This is the mail archive of the
gdb-cvs@sourceware.org
mailing list for the GDB project.
[binutils-gdb] Linux/ptrace: don't convert ptids when asking inf-ptrace layer to resume LWP
- From: Pedro Alves <palves at sourceware dot org>
- To: gdb-cvs at sourceware dot org
- Date: 3 Mar 2015 13:34:19 -0000
- Subject: [binutils-gdb] Linux/ptrace: don't convert ptids when asking inf-ptrace layer to resume LWP
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=90ad5e1d4f34d02f437ec12d1b65d7252f5b7f1c
commit 90ad5e1d4f34d02f437ec12d1b65d7252f5b7f1c
Author: Pedro Alves <palves@redhat.com>
Date: Tue Mar 3 13:33:44 2015 +0000
Linux/ptrace: don't convert ptids when asking inf-ptrace layer to resume LWP
Ref: https://sourceware.org/ml/gdb-patches/2015-03/msg00060.html
The record-btrace target can hit an assertion here:
Breakpoint 1, record_btrace_fetch_registers (ops=0x974bfc0 <record_btrace_ops>,
regcache=0x9a0a798, regno=8) at gdb/record-btrace.c:1202
1202 gdb_assert (tp != NULL);
(gdb) p regcache->ptid
$3 = {pid = 23856, lwp = 0, tid = 0}
The problem is that the linux-nat layer converts the ptid to a
single-process ptid before passing the request down to the inf-ptrace
layer, which loses information, and then record-btrace can't find the
corresponding thread in GDB's thread list:
(gdb) bt
#0 record_btrace_fetch_registers (ops=0x974bfc0 <record_btrace_ops>, regcache=0x9a0a798, regno=8)
at gdb/record-btrace.c:1202
#1 0x083f4ee2 in delegate_fetch_registers (self=0x974bfc0 <record_btrace_ops>, arg1=0x9a0a798,
arg2=8) at gdb/target-delegates.c:149
#2 0x08406562 in target_fetch_registers (regcache=0x9a0a798, regno=8)
at gdb/target.c:3279
#3 0x08355255 in regcache_raw_read (regcache=0x9a0a798, regnum=8,
buf=0xbfffe6c0 "¨\003\222\t�8kIøæÿ¿HO5\b\035]")
at gdb/regcache.c:643
#4 0x083558a7 in regcache_cooked_read (regcache=0x9a0a798, regnum=8,
buf=0xbfffe6c0 "¨\003\222\t�8kIøæÿ¿HO5\b\035]")
at gdb/regcache.c:734
#5 0x08355de3 in regcache_cooked_read_unsigned (regcache=0x9a0a798, regnum=8, val=0xbfffe738)
at gdb/regcache.c:838
#6 0x0827a106 in i386_linux_resume (ops=0x9737ca0 <linux_ops_saved>, ptid=..., step=1,
signal=GDB_SIGNAL_0) at gdb/i386-linux-nat.c:670
#7 0x08280c12 in linux_resume_one_lwp (lp=0x9a0a5b8, step=1, signo=GDB_SIGNAL_0)
at gdb/linux-nat.c:1529
#8 0x08281281 in linux_nat_resume (ops=0x98da608, ptid=..., step=1, signo=GDB_SIGNAL_0)
at gdb/linux-nat.c:1708
#9 0x0850738e in record_btrace_resume (ops=0x98da608, ptid=..., step=1, signal=GDB_SIGNAL_0)
at gdb/record-btrace.c:1760
...
The fix is just to not lose information, and let the intact ptid reach
record-btrace.c.
Tested on x86-64 Fedora 20, -m32.
gdb/ChangeLog:
2015-03-03 Pedro Alves <palves@redhat.com>
* i386-linux-nat.c (i386_linux_resume): Get the ptrace PID out of
the lwp field of ptid. Pass the full ptid to get_thread_regcache.
* inf-ptrace.c (get_ptrace_pid): New function.
(inf_ptrace_resume): Use it.
* linux-nat.c (linux_resume_one_lwp): Pass the LWP's ptid ummodified
to the lower layer.
Diff:
---
gdb/ChangeLog | 9 +++++++++
gdb/i386-linux-nat.c | 5 ++---
gdb/inf-ptrace.c | 25 ++++++++++++++++++++++---
gdb/linux-nat.c | 6 +-----
4 files changed, 34 insertions(+), 11 deletions(-)
diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 1db98ff..31a672e 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,12 @@
+2015-03-03 Pedro Alves <palves@redhat.com>
+
+ * i386-linux-nat.c (i386_linux_resume): Get the ptrace PID out of
+ the lwp field of ptid. Pass the full ptid to get_thread_regcache.
+ * inf-ptrace.c (get_ptrace_pid): New function.
+ (inf_ptrace_resume): Use it.
+ * linux-nat.c (linux_resume_one_lwp): Pass the LWP's ptid ummodified
+ to the lower layer.
+
2015-03-03 Markus Metzger <markus.t.metzger@intel.com>
* nat/linux-btrace.c: Include sys/utsname.h.
diff --git a/gdb/i386-linux-nat.c b/gdb/i386-linux-nat.c
index b95b47e..8cb8c66 100644
--- a/gdb/i386-linux-nat.c
+++ b/gdb/i386-linux-nat.c
@@ -648,8 +648,7 @@ static void
i386_linux_resume (struct target_ops *ops,
ptid_t ptid, int step, enum gdb_signal signal)
{
- int pid = ptid_get_pid (ptid);
-
+ int pid = ptid_get_lwp (ptid);
int request;
if (catch_syscall_enabled () > 0)
@@ -659,7 +658,7 @@ i386_linux_resume (struct target_ops *ops,
if (step)
{
- struct regcache *regcache = get_thread_regcache (pid_to_ptid (pid));
+ struct regcache *regcache = get_thread_regcache (ptid);
struct gdbarch *gdbarch = get_regcache_arch (regcache);
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
ULONGEST pc;
diff --git a/gdb/inf-ptrace.c b/gdb/inf-ptrace.c
index 4c22a84..606bdb4 100644
--- a/gdb/inf-ptrace.c
+++ b/gdb/inf-ptrace.c
@@ -289,6 +289,22 @@ inf_ptrace_stop (struct target_ops *self, ptid_t ptid)
kill (-inferior_process_group (), SIGINT);
}
+/* Return which PID to pass to ptrace in order to observe/control the
+ tracee identified by PTID. */
+
+static pid_t
+get_ptrace_pid (ptid_t ptid)
+{
+ pid_t pid;
+
+ /* If we have an LWPID to work with, use it. Otherwise, we're
+ dealing with a non-threaded program/target. */
+ pid = ptid_get_lwp (ptid);
+ if (pid == 0)
+ pid = ptid_get_pid (ptid);
+ return pid;
+}
+
/* Resume execution of thread PTID, or all threads if PTID is -1. If
STEP is nonzero, single-step it. If SIGNAL is nonzero, give it
that signal. */
@@ -297,13 +313,16 @@ static void
inf_ptrace_resume (struct target_ops *ops,
ptid_t ptid, int step, enum gdb_signal signal)
{
- pid_t pid = ptid_get_pid (ptid);
+ pid_t pid;
+
int request;
- if (pid == -1)
+ if (ptid_equal (minus_one_ptid, ptid))
/* Resume all threads. Traditionally ptrace() only supports
single-threaded processes, so simply resume the inferior. */
- pid = ptid_get_pid (inferior_ptid);
+ pid = get_ptrace_pid (inferior_ptid);
+ else
+ pid = get_ptrace_pid (ptid);
if (catch_syscall_enabled () > 0)
request = PT_SYSCALL;
diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 2e1133d..cb10e2c 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -1506,8 +1506,6 @@ linux_nat_detach (struct target_ops *ops, const char *args, int from_tty)
static void
linux_resume_one_lwp (struct lwp_info *lp, int step, enum gdb_signal signo)
{
- ptid_t ptid;
-
lp->step = step;
/* stop_pc doubles as the PC the LWP had when it was last resumed.
@@ -1524,9 +1522,7 @@ linux_resume_one_lwp (struct lwp_info *lp, int step, enum gdb_signal signo)
if (linux_nat_prepare_to_resume != NULL)
linux_nat_prepare_to_resume (lp);
- /* Convert to something the lower layer understands. */
- ptid = pid_to_ptid (ptid_get_lwp (lp->ptid));
- linux_ops->to_resume (linux_ops, ptid, step, signo);
+ linux_ops->to_resume (linux_ops, lp->ptid, step, signo);
lp->stop_reason = LWP_STOPPED_BY_NO_REASON;
lp->stopped = 0;
registers_changed_ptid (lp->ptid);