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>

3 files changed, 19 insertions, 19 deletions

diff --git a/common/aarch32/debug.S b/common/aarch32/debug.S
index 6be69512..cfce7ed9 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 @@ func report_exception
 	mrs	r0, cpsr
 	and	r0, #MODE32_MASK
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 endfunc report_exception
diff --git a/common/aarch64/debug.S b/common/aarch64/debug.S
index d3538792..9dd53ca9 100644
--- a/common/aarch64/debug.S
+++ b/common/aarch64/debug.S
@@ -191,5 +191,5 @@ _panic_handler:
 	/* Pass to plat_panic_handler the address from where el3_panic was
 	 * called, not the address of the call from el3_panic. */
 	mov	x30,x6
-	b	plat_panic_handler
+	no_ret	plat_panic_handler
 endfunc do_panic
diff --git a/common/aarch64/early_exceptions.S b/common/aarch64/early_exceptions.S
index ad5b4d86..be214596 100644
--- a/common/aarch64/early_exceptions.S
+++ b/common/aarch64/early_exceptions.S
@@ -47,25 +47,25 @@ vector_base early_exceptions
 vector_entry SynchronousExceptionSP0
 	mov	x0, #SYNC_EXCEPTION_SP_EL0
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size SynchronousExceptionSP0
 
 vector_entry IrqSP0
 	mov	x0, #IRQ_SP_EL0
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size IrqSP0
 
 vector_entry FiqSP0
 	mov	x0, #FIQ_SP_EL0
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size FiqSP0
 
 vector_entry SErrorSP0
 	mov	x0, #SERROR_SP_EL0
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size SErrorSP0
 
 	/* -----------------------------------------------------
@@ -75,25 +75,25 @@ vector_entry SErrorSP0
 vector_entry SynchronousExceptionSPx
 	mov	x0, #SYNC_EXCEPTION_SP_ELX
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size SynchronousExceptionSPx
 
 vector_entry IrqSPx
 	mov	x0, #IRQ_SP_ELX
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size IrqSPx
 
 vector_entry FiqSPx
 	mov	x0, #FIQ_SP_ELX
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size FiqSPx
 
 vector_entry SErrorSPx
 	mov	x0, #SERROR_SP_ELX
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size SErrorSPx
 
 	/* -----------------------------------------------------
@@ -103,25 +103,25 @@ vector_entry SErrorSPx
 vector_entry SynchronousExceptionA64
 	mov	x0, #SYNC_EXCEPTION_AARCH64
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size SynchronousExceptionA64
 
 vector_entry IrqA64
 	mov	x0, #IRQ_AARCH64
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size IrqA64
 
 vector_entry FiqA64
 	mov	x0, #FIQ_AARCH64
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size FiqA64
 
 vector_entry SErrorA64
 	mov	x0, #SERROR_AARCH64
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size SErrorA64
 
 	/* -----------------------------------------------------
@@ -131,23 +131,23 @@ vector_entry SErrorA64
 vector_entry SynchronousExceptionA32
 	mov	x0, #SYNC_EXCEPTION_AARCH32
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size SynchronousExceptionA32
 
 vector_entry IrqA32
 	mov	x0, #IRQ_AARCH32
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size IrqA32
 
 vector_entry FiqA32
 	mov	x0, #FIQ_AARCH32
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size FiqA32
 
 vector_entry SErrorA32
 	mov	x0, #SERROR_AARCH32
 	bl	plat_report_exception
-	bl	plat_panic_handler
+	no_ret	plat_panic_handler
 	check_vector_size SErrorA32