From: Denys Vlasenko <vda.linux@googlemail.com>
Date: Thu, 8 Mar 2012 11:13:44 +0000 (+0100)
Subject: Pass addr=0 instead of 1 into restarting ptrace calls
X-Git-Tag: v4.7~143
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=114aefd6183b8c073453f8def73270c42255f974;p=strace

Pass addr=0 instead of 1 into restarting ptrace calls

While we are at it, fold do_ptrace into its lone caller.
We no longer set tcp->ptrace_errno = ESRCH on ESRC error in upeek.
Other code paths where ptrace fails wern't doing it, and the code which
checks tcp->ptrace_errno even assumes it is never set to ESRCH.
(It was me who added this code sometime ago, so it was my fault
that it was a bit messy)

I ran sigkill_rain test and verified that unfinished syscalls are
still handled correctly.

* util.c (ptrace_restart): Do not pass addr=1 to ptrace(), pass 0 instead.
I have no idea why we were passing 1. Ptrace documentation says
that addr parameter is ignored.
(do_ptrace): Remove this function.
(upeek): Use ptrace() instead of do_ptrace().
* defs.h: Remove do_ptrace() declaration.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
---

diff --git a/defs.h b/defs.h
index 9c3b234c..1f0b7b51 100644
--- a/defs.h
+++ b/defs.h
@@ -466,7 +466,6 @@ extern void droptcb(struct tcb *);
 extern void set_sortby(const char *);
 extern void set_overhead(int);
 extern void qualify(const char *);
-extern long do_ptrace(int request, struct tcb *tcp, void *addr, void *data);
 extern int ptrace_restart(int request, struct tcb *tcp, int sig);
 extern int trace_syscall(struct tcb *);
 extern void count_syscall(struct tcb *, struct timeval *);
diff --git a/util.c b/util.c
index a7cb19c0..59665b70 100644
--- a/util.c
+++ b/util.c
@@ -165,31 +165,6 @@ stpcpy(char *dst, const char *src)
 }
 #endif
 
-/*
- * Generic ptrace wrapper which tracks ESRCH errors
- * by setting tcp->ptrace_errno to ESRCH.
- *
- * We assume that ESRCH indicates likely process death (SIGKILL?),
- * modulo bugs where process somehow ended up not stopped.
- * Unfortunately kernel uses ESRCH for that case too. Oh well.
- *
- * Currently used by upeek() only.
- * TODO: use this in all other ptrace() calls while decoding.
- */
-long
-do_ptrace(int request, struct tcb *tcp, void *addr, void *data)
-{
-	long l;
-
-	errno = 0;
-	l = ptrace(request, tcp->pid, addr, (long) data);
-	/* Non-ESRCH errors might be our invalid reg/mem accesses,
-	 * we do not record them. */
-	if (errno == ESRCH)
-		tcp->ptrace_errno = ESRCH;
-	return l;
-}
-
 /*
  * Used when we want to unblock stopped traced process.
  * Should be only used with PTRACE_CONT, PTRACE_DETACH and PTRACE_SYSCALL.
@@ -204,7 +179,7 @@ ptrace_restart(int op, struct tcb *tcp, int sig)
 	const char *msg;
 
 	errno = 0;
-	ptrace(op, tcp->pid, (void *) 1, (long) sig);
+	ptrace(op, tcp->pid, (void *) 0, (long) sig);
 	err = errno;
 	if (!err || err == ESRCH)
 		return 0;
@@ -219,7 +194,7 @@ ptrace_restart(int op, struct tcb *tcp, int sig)
 	if (op == PTRACE_LISTEN)
 		msg = "LISTEN";
 #endif
-	perror_msg("ptrace(PTRACE_%s,pid:%d,1,sig:%d)", msg, tcp->pid, sig);
+	perror_msg("ptrace(PTRACE_%s,pid:%d,sig:%d)", msg, tcp->pid, sig);
 	return -1;
 }
 
@@ -1011,7 +986,7 @@ upeek(struct tcb *tcp, long off, long *res)
 	long val;
 
 	errno = 0;
-	val = do_ptrace(PTRACE_PEEKUSER, tcp, (char *) off, 0);
+	val = ptrace(PTRACE_PEEKUSER, tcp->pid, (char *) off, 0);
 	if (val == -1 && errno) {
 		if (errno != ESRCH) {
 			perror_msg("upeek: PTRACE_PEEKUSER pid:%d @0x%lx)", tcp->pid, off);