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>

1 files changed, 32 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 2172f9908633..913c5725cdb2 100644
--- 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;