On 2024/01/05 16:30, Aditya Gupta wrote:
> 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 for gdb passthroughs
> to work correctly, gdb needs register values from crash, which depend on
> current context in crash.
>
> 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.
>
> Signed-off-by: Aditya Gupta <adityag@xxxxxxxxxxxxx>
> ---
> 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 455480679741..a9d7eea8a80e 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 615f3a37935a..7f7a12753658 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -7976,4 +7976,7 @@ 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 2f7d585105aa..8c1b43eb07b7 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 \
> @@ -485,6 +486,35 @@ exit 0
> return best_pst;
> }
>
> +--- 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. */
Please move this hunk to the end of gdb-10.2.patch.
Thanks,
Kazu
> --- gdb-10.2/gdb/symfile.c.orig
> +++ gdb-10.2/gdb/symfile.c
> @@ -652,7 +652,26 @@ default_symfile_offsets (struct objfile *objfile,
> diff --git a/kernel.c b/kernel.c
> index 52b7ba09f390..a8d60507dd95 100644
> --- a/kernel.c
> +++ b/kernel.c
> @@ -6504,7 +6504,13 @@ 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 ebdb5be3786f..3a190cafbacb 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);
--
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