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Commit 83163856 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'x86-debug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull x86 debug updates from Ingo Molnar:
 "This contains the x86 oops code printing reorganization and cleanups
  from Borislav Betkov, with a particular focus in enhancing opcode
  dumping all around"

* 'x86-debug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/dumpstack: Explain the reasoning for the prologue and buffer size
  x86/dumpstack: Save first regs set for the executive summary
  x86/dumpstack: Add a show_ip() function
  x86/fault: Dump user opcode bytes on fatal faults
  x86/dumpstack: Add loglevel argument to show_opcodes()
  x86/dumpstack: Improve opcodes dumping in the code section
  x86/dumpstack: Carve out code-dumping into a function
  x86/dumpstack: Unexport oops_begin()
  x86/dumpstack: Remove code_bytes
parents 0afe832e 4dba072c

Documentation/admin-guide/kernel-parameters.txt

+0 −5
Original line number Diff line number Diff line
@@ -587,11 +587,6 @@ 
			Sets the size of memory pool for coherent, atomic dma

			allocations, by default set to 256K.



	code_bytes	[X86] How many bytes of object code to print

			in an oops report.

			Range: 0 - 8192

			Default: 64



	com20020=	[HW,NET] ARCnet - COM20020 chipset

			Format:

			<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]

arch/x86/include/asm/stacktrace.h

+2 −0
Original line number Diff line number Diff line
@@ -111,4 +111,6 @@ static inline unsigned long caller_frame_pointer(void) 
	return (unsigned long)frame;

}



void show_opcodes(u8 *rip, const char *loglvl);

void show_ip(struct pt_regs *regs, const char *loglvl);

#endif /* _ASM_X86_STACKTRACE_H */

arch/x86/kernel/dumpstack.c

+70 −74
Original line number Diff line number Diff line
@@ -22,11 +22,14 @@ 
#include <asm/stacktrace.h>

#include <asm/unwind.h>



#define OPCODE_BUFSIZE 64



int panic_on_unrecovered_nmi;

int panic_on_io_nmi;

static unsigned int code_bytes = 64;

static int die_counter;



static struct pt_regs exec_summary_regs;



bool in_task_stack(unsigned long *stack, struct task_struct *task,

		   struct stack_info *info)

{
@@ -69,9 +72,62 @@ static void printk_stack_address(unsigned long address, int reliable, 
	printk("%s %s%pB\n", log_lvl, reliable ? "" : "? ", (void *)address);

}



/*

 * There are a couple of reasons for the 2/3rd prologue, courtesy of Linus:

 *

 * In case where we don't have the exact kernel image (which, if we did, we can

 * simply disassemble and navigate to the RIP), the purpose of the bigger

 * prologue is to have more context and to be able to correlate the code from

 * the different toolchains better.

 *

 * In addition, it helps in recreating the register allocation of the failing

 * kernel and thus make sense of the register dump.

 *

 * What is more, the additional complication of a variable length insn arch like

 * x86 warrants having longer byte sequence before rIP so that the disassembler

 * can "sync" up properly and find instruction boundaries when decoding the

 * opcode bytes.

 *

 * Thus, the 2/3rds prologue and 64 byte OPCODE_BUFSIZE is just a random

 * guesstimate in attempt to achieve all of the above.

 */

void show_opcodes(u8 *rip, const char *loglvl)

{

	unsigned int code_prologue = OPCODE_BUFSIZE * 2 / 3;

	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]);

	}

	pr_cont("\n");

}



void show_ip(struct pt_regs *regs, const char *loglvl)

{

#ifdef CONFIG_X86_32

	printk("%sEIP: %pS\n", loglvl, (void *)regs->ip);

#else

	printk("%sRIP: %04x:%pS\n", loglvl, (int)regs->cs, (void *)regs->ip);

#endif

	show_opcodes((u8 *)regs->ip, loglvl);

}



void show_iret_regs(struct pt_regs *regs)

{

	printk(KERN_DEFAULT "RIP: %04x:%pS\n", (int)regs->cs, (void *)regs->ip);

	show_ip(regs, KERN_DEFAULT);

	printk(KERN_DEFAULT "RSP: %04x:%016lx EFLAGS: %08lx", (int)regs->ss,

		regs->sp, regs->flags);

}
@@ -267,7 +323,6 @@ unsigned long oops_begin(void) 
	bust_spinlocks(1);

	return flags;

}

EXPORT_SYMBOL_GPL(oops_begin);

NOKPROBE_SYMBOL(oops_begin);



void __noreturn rewind_stack_do_exit(int signr);
@@ -287,6 +342,9 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr) 
	raw_local_irq_restore(flags);

	oops_exit();



	/* Executive summary in case the oops scrolled away */

	__show_regs(&exec_summary_regs, true);



	if (!signr)

		return;

	if (in_interrupt())
@@ -305,10 +363,10 @@ NOKPROBE_SYMBOL(oops_end); 


int __die(const char *str, struct pt_regs *regs, long err)

{

#ifdef CONFIG_X86_32

	unsigned short ss;

	unsigned long sp;

#endif

	/* Save the regs of the first oops for the executive summary later. */

	if (!die_counter)

		exec_summary_regs = *regs;



	printk(KERN_DEFAULT

	       "%s: %04lx [#%d]%s%s%s%s%s\n", str, err & 0xffff, ++die_counter,

	       IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT"         : "",
@@ -318,26 +376,13 @@ int __die(const char *str, struct pt_regs *regs, long err) 
	       IS_ENABLED(CONFIG_PAGE_TABLE_ISOLATION) ?

	       (boot_cpu_has(X86_FEATURE_PTI) ? " PTI" : " NOPTI") : "");



	show_regs(regs);

	print_modules();



	if (notify_die(DIE_OOPS, str, regs, err,

			current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP)

		return 1;



	print_modules();

	show_regs(regs);

#ifdef CONFIG_X86_32

	if (user_mode(regs)) {

		sp = regs->sp;

		ss = regs->ss;

	} else {

		sp = kernel_stack_pointer(regs);

		savesegment(ss, ss);

	}

	printk(KERN_EMERG "EIP: %pS SS:ESP: %04x:%08lx\n",

	       (void *)regs->ip, ss, sp);

#else

	/* Executive summary in case the oops scrolled away */

	printk(KERN_ALERT "RIP: %pS RSP: %016lx\n", (void *)regs->ip, regs->sp);

#endif

	return 0;

}

NOKPROBE_SYMBOL(__die);
@@ -356,30 +401,9 @@ void die(const char *str, struct pt_regs *regs, long err) 
	oops_end(flags, regs, sig);

}



static int __init code_bytes_setup(char *s)

{

	ssize_t ret;

	unsigned long val;



	if (!s)

		return -EINVAL;



	ret = kstrtoul(s, 0, &val);

	if (ret)

		return ret;



	code_bytes = val;

	if (code_bytes > 8192)

		code_bytes = 8192;



	return 1;

}

__setup("code_bytes=", code_bytes_setup);



void show_regs(struct pt_regs *regs)

{

	bool all = true;

	int i;



	show_regs_print_info(KERN_DEFAULT);
@@ -389,36 +413,8 @@ void show_regs(struct pt_regs *regs) 
	__show_regs(regs, all);



	/*

	 * When in-kernel, we also print out the stack and code at the

	 * time of the fault..

	 * When in-kernel, we also print out the stack at the time of the fault..

	 */

	if (!user_mode(regs)) {

		unsigned int code_prologue = code_bytes * 43 / 64;

		unsigned int code_len = code_bytes;

		unsigned char c;

		u8 *ip;



	if (!user_mode(regs))

		show_trace_log_lvl(current, regs, NULL, KERN_DEFAULT);



		printk(KERN_DEFAULT "Code: ");



		ip = (u8 *)regs->ip - code_prologue;

		if (ip < (u8 *)PAGE_OFFSET || probe_kernel_address(ip, c)) {

			/* try starting at IP */

			ip = (u8 *)regs->ip;

			code_len = code_len - code_prologue + 1;

		}

		for (i = 0; i < code_len; i++, ip++) {

			if (ip < (u8 *)PAGE_OFFSET ||

					probe_kernel_address(ip, c)) {

				pr_cont(" Bad RIP value.");

				break;

			}

			if (ip == (u8 *)regs->ip)

				pr_cont("<%02x> ", c);

			else

				pr_cont("%02x ", c);

		}

	}

	pr_cont("\n");

}

arch/x86/kernel/process_32.c

+3 −5
Original line number Diff line number Diff line
@@ -76,16 +76,14 @@ void __show_regs(struct pt_regs *regs, int all) 
		savesegment(gs, gs);

	}



	printk(KERN_DEFAULT "EIP: %pS\n", (void *)regs->ip);

	printk(KERN_DEFAULT "EFLAGS: %08lx CPU: %d\n", regs->flags,

		raw_smp_processor_id());

	show_ip(regs, KERN_DEFAULT);



	printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",

		regs->ax, regs->bx, regs->cx, regs->dx);

	printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",

		regs->si, regs->di, regs->bp, sp);

	printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",

	       (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);

	printk(KERN_DEFAULT "DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x EFLAGS: %08lx\n",

	       (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss, regs->flags);



	if (!all)

		return;

arch/x86/mm/fault.c

+5 −2
Original line number Diff line number Diff line
@@ -829,6 +829,8 @@ static inline void 
show_signal_msg(struct pt_regs *regs, unsigned long error_code,

		unsigned long address, struct task_struct *tsk)

{

	const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG;



	if (!unhandled_signal(tsk, SIGSEGV))

		return;
@@ -836,13 +838,14 @@ show_signal_msg(struct pt_regs *regs, unsigned long error_code, 
		return;



	printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx",

		task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,

		tsk->comm, task_pid_nr(tsk), address,

		loglvl, tsk->comm, task_pid_nr(tsk), address,

		(void *)regs->ip, (void *)regs->sp, error_code);



	print_vma_addr(KERN_CONT " in ", regs->ip);



	printk(KERN_CONT "\n");



	show_opcodes((u8 *)regs->ip, loglvl);

}



static void