powerpc: Add show_user_instructions()

show_user_instructions() is a slightly modified version of
show_instructions() that allows userspace instruction dump.

This will be useful within show_signal_msg() to dump userspace
instructions of the faulty location.

Here is a sample of what show_user_instructions() outputs:

  pandafault[10850]: code: 4bfffeec 4bfffee8 3c401002 38427f00 fbe1fff8 f821ffc1 7c3f0b78 3d22fffe
  pandafault[10850]: code: 392988d0 f93f0020 e93f0020 39400048 <99490000> 39200000 7d234b78 383f0040

The current->comm and current->pid printed can serve as a glue that
links the instructions dump to its originator, allowing messages to be
interleaved in the logs.

Signed-off-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/include/asm/stacktrace.h b/arch/powerpc/include/asm/stacktrace.h
new file mode 100644 (file)
index 0000000..6149b53
--- /dev/null
+++ b/arch/powerpc/include/asm/stacktrace.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Stack trace functions.
+ *
+ * Copyright 2018, Murilo Opsfelder Araujo, IBM Corporation.
+ */
+
+#ifndef _ASM_POWERPC_STACKTRACE_H
+#define _ASM_POWERPC_STACKTRACE_H
+
+void show_user_instructions(struct pt_regs *regs);
+
+#endif /* _ASM_POWERPC_STACKTRACE_H */

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 2172f99086339e76df1746edd166b582a1d9f9d5..913c5725cdb2ad416d06513ed6a72240b4e9aa6d 100644 (file)
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1299,6 +1299,38 @@ static void show_instructions(struct pt_regs *regs)
        pr_cont("\n");
 }
 
+void show_user_instructions(struct pt_regs *regs)
+{
+       unsigned long pc;
+       int i;
+
+       pc = regs->nip - (instructions_to_print * 3 / 4 * sizeof(int));
+
+       pr_info("%s[%d]: code: ", current->comm, current->pid);
+
+       for (i = 0; i < instructions_to_print; i++) {
+               int instr;
+
+               if (!(i % 8) && (i > 0)) {
+                       pr_cont("\n");
+                       pr_info("%s[%d]: code: ", current->comm, current->pid);
+               }
+
+               if (probe_kernel_address((unsigned int __user *)pc, instr)) {
+                       pr_cont("XXXXXXXX ");
+               } else {
+                       if (regs->nip == pc)
+                               pr_cont("<%08x> ", instr);
+                       else
+                               pr_cont("%08x ", instr);
+               }
+
+               pc += sizeof(int);
+       }
+
+       pr_cont("\n");
+}
+
 struct regbit {
        unsigned long bit;
        const char *name;