2:40 a.m.
Hi Aditya,
thanks for the update, 'info threads' worked well.
On 2024/02/05 15:36, 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.
Is this true?
CURRENT_CONTEXT() is used in ppc64_get_cpu_reg, but get_cpu_reg returns
a register value from a cpu, so can't we use get_active_task(cpu) and
task_to_context()? if usable, maybe some of the temporary set_cpu()s
can be removed.
The synchronization between crash and gdb is nice for usability, though.
(it's very helpful if you would rebase the patch set to the latest, when
you update this.)
Thanks,
Kazu
>
> 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(a)linux.ibm.com>
> ---
> 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..4698079ca343 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 \
> @@ -3237,3 +3238,32 @@ exit 0
>
> for (compunit_symtab *cust : objfile->compunits ())
> {
> +--- 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 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);