6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Clément Léger <cleger@xxxxxxxxxxxx>
[ Upstream commit 51356ce60e5915a6bd812873186ed54e45c2699d ]
Prior to commit 5d5fc33ce58e ("riscv: Improve exception and system call
latency"), backtrace through exception worked since ra was filled with
ret_from_exception symbol address and the stacktrace code checked 'pc' to
be equal to that symbol. Now that handle_exception uses regular 'call'
instructions, this isn't working anymore and backtrace stops at
handle_exception(). Since there are multiple call site to C code in the
exception handling path, rather than checking multiple potential return
addresses, add a new symbol at the end of exception handling and check pc
to be in that range.
Fixes: 5d5fc33ce58e ("riscv: Improve exception and system call latency")
Signed-off-by: Clément Léger <cleger@xxxxxxxxxxxx>
Tested-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
Reviewed-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20241209155714.1239665-1-cleger@xxxxxxxxxxxx
Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
arch/riscv/kernel/entry.S | 1 +
arch/riscv/kernel/stacktrace.c | 4 +++-
2 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index c200d329d4bd..7a6c48e6d211 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -278,6 +278,7 @@ SYM_CODE_START_NOALIGN(ret_from_exception)
#else
sret
#endif
+SYM_INNER_LABEL(ret_from_exception_end, SYM_L_GLOBAL)
SYM_CODE_END(ret_from_exception)
ASM_NOKPROBE(ret_from_exception)
diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
index 153a2db4c5fa..d4355c770c36 100644
--- a/arch/riscv/kernel/stacktrace.c
+++ b/arch/riscv/kernel/stacktrace.c
@@ -17,6 +17,7 @@
#ifdef CONFIG_FRAME_POINTER
extern asmlinkage void handle_exception(void);
+extern unsigned long ret_from_exception_end;
static inline int fp_is_valid(unsigned long fp, unsigned long sp)
{
@@ -71,7 +72,8 @@ void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
fp = frame->fp;
pc = ftrace_graph_ret_addr(current, &graph_idx, frame->ra,
&frame->ra);
- if (pc == (unsigned long)handle_exception) {
+ if (pc >= (unsigned long)handle_exception &&
+ pc < (unsigned long)&ret_from_exception_end) {
if (unlikely(!__kernel_text_address(pc) || !fn(arg, pc)))
break;
--
2.39.5
