* Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> wrote:
> From: Tetsuo Handa <penguin-ker...@i-love.skaura.ne.jp> > > Since syzbot is confused by concurrent printk() messages [1], > this patch changes show_opcodes() to use snprintf(). > > When we start adding prefix to each line of printk() output, > we will be able to handle concurrent printk() messages. > > [1] https://syzkaller.appspot.com/text?tag=CrashReport&x=139d342c400000 > > Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.skaura.ne.jp> > Cc: Borislav Petkov <b...@suse.de> > Cc: Thomas Gleixner <t...@linutronix.de> > Cc: Peter Zijlstra <pet...@infradead.org> > Cc: Josh Poimboeuf <jpoim...@redhat.com> > Cc: Linus Torvalds <torva...@linux-foundation.org> > Cc: Andy Lutomirski <l...@amacapital.net> > --- > arch/x86/kernel/dumpstack.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c > index 666a284..bb47426 100644 > --- a/arch/x86/kernel/dumpstack.c > +++ b/arch/x86/kernel/dumpstack.c > @@ -97,22 +97,24 @@ void show_opcodes(u8 *rip, const char *loglvl) > u8 opcodes[OPCODE_BUFSIZE]; > u8 *ip; > int i; > - > - printk("%sCode: ", loglvl); > + int pos = 0; > + char buf[(3 * OPCODE_BUFSIZE + 2) + 1]; > > ip = (u8 *)rip - code_prologue; > if (probe_kernel_read(opcodes, ip, OPCODE_BUFSIZE)) { > - pr_cont("Bad RIP value.\n"); > + printk("%sCode: Bad RIP value.\n", loglvl); > return; > } > > for (i = 0; i < OPCODE_BUFSIZE; i++, ip++) { > if (ip == rip) > - pr_cont("<%02x> ", opcodes[i]); > + pos += snprintf(buf + pos, sizeof(buf) - pos, > + "<%02x> ", opcodes[i]); > else > - pr_cont("%02x ", opcodes[i]); > + pos += snprintf(buf + pos, sizeof(buf) - pos, > + "%02x ", opcodes[i]); > } > - pr_cont("\n"); > + printk("%sCode: %s\n", loglvl, buf); Does this change the output? - If yes, could you show the before/after output in the changelog, - If not (i.e. if only the number of printk calls is changed, the output is the same), could you say so in the changelog? Also, 3*OPCODE_BUFSIZE+2+1 is 195 bytes - isn't that a bit too much on-stack footprint? Thanks, Ingo
