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authorVasily Gorbik <gor@linux.ibm.com>2019-11-22 15:58:42 +0100
committerVasily Gorbik <gor@linux.ibm.com>2019-11-30 10:52:45 +0100
commit97806dfb6f3838ee4b7bc69e6f160d83eadbc74a (patch)
tree948227e65b97d4901b2fba6de1b9a36c871f54de
parent67f5593419878798bb306632cdca0698a2dd3cbd (diff)
downloadlinux-97806dfb6f3838ee4b7bc69e6f160d83eadbc74a.tar.bz2
s390/unwind: make reuse_sp default when unwinding pt_regs
Currently unwinder yields 2 entries when pt_regs are met: sp="address of pt_regs itself" ip=pt_regs->psw sp=pt_regs->gprs[15] ip="r14 from stack frame pointed by pt_regs->gprs[15]" And neither of those 2 states (combination of sp and ip) ever happened. reuse_sp has been introduced by commit a1d863ac3e10 ("s390/unwind: fix mixing regs and sp"). reuse_sp=true makes unwinder keen to produce the following result, when pt_regs are given (as an arg to unwind_start): sp=pt_regs->gprs[15] ip=pt_regs->psw sp=pt_regs->gprs[15] ip="r14 from stack frame pointed by pt_regs->gprs[15]" The first state is an actual state in which a task was when pt_regs were collected. The second state is marked unreliable and is for debugging purposes to cover the case when a task has been interrupted in between stack frame allocation and writing back_chain - in this case r14 might show an actual caller. Make unwinder behaviour enabled via reuse_sp=true default and drop the special case handling. Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
-rw-r--r--arch/s390/include/asm/unwind.h1
-rw-r--r--arch/s390/kernel/unwind_bc.c21
2 files changed, 7 insertions, 15 deletions
diff --git a/arch/s390/include/asm/unwind.h b/arch/s390/include/asm/unwind.h
index a2d8dd766987..5d6c8fe7a271 100644
--- a/arch/s390/include/asm/unwind.h
+++ b/arch/s390/include/asm/unwind.h
@@ -35,7 +35,6 @@ struct unwind_state {
struct task_struct *task;
struct pt_regs *regs;
unsigned long sp, ip;
- bool reuse_sp;
int graph_idx;
bool reliable;
bool error;
diff --git a/arch/s390/kernel/unwind_bc.c b/arch/s390/kernel/unwind_bc.c
index fd90b6e21663..ac6cfab567d1 100644
--- a/arch/s390/kernel/unwind_bc.c
+++ b/arch/s390/kernel/unwind_bc.c
@@ -46,16 +46,7 @@ bool unwind_next_frame(struct unwind_state *state)
regs = state->regs;
if (unlikely(regs)) {
- if (state->reuse_sp) {
- sp = state->sp;
- state->reuse_sp = false;
- } else {
- sp = READ_ONCE_NOCHECK(regs->gprs[15]);
- if (unlikely(outside_of_stack(state, sp))) {
- if (!update_stack_info(state, sp))
- goto out_err;
- }
- }
+ sp = state->sp;
sf = (struct stack_frame *) sp;
ip = READ_ONCE_NOCHECK(sf->gprs[8]);
reliable = false;
@@ -81,6 +72,11 @@ bool unwind_next_frame(struct unwind_state *state)
if (READ_ONCE_NOCHECK(regs->psw.mask) & PSW_MASK_PSTATE)
goto out_stop;
ip = READ_ONCE_NOCHECK(regs->psw.addr);
+ sp = READ_ONCE_NOCHECK(regs->gprs[15]);
+ if (unlikely(outside_of_stack(state, sp))) {
+ if (!update_stack_info(state, sp))
+ goto out_err;
+ }
reliable = true;
}
}
@@ -107,7 +103,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
{
struct stack_info *info = &state->stack_info;
unsigned long *mask = &state->stack_mask;
- bool reliable, reuse_sp;
+ bool reliable;
struct stack_frame *sf;
unsigned long ip;
@@ -134,12 +130,10 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
if (regs) {
ip = READ_ONCE_NOCHECK(regs->psw.addr);
reliable = true;
- reuse_sp = true;
} else {
sf = (struct stack_frame *) sp;
ip = READ_ONCE_NOCHECK(sf->gprs[8]);
reliable = false;
- reuse_sp = false;
}
ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, ip, NULL);
@@ -148,6 +142,5 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
state->sp = sp;
state->ip = ip;
state->reliable = reliable;
- state->reuse_sp = reuse_sp;
}
EXPORT_SYMBOL_GPL(__unwind_start);