arm64: print instructions leading to exception

If an exception occurs in a loaded image and the relocation offset is
unknown, it is helpful to know the instructions pointed to by the
program counter. This patch adds the missing output.

A possible output is:
    Code: 910c4021 aa1303e0 f9400662 d63f0040 (e7f7defb)

The parentheses indicate the instruction causing the exception.

The output can be disassembled using scripts/decodecode:

echo 'Code: 90000360 9100b800 94002782 17ffff8f (e7f7defb)' | \
  ARCH=arm64 scripts/decodecode

Code: 90000360 9100b800 94002782 17ffff8f (e7f7defb)
All code
========
   0:   90000360    adrp    x0, 0x6c000
   4:   9100b800    add     x0, x0, #0x2e
   8:   94002782    bl      0x9e10
   c:   17ffff8f    b       0xfffffffffffffe48
  10:*  e7f7defb    .inst   0xe7f7defb ; undefined <-- trapping instruction

Code starting with the faulting instruction
===========================================
   0:   e7f7defb    .inst   0xe7f7defb ; undefined

We already have implemented the same for armv7.

For testing command 'exception undefined' can be used.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

diff --git a/arch/arm/lib/interrupts_64.c b/arch/arm/lib/interrupts_64.c
index 0bfdb8d93d256656d8fc2f5969d51fec56c47ef3..a32a4b68684764423fd480a03d7705d3aa2f955f 100644 (file)
--- a/arch/arm/lib/interrupts_64.c
+++ b/arch/arm/lib/interrupts_64.c
@@ -30,6 +30,17 @@ static void show_efi_loaded_images(struct pt_regs *regs)
        efi_print_image_infos((void *)regs->elr);
 }
 
+static void dump_instr(struct pt_regs *regs)
+{
+       u32 *addr = (u32 *)(regs->elr & ~3UL);
+       int i;
+
+       printf("Code: ");
+       for (i = -4; i < 1; i++)
+               printf(i == 0 ? "(%08x) " : "%08x ", addr[i]);
+       printf("\n");
+}
+
 void show_regs(struct pt_regs *regs)
 {
        int i;
@@ -44,6 +55,7 @@ void show_regs(struct pt_regs *regs)
                printf("x%-2d: %016lx x%-2d: %016lx\n",
                       i, regs->regs[i], i+1, regs->regs[i+1]);
        printf("\n");
+       dump_instr(regs);
 }
 
 /*