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From: "tarek.bouchkati at gmail dot com" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug gdb/28549] ARM/Cortex-M: improper stack unwinding when the
 target is in lockup state
Date: Fri, 05 Nov 2021 10:59:15 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D28549

--- Comment #2 from Tarek BOCHKATI <tarek.bouchkati at gmail dot com> ---
according to ARM: ref https://developer.arm.com/documentation/ka001181/late=
st

quote:
 > During LOCKUP, the PC will be forced to 0xFFFFFFFx and will keep fetching
from that address

applying this minor change to test the theory seem to work perfectly:

diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 5b60831bbe9..930eba7155e 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -543,6 +543,7 @@ arm_m_addr_is_magic (CORE_ADDR addr)
 {
   switch (addr)
     {
+      case 0xfffffffe:
       /* Values from ARMv8-M Architecture Technical Reference.  */
       case 0xffffffb0:
       case 0xffffffb8:



now gdb reports:

(gdb) tar ext :3333
Remote debugging using :3333
warning: No executable has been specified and target does not support
determining executable automatically.  Try using the "file" command.
<signal handler called>
(gdb) c
Continuing.
stm32h7x.cpu0 -- clearing lockup after double fault

Program received signal SIGINT, Interrupt.
<signal handler called>
(gdb)

--=20
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