2020-03-12 17:33:47

by Josh Poimboeuf

Subject: [PATCH 10/14] x86/unwind/orc: Prevent unwinding before ORC initialization

If the unwinder is called before the ORC data has been initialized,
orc_find() returns NULL, and it tries to fall back to using frame
pointers. This can cause some unexpected warnings during boot.

Move the 'orc_init' check from orc_find() to __unwind_init(), so that it
doesn't even try to unwind from an uninitialized state.

Fixes: ee9f8fce9964 ("x86/unwind: Add the ORC unwinder")
Signed-off-by: Josh Poimboeuf <[email protected]>
---
arch/x86/kernel/unwind_orc.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index e9f5a20c69c6..cb11567361cc 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -148,9 +148,6 @@ static struct orc_entry *orc_find(unsigned long ip)
{
static struct orc_entry *orc;

- if (!orc_init)
- return NULL;
-
if (ip == 0)
return &null_orc_entry;

@@ -591,6 +588,9 @@ EXPORT_SYMBOL_GPL(unwind_next_frame);
void __unwind_start(struct unwind_state *state, struct task_struct *task,
struct pt_regs *regs, unsigned long *first_frame)
{
+ if (!orc_init)
+ goto done;
+
memset(state, 0, sizeof(*state));
state->task = task;

--
2.21.1

2020-03-13 12:25:20

by Miroslav Benes

Subject: Re: [PATCH 10/14] x86/unwind/orc: Prevent unwinding before ORC initialization

On Thu, 12 Mar 2020, Josh Poimboeuf wrote:

> If the unwinder is called before the ORC data has been initialized,
> orc_find() returns NULL, and it tries to fall back to using frame
> pointers. This can cause some unexpected warnings during boot.
>
> Move the 'orc_init' check from orc_find() to __unwind_init(), so that it

s/__unwind_init()/__unwind_start()/

> void __unwind_start(struct unwind_state *state, struct task_struct *task,
> struct pt_regs *regs, unsigned long *first_frame)
> {
> + if (!orc_init)
> + goto done;
> +
> memset(state, 0, sizeof(*state));
> state->task = task;

Miroslav