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author | Pedro Alves <palves@redhat.com> | 2015-03-03 13:33:44 +0000 |
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committer | Pedro Alves <palves@redhat.com> | 2015-03-03 13:33:44 +0000 |
commit | 90ad5e1d4f34d02f437ec12d1b65d7252f5b7f1c (patch) | |
tree | 8e59c13d4bb5feafa976abdbb25a46dd2250b4b6 /gdb/inf-ptrace.c | |
parent | dd2ac17449b62de57f128f670b1783bb6728eac6 (diff) | |
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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\tÀ8kIøæÿ¿HO5\b\035]")
at gdb/regcache.c:643
#4 0x083558a7 in regcache_cooked_read (regcache=0x9a0a798, regnum=8,
buf=0xbfffe6c0 "¨\003\222\tÀ8kIøæÿ¿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.
Diffstat (limited to 'gdb/inf-ptrace.c')
-rw-r--r-- | gdb/inf-ptrace.c | 25 |
1 files changed, 22 insertions, 3 deletions
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; |