Messages in this thread Patch in this message | | | Date | Fri, 2 Mar 2018 18:16:37 +0000 | From | Mark Rutland <> | Subject | Re: [PATCH] arm64/debug: Fix registers on sleeping tasks |
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On Fri, Mar 02, 2018 at 06:01:31PM +0000, Will Deacon wrote: > On Thu, Mar 01, 2018 at 11:38:03AM -0800, Douglas Anderson wrote: > > This is the equivalent of commit 001bf455d206 ("ARM: 8428/1: kgdb: Fix > > registers on sleeping tasks") but for arm64. Nuff said. > > It's a pity that 001bf455d206 doesn't explain *why* past_pt_regs doesn't > work.
The task_pt_regs are the userspace regs at the highest address on the kernel stack:
#define task_pt_regs(p) \ ((struct pt_regs *)(THREAD_SIZE + task_stack_page(p)) - 1)
... for kernel tasks, that's meaningless, and for user tasks, that won't correspond to kernel state.
> > diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c > > index 2122cd187f19..01285d4dcdc3 100644 > > --- a/arch/arm64/kernel/kgdb.c > > +++ b/arch/arm64/kernel/kgdb.c > > @@ -138,14 +138,26 @@ 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_struct *thread = &task->thread; > > + struct cpu_context *cpu_context = &thread->cpu_context;
We can do this in one go:
struct cpu_context *cpu_context = &task->thread.cpu_context;
... since we don't need the thread variable otherwise.
> > > > /* Initialize to zero */ > > memset((char *)gdb_regs, 0, NUMREGBYTES); > > - thread_regs = task_pt_regs(task); > > - memcpy((void *)gdb_regs, (void *)thread_regs->regs, GP_REG_BYTES); > > - /* Special case for PSTATE (check comments in asm/kgdb.h for details) */ > > - dbg_get_reg(33, gdb_regs + GP_REG_BYTES, thread_regs); > > + > > + gdb_regs[19] = cpu_context->x19; > > + gdb_regs[20] = cpu_context->x20; > > + gdb_regs[21] = cpu_context->x21; > > + gdb_regs[22] = cpu_context->x22; > > + gdb_regs[23] = cpu_context->x23; > > + gdb_regs[24] = cpu_context->x24; > > + gdb_regs[25] = cpu_context->x25; > > + gdb_regs[26] = cpu_context->x26; > > + gdb_regs[27] = cpu_context->x27; > > + gdb_regs[28] = cpu_context->x28; > > + gdb_regs[29] = cpu_context->fp; > > + > > + gdb_regs[31] = cpu_context->sp; > > + gdb_regs[32] = cpu_context->pc;
Are the other reg fields initialised elsewhere?
We might want to zero them here.
Thanks, Mark.
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