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Commit a25ffd3a authored by Will Deacon's avatar Will Deacon
Browse files

arm64: traps: Don't print stack or raw PC/LR values in backtraces 



Printing raw pointer values in backtraces has potential security
implications and are of questionable value anyway.

This patch follows x86's lead and removes the "Exception stack:" dump
from kernel backtraces, as well as converting PC/LR values to symbols
such as "sysrq_handle_crash+0x20/0x30".

Tested-by: default avatarLaura Abbott <labbott@redhat.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 42dbf54e

arch/arm64/kernel/process.c

+3 −5
Original line number Diff line number Diff line
@@ -186,11 +186,9 @@ void __show_regs(struct pt_regs *regs) 
	}



	show_regs_print_info(KERN_DEFAULT);

	print_symbol("PC is at %s\n", instruction_pointer(regs));

	print_symbol("LR is at %s\n", lr);

	printk("pc : [<%016llx>] lr : [<%016llx>] pstate: %08llx\n",

	       regs->pc, lr, regs->pstate);

	printk("sp : %016llx\n", sp);

	print_symbol("pc : %s\n", regs->pc);

	print_symbol("lr : %s\n", lr);

	printk("sp : %016llx pstate : %08llx\n", sp, regs->pstate);



	i = top_reg;

arch/arm64/kernel/traps.c

+3 −62
Original line number Diff line number Diff line
@@ -58,55 +58,9 @@ static const char *handler[]= { 


int show_unhandled_signals = 1;



/*

 * Dump out the contents of some kernel memory nicely...

 */

static void dump_mem(const char *lvl, const char *str, unsigned long bottom,

		     unsigned long top)

{

	unsigned long first;

	mm_segment_t fs;

	int i;



	/*

	 * We need to switch to kernel mode so that we can use __get_user

	 * to safely read from kernel space.

	 */

	fs = get_fs();

	set_fs(KERNEL_DS);



	printk("%s%s(0x%016lx to 0x%016lx)\n", lvl, str, bottom, top);



	for (first = bottom & ~31; first < top; first += 32) {

		unsigned long p;

		char str[sizeof(" 12345678") * 8 + 1];



		memset(str, ' ', sizeof(str));

		str[sizeof(str) - 1] = '\0';



		for (p = first, i = 0; i < (32 / 8)

					&& p < top; i++, p += 8) {

			if (p >= bottom && p < top) {

				unsigned long val;



				if (__get_user(val, (unsigned long *)p) == 0)

					sprintf(str + i * 17, " %016lx", val);

				else

					sprintf(str + i * 17, " ????????????????");

			}

		}

		printk("%s%04lx:%s\n", lvl, first & 0xffff, str);

	}



	set_fs(fs);

}



static void dump_backtrace_entry(unsigned long where)

{

	/*

	 * Note that 'where' can have a physical address, but it's not handled.

	 */

	print_ip_sym(where);

	printk(" %pS\n", (void *)where);

}



static void __dump_instr(const char *lvl, struct pt_regs *regs)
@@ -171,10 +125,7 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) 


	skip = !!regs;

	printk("Call trace:\n");

	while (1) {

		unsigned long stack;

		int ret;



	do {

		/* skip until specified stack frame */

		if (!skip) {

			dump_backtrace_entry(frame.pc);
@@ -189,17 +140,7 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) 
			 */

			dump_backtrace_entry(regs->pc);

		}

		ret = unwind_frame(tsk, &frame);

		if (ret < 0)

			break;

		if (in_entry_text(frame.pc)) {

			stack = frame.fp - offsetof(struct pt_regs, stackframe);



			if (on_accessible_stack(tsk, stack))

				dump_mem("", "Exception stack", stack,

					 stack + sizeof(struct pt_regs));

		}

	}

	} while (!unwind_frame(tsk, &frame));



	put_task_stack(tsk);

}