[PATCH v2 2/8] newlib: libc: strcmp M-profile PACBTI-enablement

Add function prologue/epilogue to conditionally add BTI landing pads
and/or PAC code generation & authentication instructions depending on
compilation flags.

This patch enables PACBTI for all relevant variants of strcmp:
     * Newlib for armv8.1-m.main+pacbti
     * Newlib for armv8.1-m.main+pacbti+mve
     * Newlib-nano
---
 newlib/libc/machine/arm/strcmp-arm-tiny.S |  7 +++-
 newlib/libc/machine/arm/strcmp-armv7.S    | 45 +++++++++++++++++------
 newlib/libc/machine/arm/strcmp-armv7m.S   | 36 +++++++++++++++---
 3 files changed, 71 insertions(+), 17 deletions(-)

diff --git a/newlib/libc/machine/arm/strcmp-arm-tiny.S b/newlib/libc/machine/arm/strcmp-arm-tiny.S
index 607a41daf..8085eb4df 100644
--- a/newlib/libc/machine/arm/strcmp-arm-tiny.S
+++ b/newlib/libc/machine/arm/strcmp-arm-tiny.S
@@ -29,10 +29,14 @@
 /* Tiny version of strcmp in ARM state.  Used only when optimizing
    for size.  Also supports Thumb-2.  */
 
+#include "pacbti.h"
+
 	.syntax unified
 def_fn strcmp
+	.fnstart
 	.cfi_sections .debug_frame
 	.cfi_startproc
+	pacbti_prologue
 1:
 	ldrb	r2, [r0], #1
 	ldrb	r3, [r1], #1
@@ -42,6 +46,7 @@ def_fn strcmp
 	beq	1b
 2:
 	subs	r0, r2, r3
-	bx	lr
+	pacbti_epilogue
 	.cfi_endproc
+	.fnend
 	.size	strcmp, . - strcmp
diff --git a/newlib/libc/machine/arm/strcmp-armv7.S b/newlib/libc/machine/arm/strcmp-armv7.S
index 2f93bfb73..584c89f7e 100644
--- a/newlib/libc/machine/arm/strcmp-armv7.S
+++ b/newlib/libc/machine/arm/strcmp-armv7.S
@@ -45,6 +45,8 @@
 	.thumb
 	.syntax unified
 
+#include "pacbti.h"
+
 /* Parameters and result.  */
 #define src1		r0
 #define src2		r1
@@ -91,8 +93,9 @@
 	ldrd	r4, r5, [sp], #16
 	.cfi_restore 4
 	.cfi_restore 5
+	.cfi_adjust_cfa_offset -16
 	sub	result, result, r1, lsr #24
-	bx	lr
+	pacbti_epilogue
 #else
 	/* To use the big-endian trick we'd have to reverse all three words.
 	   that's slower than this approach.  */
@@ -112,22 +115,28 @@
 	ldrd	r4, r5, [sp], #16
 	.cfi_restore 4
 	.cfi_restore 5
+	.cfi_adjust_cfa_offset -16
 	sub	result, result, r1
 
-	bx	lr
+	pacbti_epilogue
 #endif
 	.endm
 
+
 	.text
 	.p2align	5
+	.fnstart
+	.cfi_sections .debug_frame
+	.cfi_startproc
 .Lstrcmp_start_addr:
 #ifndef STRCMP_NO_PRECHECK
 .Lfastpath_exit:
 	sub	r0, r2, r3
-	bx	lr
+	pacbti_epilogue
 	nop
 #endif
 def_fn	strcmp
+	pacbti_prologue
 #ifndef STRCMP_NO_PRECHECK
 	ldrb	r2, [src1]
 	ldrb	r3, [src2]
@@ -136,16 +145,26 @@ def_fn	strcmp
 	cmpcs	r2, r3
 	bne	.Lfastpath_exit
 #endif
-	.cfi_sections .debug_frame
-	.cfi_startproc
 	strd	r4, r5, [sp, #-16]!
-	.cfi_def_cfa_offset 16
+	.save {r4, r5}
+	.cfi_adjust_cfa_offset 16
+#if __HAVE_PAC_LEAF
+	.cfi_offset 4, -20
+	.cfi_offset 5, -16
+#else
 	.cfi_offset 4, -16
 	.cfi_offset 5, -12
+#endif /* __HAVE_PAC_LEAF */
 	orr	tmp1, src1, src2
 	strd	r6, r7, [sp, #8]
+	.save {r6, r7}
+#if __HAVE_PAC_LEAF
+	.cfi_offset 6, -12
+	.cfi_offset 7, -8
+#else
 	.cfi_offset 6, -8
 	.cfi_offset 7, -4
+#endif /* __HAVE_PAC_LEAF */
 	mvn	const_m1, #0
 	lsl	r2, tmp1, #29
 	cbz	r2, .Lloop_aligned8
@@ -270,7 +289,6 @@ def_fn	strcmp
 	ldr	data1, [src1], #4
 	beq	.Laligned_m2
 	bcs	.Laligned_m1
-
 #ifdef STRCMP_NO_PRECHECK
 	ldrb	data2, [src2, #1]
 	uxtb	tmp1, data1, ror #BYTE1_OFFSET
@@ -314,7 +332,8 @@ def_fn	strcmp
 	mov	result, tmp1
 	ldr	r4, [sp], #16
 	.cfi_restore 4
-	bx	lr
+	.cfi_adjust_cfa_offset -16
+	pacbti_epilogue
 
 #ifndef STRCMP_NO_PRECHECK
 .Laligned_m1:
@@ -364,8 +383,9 @@ def_fn	strcmp
 	/* R6/7 Not used in this sequence.  */
 	.cfi_restore 6
 	.cfi_restore 7
+	.cfi_adjust_cfa_offset -16
 	neg	result, result
-	bx	lr
+	pacbti_epilogue
 
 6:
 	.cfi_restore_state
@@ -441,7 +461,8 @@ def_fn	strcmp
 	/* R6/7 not used in this sequence.  */
 	.cfi_restore 6
 	.cfi_restore 7
-	bx	lr
+	.cfi_adjust_cfa_offset -16
+	pacbti_epilogue
 
 .Lstrcmp_tail:
 	.cfi_restore_state
@@ -463,7 +484,9 @@ def_fn	strcmp
 	/* R6/7 not used in this sequence.  */
 	.cfi_restore 6
 	.cfi_restore 7
+	.cfi_adjust_cfa_offset -16
 	sub	result, result, data2, lsr #24
-	bx	lr
+	pacbti_epilogue
 	.cfi_endproc
+	.fnend
 	.size strcmp, . - .Lstrcmp_start_addr
diff --git a/newlib/libc/machine/arm/strcmp-armv7m.S b/newlib/libc/machine/arm/strcmp-armv7m.S
index cdb4912df..fe1519f4d 100644
--- a/newlib/libc/machine/arm/strcmp-armv7m.S
+++ b/newlib/libc/machine/arm/strcmp-armv7m.S
@@ -29,6 +29,8 @@
 /* Very similar to the generic code, but uses Thumb2 as implemented
    in ARMv7-M.  */
 
+#include "pacbti.h"
+
 /* Parameters and result.  */
 #define src1		r0
 #define src2		r1
@@ -44,8 +46,10 @@
 	.thumb
 	.syntax unified
 def_fn strcmp
+	.fnstart
 	.cfi_sections .debug_frame
 	.cfi_startproc
+	pacbti_prologue
 	eor	tmp1, src1, src2
 	tst	tmp1, #3
 	/* Strings not at same byte offset from a word boundary.  */
@@ -106,7 +110,7 @@ def_fn strcmp
 	lsrs	result, result, #24
 	subs	result, result, data2
 #endif
-	bx	lr
+	pacbti_epilogue
 
 
 #if 0
@@ -214,12 +218,18 @@ def_fn strcmp
 	cmpcs	data1, data2
 	beq	.Lstrcmp_unaligned
 	sub	result, data1, data2
-	bx	lr
+	pacbti_epilogue
 
 2:
 	stmfd	sp!, {r5}
-	.cfi_def_cfa_offset 4
+	.save {r5}
+	.cfi_adjust_cfa_offset 4
+#if __HAVE_PAC_LEAF
+	.cfi_offset 5, -8 /* Account for ip register already on stack.  */
+#else
 	.cfi_offset 5, -4
+#endif /* __HAVE_PAC_LEAF */
+
 
 	ldr	data1, [src1], #4
 	and	tmp2, src2, #3
@@ -353,10 +363,17 @@ def_fn strcmp
 .Lstrcmp_done_equal:
 	mov	result, #0
 	.cfi_remember_state
+#if __HAVE_PAC_LEAF
+	pop {r5, ip}
+	.cfi_restore 5
+	.cfi_restore 143
+	aut ip, lr, sp
+#else
 	ldmfd	sp!, {r5}
 	.cfi_restore 5
+#endif /* __HAVE_PAC_LEAF */
 	.cfi_def_cfa_offset 0
-	bx	lr
+	bx lr
 
 .Lstrcmp_tail:
 	.cfi_restore_state
@@ -370,9 +387,18 @@ def_fn strcmp
 	S2LOEQ	data2, data2, #8
 	beq	.Lstrcmp_tail
 	sub	result, r2, result
+#if __HAVE_PAC_LEAF
+	pop {r5, ip}
+	.cfi_restore 5
+	.cfi_restore 143
+	.cfi_def_cfa_offset 0
+	aut ip, lr, sp
+#else
 	ldmfd	sp!, {r5}
 	.cfi_restore 5
 	.cfi_def_cfa_offset 0
-	bx	lr
+#endif /* __HAVE_PAC_LEAF */
+	bx lr
 	.cfi_endproc
+	.fnend
 	.size strcmp, . - strcmp
-- 
2.36.1