From a806dad58c4cf752238d7bbffbc9a1ce17f63cea Mon Sep 17 00:00:00 2001 From: Jeenu Viswambharan Date: Wed, 30 Nov 2016 15:21:11 +0000 Subject: 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 Signed-off-by: Jeenu Viswambharan --- lib/psci/aarch32/psci_helpers.S | 2 +- lib/psci/aarch64/psci_helpers.S | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) (limited to 'lib/psci') diff --git a/lib/psci/aarch32/psci_helpers.S b/lib/psci/aarch32/psci_helpers.S index 36d5d7d9..27d651e3 100644 --- a/lib/psci/aarch32/psci_helpers.S +++ b/lib/psci/aarch32/psci_helpers.S @@ -176,5 +176,5 @@ endfunc do_stack_maintenance func psci_power_down_wfi dsb sy // ensure write buffer empty wfi - bl plat_panic_handler + no_ret plat_panic_handler endfunc psci_power_down_wfi diff --git a/lib/psci/aarch64/psci_helpers.S b/lib/psci/aarch64/psci_helpers.S index ff250a06..eaa17c72 100644 --- a/lib/psci/aarch64/psci_helpers.S +++ b/lib/psci/aarch64/psci_helpers.S @@ -167,7 +167,7 @@ endfunc psci_do_pwrup_cache_maintenance func psci_power_down_wfi dsb sy // ensure write buffer empty wfi - bl plat_panic_handler + no_ret plat_panic_handler endfunc psci_power_down_wfi /* ----------------------------------------------------------------------- -- cgit v1.2.3