x86: Avoid pr_cont() in show_opcodes() (8e974b3b) · Commits · 戴 / test

If concurrent printk() messages are emitted, then pr_cont() is making it extremly hard to decode which part of the output belongs to what. See the convoluted example at: https://syzkaller.appspot.com/text?tag=CrashReport&x=139d342c400000 Avoid this by using a proper prefix for each line and by using %ph format in show_opcodes() which emits the 'Code:' line in one go. Signed-off-by:

Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by:

Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by:

Thomas Gleixner <tglx@linutronix.de> Acked-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Cc: joe@perches.com Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@suse.de> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lkml.kernel.org/r/1532009278-5953-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp

arch/x86/kernel/dumpstack.c

+9 −19

Original line number	Diff line number	Diff line
		@@ -22,8 +22,6 @@
		#include <asm/stacktrace.h>
		#include <asm/unwind.h>

		#define OPCODE_BUFSIZE 64

		int panic_on_unrecovered_nmi;
		int panic_on_io_nmi;
		static int die_counter;
		@@ -93,26 +91,18 @@ static void printk_stack_address(unsigned long address, int reliable,
		*/
		void show_opcodes(u8 rip, const char loglvl)
		{
		unsigned int code_prologue = OPCODE_BUFSIZE * 2 / 3;
		#define PROLOGUE_SIZE 42
		#define EPILOGUE_SIZE 21
		#define OPCODE_BUFSIZE (PROLOGUE_SIZE + 1 + EPILOGUE_SIZE)
		u8 opcodes[OPCODE_BUFSIZE];
		u8 *ip;
		int i;

		printk("%sCode: ", loglvl);

		ip = (u8 *)rip - code_prologue;
		if (probe_kernel_read(opcodes, ip, OPCODE_BUFSIZE)) {
		pr_cont("Bad RIP value.\n");
		return;
		}

		for (i = 0; i < OPCODE_BUFSIZE; i++, ip++) {
		if (ip == rip)
		pr_cont("<%02x> ", opcodes[i]);
		else
		pr_cont("%02x ", opcodes[i]);
		if (probe_kernel_read(opcodes, rip - PROLOGUE_SIZE, OPCODE_BUFSIZE)) {
		printk("%sCode: Bad RIP value.\n", loglvl);
		} else {
		printk("%sCode: %" __stringify(PROLOGUE_SIZE) "ph <%02x> %"
		__stringify(EPILOGUE_SIZE) "ph\n", loglvl, opcodes,
		opcodes[PROLOGUE_SIZE], opcodes + PROLOGUE_SIZE + 1);
		}
		pr_cont("\n");
		}

		void show_ip(struct pt_regs regs, const char loglvl)

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