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Subject[PATCH 2/3] x86/unwind: read stack return address in update_stack_state()
Date
Instead of reading the return address when unwind_get_return_address()
is called, read it from update_stack_state() and store it in the unwind
state. This enables the next patch to check the return address from
unwind_next_frame() so it can detect an entry code frame.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
arch/x86/include/asm/unwind.h | 1 +
arch/x86/kernel/unwind_frame.c | 25 +++++++++++++------------
2 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
index 6fa75b1..5663425 100644
--- a/arch/x86/include/asm/unwind.h
+++ b/arch/x86/include/asm/unwind.h
@@ -14,6 +14,7 @@ struct unwind_state {
#ifdef CONFIG_FRAME_POINTER
unsigned long *bp, *orig_sp;
struct pt_regs *regs;
+ unsigned long ip;
#else
unsigned long *sp;
#endif
diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index 9098ef1..c67a059 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -56,20 +56,10 @@ static void unwind_dump(struct unwind_state *state, unsigned long *sp)

unsigned long unwind_get_return_address(struct unwind_state *state)
{
- unsigned long addr;
- unsigned long *addr_p = unwind_get_return_address_ptr(state);
-
if (unwind_done(state))
return 0;

- if (state->regs && user_mode(state->regs))
- return 0;
-
- addr = READ_ONCE_TASK_STACK(state->task, *addr_p);
- addr = ftrace_graph_ret_addr(state->task, &state->graph_idx, addr,
- addr_p);
-
- return __kernel_text_address(addr) ? addr : 0;
+ return __kernel_text_address(state->ip) ? state->ip : 0;
}
EXPORT_SYMBOL_GPL(unwind_get_return_address);

@@ -141,7 +131,7 @@ static bool update_stack_state(struct unwind_state *state,
struct stack_info *info = &state->stack_info;
enum stack_type prev_type = info->type;
struct pt_regs *regs;
- unsigned long *frame, *prev_frame_end;
+ unsigned long *frame, *prev_frame_end, *addr_p, addr;
size_t len;

if (state->regs)
@@ -185,6 +175,16 @@ static bool update_stack_state(struct unwind_state *state,
state->regs = NULL;
}

+ /* Save the return address: */
+ if (state->regs && user_mode(state->regs))
+ state->ip = 0;
+ else {
+ addr_p = unwind_get_return_address_ptr(state);
+ addr = READ_ONCE_TASK_STACK(state->task, *addr_p);
+ state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
+ addr, addr_p);
+ }
+
/* Save the original stack pointer for unwind_dump(): */
if (!state->orig_sp || info->type != prev_type)
state->orig_sp = frame;
@@ -228,6 +228,7 @@ bool unwind_next_frame(struct unwind_state *state)
*/
state->regs = regs;
state->bp = NULL;
+ state->ip = 0;
return true;
}

--
2.7.4
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