diff mbox series

[4.4,07/16] arm64: traps: Don't print stack or raw PC/LR values in backtraces

Message ID 20200423204014.784944-8-lee.jones@linaro.org
State New
Headers show
Series [4.4,01/16] drm/msm: stop abusing dma_map/unmap for cache | expand

Commit Message

Lee Jones April 23, 2020, 8:40 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 |  9 +++--
 arch/arm64/kernel/traps.c   | 72 ++-----------------------------------
 2 files changed, 7 insertions(+), 74 deletions(-)
diff mbox series

Patch

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 10d6627673cbf..2733b04900d1c 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -180,11 +180,10 @@  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);
+
 	for (i = top_reg; i >= 0; i--) {
 		printk("x%-2d: %016llx ", i, regs->regs[i]);
 		if (i % 2 == 0)
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 02710f99c1374..0cc78d60dac33 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -51,63 +51,9 @@  static const char *handler[]= {
 
 int show_unhandled_signals = 0;
 
-/*
- * Dump out the contents of some memory nicely...
- */
-static void dump_mem(const char *lvl, const char *str, unsigned long bottom,
-		     unsigned long top, bool compat)
-{
-	unsigned long first;
-	mm_segment_t fs;
-	int i;
-	unsigned int width = compat ? 4 : 8;
-
-	/*
-	 * 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 / width)
-					&& p < top; i++, p += width) {
-			if (p >= bottom && p < top) {
-				unsigned long val;
-
-				if (width == 8) {
-					if (__get_user(val, (unsigned long *)p) == 0)
-						sprintf(str + i * 17, " %016lx", val);
-					else
-						sprintf(str + i * 17, " ????????????????");
-				} else {
-					if (__get_user(val, (unsigned int *)p) == 0)
-						sprintf(str + i * 9, " %08lx", val);
-					else
-						sprintf(str + i * 9, " ????????");
-				}
-			}
-		}
-		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)
@@ -170,20 +116,11 @@  static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 	}
 
 	pr_emerg("Call trace:\n");
-	while (1) {
+	do {
 		unsigned long where = frame.pc;
-		unsigned long stack;
-		int ret;
 
 		dump_backtrace_entry(where);
-		ret = unwind_frame(&frame);
-		if (ret < 0)
-			break;
-		stack = frame.sp;
-		if (in_exception_text(where))
-			dump_mem("", "Exception stack", stack,
-				 stack + sizeof(struct pt_regs), false);
-	}
+	} while (!unwind_frame(&frame));
 }
 
 void show_stack(struct task_struct *tsk, unsigned long *sp)
@@ -220,9 +157,6 @@  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) || in_interrupt()) {
-		dump_mem(KERN_EMERG, "Stack: ", regs->sp,
-			 THREAD_SIZE + (unsigned long)task_stack_page(tsk),
-			 compat_user_mode(regs));
 		dump_backtrace(regs, tsk);
 		dump_instr(KERN_EMERG, regs);
 	}