From 9b69093e623f1d54c373b1e091900d40576c059b Mon Sep 17 00:00:00 2001 From: Song Shuai Date: Tue, 12 Dec 2023 18:20:51 +0800 Subject: [PATCH 11/14] RISCV64: Fix 'bt' output when no ra on the stack top Same as the Linux commit f766f77a74f5 ("riscv/stacktrace: Fix stack output without ra on the stack top"). When a function doesn't have a callee, then it will not push ra into the stack, such as lkdtm functions, so correct the FP of the second frame and use pt_regs to get the right PC of the second frame. Before this patch, the `bt -f` outputs only the first frame with the wrong PC and FP of next frame: ``` crash> bt -f PID: 1 TASK: ff600000000e0000 CPU: 1 COMMAND: "sh" #0 [ff20000000013cf0] lkdtm_EXCEPTION at ffffffff805303c0 [PC: ffffffff805303c0 RA: ff20000000013d10 SP: ff20000000013cf0 SIZE: 16] <- wrong next PC ff20000000013cf0: 0000000000000001 ff20000000013d10 <- next FP ff20000000013d00: ff20000000013d40 crash> ``` After this patch, the `bt` outputs the full frames: ``` crash> bt PID: 1 TASK: ff600000000e0000 CPU: 1 COMMAND: "sh" #0 [ff20000000013cf0] lkdtm_EXCEPTION at ffffffff805303c0 #1 [ff20000000013d00] lkdtm_do_action at ffffffff8052fe36 #2 [ff20000000013d10] direct_entry at ffffffff80530018 #3 [ff20000000013d40] full_proxy_write at ffffffff80305044 #4 [ff20000000013d80] vfs_write at ffffffff801b68b4 #5 [ff20000000013e30] ksys_write at ffffffff801b6c4a #6 [ff20000000013e80] __riscv_sys_write at ffffffff801b6cc4 #7 [ff20000000013e90] do_trap_ecall_u at ffffffff80836798 crash> ``` Acked-by: Kazuhito Hagio Signed-off-by: Song Shuai Signed-off-by: Lianbo Jiang --- riscv64.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/riscv64.c b/riscv64.c index 0aaa14b2671e..872be594d72b 100644 --- a/riscv64.c +++ b/riscv64.c @@ -747,11 +747,14 @@ riscv64_back_trace_cmd(struct bt_info *bt) { struct riscv64_unwind_frame current, previous; struct stackframe curr_frame; + struct riscv64_register * regs; int level = 0; if (bt->flags & BT_REGS_NOT_FOUND) return; + regs = (struct riscv64_register *) bt->machdep; + current.pc = bt->instptr; current.sp = bt->stkptr; current.fp = bt->frameptr; @@ -788,8 +791,16 @@ riscv64_back_trace_cmd(struct bt_info *bt) sizeof(curr_frame), "get stack frame", RETURN_ON_ERROR)) return; - previous.pc = curr_frame.ra; - previous.fp = curr_frame.fp; + /* correct PC and FP of the second frame when the first frame has no callee */ + + if (regs && (regs->regs[RISCV64_REGS_EPC] == current.pc) && curr_frame.fp & 0x7){ + previous.pc = regs->regs[RISCV64_REGS_RA]; + previous.fp = curr_frame.ra; + } else { + previous.pc = curr_frame.ra; + previous.fp = curr_frame.fp; + } + previous.sp = current.fp; riscv64_dump_backtrace_entry(bt, symbol, ¤t, &previous, level++); -- 2.41.0