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Commit 9a82bfb4 authored by Willy Tarreau's avatar Willy Tarreau Committed by Greg Kroah-Hartman
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tools/nolibc: fix incorrect truncation of exit code 



commit de0244ae40ae91145faaf164a4252347607c3711 upstream.

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: default avatarAmmar Faizi <ammar.faizi@students.amikom.ac.id>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarWilly Tarreau <w@1wt.eu>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2e83886c

tools/include/nolibc/nolibc.h

+5 −8
Original line number Diff line number Diff line
@@ -437,7 +437,7 @@ 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
@@ -625,7 +625,7 @@ 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

    "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
@@ -811,7 +811,6 @@ 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"

    "");
@@ -1008,7 +1007,6 @@ 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"

    "");
@@ -1213,7 +1211,7 @@ 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"
@@ -1411,7 +1409,6 @@ 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"

    "");