target/cortex_m: workaround Cortex-M7 erratum 3092511

When an asynchronous exception occurs at the same time
as a breakpoint event (either hardware breakpoint or software breakpoint),
it is possible for the processor to halt at the beginning of the
exception handler instead of the instruction address pointed
by the breakpoint.

During debug entry in exception handler state and with BKPT bit set
as the only break reason in DFSR, check if there is a breakpoint, which
have triggered the debug halt. If there is no such breakpoint,
resume execution. The processor services the interrupt and
halts again at the correct breakpoint address.

The workaround is not needed during target algo run (debug_execution)
because interrupts are disabled in PRIMASK register.

Also after single step the workaround resume never takes place:
the situation is treated as error.

Link: https://developer.arm.com/documentation/SDEN1068427/latest/
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Change-Id: I8b23f39cedd7dccabe7e7066d616fb972b69f769
Reviewed-on: https://review.openocd.org/c/openocd/+/8332
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-by: Liviu Ionescu

src/target/target.h

@@ -799,6 +799,7 @@ int target_profiling_default(struct target *target, uint32_t *samples, uint32_t
 #define ERROR_TARGET_ALGO_EXIT  (-313)
 #define ERROR_TARGET_SIZE_NOT_SUPPORTED  (-314)
 #define ERROR_TARGET_PACKING_NOT_SUPPORTED  (-315)
+#define ERROR_TARGET_HALTED_DO_RESUME  (-316)	/* used to workaround incorrect debug halt */
 
 extern bool get_target_reset_nag(void);