Define and use no_ret macro where no return is expected
There are many instances in ARM Trusted Firmware where control is
transferred to functions from which return isn't expected. Such jumps
are made using 'bl' instruction to provide the callee with the location
from which it was jumped to. Additionally, debuggers infer the caller by
examining where 'lr' register points to. If a 'bl' of the nature
described above falls at the end of an assembly function, 'lr' will be
left pointing to a location outside of the function range. This misleads
the debugger back trace.
This patch defines a 'no_ret' macro to be used when jumping to functions
from which return isn't expected. The macro ensures to use 'bl'
instruction for the jump, and also, for debug builds, places a 'nop'
instruction immediately thereafter (unless instructed otherwise) so as
to leave 'lr' pointing within the function range.
Change-Id: Ib34c69fc09197cfd57bc06e147cc8252910e01b0
Co-authored-by: Douglas Raillard <douglas.raillard@arm.com>
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
diff --git a/common/aarch32/debug.S b/common/aarch32/debug.S
index 6be6951..cfce7ed 100644
--- a/common/aarch32/debug.S
+++ b/common/aarch32/debug.S
@@ -38,7 +38,7 @@
* The common implementation of do_panic for all BL stages
***********************************************************/
func do_panic
- b plat_panic_handler
+ no_ret plat_panic_handler
endfunc do_panic
/***********************************************************
@@ -50,5 +50,5 @@
mrs r0, cpsr
and r0, #MODE32_MASK
bl plat_report_exception
- bl plat_panic_handler
+ no_ret plat_panic_handler
endfunc report_exception