rax\n" // NR_exit == 60 "syscall\n" // really exit "hlt\n" // ensure it does not return @@ -602,9 +602,9 @@ asm(".section .text\n" "push %ebx\n" // support both regparm and plain stack modes "push %eax\n" "call main\n" // main() returns the status code in %eax - "movzbl %al, %ebx\n" // retrieve exit code from lower 8 bits - "movl $1, %eax\n" // NR_exit == 1 - "int $0x80\n" // exit now + "mov %eax, %ebx\n" // retrieve exit code (32-bit int) + "movl $1, %eax\n" // NR_exit == 1 + "int $0x80\n" // exit now "hlt\n" // ensure it does not "");
@@ -788,7 +788,6 @@ asm(".section .text\n" "and %r3, %r1, $-8\n" // AAPCS : sp must be 8-byte aligned in the "mov %sp, %r3\n" // callee, an bl doesn't push (lr=pc) "bl main\n" // main() returns the status code, we'll exit with it. - "and %r0, %r0, $0xff\n" // limit exit code to 8 bits "movs r7, $1\n" // NR_exit == 1 "svc $0x00\n" ""); @@ -985,7 +984,6 @@ asm(".section .text\n" "add x2, x2, x1\n" // + argv "and sp, x1, -16\n" // sp must be 16-byte aligned in the callee "bl main\n" // main() returns the status code, we'll exit with it. - "and x0, x0, 0xff\n" // limit exit code to 8 bits "mov x8, 93\n" // NR_exit == 93 "svc #0\n" ""); @@ -1190,7 +1188,7 @@ asm(".section .text\n" "addiu $sp,$sp,-16\n" // the callee expects to save a0..a3 there! "jal main\n" // main() returns the status code, we'll exit with it. "nop\n" // delayed slot - "and $a0, $v0, 0xff\n" // limit exit code to 8 bits + "move $a0, $v0\n" // retrieve 32-bit exit code from v0 "li $v0, 4001\n" // NR_exit == 4001 "syscall\n" ".end __start\n" @@ -1388,7 +1386,6 @@ asm(".section .text\n" "add a2,a2,a1\n" // + argv "andi sp,a1,-16\n" // sp must be 16-byte aligned "call main\n" // main() returns the status code, we'll exit with it. - "andi a0, a0, 0xff\n" // limit exit code to 8 bits "li a7, 93\n" // NR_exit == 93 "ecall\n" "");