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()") Cc: Murilo Opsfelder Araujo <muri...@linux.ibm.com> Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr> --- 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 e108e1ef2b85..2a39f7aca846 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> @@ -1303,33 +1304,33 @@ 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)); - 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