From e058560a48b3351da8c2de4355368e3e001fe117 Mon Sep 17 00:00:00 2001 From: Aditya Gupta Date: Fri, 9 Jun 2023 12:38:01 +0530 Subject: [PATCH] synchronise cpu context changes between crash/gdb MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Currently, both crash context and gdb's current thread context were pretty independent, and could be different, for example, crash commands might be working on thread 6 (CPU 5), but GDB passthroughs will be working on thread 2 (CPU 1). This was not a problem earlier since interaction of crash and gdb was not depending on current context for most part. But with more interactions, this patch should solve any issues due to mismatch in context in crash/gdb. Synchronise 'thread' command in gdb with 'set -c' command in crash. 1. crash -> gdb synchronisation: Everytime crash's context changes, a helper is called to switch to the thread on that CPU in gdb. The function has been implemented in crash_target.c, since gdb functions are accessible inside 'crash_target.c', and the thread ID to CPU ID mapping is also done by the crash_target, during initially registering the threads with gdb. With this implementation, GDB's default thread initially also changes to the crashing thread, so a switch to crashing thread manually isn't required anymore 2. gdb -> crash synchronisation: gdb has been patched to call 'set_cpu' whenever user switches to any thread. Cc: Sourabh Jain Cc: Hari Bathini Cc: Mahesh J Salgaonkar Cc: Naveen N. Rao Cc: Lianbo Jiang Cc: HAGIO KAZUHITO(萩尾 一仁) Cc: Tao Liu Signed-off-by: Aditya Gupta --- crash_target.c | 24 ++++++++++++++++++++++++ defs.h | 3 +++ gdb-10.2.patch | 30 ++++++++++++++++++++++++++++++ kernel.c | 8 +++++++- task.c | 4 +++- 5 files changed, 67 insertions(+), 2 deletions(-) diff --git a/crash_target.c b/crash_target.c index 45548067..a9d7eea8 100644 --- a/crash_target.c +++ b/crash_target.c @@ -29,6 +29,8 @@ 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" int set_cpu (int cpu); /* The crash target. */ @@ -133,3 +135,25 @@ crash_target_init (void) /* Now, set up the frame cache. */ reinit_frame_cache (); } + +/* + * Change gdb's thread context to the thread on given CPU + **/ +extern "C" int +gdb_change_cpu_context(unsigned int cpu) +{ + 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) + return FALSE; + + /* Making sure that crash's context is same */ + set_cpu(cpu); + + /* Switch to the thread */ + switch_to_thread(tp); + return TRUE; +} + diff --git a/defs.h b/defs.h index 694d2809..50fe25c0 100644 --- a/defs.h +++ b/defs.h @@ -8173,4 +8173,7 @@ enum ppc64_regnum { PPC64_VRSAVE_REGNU = 139 }; +/* crash_target.c */ +extern int gdb_change_cpu_context (unsigned int cpu); + #endif /* !GDB_COMMON */ diff --git a/gdb-10.2.patch b/gdb-10.2.patch index a7018a24..677bd9b3 100644 --- a/gdb-10.2.patch +++ b/gdb-10.2.patch @@ -10,6 +10,7 @@ tar xvzmf gdb-10.2.tar.gz \ gdb-10.2/gdb/symtab.c \ + gdb-10.2/gdb/thread.c \ gdb-10.2/gdb/printcmd.c \ gdb-10.2/gdb/symfile.c \ gdb-10.2/gdb/Makefile.in \ @@ -16057,3 +16058,32 @@ 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. */ diff --git a/kernel.c b/kernel.c index 661ef0e2..93af36fc 100644 --- a/kernel.c +++ b/kernel.c @@ -6527,7 +6527,13 @@ set_cpu(int cpu) if (hide_offline_cpu(cpu)) error(FATAL, "invalid cpu number: cpu %d is OFFLINE\n", cpu); - if ((task = get_active_task(cpu))) + task = get_active_task(cpu); + + /* Check if context is already set to given cpu */ + if (task == CURRENT_TASK()) + return; + + if (task) set_context(task, NO_PID); else error(FATAL, "cannot determine active task on cpu %ld\n", cpu); diff --git a/task.c b/task.c index ebdb5be3..3a190caf 100644 --- a/task.c +++ b/task.c @@ -5301,7 +5301,9 @@ set_context(ulong task, ulong pid) if (found) { CURRENT_CONTEXT() = tc; - return TRUE; + + /* change the selected thread in gdb, according to current context */ + return gdb_change_cpu_context(tc->processor); } else { if (task) error(INFO, "cannot set context for task: %lx\n", task);