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powerpc/process: Fix interleaved output in show_user_instructions() 

When two processes crash at the same time, we sometimes encounter
interleaving in the middle of a line:

  init[1]: segfault (11) at 0 nip 0 lr 0 code 1
  init[1]: code: XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
  init[74]: segfault (11) at 10a74 nip 1000c198 lr 100078c8 code 1 in sh[10000000+14000]
  XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
  init[1]: code: XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
  init[74]: code: 90010024 bf61000c 91490a7c 3fa01002 3be00000 7d3e4b78 3bbd0c20 3b600000
  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: 88b0fe1757 ("powerpc: Add show_user_instructions()")
Reviewed-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
[mpe: Use seq_buf_printf() not seq_buf_puts() which doesn't NULL terminate]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Christophe Leroy 2018-10-06 16:51:14 +00:00 committed by Michael Ellerman
parent c9386bfd37
commit fb2d9505c0
1 changed files with 20 additions and 19 deletions
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35
arch/powerpc/kernel/process.c
View File

@ -43,6 +43,7 @@
#include <linux/uaccess.h> #include <linux/uaccess.h>
#include <linux/elf-randomize.h> #include <linux/elf-randomize.h>
#include <linux/pkeys.h> #include <linux/pkeys.h>
#include <linux/seq_buf.h>
#include <asm/pgtable.h> #include <asm/pgtable.h>
#include <asm/io.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) void show_user_instructions(struct pt_regs *regs)
{ {
unsigned long pc; 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)); pc = regs->nip - (instructions_to_print * 3 / 4 * sizeof(int));
@ -1314,29 +1317,27 @@ void show_user_instructions(struct pt_regs *regs)
return; 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++) { while (n) {
int i;
seq_buf_clear(&s);
for (i = 0; i < 8 && n; i++, n--, pc += sizeof(int)) {
int instr; int instr;
if (!(i % 8) && (i > 0)) {
pr_cont("\n");
pr_info("%s[%d]: code: ", current->comm, current->pid);
}
if (probe_kernel_address((const void *)pc, instr)) { if (probe_kernel_address((const void *)pc, instr)) {
pr_cont("XXXXXXXX "); seq_buf_printf(&s, "XXXXXXXX ");
} else { continue;
if (regs->nip == pc) }
pr_cont("<%08x> ", instr); seq_buf_printf(&s, regs->nip == pc ? "<%08x> " : "%08x ", instr);
else
pr_cont("%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 { struct regbit {