* [PATCH v4 2/3] powerpc/process: fix interleaved output in show_user_instructions()
2018-10-06 16:51 [PATCH v4 1/3] powerpc/process: fix casting and missing header Christophe Leroy
@ 2018-10-06 16:51 ` Christophe Leroy
2018-10-06 16:51 ` [PATCH v4 3/3] powerpc/process: Constify the number of insns printed by show instructions functions Christophe Leroy
2018-10-15 4:01 ` [v4,1/3] powerpc/process: fix casting and missing header Michael Ellerman
2 siblings, 0 replies; 4+ messages in thread
From: Christophe Leroy @ 2018-10-06 16:51 UTC (permalink / raw)
To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman, muriloo
Cc: linuxppc-dev, linux-kernel
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
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH v4 3/3] powerpc/process: Constify the number of insns printed by show instructions functions.
2018-10-06 16:51 [PATCH v4 1/3] powerpc/process: fix casting and missing header Christophe Leroy
2018-10-06 16:51 ` [PATCH v4 2/3] powerpc/process: fix interleaved output in show_user_instructions() Christophe Leroy
@ 2018-10-06 16:51 ` Christophe Leroy
2018-10-15 4:01 ` [v4,1/3] powerpc/process: fix casting and missing header Michael Ellerman
2 siblings, 0 replies; 4+ messages in thread
From: Christophe Leroy @ 2018-10-06 16:51 UTC (permalink / raw)
To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman, muriloo
Cc: linuxppc-dev, linux-kernel
instructions_to_print var is assigned value 16 and there is no
way to change it.
This patch replaces it by a constant.
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: no change
arch/powerpc/kernel/process.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 8dabf656d924..dd8447d3f0bf 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1258,17 +1258,16 @@ struct task_struct *__switch_to(struct task_struct *prev,
return last;
}
-static int instructions_to_print = 16;
+#define NR_INSN_TO_PRINT 16
static void show_instructions(struct pt_regs *regs)
{
int i;
- unsigned long pc = regs->nip - (instructions_to_print * 3 / 4 *
- sizeof(int));
+ unsigned long pc = regs->nip - (NR_INSN_TO_PRINT * 3 / 4 * sizeof(int));
printk("Instruction dump:");
- for (i = 0; i < instructions_to_print; i++) {
+ for (i = 0; i < NR_INSN_TO_PRINT; i++) {
int instr;
if (!(i % 8))
@@ -1301,17 +1300,17 @@ static void show_instructions(struct pt_regs *regs)
void show_user_instructions(struct pt_regs *regs)
{
unsigned long pc;
- int n = instructions_to_print;
+ int n = NR_INSN_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));
+ pc = regs->nip - (NR_INSN_TO_PRINT * 3 / 4 * sizeof(int));
/*
* Make sure the NIP points at userspace, not kernel text/data or
* elsewhere.
*/
- if (!__access_ok(pc, instructions_to_print * sizeof(int), USER_DS)) {
+ if (!__access_ok(pc, NR_INSN_TO_PRINT * sizeof(int), USER_DS)) {
pr_info("%s[%d]: Bad NIP, not dumping instructions.\n",
current->comm, current->pid);
return;
--
2.13.3
^ permalink raw reply related [flat|nested] 4+ messages in thread