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.
This commit is contained in:
Victor L. Do Nascimento 2022-12-21 11:24:00 +00:00 committed by Richard Earnshaw
parent 5582536896
commit db30cbee41
1 changed files with 44 additions and 6 deletions

View File

@ -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'
#if __ARM_ARCH >= 8
/* keep config inherited from -march=. */
#else
.arch armv7e-m
#endif /* __ARM_ARCH >= 8 */
#else
.arch armv6t2
#endif
#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