x86: ia32 ptrace vs -ENOSYS

When we're stopped at syscall entry tracing, ptrace can change the %eax
value from -ENOSYS to something else.  If no system call is actually made
because the syscall number (now in orig_eax) is bad, then the %eax value
set by ptrace should be returned to the user.  But, instead it gets reset
to -ENOSYS again.  This is a regression from the native 32-bit kernel.

This change fixes it by leaving the return value alone after entry tracing.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 8022d3c..30f4929 100644 (file)
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -325,7 +325,7 @@ ENTRY(ia32_syscall)
        jnz ia32_tracesys
 ia32_do_syscall:       
        cmpl $(IA32_NR_syscalls-1),%eax
-       ja  ia32_badsys
+       ja  int_ret_from_sys_call       /* ia32_tracesys has set RAX(%rsp) */
        IA32_ARG_FIXUP
        call *ia32_sys_call_table(,%rax,8) # xxx: rip relative
 ia32_sysret:
@@ -335,7 +335,7 @@ ia32_sysret:
 ia32_tracesys:                  
        SAVE_REST
        CLEAR_RREGS
-       movq $-ENOSYS,RAX(%rsp) /* really needed? */
+       movq $-ENOSYS,RAX(%rsp) /* ptrace can change this for a bad syscall */
        movq %rsp,%rdi        /* &pt_regs -> arg1 */
        call syscall_trace_enter
        LOAD_ARGS32 ARGOFFSET  /* reload args from stack in case ptrace changed it */