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From: Richard Earnshaw <rearnsha@sourceware.org> To: newlib-cvs@sourceware.org Subject: [newlib-cygwin] newlib: libc: memchr M-profile PACBTI-enablement Date: Tue, 10 Jan 2023 16:49:34 +0000 (GMT) [thread overview] Message-ID: <20230110164934.F219138582A4@sourceware.org> (raw) 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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