Paul Clarke wrote:
What are the circumstances in which raw_syscalls:sys_exit reports "-1" for the
syscall ID?
perf 5375 [007] 59632.478528: raw_syscalls:sys_enter: NR 1 (3, 9fb888,
8, 2d83740, 1, 7ffff)
perf 5375 [007] 59632.478532: raw_syscalls:sys_exit: NR 1 = 8
perf 5375 [007] 59632.478538: raw_syscalls:sys_enter: NR 15 (11,
7ffffca734b0, 7ffffca73380, 2d83740, 1, 7ffff)
perf 5375 [007] 59632.478539: raw_syscalls:sys_exit: NR -1 = 8
perf 5375 [007] 59632.478543: raw_syscalls:sys_enter: NR 16 (4, 2401, 0,
2d83740, 1, 0)
perf 5375 [007] 59632.478551: raw_syscalls:sys_exit: NR 16 = 0
Which architecture?
For powerpc, see:
static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
{
/*
* Note that we are returning an int here. That means 0xffffffff, ie.
* 32-bit negative 1, will be interpreted as -1 on a 64-bit kernel.
* This is important for seccomp so that compat tasks can set r0 = -1
* to reject the syscall.
*/
return TRAP(regs) == 0xc00 ? regs->gpr[0] : -1;
}
- Naveen
