[Crash-utility] Re: [PATCH v3 2/5] Call cmd_bt silently after "set pid"

Thank you for working on this. On Tue, Jun 3, 2025 at 1:15 PM <devel-request(a)lists.crash-utility.osci.io&gt; wrote: > > Date: Tue, 3 Jun 2025 17:11:35 +1200 > From: Tao Liu <ltao(a)redhat.com&gt; > Subject: [Crash-utility] [PATCH v3 2/5] Call cmd_bt silently after > "set pid" > To: devel(a)lists.crash-utility.osci.io > Cc: Alexey Makhalov <alexey.makhalov(a)broadcom.com&gt; > Message-ID: <20250603051138.59896-3-ltao(a)redhat.com&gt; > Content-Type: text/plain; charset="US-ASCII"; x-default=true > > Cmd bt will list multi-stacks of one task. After we "set <pid>" switch > context to one task, we first need a bt call to detect the multi-stacks, > however we don't want any console output from it, so a nullfp is used for > output receive. The silent bt call is only triggered once as part of task > context switch by cmd set. > > A array of user_regs pointers is reserved for each supported arch. If one > extra stack found, a user_regs structure will be allocated for storing regs > value of the stack. > > Co-developed-by: Alexey Makhalov <alexey.makhalov(a)broadcom.com&gt; > Co-developed-by: Tao Liu <ltao(a)redhat.com&gt; > Signed-off-by: Tao Liu <ltao(a)redhat.com&gt; > --- > arm64.c | 4 ++++ > crash_target.c | 7 +++++++ > kernel.c | 43 +++++++++++++++++++++++++++++++++++++++++++ > ppc64.c | 4 ++++ > task.c | 4 ++-- > x86_64.c | 3 +++ > 6 files changed, 63 insertions(+), 2 deletions(-) > > diff --git a/arm64.c b/arm64.c > index 1cdde5f..8291301 100644 > --- a/arm64.c > +++ b/arm64.c > @@ -126,6 +126,10 @@ struct user_regs_bitmap_struct { > ulong bitmap[32]; > }; > > +#define MAX_EXCEPTION_STACKS 7 > +ulong extra_stacks_idx = 0; > +struct user_regs_bitmap_struct *extra_stacks_regs[MAX_EXCEPTION_STACKS] = {0}; > + > static inline bool is_mte_kvaddr(ulong addr) > { > /* check for ARM64_MTE enabled */ > diff --git a/crash_target.c b/crash_target.c > index 71998ef..ad1480c 100644 > --- a/crash_target.c > +++ b/crash_target.c > @@ -31,6 +31,9 @@ extern "C" int crash_get_current_task_reg (int regno, const char *regname, > extern "C" int gdb_change_thread_context (void); > extern "C" int gdb_add_substack (int); > extern "C" void crash_get_current_task_info(unsigned long *pid, char **comm); > +#if defined (X86_64) || defined (ARM64) || defined (PPC64) > +extern "C" void silent_call_bt(void); > +#endif > > /* The crash target. */ > > @@ -164,6 +167,10 @@ gdb_change_thread_context (void) > /* 3rd, refresh regcache for tid 0 */ > target_fetch_registers(get_thread_regcache(inferior_thread()), -1); > reinit_frame_cache(); > +#if defined (X86_64) || defined (ARM64) || defined (PPC64) > + /* 4th, invoke bt silently to refresh the additional stacks */ > + silent_call_bt(); > +#endif > return TRUE; > } > > diff --git a/kernel.c b/kernel.c > index b8d3b79..b15c32c 100644 > --- a/kernel.c > +++ b/kernel.c > @@ -12002,3 +12002,46 @@ int get_linux_banner_from_vmlinux(char *buf, size_t size) > > return TRUE; > } > + > +#if defined(X86_64) || defined(ARM64) || defined(PPC64) > +extern ulong extra_stacks_idx; > +extern void *extra_stacks_regs[]; > +void silent_call_bt(void) > +{ > + jmp_buf main_loop_env_save; > + unsigned long long flags_save = pc->flags; > + FILE *fp_save = fp; > + FILE *error_fp_save = pc->error_fp; > + /* Redirect all cmd_bt() outputs into null */ > + fp = pc->nullfp; > + pc->error_fp = pc->nullfp; > + > + for (int i = 0; i < extra_stacks_idx; i++) { > + /* Note: GETBUF/FREEBUF is not applicable for extra_stacks_regs, > + because we are reserving extra_stacks_regs by cmd_bt() > + for later use. But GETBUF/FREEBUF is designed for use only > + within one cmd. See process_command_line() -> restore_sanity() > + -> free_all_bufs(). So we use malloc/free instead. */ > + free(extra_stacks_regs[i]); > + extra_stacks_regs[i] = NULL; > + } > + /* Prepare args used by cmd_bt() */ > + sprintf(pc->command_line, "bt\n"); > + argcnt = parse_line(pc->command_line, args); > + optind = 1; > + pc->flags |= RUNTIME; Is this unnecessary? The flag 'RUNTIME' is set only once when initializing(see the main_loop()), and will never be cleared.

Again: a warning observed gcc -c -g -DX86_64 -DLZO -DGDB_16_2 kernel.c -I./gdb-16.2/bfd -I./gdb-16.2/include -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector -Wformat-security kernel.c:12009:6: warning: no previous prototype for ‘silent_call_bt’ [-Wmissing-prototypes] 12009 | void silent_call_bt(void) | ^~~~~~~~~~~~~~

Thanks Lianbo > + > + /* Catch error FATAL generated by cmd_bt() if any */ > + memcpy(&main_loop_env_save, &pc->main_loop_env, sizeof(jmp_buf)); > + if (setjmp(pc->main_loop_env)) { > + goto out; > + } > + cmd_bt(); > +out: > + /* Restore all */ > + memcpy(&pc->main_loop_env, &main_loop_env_save, sizeof(jmp_buf)); > + pc->flags = flags_save; > + fp = fp_save; > + pc->error_fp = error_fp_save; > +} > +#endif > diff --git a/ppc64.c b/ppc64.c > index 7ac12fe..532eb3f 100644 > --- a/ppc64.c > +++ b/ppc64.c > @@ -80,6 +80,10 @@ struct user_regs_bitmap_struct { > ulong bitmap[32]; > }; > > +#define MAX_EXCEPTION_STACKS 7 > +ulong extra_stacks_idx = 0; > +struct user_regs_bitmap_struct *extra_stacks_regs[MAX_EXCEPTION_STACKS] = {0}; > + > static int is_opal_context(ulong sp, ulong nip) > { > uint64_t opal_start, opal_end; > diff --git a/task.c b/task.c > index e07b479..ec04b55 100644 > --- a/task.c > +++ b/task.c > @@ -3062,7 +3062,7 @@ sort_context_array(void) > curtask = CURRENT_TASK(); > qsort((void *)tt->context_array, (size_t)tt->running_tasks, > sizeof(struct task_context), sort_by_pid); > - set_context(curtask, NO_PID, TRUE); > + set_context(curtask, NO_PID, FALSE); > > sort_context_by_task(); > } > @@ -3109,7 +3109,7 @@ sort_context_array_by_last_run(void) > curtask = CURRENT_TASK(); > qsort((void *)tt->context_array, (size_t)tt->running_tasks, > sizeof(struct task_context), sort_by_last_run); > - set_context(curtask, NO_PID, TRUE); > + set_context(curtask, NO_PID, FALSE); > > sort_context_by_task(); > } > diff --git a/x86_64.c b/x86_64.c > index a46fb9d..ee23d8b 100644 > --- a/x86_64.c > +++ b/x86_64.c > @@ -160,6 +160,9 @@ struct user_regs_bitmap_struct { > ulong bitmap[32]; > }; > > +ulong extra_stacks_idx = 0; > +struct user_regs_bitmap_struct *extra_stacks_regs[MAX_EXCEPTION_STACKS] = {0}; > + > /* > * Do all necessary machine-specific setup here. This is called several > * times during initialization. > -- > 2.47.0 -- Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io To unsubscribe send an email to devel-leave(a)lists.crash-utility.osci.io https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ Contribution Guidelines: https://github.com/crash-utility/crash/wiki