Messages in this thread | | | Date | Fri, 27 Nov 2009 18:46:27 +0100 | From | Veaceslav Falico <> | Subject | Re: powerpc: fork && stepping (Was: [RFC,PATCH 0/14] utrace/ptrace) |
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On Thu, Nov 26, 2009 at 11:37:03PM +0100, Oleg Nesterov wrote: > > Could you look at this > > ptrace-copy_process-should-disable-stepping.patch > http://marc.info/?l=linux-mm-commits&m=125789789322573 > > patch? It is not clear to me how we can modify the test-case to > verify it fixes the original problem for powerpc.
I modified the test-case, it confirms that ptrace-copy_process-should-disable-stepping.patch fixes the problem with TIF_SINGLESTEP copied by fork() on powerpc.
Probably we need a similar fix for step-fork.c in ptrace-tests.
Modified the original testcase to call fork via syscall(__NR_fork), to avoid the looping inside libc's fork() on powerpc. The parent singlesteps until he sees that the child has forked, after that the parent PTRACE_CONTs until the child exits.
#include <stdio.h> #include <unistd.h> #include <signal.h> #include <sys/ptrace.h> #include <sys/wait.h> #include <assert.h> #include <sys/syscall.h>
int main(void) { void *addr_after_fork = &&after_fork; int pid, status;
if (!(pid = fork())) { assert(ptrace(PTRACE_TRACEME) == 0); kill(getpid(), SIGSTOP);
if (!syscall(__NR_fork)) { /* kernel bug: this child will be killed by SIGTRAP */ printf("Hello world\n"); return 43; }
after_fork: wait(&status); return WEXITSTATUS(status); }
for (;;) { siginfo_t info;
assert(pid == wait(&status)); assert(ptrace(PTRACE_GETSIGINFO, pid, 0,&info) == 0); if (info.si_addr == addr_after_fork) break; assert(ptrace(PTRACE_SINGLESTEP, pid, 0,0) == 0); }
for (;;) { if (WIFEXITED(status)) break; assert(ptrace(PTRACE_CONT, pid, 0,0) == 0); assert(pid == wait(&status)); }
assert(WEXITSTATUS(status) == 43); return 0; }
-- Veaceslav
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