6.6-stable review patch. If anyone has any objections, please let me know.
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From: Clément Léger cleger@rivosinc.com
commit 51356ce60e5915a6bd812873186ed54e45c2699d upstream.
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: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/riscv/kernel/entry.S | 1 + arch/riscv/kernel/stacktrace.c | 4 +++- 2 files changed, 4 insertions(+), 1 deletion(-)
--- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -174,6 +174,7 @@ SYM_CODE_START_NOALIGN(ret_from_exceptio #else sret #endif +SYM_INNER_LABEL(ret_from_exception_end, SYM_L_GLOBAL) SYM_CODE_END(ret_from_exception) ASM_NOKPROBE(ret_from_exception)
--- a/arch/riscv/kernel/stacktrace.c +++ b/arch/riscv/kernel/stacktrace.c @@ -33,6 +33,7 @@ })
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) { @@ -88,7 +89,8 @@ void notrace walk_stackframe(struct task pc = READ_ONCE_TASK_STACK(task, frame->ra); pc = ftrace_graph_ret_addr(current, &graph_idx, pc, &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;