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Fix regression introduced by "Properly handle real SIGTRAPs" change

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Commit 3454e4b463e6c22c7ea8c5461ef5a077f4650a54
introduced a bug: sometimes, TRACECLONE/TRACE[V]FORK opts were not set.
The check (tcp->parent == NULL) in old code was meant to check
"if we are not a child created by auto-attach" - in this case,
options need to be set on the child; otherwise they are inherited
and do not need to be set.
I misunderstood the check and if tcp->parent is not NULL, I was
setting only ptrace_setoptions_for_all bits.
This change fixes the problem. Since the fixed logic makes it
unnecessary to keep two sets of options in separate variables,
I merge them back into one variable, ptrace_setoptions.

* defs.h: Merge ptrace_setoptions_followfork and ptrace_setoptions_for_all
  into one variable, ptrace_setoptions.
* strace.c: Likewise.
  (test_ptrace_setoptions_followfork): Use ptrace_setoptions variable.
  (test_ptrace_setoptions_for_all): Likewise.
  (main): Likewise.
* process.c (internal_fork): Likewise.
  (internal_exec): Likewise.
* strace.c (trace): Fix the bug where different options were set
  depending on "tcp->parent == NULL" condition. Add a comment
  which makes it more clear why this condition is checked.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
This commit is contained in:
Denys Vlasenko 2011-06-21 14:34:10 +02:00
parent 0df9ed47af
commit f44cce48bb
3 changed files with 21 additions and 23 deletions
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3
defs.h
View File

@ -508,8 +508,7 @@ typedef enum {
extern struct tcb **tcbtab;
extern int *qual_flags;
extern int debug, followfork;
extern unsigned int ptrace_setoptions_followfork;
extern unsigned int ptrace_setoptions_for_all;
extern unsigned int ptrace_setoptions;
extern int dtime, xflag, qflag;
extern cflag_t cflag;
extern int acolumn;

4
process.c
View File

@ -904,7 +904,7 @@ Process %u resumed (parent %d ready)\n",
int
internal_fork(struct tcb *tcp)
{
if ((ptrace_setoptions_followfork
if ((ptrace_setoptions
& (PTRACE_O_TRACECLONE | PTRACE_O_TRACEFORK | PTRACE_O_TRACEVFORK))
== (PTRACE_O_TRACECLONE | PTRACE_O_TRACEFORK | PTRACE_O_TRACEVFORK))
return 0;
@ -1751,7 +1751,7 @@ internal_exec(struct tcb *tcp)
tcp->flags &= ~TCB_WAITEXECVE;
else {
/* Maybe we have post-execve SIGTRAP suppressed? */
if (!(ptrace_setoptions_for_all & PTRACE_O_TRACEEXEC))
if (!(ptrace_setoptions & PTRACE_O_TRACEEXEC))
tcp->flags |= TCB_WAITEXECVE; /* no */
}
#endif /* LINUX && TCB_WAITEXECVE */

37
strace.c
View File

@ -84,8 +84,7 @@ extern char *optarg;
int debug = 0, followfork = 0;
unsigned int ptrace_setoptions_followfork = 0;
unsigned int ptrace_setoptions_for_all = 0;
unsigned int ptrace_setoptions = 0;
/* Which WSTOPSIG(status) value marks syscall traps? */
static unsigned int syscall_trap_sig = SIGTRAP;
int dtime = 0, xflag = 0, qflag = 0;
@ -826,7 +825,7 @@ test_ptrace_setoptions_followfork(void)
}
}
if (expected_grandchild && expected_grandchild == found_grandchild)
ptrace_setoptions_followfork |= test_options;
ptrace_setoptions |= test_options;
return 0;
}
@ -907,10 +906,10 @@ test_ptrace_setoptions_for_all(void)
if (it_worked) {
syscall_trap_sig = (SIGTRAP | 0x80);
ptrace_setoptions_for_all = test_options;
ptrace_setoptions |= test_options;
if (debug)
fprintf(stderr, "ptrace_setoptions_for_all = %#x\n",
ptrace_setoptions_for_all);
fprintf(stderr, "ptrace_setoptions = %#x\n",
ptrace_setoptions);
return;
}
@ -1136,11 +1135,11 @@ main(int argc, char *argv[])
fprintf(stderr,
"Test for options supported by PTRACE_SETOPTIONS "
"failed, giving up using this feature.\n");
ptrace_setoptions_followfork = 0;
ptrace_setoptions = 0;
}
if (debug)
fprintf(stderr, "ptrace_setoptions_followfork = %#x\n",
ptrace_setoptions_followfork);
fprintf(stderr, "ptrace_setoptions = %#x\n",
ptrace_setoptions);
}
test_ptrace_setoptions_for_all();
#endif
@ -2679,16 +2678,16 @@ Process %d attached (waiting for parent)\n",
}
}
#ifdef LINUX
int options = ptrace_setoptions_for_all;
if (followfork && (tcp->parent == NULL))
options |= ptrace_setoptions_followfork;
if (options) {
if (debug)
fprintf(stderr, "setting opts %x on pid %d\n", options, tcp->pid);
if (ptrace(PTRACE_SETOPTIONS, tcp->pid, NULL, options) < 0) {
if (errno != ESRCH) {
/* Should never happen, really */
perror_msg_and_die("PTRACE_SETOPTIONS");
/* If options were not set for this tracee yet */
if (tcp->parent == NULL) {
if (ptrace_setoptions) {
if (debug)
fprintf(stderr, "setting opts %x on pid %d\n", ptrace_setoptions, tcp->pid);
if (ptrace(PTRACE_SETOPTIONS, tcp->pid, NULL, ptrace_setoptions) < 0) {
if (errno != ESRCH) {
/* Should never happen, really */
perror_msg_and_die("PTRACE_SETOPTIONS");
}
}
}
}