Re: [PATCH v4 5/6] powerpc: Add show_user_instructions()
From: Christophe LEROY
Date: Fri Aug 03 2018 - 02:38:31 EST
Hi Murilo,
Le 03/08/2018 Ã 02:42, Murilo Opsfelder Araujo a ÃcritÂ:
Hi, Christophe.
On Thu, Aug 02, 2018 at 07:26:20AM +0200, Christophe LEROY wrote:
Le 01/08/2018 Ã 23:33, Murilo Opsfelder Araujo a ÃcritÂ:
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@xxxxxxxxxxxxx>
---
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 ?
Because it doesn't compile:
arch/powerpc/kernel/process.c:1317:10: error: expected â)â before âprefixâ
pr_info(prefix, current->comm, current->pid);
^
./include/linux/printk.h:288:21: note: in definition of macro âpr_fmtâ
#define pr_fmt(fmt) fmt
^
`pr_info(prefix, ...)` expands to `printk("\001" "6" prefix, ...)`,
which is an invalid string concatenation.
`pr_info("%s", ...)` expands to `printk("\001" "6" "%s", ...)`, which is
valid.
Then what about using directly:
pr_info("%s[%d]: code: ", ...);
+
+ 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 ?
I don't think so.
pc gets incremented at the bottom of the loop:
pc += sizeof(int);
Adjusting pc is necessary at each iteration. Leaving this block inside
the loop seems correct.
This looks pretty strange.
The first time, pc is a physical address, that you change to a virtual
address. Then when you increment it it is still a virtual address.
So when you call phys_to_virt(pc) for the second time, pc is already a
virt address, so what happens indeed ?
Christophe
Cheers
Murilo