On Thu, Apr 18, 2013 at 08:44:25PM +0200, Oleg Nesterov wrote:
> Change ptrace_detach() to call flush_ptrace_hw_breakpoint(child).
> This frees the slots for non-ptrace PERF_TYPE_BREAKPOINT users, and
> this ensures that the tracee won't be killed by SIGTRAP triggered by
> the active breakpoints.
>
> Test-case:
>
> unsigned long encode_dr7(int drnum, int enable, unsigned int type,
> unsigned int len)
> {
> unsigned long dr7;
>
> dr7 = ((len | type) & 0xf)
> << (DR_CONTROL_SHIFT + drnum * DR_CONTROL_SIZE);
> if (enable)
> dr7 |= (DR_GLOBAL_ENABLE << (drnum * DR_ENABLE_SIZE));
>
> return dr7;
> }
>
> int write_dr(int pid, int dr, unsigned long val)
> {
> return ptrace(PTRACE_POKEUSER, pid,
> offsetof (struct user, u_debugreg[dr]),
> val);
> }
>
> void func(void)
> {
> }
>
> int main(void)
> {
> int pid, stat;
> unsigned long dr7;
>
> pid = fork();
> if (!pid) {
> assert(ptrace(PTRACE_TRACEME, 0,0,0) == 0);
> kill(getpid(), SIGHUP);
>
> func();
> return 0x13;
> }
>
> assert(pid == waitpid(-1, &stat, 0));
> assert(WSTOPSIG(stat) == SIGHUP);
>
> assert(write_dr(pid, 0, (long)func) == 0);
> dr7 = encode_dr7(0, 1, DR_RW_EXECUTE, DR_LEN_1);
> assert(write_dr(pid, 7, dr7) == 0);
>
> assert(ptrace(PTRACE_DETACH, pid, 0,0) == 0);
> assert(pid == waitpid(-1, &stat, 0));
> assert(stat == 0x1300);
>
> return 0;
> }
>
> Before this patch the child is killed after PTRACE_DETACH.
>
> Signed-off-by: Oleg Nesterov <[email protected]>
ACK.
Thanks a lot for this very nice series!
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