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: Laura Abbott <labbott@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 2dc0f84822109b542e21d71deba5206b624f4fc6..c20896b8fb2df812eb366a934e9ad948ab50b33d 100644 (file)
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -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;
 

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index a1b7d6420d09ec23651b21f96358273a5fda506e..afb6b19677dc2eae5430235ae73bd9b8c6f3a541 100644 (file)
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -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);
 }