Messages in this thread | ![/](/images/icornerl.gif) | | Subject | x86: SIGTRAP handling differences from 2.4 to 2.6 | From | Daniel Barlow <> | Date | Sat, 22 Nov 2003 18:29:00 +0000 |
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There is a difference between 2.4 (tested in 2.4.23-rc2) and 2.6 (tested in 2.6.0-pre9) in the handling of "int 3" inside a SIGTRAP handler.
In 2.4, the handler appears to be recursively re-entered. In 2.6 the task is killed, along with any other tasks that share the same VM (I'm not talking about thread groups; I have CLONE_PARENT and CLONE_VM set but not CLONE_THREAD).
I'm not sure what the correct answer is, if indeed it's specified. For contrast, in FreeBSD 5.1 I'm told that the signal handler runs to completion and only on exit is it called again. I would suggest that this behaviour is probably more in keeping with the principle of least astonishment, but maybe I astonish in atypical ways.
Nasty short brutish test program appended. Change the #if 0 s to #if 1 if you want to see it lay waste to the other threads as well.
I'm reading linux-kernel through the archives, so a CC would be appreciated if you want me to see answers fast.
---cut here--- #include <signal.h> #if 0 #include <sched.h> #include <linux/unistd.h> #endif
void sigtrap_handler(int sig, struct siginfo *si, void * sc) { printf("entered sigtrap handler, %d %x %x\n", sig,si,sc); sleep(2); asm("int3" : :); printf("leaving sigtrap handler, %d %x %x\n", sig,si,sc); }
void do_stuff() { pause(); }
main() { struct sigaction sa; int i,j; #if 0 i=clone(do_stuff,malloc(1024*1024)+1024*1024, CLONE_VM|SIGCHLD|CLONE_PARENT,0); j=clone(do_stuff,malloc(1024*1024)+1024*1024, CLONE_VM|SIGCHLD|CLONE_PARENT,0); #endif sigemptyset(&sa.sa_mask); sa.sa_sigaction=sigtrap_handler; sa.sa_flags=SA_SIGINFO|SA_RESTART; sigaction(SIGTRAP,&sa,0); printf("go\n"); sleep(2); asm("int3" : :); sleep(3600); } ---cut here---
-dan
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