From 0e76a16545873e519ca0b51f7acccbe673a8ebbb Mon Sep 17 00:00:00 2001
From: YAMAMOTO Takashi <yamamoto@midokura.com>
Date: Thu, 24 Jun 2021 18:17:05 +0900
Subject: [PATCH] tools/esp32/backtrace.gdbscript: don't modify registers

* it wasn't intended.

* it doesn't always work:

    (gdb) source tools/esp32/backtrace.gdbscript
    (gdb) esp32_bt 0x40139706 0x80139811 0x3ffafd40
    Attempt to assign to an unmodifiable value.
    (gdb)
---
 tools/esp32/backtrace.gdbscript | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/tools/esp32/backtrace.gdbscript b/tools/esp32/backtrace.gdbscript
index c38cf3049a3..5f825eee75c 100644
--- a/tools/esp32/backtrace.gdbscript
+++ b/tools/esp32/backtrace.gdbscript
@@ -54,19 +54,19 @@
 #   4.7.1.5 Windowed Procedure-Call Protocol
 
 define esp32_bt
-    set $pc = $arg0
-    set $a0 = $arg1
-    set $a1 = $arg2
-    set $pc_topbits = (int)$pc & 0xc0000000
+    set $x_pc = $arg0
+    set $x_a0 = $arg1
+    set $x_a1 = $arg2
+    set $pc_topbits = (int)$x_pc & 0xc0000000
     # The return address from xtensa_sig_deliver to _xtensa_sig_trampoline
     set $sig_tramp_ra = (int)(_xtensa_sig_trampoline + 2 * 3)
-    print/a $pc
+    print/a $x_pc
     while (1)
         # Note: "- 3" to workaround the case where "call" is
         # the last instruction in the calling function.
-        set $next_pc = (($a0 & 0x3fffffff) | $pc_topbits) - 3
+        set $next_pc = (($x_a0 & 0x3fffffff) | $pc_topbits) - 3
         print/a $next_pc
-        if ($a0 == $sig_tramp_ra)
+        if ($x_a0 == $sig_tramp_ra)
             # A special logic for xtensa_sig_deliver
 
             print "--- SIGNAL ---"
@@ -77,14 +77,14 @@ define esp32_bt
             print/a $next_pc
 
             # XXX local var offset assumption
-            set $regs = (int *)$a1
+            set $regs = (int *)$x_a1
 
             # Note: REG_A0 == 2
             # Note: REG_A1 == 3
             set $next_a0 = $regs[2]
             set $next_a1 = $regs[3]
         else
-            set $next_bsa = (int *)($a1 - 16)
+            set $next_bsa = (int *)($x_a1 - 16)
             set $next_a0 = $next_bsa[0]
             set $next_a1 = $next_bsa[1]
         end
@@ -95,11 +95,11 @@ define esp32_bt
             # on the stack must be explicitly set to zero."
             loop_break
         end
-        if ($next_a1 <= $a1)
+        if ($next_a1 <= $x_a1)
             print "stack went backward. corrupted?"
             loop_break
         end
-        set $a0 = $next_a0
-        set $a1 = $next_a1
+        set $x_a0 = $next_a0
+        set $x_a1 = $next_a1
     end
 end