diff mbox series

[4.9,09/24] arm64: traps: Don't print stack or raw PC/LR values in backtraces

Message ID 20200402191747.789097-9-lee.jones@linaro.org
State New
Headers show
Series [4.9,01/24] clk: qcom: rcg: Return failure for RCG update | expand

Commit Message

Lee Jones April 2, 2020, 7:17 p.m. UTC 
From: Will Deacon <will.deacon@arm.com>

[ Upstream commit a25ffd3a6302a67814280274d8f1aa4ae2ea4b59 ]

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: Laura Abbott <labbott@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
 arch/arm64/kernel/process.c |  8 ++--
 arch/arm64/kernel/traps.c   | 74 ++-----------------------------------
 2 files changed, 6 insertions(+), 76 deletions(-)
diff mbox series

Patch

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index e917d119490ce..6b073a31eec1c 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -182,11 +182,9 @@  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;
 
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 5962badb33462..ac73d8d8cd81d 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -52,55 +52,9 @@  static const char *handler[]= {
 
 int show_unhandled_signals = 0;
 
-/*
- * 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)
@@ -174,10 +128,8 @@  static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 
 	skip = !!regs;
 	printk("Call trace:\n");
-	while (1) {
+	do {
 		unsigned long where = frame.pc;
-		unsigned long stack;
-		int ret;
 
 		/* skip until specified stack frame */
 		if (!skip) {
@@ -193,25 +145,7 @@  static 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;
-		stack = frame.sp;
-		if (in_exception_text(where)) {
-			/*
-			 * If we switched to the irq_stack before calling this
-			 * exception handler, then the pt_regs will be on the
-			 * task stack. The easiest way to tell is if the large
-			 * pt_regs would overlap with the end of the irq_stack.
-			 */
-			if (stack < irq_stack_ptr &&
-			    (stack + sizeof(struct pt_regs)) > irq_stack_ptr)
-				stack = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
-
-			dump_mem("", "Exception stack", stack,
-				 stack + sizeof(struct pt_regs));
-		}
-	}
+	} while (!unwind_frame(tsk, &frame));
 }
 
 void show_stack(struct task_struct *tsk, unsigned long *sp)
@@ -248,8 +182,6 @@  static int __die(const char *str, int err, struct thread_info *thread,
 		 TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk), thread + 1);
 
 	if (!user_mode(regs)) {
-		dump_mem(KERN_EMERG, "Stack: ", regs->sp,
-			 THREAD_SIZE + (unsigned long)task_stack_page(tsk));
 		dump_backtrace(regs, tsk);
 		dump_instr(KERN_EMERG, regs);
 	}