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s390/unwind: stop gracefully at task pt_regs

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Consider reaching task pt_regs graceful unwinder termination. Task
pt_regs itself never contains a valid state to which a task might return
within the kernel context (user task pt_regs is a special case). Since
we already avoid printing user task pt_regs and in most cases we don't
even bother filling task pt_regs psw and r15 with something reasonable
simply skip task pt_regs altogether. With this change unwind_error() now
accurately represent whether unwinder reached task pt_regs successfully
or failed along the way.

Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Vasily Gorbik 2019-11-22 16:49:13 +01:00
parent cb7948e8c3
commit e76e69611e
1 changed files with 7 additions and 1 deletions
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8
arch/s390/kernel/unwind_bc.c
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@ -36,6 +36,12 @@ static bool update_stack_info(struct unwind_state *state, unsigned long sp)
return true; return true;
} }
static inline bool is_task_pt_regs(struct unwind_state *state,
struct pt_regs *regs)
{
return task_pt_regs(state->task) == regs;
}
bool unwind_next_frame(struct unwind_state *state) bool unwind_next_frame(struct unwind_state *state)
{ {
struct stack_info *info = &state->stack_info; struct stack_info *info = &state->stack_info;
@ -69,7 +75,7 @@ bool unwind_next_frame(struct unwind_state *state)
if (!on_stack(info, sp, sizeof(struct pt_regs))) if (!on_stack(info, sp, sizeof(struct pt_regs)))
goto out_err; goto out_err;
regs = (struct pt_regs *) sp; regs = (struct pt_regs *) sp;
if (READ_ONCE_NOCHECK(regs->psw.mask) & PSW_MASK_PSTATE) if (is_task_pt_regs(state, regs))
goto out_stop; goto out_stop;
ip = READ_ONCE_NOCHECK(regs->psw.addr); ip = READ_ONCE_NOCHECK(regs->psw.addr);
sp = READ_ONCE_NOCHECK(regs->gprs[15]); sp = READ_ONCE_NOCHECK(regs->gprs[15]);