[gcc(refs/vendors/ARM/heads/morello)] Add a capability version of the crti.S and crtn.S files

[Matthew Malcomson <matmal01@gcc.gnu.org>]

https://gcc.gnu.org/g:3d93394b6134556de82bb8ae9e7b9e10faa6d93d

commit 3d93394b6134556de82bb8ae9e7b9e10faa6d93d
Author: Matthew Malcomson <matthew.malcomson@arm.com>
Date:   Mon Aug 9 10:51:00 2021 +0100

    Add a capability version of the crti.S and crtn.S files
    
    These files define the FUNC_START and FUNC_END macros to implement the
    function prologues and epilogues for the .init and .fini sections.
    
    It seems the implementation in libgcc is just to save the callee-saved
    registers, so we simply do that for the pure capability version too.

Diff:
---
 libgcc/config/aarch64/crti.S | 17 +++++++++++++++++
 libgcc/config/aarch64/crtn.S | 19 +++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/libgcc/config/aarch64/crti.S b/libgcc/config/aarch64/crti.S
index b105b93756c..bd4697f5b04 100644
--- a/libgcc/config/aarch64/crti.S
+++ b/libgcc/config/aarch64/crti.S
@@ -37,6 +37,22 @@
 #define TYPE(x)
 #endif
 
+#ifdef __CHERI_PURE_CAPABILITY__
+
+	# Note - this macro is complemented by the FUNC_END macro
+	# in crtn.S.  If you change this macro you must also change
+	# that macro to match.
+.macro FUNC_START
+	#  Create a stack frame and save any call-preserved registers
+	stp	c29, c30, [csp, #-32]!
+	stp	c27, c28, [csp, #-32]!
+	stp	c25, c26, [csp, #-32]!
+	stp	c23, c24, [csp, #-32]!
+	stp	c21, c22, [csp, #-32]!
+	stp	c19, c20, [csp, #-32]!
+.endm
+#else
+
 	# Note - this macro is complemented by the FUNC_END macro
 	# in crtn.S.  If you change this macro you must also change
 	# that macro match.
@@ -50,6 +66,7 @@
 	stp	x19, x20, [sp, #-16]!
 .endm
 
+#endif
 	.section	".init"
 	.align 2
 	.global	_init
diff --git a/libgcc/config/aarch64/crtn.S b/libgcc/config/aarch64/crtn.S
index 109c0cb449b..c23e37335c6 100644
--- a/libgcc/config/aarch64/crtn.S
+++ b/libgcc/config/aarch64/crtn.S
@@ -31,6 +31,24 @@
 # fact return.  Users may put any desired instructions in those sections.
 # This file is the last thing linked into any executable.
 
+
+#ifdef __CHERI_PURE_CAPABILITY__
+
+	# Note - this macro is complemented by the FUNC_START macro
+	# in crti.S.  If you change this macro you must also change
+	# that macro to match.
+.macro FUNC_END
+	#  Restore all save registers including the link register, and then
+	#  perform the correct function return instruction.
+	ldp	c19, c20, [csp], #32
+	ldp	c21, c22, [csp], #32
+	ldp	c23, c24, [csp], #32
+	ldp	c25, c26, [csp], #32
+	ldp	c27, c28, [csp], #32
+	ldp	c29, c30, [csp], #32
+	ret
+.endm
+#else
 	# Note - this macro is complemented by the FUNC_START macro
 	# in crti.S.  If you change this macro you must also change
 	# that macro match.
@@ -49,6 +67,7 @@
 	ret
 .endm
 
+#endif
 
 	.section	".init"
 	;;