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ARM: 8428/1: kgdb: Fix registers on sleeping tasks

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Dumping registers from other sleeping tasks in KGDB was totally
failing for me.  All registers were reported as 0 in many cases.

The code was using task_pt_regs(task) to try to get other thread
registers.  This doesn't appear to be the right place to look.  From
my tests, I saw non-zero values in this structure when we were looking
at a kernel thread that had a userspace task associated with it, but
it contained the register values from the userspace task.  So even in
the cases where registers weren't reported as 0 we were still not
showing the right thing.

Instead of using task_pt_regs(task) let's use task_thread_info(task).
This is the same place that is referred to when doing a dump of all
sleeping task stacks (kdb_show_stack() -> show_stack() ->
dump_backtrace() -> unwind_backtrace() -> thread_saved_sp()).

As further evidence that this is the right thing to do, you can find
the following comment in "gdbstub.c" right before it calls
sleeping_thread_to_gdb_regs():
  Pull stuff saved during switch_to; nothing else is accessible (or
  even particularly relevant).  This should be enough for a stack
  trace.
...and if you look at switch_to() it only saves r4-r11, sp and lr.
Those are the same registers that I'm getting out of the
task_thread_info().

With this change you can use "info thread" to see all tasks in the
kernel and you can switch to other tasks and examine them in gdb.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Tested-by: Stephen Boyd <sboyd@codeurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Doug Anderson 2015-09-02 03:39:19 +01:00 committed by Russell King
parent 7e31210349
commit 001bf455d2
1 changed files with 12 additions and 19 deletions
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31
arch/arm/kernel/kgdb.c
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@ -74,7 +74,7 @@ int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
void
sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
{
struct pt_regs *thread_regs;
struct thread_info *ti;
int regno;
/* Just making sure... */
@ -86,24 +86,17 @@ sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
gdb_regs[regno] = 0;
/* Otherwise, we have only some registers from switch_to() */
thread_regs = task_pt_regs(task);
gdb_regs[_R0] = thread_regs->ARM_r0;
gdb_regs[_R1] = thread_regs->ARM_r1;
gdb_regs[_R2] = thread_regs->ARM_r2;
gdb_regs[_R3] = thread_regs->ARM_r3;
gdb_regs[_R4] = thread_regs->ARM_r4;
gdb_regs[_R5] = thread_regs->ARM_r5;
gdb_regs[_R6] = thread_regs->ARM_r6;
gdb_regs[_R7] = thread_regs->ARM_r7;
gdb_regs[_R8] = thread_regs->ARM_r8;
gdb_regs[_R9] = thread_regs->ARM_r9;
gdb_regs[_R10] = thread_regs->ARM_r10;
gdb_regs[_FP] = thread_regs->ARM_fp;
gdb_regs[_IP] = thread_regs->ARM_ip;
gdb_regs[_SPT] = thread_regs->ARM_sp;
gdb_regs[_LR] = thread_regs->ARM_lr;
gdb_regs[_PC] = thread_regs->ARM_pc;
gdb_regs[_CPSR] = thread_regs->ARM_cpsr;
ti = task_thread_info(task);
gdb_regs[_R4] = ti->cpu_context.r4;
gdb_regs[_R5] = ti->cpu_context.r5;
gdb_regs[_R6] = ti->cpu_context.r6;
gdb_regs[_R7] = ti->cpu_context.r7;
gdb_regs[_R8] = ti->cpu_context.r8;
gdb_regs[_R9] = ti->cpu_context.r9;
gdb_regs[_R10] = ti->cpu_context.sl;
gdb_regs[_FP] = ti->cpu_context.fp;
gdb_regs[_SPT] = ti->cpu_context.sp;
gdb_regs[_PC] = ti->cpu_context.pc;
}
void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)