[PATCH 4/8] newlib: libc: memchr M-profile PACBTI-enablement
Victor Do Nascimento
victor.donascimento@arm.com
Tue Jul 5 13:58:14 GMT 2022
Add function prologue/epilogue to conditionally add BTI landing pads
and/or PAC code generation & authentication instructions depending on
compilation flags.
---
newlib/libc/machine/arm/memchr.S | 49 ++++++++++++++++++++++++++++----
1 file changed, 44 insertions(+), 5 deletions(-)
diff --git a/newlib/libc/machine/arm/memchr.S b/newlib/libc/machine/arm/memchr.S
index 1a4c6512c..644cfda3f 100644
--- a/newlib/libc/machine/arm/memchr.S
+++ b/newlib/libc/machine/arm/memchr.S
@@ -76,6 +76,7 @@
.syntax unified
#include "acle-compat.h"
+#include "pacbti.h"
@ NOTE: This ifdef MUST match the one in memchr-stub.c
#if defined (__ARM_NEON__) || defined (__ARM_NEON)
@@ -266,7 +267,9 @@ memchr:
#elif __ARM_ARCH_ISA_THUMB >= 2 && defined (__ARM_FEATURE_DSP)
-#if __ARM_ARCH_PROFILE == 'M'
+#if __ARM_ARCH_8M_MAIN__
+ /* keep config inherited from -march= */
+#elif __ARM_ARCH_PROFILE == 'M'
.arch armv7e-m
#else
.arch armv6t2
@@ -287,11 +290,14 @@ memchr:
.p2align 4,,15
.global memchr
.type memchr,%function
+ .fnstart
+ .cfi_startproc
memchr:
@ r0 = start of memory to scan
@ r1 = character to look for
@ r2 = length
@ returns r0 = pointer to character or NULL if not found
+ pacbti_prologue
and r1,r1,#0xff @ Don't trust the caller to pass a char
cmp r2,#16 @ If short don't bother with anything clever
@@ -313,6 +319,19 @@ memchr:
10:
@ We are aligned, we know we have at least 8 bytes to work with
push {r4,r5,r6,r7}
+ .save {r4-r7}
+ .cfi_adjust_cfa_offset 16
+#ifdef __ARM_FEATURE_PAC_DEFAULT
+ .cfi_offset 4, -20
+ .cfi_offset 5, -16
+ .cfi_offset 6, -12
+ .cfi_offset 7, -8
+#else
+ .cfi_offset 4, -16
+ .cfi_offset 5, -12
+ .cfi_offset 6, -8
+ .cfi_offset 7, -4
+#endif /* __ARM_FEATURE_PAC_DEFAULT */
orr r1, r1, r1, lsl #8 @ expand the match word across all bytes
orr r1, r1, r1, lsl #16
bic r4, r2, #7 @ Number of double words to work with * 8
@@ -334,6 +353,11 @@ memchr:
bne 15b @ (Flags from the subs above)
pop {r4,r5,r6,r7}
+ .cfi_restore 7
+ .cfi_restore 6
+ .cfi_restore 5
+ .cfi_restore 4
+ .cfi_adjust_cfa_offset -16
and r1,r1,#0xff @ r1 back to a single character
and r2,r2,#7 @ Leave the count remaining as the number
@ after the double words have been done
@@ -350,11 +374,11 @@ memchr:
40:
movs r0,#0 @ not found
- bx lr
+ pacbti_epilogue
50:
subs r0,r0,#1 @ found
- bx lr
+ pacbti_epilogue
60: @ We're here because the fast path found a hit
@ now we have to track down exactly which word it was
@@ -378,9 +402,24 @@ memchr:
addeq r0,r0,#1
61:
- pop {r4,r5,r6,r7}
subs r0,r0,#1
- bx lr
+#if __ARM_FEATURE_PAC_DEFAULT
+ pop {r4,r5,r6,r7,ip}
+ .cfi_restore 143
+#else
+ pop {r4,r5,r6,r7}
+#endif /* __ARM_FEATURE_PAC_DEFAULT */
+ .cfi_restore 7
+ .cfi_restore 6
+ .cfi_restore 5
+ .cfi_restore 4
+ .cfi_def_cfa_offset 0
+#if __ARM_FEATURE_PAC_DEFAULT
+ aut ip, lr, sp
+#endif /* __ARM_FEATURE_PAC_DEFAULT */
+ bx lr
+ .cfi_endproc
+ .fnend
#else
/* Defined in memchr-stub.c. */
#endif
--
2.36.1
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