6.12-stable review patch. If anyone has any objections, please let me know.
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From: Clément Léger cleger@rivosinc.com
[ 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@rivosinc.com Tested-by: Alexandre Ghiti alexghiti@rivosinc.com Reviewed-by: Alexandre Ghiti alexghiti@rivosinc.com Link: https://lore.kernel.org/r/20241209155714.1239665-1-cleger@rivosinc.com Signed-off-by: Palmer Dabbelt palmer@rivosinc.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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;