Re: [PATCH v4 5/6] powerpc: Add show_user_instructions()

[Christophe LEROY]

Le 01/08/2018 à 23:33, Murilo Opsfelder Araujo a écrit :

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 <muri...@linux.ibm.com>
---
  arch/powerpc/include/asm/stacktrace.h | 13 +++++++++
  arch/powerpc/kernel/process.c         | 40 +++++++++++++++++++++++++++
  2 files changed, 53 insertions(+)
  create mode 100644 arch/powerpc/include/asm/stacktrace.h

diff --git a/arch/powerpc/include/asm/stacktrace.h 
b/arch/powerpc/include/asm/stacktrace.h
new file mode 100644
index 000000000000..6149b53b3bc8
--- /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 e9533b4d2f08..364645ac732c 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1299,6 +1299,46 @@ static void show_instructions(struct pt_regs *regs)
        pr_cont("\n");
  }

+void show_user_instructions(struct pt_regs *regs)

+{
+       int i;
+       const char *prefix = KERN_INFO "%s[%d]: code: ";
+       unsigned long pc = regs->nip - (instructions_to_print * 3 / 4 *
+                                       sizeof(int));
+
+       printk(prefix, current->comm, current->pid);

Why not use pr_info() and remove KERN_INFO from *prefix ?

+
+       for (i = 0; i < instructions_to_print; i++) {
+               int instr;
+
+               if (!(i % 8) && (i > 0)) {
+                       pr_cont("\n");
+                       printk(prefix, current->comm, current->pid);
+               }
+
+#if !defined(CONFIG_BOOKE)
+               /* If executing with the IMMU off, adjust pc rather
+                * than print XXXXXXXX.
+                */
+               if (!(regs->msr & MSR_IR))
+                       pc = (unsigned long)phys_to_virt(pc);

Shouldn't this be done outside of the loop, only once ?

Christophe

+#endif
+
+               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;