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[S390] ptrace: fix return value of do_syscall_trace_enter() 

strace may change the system call number, so regs->gprs[2] must not
be read before tracehook_report_syscall_entry(). This fixes a bug
where "strace -f" will hang after a vfork().

Cc: <stable@kernel.org>
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Gerald Schaefer 2010-05-12 09:32:12 +02:00 committed by Martin Schwidefsky
parent 1c1e093cbf
commit 545c174d1f
1 changed files with 2 additions and 3 deletions
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5
arch/s390/kernel/ptrace.c
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@ -640,7 +640,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
asmlinkage long do_syscall_trace_enter(struct pt_regs *regs) asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
{ {
long ret; long ret = 0;
/* Do the secure computing check first. */ /* Do the secure computing check first. */
secure_computing(regs->gprs[2]); secure_computing(regs->gprs[2]);
@ -649,7 +649,6 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
* The sysc_tracesys code in entry.S stored the system * The sysc_tracesys code in entry.S stored the system
* call number to gprs[2]. * call number to gprs[2].
*/ */
ret = regs->gprs[2];
if (test_thread_flag(TIF_SYSCALL_TRACE) && if (test_thread_flag(TIF_SYSCALL_TRACE) &&
(tracehook_report_syscall_entry(regs) || (tracehook_report_syscall_entry(regs) ||
regs->gprs[2] >= NR_syscalls)) { regs->gprs[2] >= NR_syscalls)) {
@ -671,7 +670,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
regs->gprs[2], regs->orig_gpr2, regs->gprs[2], regs->orig_gpr2,
regs->gprs[3], regs->gprs[4], regs->gprs[3], regs->gprs[4],
regs->gprs[5]); regs->gprs[5]);
return ret; return ret ?: regs->gprs[2];
} }
asmlinkage void do_syscall_trace_exit(struct pt_regs *regs) asmlinkage void do_syscall_trace_exit(struct pt_regs *regs)