[Crash-utility] Re: [PATCH v6 5/5] fix 'info threads' command

Currently the output is like this ppc64le: crash> info threads Id Target Id Frame 1 CPU 0 <unavailable> in ?? () 2 CPU 1 0xc000000000025d00 in ppc_panic_event (this=<optimized out>, event=<optimized out>, ptr=0x0) at arch/powerpc/kernel/setup-common.c:712 3 CPU 2 0xc000000000025d00 in ppc_panic_event (this=<optimized out>, event=<optimized out>, ptr=0x0) at arch/powerpc/kernel/setup-common.c:712 4 CPU 3 0xc000000000025d00 in ppc_panic_event (this=<optimized out>, event=<optimized out>, ptr=0x0) at arch/powerpc/kernel/setup-common.c:712 * 5 CPU 4 0xc000000000025d00 in ppc_panic_event (this=<optimized out>, event=<optimized out>, ptr=0x0) at arch/powerpc/kernel/setup-common.c:712 6 CPU 5 0xc000000000025d00 in ppc_panic_event (this=<optimized out>, event=<optimized out>, ptr=0x0) at arch/powerpc/kernel/setup-common.c:712 7 CPU 6 0xc000000000025d00 in ppc_panic_event (this=<optimized out>, event=<optimized out>, ptr=0x0) at arch/powerpc/kernel/setup-common.c:712 8 CPU 7 0xc000000000025d00 in ppc_panic_event (this=<optimized out>, event=<optimized out>, ptr=0x0) at arch/powerpc/kernel/setup-common.c:712 There are two issues here: 1. CPU 0 always shows '<unavailable>' frame: This is due to 'thread 0' being initialised in 'crash_target_init', but it's very early in crash init, so it could not get any registers from the vmcore. And, since GDB caches registers (whether it is there or now), it keeps thinking that registers for this thread are unavailable, so all future usage of thread 0 also shows unavailable registers & frame Fix this by refreshing the register cache of all threads in 'gdb_refresh_regcache', at task_init 2. All other CPUs show the same frame: For each thread, GDB depends on crash to give it registers, ie. crash_target::fetch_registers, but this in turn depends on crash's current context GDB internally switches it's thread context internally to each thread one by one, while printing the thread's frame, similarly switch crash's context when the thread context is changed, so that it matches the thread context in gdb (such as, CPU 3 in crash for thread 2(CPU 3) in gdb). Also, since we are switching context multiple times, add an argument to 'set_cpu' to not print the context everytime With these fixed, it will show all threads, as well as correct registers and frame. It might still show similar frame for many threads, due to all of them being on same NMI exception crash path, but if checked with 'info registers', they will have different registers. Signed-off-by: Aditya Gupta <adityag(a)linux.ibm.com&gt; --- crash_target.c | 37 +++++++++++++++++++++++++++++++++++-- defs.h | 5 +++-- gdb-10.2.patch | 40 +++++++++++++++++++++++++++++++++++++--- kernel.c | 8 +++++--- task.c | 30 ++++++++++++++++++++++-------- tools.c | 10 +++++----- 6 files changed, 107 insertions(+), 23 deletions(-) diff --git a/crash_target.c b/crash_target.c index a9d7eea8a80e..d06383f594aa 100644 --- a/crash_target.c +++ b/crash_target.c @@ -30,7 +30,8 @@ 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" int set_cpu (int cpu); +extern "C" void gdb_refresh_regcache(unsigned int cpu); +extern "C" int set_cpu(int cpu, int print_context); /* The crash target. */ @@ -150,10 +151,42 @@ gdb_change_cpu_context(unsigned int cpu) return FALSE; /* Making sure that crash's context is same */ - set_cpu(cpu); + set_cpu(cpu, FALSE); /* Switch to the thread */ switch_to_thread(tp); + + /* Fetch/Refresh thread's registers */ + gdb_refresh_regcache(cpu); + return TRUE; } +/* Refresh regcache of gdb thread on given CPU + * + * When gdb threads were initially added by 'crash_target_init', crash was not + * yet initialised, and hence crash_target::fetch_registers didn't give any + * registers to gdb. + * + * This is meant to be called after tasks in crash have been initialised, and + * possible machdep->get_cpu_reg is also set so architecture can give registers + */ +extern "C" void +gdb_refresh_regcache(unsigned int cpu) +{ + int saved_cpu = inferior_thread()->ptid.tid(); + ptid_t ptid = ptid_t(CRASH_INFERIOR_PID, 0, cpu); + inferior *inf = current_inferior(); + thread_info *tp = find_thread_ptid (inf, ptid); + + if (tp == NULL) { + warning("gdb thread for cpu %d not found\n", cpu); + return; + } + + /* temporarily switch to the cpu so we get correct registers */ + set_cpu(cpu, FALSE); + target_fetch_registers(get_thread_regcache(tp), -1); + + set_cpu(saved_cpu, FALSE); +} diff --git a/defs.h b/defs.h index 7f7a12753658..ba4a6a606f66 100644 --- a/defs.h +++ b/defs.h @@ -5940,7 +5940,7 @@ extern char *help_map[]; * task.c */ void task_init(void); -int set_context(ulong, ulong); +int set_context(ulong, ulong, uint); void show_context(struct task_context *); ulong pid_to_task(ulong); ulong task_to_pid(ulong); @@ -6044,7 +6044,7 @@ void parse_kernel_version(char *); #define SHOW_LOG_AUDIT (0x8) #define SHOW_LOG_CTIME (0x10) #define SHOW_LOG_SAFE (0x20) -void set_cpu(int); +void set_cpu(int cpu, int print_context); void clear_machdep_cache(void); struct stack_hook *gather_text_list(struct bt_info *); int get_cpus_online(void); @@ -7978,5 +7978,6 @@ 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 a4e45fa0e6fa..9051c83ac784 100644 --- a/gdb-10.2.patch +++ b/gdb-10.2.patch @@ -494,13 +494,47 @@ exit 0 +#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 in a given list of threads. */ -@@ -1896,7 +1901,13 @@ thread_command (const char *tidstr, int from_tty) +@@ -1093,6 +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 ()) + { +@@ -1108,6 +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) +@@ -1180,6 +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) +@@ -1896,7 +1914,13 @@ thread_command (const char *tidstr, int from_tty) { ptid_t previous_ptid = inferior_ptid; @@ -508,7 +542,7 @@ exit 0 + 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);