riscv: add userland instruction dump to RISC-V splats

Add userland instruction dump and rename dump_kernel_instr()
to dump_instr().

An example:
[    0.822439] Freeing unused kernel image (initmem) memory: 6916K
[    0.823817] Run /init as init process
[    0.839411] init[1]: unhandled signal 4 code 0x1 at 0x000000000005be18 in bb[10000+5fb000]
[    0.840751] CPU: 0 PID: 1 Comm: init Not tainted 5.14.0-rc4-00049-gbd644290aa72-dirty #187
[    0.841373] Hardware name:  , BIOS
[    0.841743] epc : 000000000005be18 ra : 0000000000079e74 sp : 0000003fffcafda0
[    0.842271]  gp : ffffffff816e9dc8 tp : 0000000000000000 t0 : 0000000000000000
[    0.842947]  t1 : 0000003fffc9fdf0 t2 : 0000000000000000 s0 : 0000000000000000
[    0.843434]  s1 : 0000000000000000 a0 : 0000003fffca0190 a1 : 0000003fffcafe18
[    0.843891]  a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000
[    0.844357]  a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000000000000
[    0.844803]  s2 : 0000000000000000 s3 : 0000000000000000 s4 : 0000000000000000
[    0.845253]  s5 : 0000000000000000 s6 : 0000000000000000 s7 : 0000000000000000
[    0.845722]  s8 : 0000000000000000 s9 : 0000000000000000 s10: 0000000000000000
[    0.846180]  s11: 0000000000d144e0 t3 : 0000000000000000 t4 : 0000000000000000
[    0.846616]  t5 : 0000000000000000 t6 : 0000000000000000
[    0.847204] status: 0000000200000020 badaddr: 00000000f0028053 cause: 0000000000000002
[    0.848219] Code: f06f ff5f 3823 fa11 0113 fb01 2e23 0201 0293 0000 (8053) f002
[    0.851016] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004

Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20230912021349.28302-1-cuiyunhui@bytedance.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 8895c81975196d8faae5eb0de420832eda16b136..141036d06015c79ec2e59389d04403a18e840bdb 100644 (file)
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -34,7 +34,21 @@ int show_unhandled_signals = 1;
 
 static DEFINE_SPINLOCK(die_lock);
 
-static void dump_kernel_instr(const char *loglvl, struct pt_regs *regs)
+static int copy_code(struct pt_regs *regs, u16 *val, const u16 *insns)
+{
+       const void __user *uaddr = (__force const void __user *)insns;
+
+       if (!user_mode(regs))
+               return get_kernel_nofault(*val, insns);
+
+       /* The user space code from other tasks cannot be accessed. */
+       if (regs != task_pt_regs(current))
+               return -EPERM;
+
+       return copy_from_user_nofault(val, uaddr, sizeof(*val));
+}
+
+static void dump_instr(const char *loglvl, struct pt_regs *regs)
 {
        char str[sizeof("0000 ") * 12 + 2 + 1], *p = str;
        const u16 *insns = (u16 *)instruction_pointer(regs);
@@ -43,7 +57,7 @@ static void dump_kernel_instr(const char *loglvl, struct pt_regs *regs)
        int i;
 
        for (i = -10; i < 2; i++) {
-               bad = get_kernel_nofault(val, &insns[i]);
+               bad = copy_code(regs, &val, &insns[i]);
                if (!bad) {
                        p += sprintf(p, i == 0 ? "(%04hx) " : "%04hx ", val);
                } else {
@@ -72,7 +86,7 @@ void die(struct pt_regs *regs, const char *str)
        print_modules();
        if (regs) {
                show_regs(regs);
-               dump_kernel_instr(KERN_EMERG, regs);
+               dump_instr(KERN_EMERG, regs);
        }
 
        cause = regs ? regs->cause : -1;
@@ -105,6 +119,7 @@ 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);
+               dump_instr(KERN_EMERG, regs);
        }
 
        force_sig_fault(signo, code, (void __user *)addr);