Messages in this thread Patch in this message | | | From | Yunhui Cui <> | Subject | [PATCH] riscv/fault: Dump user opcode bytes on fatal faults | Date | Mon, 27 Mar 2023 19:56:42 +0800 |
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We encountered such a problem(logs are below). We are more curious about which instruction execution caused the exception. After dumping it through show_opcodes(), we found that it was caused by a floating-point instruction.
In this way, we found the problem: in the system bringup , it is precisely that we have not enabled the floating point function.
So when an exception occurs, it is necessary to dump the instruction that caused the exception, like x86/fault (ba54d856a9d8).
Logs: [ 0.822481] Run /init as init process [ 0.837569] init[1]: unhandled signal 4 code 0x1 at 0x000000000005e028 in bb[10000+5fe000] [ 0.932292] CPU: 0 PID: 1 Comm: init Not tainted 5.14.0-rc4-00048-g4a843c9043e8-dirty #138 [ 0.932949] Hardware name: , BIOS [ 0.933399] epc : 000000000005e028 ra : 000000000007c7c4 sp : 0000003fffd45da0 [ 0.933855] gp : ffffffff816ea2d8 tp : 0000000000000000 t0 : 0000000000000000 [ 0.934303] t1 : 0000003fffd35df0 t2 : 0000000000000000 s0 : 0000000000000000 [ 0.934734] s1 : 0000000000000000 a0 : 0000003fffd36190 a1 : 0000003fffd45e18 [ 0.935200] a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000 [ 0.935622] a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000000000000 [ 0.936073] s2 : 0000000000000000 s3 : 0000000000000000 s4 : 0000000000000000 [ 0.936495] s5 : 0000000000000000 s6 : 0000000000000000 s7 : 0000000000000000 [ 0.936947] s8 : 0000000000000000 s9 : 0000000000000000 s10: 0000000000000000 [ 0.937487] s11: 0000000000d14980 t3 : 0000000000000000 t4 : 0000000000000000 [ 0.937954] t5 : 0000000000000000 t6 : 0000000000000000 [ 0.938510] status: 0000000200000020 badaddr: 00000000f0028053 cause: 0000000000000002
Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com> --- arch/riscv/include/asm/bug.h | 1 + arch/riscv/kernel/process.c | 30 ++++++++++++++++++++++++++++++ arch/riscv/kernel/traps.c | 1 + 3 files changed, 32 insertions(+)
diff --git a/arch/riscv/include/asm/bug.h b/arch/riscv/include/asm/bug.h index d3804a2f9aad..77655dd10a2c 100644 --- a/arch/riscv/include/asm/bug.h +++ b/arch/riscv/include/asm/bug.h @@ -86,6 +86,7 @@ struct pt_regs; struct task_struct; void __show_regs(struct pt_regs *regs); +void show_opcodes(struct pt_regs *regs); void die(struct pt_regs *regs, const char *str); void do_trap(struct pt_regs *regs, int signo, int code, unsigned long addr); diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index 03ac3aa611f5..759dc74fe160 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -83,6 +83,36 @@ void show_regs(struct pt_regs *regs) dump_backtrace(regs, NULL, KERN_DEFAULT); } +static int copy_code(struct pt_regs *regs, u8 *buf, unsigned long src, + unsigned int nbytes) +{ + if (!user_mode(regs)) + return copy_from_kernel_nofault(buf, (u8 *)src, nbytes); + + /* The user space code from other tasks cannot be accessed. */ + if (regs != task_pt_regs(current)) + return -EPERM; + + return copy_from_user_nofault(buf, (void __user *)src, nbytes); +} + +void show_opcodes(struct pt_regs *regs) +{ + u8 opcodes[4]; + + switch (copy_code(regs, opcodes, regs->epc, sizeof(opcodes))) { + case 0: + pr_info("Opcode: %4ph", opcodes); + break; + case -EPERM: + pr_err("Unable to access userspace of other tasks"); + break; + default: + pr_err("Failed to access opcode"); + break; + } +} + void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp) { diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index 0a98fd0ddfe9..a6f6851e4e87 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -68,6 +68,7 @@ void do_trap(struct pt_regs *regs, int signo, int code, unsigned long addr) print_vma_addr(KERN_CONT " in ", instruction_pointer(regs)); pr_cont("\n"); __show_regs(regs); + show_opcodes(regs); } force_sig_fault(signo, code, (void __user *)addr); -- 2.20.1
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