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Commit fb2d9505 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

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: 88b0fe17 ("powerpc: Add show_user_instructions()")
Reviewed-by: default avatarMurilo Opsfelder Araujo <muriloo@linux.ibm.com>
Signed-off-by: default avatarChristophe Leroy <christophe.leroy@c-s.fr>
[mpe: Use seq_buf_printf() not seq_buf_puts() which doesn't NULL terminate]
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent c9386bfd

arch/powerpc/kernel/process.c

+19 −18
Original line number Diff line number Diff line
@@ -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);



		for (i = 0; i < 8 && n; i++, n--, pc += sizeof(int)) {

			int instr;



			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);

				seq_buf_printf(&s, "XXXXXXXX ");

				continue;

			}



		pc += sizeof(int);

			seq_buf_printf(&s, regs->nip == pc ? "<%08x> " : "%08x ", instr);

		}



	pr_cont("\n");

		if (!seq_buf_has_overflowed(&s))

			pr_info("%s[%d]: code: %s\n", current->comm,

				current->pid, s.buffer);

	}

}



struct regbit {