lkml.org 
[lkml]   [2018]   [Oct]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v4 2/3] powerpc/process: fix interleaved output in show_user_instructions()
Date
When two processes crash at the same time, we sometimes encounter
interleaving in the middle of a line:

[ 4.365317] init[1]: segfault (11) at 0 nip 0 lr 0 code 1
[ 4.370452] init[1]: code: XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
[ 4.372042] init[74]: segfault (11) at 10a74 nip 1000c198 lr 100078c8 code 1 in sh[10000000+14000]
[ 4.386829] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
[ 4.391542] init[1]: code: XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
[ 4.400863] init[74]: code: 90010024 bf61000c 91490a7c 3fa01002 3be00000 7d3e4b78 3bbd0c20 3b600000
[ 4.409867] init[74]: code: 3b9d0040 7c7fe02e 2f830000 419e0028 <89230000> 2f890000 41be001c 4b7f6e79

This patch fixes it by preparing complete lines in a buffer and
printing it at once.

Fixes: 88b0fe1757359 ("powerpc: Add show_user_instructions()")
Reviewed-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
v4: rebased
v3: no change
v2: Using seq_buf and reworked the loop to avoid redundant prints.

arch/powerpc/kernel/process.c | 37 +++++++++++++++++++------------------
1 file changed, 19 insertions(+), 18 deletions(-)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 3396c419abf2..8dabf656d924 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -43,6 +43,7 @@
#include <linux/uaccess.h>
#include <linux/elf-randomize.h>
#include <linux/pkeys.h>
+#include <linux/seq_buf.h>

#include <asm/pgtable.h>
#include <asm/io.h>
@@ -1300,7 +1301,9 @@ static void show_instructions(struct pt_regs *regs)
void show_user_instructions(struct pt_regs *regs)
{
unsigned long pc;
- int i;
+ int n = instructions_to_print;
+ struct seq_buf s;
+ char buf[96]; /* enough for 8 times 9 + 2 chars */

pc = regs->nip - (instructions_to_print * 3 / 4 * sizeof(int));

@@ -1314,29 +1317,27 @@ void show_user_instructions(struct pt_regs *regs)
return;
}

- pr_info("%s[%d]: code: ", current->comm, current->pid);
+ seq_buf_init(&s, buf, sizeof(buf));

- for (i = 0; i < instructions_to_print; i++) {
- int instr;
+ while (n) {
+ int i;

- if (!(i % 8) && (i > 0)) {
- pr_cont("\n");
- pr_info("%s[%d]: code: ", current->comm, current->pid);
- }
+ seq_buf_clear(&s);

- if (probe_kernel_address((const void *)pc, instr)) {
- pr_cont("XXXXXXXX ");
- } else {
- if (regs->nip == pc)
- pr_cont("<%08x> ", instr);
- else
- pr_cont("%08x ", instr);
+ for (i = 0; i < 8 && n; i++, n--, pc += sizeof(int)) {
+ int instr;
+
+ if (probe_kernel_address((const void *)pc, instr)) {
+ seq_buf_puts(&s, "XXXXXXXX ");
+ continue;
+ }
+ seq_buf_printf(&s, regs->nip == pc ? "<%08x> " : "%08x ", instr);
}

- pc += sizeof(int);
+ if (!seq_buf_has_overflowed(&s))
+ pr_info("%s[%d]: code: %s\n", current->comm,
+ current->pid, s.buffer);
}
-
- pr_cont("\n");
}

struct regbit {
--
2.13.3
\
 
 \ /
  Last update: 2018-10-06 18:52    [W:0.076 / U:4.260 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site