[Crash-utility] [PATCH 2/5] Enable crash to change gdb thread context

Previously we can only view the stack unwinding for the tasks which are running on each CPUs. This patch will enable the ability to view arbitrary tasks stack unwinding. After crash get initialized, "info threads" will output like the following: crash> info threads Id Target Id Frame 1 CPU 0 native_safe_halt () at arch/x86/include/asm/irqflags.h:54 ... * 8 CPU 7 blk_mq_rq_timed_out (req=0xffff880fdb246000, reserved=reserved@entry=false) at block/blk-mq.c:640 ... 13 CPU 12 <unavailable> in ?? () 14 CPU 13 native_safe_halt () at arch/x86/include/asm/irqflags.h:54 ... crash> ps PID PPID CPU TASK ST %MEM VSZ RSS COMM ... 0 0 23 ffff8801694e0000 RU 0.0 0 0 [swapper/23] 1 0 13 ffff880169b30000 IN 0.0 193052 4180 systemd "info threads" show the tasks which are currently running on each CPU. If we'd like to view systemd task's stack unwinding, which is inactive status, we do the following: crash> set 1 or crash> set ffff880169b30000 Then the register cache of systemd will be swapped into CPU 13: crash> info threads Id Target Id Frame 1 CPU 0 native_safe_halt () at arch/x86/include/asm/irqflags.h:54 ... 8 CPU 7 blk_mq_rq_timed_out (req=0xffff880fdb246000, reserved=reserved@entry=false) at block/blk-mq.c:640 ... 13 CPU 12 <unavailable> in ?? () * 14 CPU 13 0xffffffff816a8f65 in context_switch (rq=0x0, next=0x0, prev=0xffff880169b30000) at kernel/sched/core.c:2527 ... And we can view the stack unwinding of systemd: crash> bt PID: 1 TASK: ffff880169b30000 CPU: 13 COMMAND: "systemd" #0 [ffff880169b3bd58] __schedule at ffffffff816a8f65 #1 [ffff880169b3bdc0] schedule at ffffffff816a94e9 #2 [ffff880169b3bdd0] schedule_hrtimeout_range_clock at ffffffff816a86fd #3 [ffff880169b3be68] schedule_hrtimeout_range at ffffffff816a8733 #4 [ffff880169b3be78] ep_poll at ffffffff8124bb7e #5 [ffff880169b3bf30] sys_epoll_wait at ffffffff8124d00d #6 [ffff880169b3bf80] system_call_fastpath at ffffffff816b5009 RIP: 00007f0449407923 RSP: 00007ffc35a3c378 RFLAGS: 00010246 RAX: 00000000000000e8 RBX: ffffffff816b5009 RCX: 0000000000000071 RDX: 000000000000001d RSI: 00007ffc35a3d5a0 RDI: 0000000000000004 RBP: 00007ffc35a3d810 R8: 0000000000000000 R9: 0000000000000000 R10: 00000000ffffffff R11: 0000000000000293 R12: 0000563ca2ebe980 R13: 0000000000000003 R14: ffffffffffffffff R15: 0000000000000001 ORIG_RAX: 00000000000000e8 CS: 0033 SS: 002b crash> gdb bt #0 0xffffffff816a8f65 in context_switch (rq=0x0, next=0x0, prev=0xffff880169b30000) at kernel/sched/core.c:2527 #1 __schedule () at kernel/sched/core.c:3540 #2 0xffffffff816a94e9 in schedule () at kernel/sched/core.c:3577 #3 0xffffffff816a86fd in schedule_hrtimeout_range_clock (expires=expires@entry=0x0, delta=delta@entry=0, mode=mode@entry=HRTIMER_MODE_ABS, clock=clock@entry=1) at kernel/hrtimer.c:1724 #4 0xffffffff816a8733 in schedule_hrtimeout_range (expires=expires@entry=0x0, delta=delta@entry=0, mode=mode@entry=HRTIMER_MODE_ABS) at kernel/hrtimer.c:1778 #5 0xffffffff8124bb7e in ep_poll (ep=0xffff880fd861f8c0, events=events@entry=0x7ffc35a3d5a0, maxevents=maxevents@entry=29, timeout=timeout@entry=-1) at fs/eventpoll.c:1669 #6 0xffffffff8124d00d in SYSC_epoll_wait (timeout=<optimized out>, maxevents=29, events=<optimized out>, epfd=<optimized out>) at fs/eventpoll.c:2043 #7 SyS_epoll_wait (epfd=<optimized out>, events=140721208415648, maxevents=29, timeout=4294967295) at fs/eventpoll.c:2008 #8 <signal handler called> #9 0x00007f0449407923 in ?? () Signed-off-by: Tao Liu <ltao(a)redhat.com&gt; --- crash_target.c | 50 ++++++++++++++++------------- defs.h | 3 +- gdb-10.2.patch | 85 +------------------------------------------------- kernel.c | 22 +++++++++++++ task.c | 5 +-- 5 files changed, 57 insertions(+), 108 deletions(-) diff --git a/crash_target.c b/crash_target.c index d06383f..8efe2d6 100644 --- a/crash_target.c +++ b/crash_target.c @@ -29,10 +29,10 @@ extern "C" int gdb_readmem_callback(unsigned long, void *, int, int); extern "C" int crash_get_nr_cpus(void); extern "C" int crash_get_cpu_reg (int cpu, int regno, const char *regname, int regsize, void *val); -extern "C" int gdb_change_cpu_context (unsigned int cpu); extern "C" void gdb_refresh_regcache(unsigned int cpu); extern "C" int set_cpu(int cpu, int print_context); - +extern "C" int crash_set_thread(ulong); +extern "C" int gdb_change_thread_context (ulong); /* The crash target. */ @@ -110,11 +110,13 @@ crash_target::xfer_partial (enum target_object object, const char *annex, #define CRASH_INFERIOR_PID 1 +crash_target *target = NULL; + void crash_target_init (void) { int nr_cpus = crash_get_nr_cpus(); - crash_target *target = new crash_target (); + target = new crash_target (); /* Own the target until it is successfully pushed. */ target_ops_up target_holder (target); @@ -137,29 +139,35 @@ crash_target_init (void) reinit_frame_cache (); } -/* - * Change gdb's thread context to the thread on given CPU - **/ extern "C" int -gdb_change_cpu_context(unsigned int cpu) +gdb_change_thread_context (ulong task) { - ptid_t ptid = ptid_t(CRASH_INFERIOR_PID, 0, cpu); - inferior *inf = current_inferior (); - thread_info *tp = find_thread_ptid (inf, ptid); - - if (tp == nullptr) + int tried = 0; + inferior* inf = current_inferior(); + int cpu = crash_set_thread(task); + if (cpu < 0) return FALSE; - /* Making sure that crash's context is same */ - set_cpu(cpu, FALSE); - - /* Switch to the thread */ - switch_to_thread(tp); - - /* Fetch/Refresh thread's registers */ - gdb_refresh_regcache(cpu); + ptid_t ptid = ptid_t(CRASH_INFERIOR_PID, 0, cpu); - return TRUE; +retry: + thread_info *tp = find_thread_ptid (inf, ptid); + if (tp == nullptr && !tried) { + thread_info *thread = add_thread_silent(target, + ptid_t(CRASH_INFERIOR_PID, 0, cpu)); + tried++; + if (thread) { + goto retry; + } + } + + if (tp == nullptr && tried) + return FALSE; + + target_fetch_registers(get_thread_regcache(tp), -1); + switch_to_thread(tp); + reinit_frame_cache (); + return TRUE; } /* Refresh regcache of gdb thread on given CPU diff --git a/defs.h b/defs.h index 06bd27d..1ddfc5e 100644 --- a/defs.h +++ b/defs.h @@ -6083,6 +6083,7 @@ void sort_tgid_array(void); int sort_by_tgid(const void *, const void *); int in_irq_ctx(ulonglong, int, ulong); void check_stack_overflow(void); +int gdb_change_thread_context (ulong); /* * extensions.c @@ -6123,6 +6124,7 @@ void dump_kernel_table(int); void dump_bt_info(struct bt_info *, char *where); void dump_log(int); void parse_kernel_version(char *); +int crash_set_thread(ulong); #define LOG_LEVEL(v) ((v) & 0x07) #define SHOW_LOG_LEVEL (0x1) @@ -8191,7 +8193,6 @@ enum ppc64_regnum { }; /* crash_target.c */ -extern int gdb_change_cpu_context (unsigned int cpu); extern void gdb_refresh_regcache (unsigned int cpu); #endif /* !GDB_COMMON */ diff --git a/gdb-10.2.patch b/gdb-10.2.patch index 138413f..3e6677d 100644 --- a/gdb-10.2.patch +++ b/gdb-10.2.patch @@ -16058,35 +16058,6 @@ exit 0 m10200-dis.c m10200-opc.c m10300-dis.c ---- gdb-10.2/gdb/thread.c.orig -+++ gdb-10.2/gdb/thread.c -@@ -58,6 +58,11 @@ static int highest_thread_num; - /* The current/selected thread. */ - static thread_info *current_thread_; - -+#ifdef CRASH_MERGE -+/* Function to set cpu, defined by crash-utility */ -+extern "C" void set_cpu (int); -+#endif -+ - /* RAII type used to increase / decrease the refcount of each thread - in a given list of threads. */ - -@@ -1896,7 +1901,13 @@ thread_command (const char *tidstr, int from_tty) - { - ptid_t previous_ptid = inferior_ptid; - -- thread_select (tidstr, parse_thread_id (tidstr, NULL)); -+ struct thread_info* thread_id = parse_thread_id (tidstr, NULL); -+ -+#ifdef CRASH_MERGE -+ set_cpu(thread_id->ptid.tid()); -+#endif -+ -+ thread_select (tidstr, thread_id); - - /* Print if the thread has not changed, otherwise an event will - be sent. */ --- gdb-10.2/gdb/ui-file.h.orig +++ gdb-10.2/gdb/ui-file.h @@ -195,6 +195,7 @@ public: @@ -16139,58 +16110,4 @@ exit 0 + (dynamic_cast<stdio_file *>gdb_stderr)->set_stream(original_stderr_stream); } - /* ---- gdb-10.2/gdb/thread.c.orig -+++ gdb-10.2/gdb/thread.c -@@ -60,7 +60,7 @@ static thread_info *current_thread_; - - #ifdef CRASH_MERGE - /* Function to set cpu, defined by crash-utility */ --extern "C" void set_cpu (int); -+extern "C" void set_cpu(int cpu, int print_context); - #endif - - /* RAII type used to increase / decrease the refcount of each thread -@@ -1098,6 +1098,9 @@ print_thread_info_1 (struct ui_out *uiout, const char *requested_threads, - uiout->table_body (); - } - -+#ifdef CRASH_MERGE -+ int current_cpu = current_thread ? current_thread->ptid.tid() : 0; -+#endif - for (inferior *inf : all_inferiors ()) - for (thread_info *tp : inf->threads ()) - { -@@ -1113,6 +1116,11 @@ print_thread_info_1 (struct ui_out *uiout, const char *requested_threads, - - ui_out_emit_tuple tuple_emitter (uiout, NULL); - -+ /* Switch to the thread's CPU in crash */ -+#ifdef CRASH_MERGE -+ set_cpu(tp->ptid.tid(), FALSE); -+#endif -+ - if (!uiout->is_mi_like_p ()) - { - if (tp == current_thread) -@@ -1185,6 +1193,11 @@ print_thread_info_1 (struct ui_out *uiout, const char *requested_threads, - /* This end scope restores the current thread and the frame - selected before the "info threads" command, and it finishes the - ui-out list or table. */ -+ -+#ifdef CRASH_MERGE -+ /* Restore crash's context */ -+ set_cpu(current_cpu, FALSE); -+#endif - } - - if (pid == -1 && requested_threads == NULL) -@@ -1904,7 +1917,7 @@ thread_command (const char *tidstr, int from_tty) - struct thread_info* thread_id = parse_thread_id (tidstr, NULL); - - #ifdef CRASH_MERGE -- set_cpu(thread_id->ptid.tid()); -+ set_cpu(thread_id->ptid.tid(), FALSE); - #endif - - thread_select (tidstr, thread_id); + /* \ No newline at end of file diff --git a/kernel.c b/kernel.c index c7de73a..49d422b 100644 --- a/kernel.c +++ b/kernel.c @@ -6543,6 +6543,28 @@ set_cpu(int cpu, int print_context) show_context(CURRENT_CONTEXT()); } +int +crash_set_thread(ulong task) +{ + bool found = FALSE; + struct task_context *tc = FIRST_CONTEXT(); + + for (int i = 0; i < RUNNING_TASKS(); i++, tc++) { + if (tc->task == task) { + found = TRUE; + break; + } + } + + if (!found) + return -1; + + if (CURRENT_TASK() == tc->task) + return tc->processor; + + set_context(tc->task, NO_PID, TRUE); + return tc->processor; +} /* * Collect the irq_desc[] entry along with its associated handler and diff --git a/task.c b/task.c index a405b05..ef79f53 100644 --- a/task.c +++ b/task.c @@ -715,7 +715,8 @@ task_init(void) * crash_target::fetch_registers, so CPU 0's registers are shown as * <unavailable> in gdb mode * */ - gdb_refresh_regcache(0); + for (int i = 0; i < get_cpus_online(); i++) + gdb_refresh_regcache(i); tt->flags |= TASK_INIT_DONE; } @@ -5315,7 +5316,7 @@ set_context(ulong task, ulong pid, uint update_gdb_thread) /* change the selected thread in gdb, according to current context */ if (update_gdb_thread) - return gdb_change_cpu_context(tc->processor); + return gdb_change_thread_context(tc->task); else return TRUE; } else { -- 2.40.1