* util.c [LINUX] (setbpt): Refactor so that fetching and setting
syscall arguments use a common code path and do it in a consistent
way. Previous code calls get_arg{0,1}in fork/vfork case, but reads
tcp->u_arg[] without get_arg{0,1} in clone case. That looks like it
might be a real bug on some architectures. If not, it's still
interface abuse. New code is also consistent about the new clone
flags being always stored in tcp->u_arg[] afterwards.
Signed-off-by: Jamie Lokier <ja...@shareable.org>
---
util.c | 93 ++++++++++++++++++++++++++++++++++++++-------------------------
1 files changed, 56 insertions(+), 37 deletions(-)
diff --git a/util.c b/util.c
index 82dd9b5..0c4a882 100644
--- a/util.c
+++ b/util.c
@@ -1475,6 +1475,7 @@ setbpt(struct tcb *tcp)
{
static int clone_scno[SUPPORTED_PERSONALITIES] = { SYS_clone };
arg_setup_state state;
+ int real_scno;
if (tcp->flags & TCB_BPTSET) {
fprintf(stderr, "PANIC: fork breakpoint already set in pid
%u\n",
@@ -1496,59 +1497,77 @@ setbpt(struct tcb *tcp)
}
}
- switch (known_scno(tcp)) {
+ real_scno = known_scno(tcp);
+
+ switch (real_scno) {
# ifdef SYS_vfork
case SYS_vfork:
# endif
# ifdef SYS_fork
case SYS_fork:
# endif
-# if defined SYS_fork || defined SYS_vfork
- if (arg_setup (tcp, &state) < 0
- || get_arg0 (tcp, &state, &tcp->inst[0]) < 0
- || get_arg1 (tcp, &state, &tcp->inst[1]) < 0
- || change_syscall(tcp, clone_scno[current_personality]) < 0
- || set_arg0 (tcp, &state, CLONE_PTRACE|SIGCHLD) < 0
- || set_arg1 (tcp, &state, 0) < 0
- || arg_finish_change (tcp, &state) < 0)
- return -1;
- tcp->u_arg[arg0_index] = CLONE_PTRACE|SIGCHLD;
- tcp->u_arg[arg1_index] = 0;
- tcp->flags |= TCB_BPTSET;
- return 0;
-# endif
-
case SYS_clone:
# ifdef SYS_clone2
case SYS_clone2:
# endif
- /* ia64 calls directly `clone (CLONE_VFORK | CLONE_VM)'
- contrary to x86 SYS_vfork above. Even on x86 we turn the
- vfork semantics into plain fork - each application must not
- depend on the vfork specifics according to POSIX. We would
- hang waiting for the parent resume otherwise. We need to
- clear also CLONE_VM but only in the CLONE_VFORK case as
- otherwise we would break pthread_create. */
-
- if ((arg_setup (tcp, &state) < 0
- || set_arg0 (tcp, &state,
- (tcp->u_arg[arg0_index] | CLONE_PTRACE)
- & ~(tcp->u_arg[arg0_index] & CLONE_VFORK
- ? CLONE_VFORK | CLONE_VM : 0)) < 0
- || arg_finish_change (tcp, &state) < 0))
- return -1;
- tcp->flags |= TCB_BPTSET;
- tcp->inst[0] = tcp->u_arg[arg0_index];
- tcp->inst[1] = tcp->u_arg[arg1_index];
- return 0;
-
+ break;
default:
fprintf(stderr, "PANIC: setbpt for syscall %ld on %u???\n",
tcp->scno, tcp->pid);
+ return -1;
+ }
+
+ if (arg_setup (tcp, &state) < 0
+ || get_arg0 (tcp, &state, &tcp->inst[0]) < 0
+ || get_arg1 (tcp, &state, &tcp->inst[1]) < 0)
+ return -1;
+
+ switch (real_scno) {
+# ifdef SYS_vfork
+ case SYS_vfork:
+# endif
+# ifdef SYS_fork
+ case SYS_fork:
+# endif
+# if defined SYS_fork || defined SYS_vfork
+ /*
+ * Change to clone(CLONE_PTRACE|SIGCHLD). Even vfork,
+ * effectively changing it to fork, otherwise we'd
+ * hang waiting for the parent syscall to return while
+ * the child is stopped for tracing. All applications
+ * should accept fork instead, following both POSIX
+ * and unix tradition.
+ */
+ if (change_syscall(tcp, clone_scno[current_personality]) < 0)
+ return -1;
+ tcp->u_arg[arg0_index] = CLONE_PTRACE|SIGCHLD;
+ tcp->u_arg[arg1_index] = 0;
+ break;
+# endif
+
+ default: /* clone, clone2 */
+ /*
+ * Some archs call `clone (CLONE_VFORK | CLONE_VM)'
+ * instead of SYS_vfork, but anyone is allowed to use
+ * CLONE_VFORK. Clear CLONE_VFORK and CLONE_VM, which
+ * changes it to fork while preserving any other
+ * requested clone flags. If it's not vfork, CLONE_VM
+ * must stay for threads.
+ */
+ tcp->u_arg[arg0_index] = tcp->inst[0] | CLONE_PTRACE;
+ if (tcp->u_arg[arg0_index] & CLONE_VFORK)
+ tcp->u_arg[arg0_index] &= ~(CLONE_VFORK | CLONE_VM);
+ tcp->u_arg[arg1_index] = tcp->inst[1];
break;
}
- return -1;
+ if (set_arg0 (tcp, &state, tcp->u_arg[0]) < 0
+ || set_arg1 (tcp, &state, tcp->u_arg[1]) < 0
+ || arg_finish_change (tcp, &state) < 0)
+ return -1;
+
+ tcp->flags |= TCB_BPTSET;
+ return 0;
}
int
--
1.7.0.4
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