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* [newlib-cygwin] newlib: libc: memchr M-profile PACBTI-enablement
@ 2023-01-10 16:49 Richard Earnshaw
0 siblings, 0 replies; only message in thread
From: Richard Earnshaw @ 2023-01-10 16:49 UTC (permalink / raw)
To: newlib-cvs
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=db30cbee419b6c4d05da8072dc1e869697b93ff1
commit db30cbee419b6c4d05da8072dc1e869697b93ff1
Author: Victor L. Do Nascimento <victor.donascimento@arm.com>
Date: Wed Dec 21 11:24:00 2022 +0000
newlib: libc: memchr 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.
Diff:
---
newlib/libc/machine/arm/memchr.S | 50 +++++++++++++++++++++++++++++++++++-----
1 file changed, 44 insertions(+), 6 deletions(-)
diff --git a/newlib/libc/machine/arm/memchr.S b/newlib/libc/machine/arm/memchr.S
index 1a4c6512c..3c11addad 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 "arm_asm.h"
@ NOTE: This ifdef MUST match the one in memchr-stub.c
#if defined (__ARM_NEON__) || defined (__ARM_NEON)
@@ -267,10 +268,14 @@ memchr:
#elif __ARM_ARCH_ISA_THUMB >= 2 && defined (__ARM_FEATURE_DSP)
#if __ARM_ARCH_PROFILE == 'M'
- .arch armv7e-m
+#if __ARM_ARCH >= 8
+ /* keep config inherited from -march=. */
#else
- .arch armv6t2
-#endif
+ .arch armv7e-m
+#endif /* __ARM_ARCH >= 8 */
+#else
+ .arch armv6t2
+#endif /* __ARM_ARCH_PROFILE == 'M' */
@ this lets us check a flag in a 00/ff byte easily in either endianness
#ifdef __ARMEB__
@@ -287,11 +292,14 @@ 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
+ 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 +321,11 @@ memchr:
10:
@ We are aligned, we know we have at least 8 bytes to work with
push {r4,r5,r6,r7}
+ .cfi_adjust_cfa_offset 16
+ .cfi_rel_offset 4, 0
+ .cfi_rel_offset 5, 4
+ .cfi_rel_offset 6, 8
+ .cfi_rel_offset 7, 12
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 +347,11 @@ 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
@@ -349,17 +367,29 @@ memchr:
bne 21b @ on r2 flags
40:
+ .cfi_remember_state
movs r0,#0 @ not found
- bx lr
+ epilogue
50:
+ .cfi_restore_state
+ .cfi_remember_state
subs r0,r0,#1 @ found
- bx lr
+ epilogue
60: @ We're here because the fast path found a hit
@ now we have to track down exactly which word it was
@ r0 points to the start of the double word after the one tested
@ r5 has the 00/ff pattern for the first word, r6 has the chained value
+ @ This point is reached from cbnz midway through label 15 prior to
+ @ popping r4-r7 off the stack. .cfi_restore_state alone disregards
+ @ this, so we manually correct this.
+ .cfi_restore_state @ Standard post-prologue state
+ .cfi_adjust_cfa_offset 16
+ .cfi_rel_offset 4, 0
+ .cfi_rel_offset 5, 4
+ .cfi_rel_offset 6, 8
+ .cfi_rel_offset 7, 12
cmp r5, #0
itte eq
moveq r5, r6 @ the end is in the 2nd word
@@ -379,8 +409,16 @@ memchr:
61:
pop {r4,r5,r6,r7}
+ .cfi_restore 7
+ .cfi_restore 6
+ .cfi_restore 5
+ .cfi_restore 4
+ .cfi_adjust_cfa_offset -16
subs r0,r0,#1
- bx lr
+ epilogue
+ .cfi_endproc
+ .cantunwind
+ .fnend
#else
/* Defined in memchr-stub.c. */
#endif
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