[PATCH v5 2/8] newlib: libc: strcmp M-profile PACBTI-enablement
Victor L. Do Nascimento
victor.donascimento@arm.com
Wed Dec 21 11:21:22 GMT 2022
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 | 8 +++-
newlib/libc/machine/arm/strcmp-armv7.S | 57 ++++++++++++++---------
newlib/libc/machine/arm/strcmp-armv7m.S | 26 +++++++----
3 files changed, 60 insertions(+), 31 deletions(-)
diff --git a/newlib/libc/machine/arm/strcmp-arm-tiny.S b/newlib/libc/machine/arm/strcmp-arm-tiny.S
index 607a41daf..0bd2a2e6e 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 "arm_asm.h"
+
.syntax unified
def_fn strcmp
+ .fnstart
.cfi_sections .debug_frame
.cfi_startproc
+ prologue
1:
ldrb r2, [r0], #1
ldrb r3, [r1], #1
@@ -42,6 +46,8 @@ def_fn strcmp
beq 1b
2:
subs r0, r2, r3
- bx lr
+ epilogue
.cfi_endproc
+ .cantunwind
+ .fnend
.size strcmp, . - strcmp
diff --git a/newlib/libc/machine/arm/strcmp-armv7.S b/newlib/libc/machine/arm/strcmp-armv7.S
index 2f93bfb73..7cafca151 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 "arm_asm.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
+ epilogue push_ip=HAVE_PAC_LEAF
#else
/* To use the big-endian trick we'd have to reverse all three words.
that's slower than this approach. */
@@ -112,22 +115,21 @@
ldrd r4, r5, [sp], #16
.cfi_restore 4
.cfi_restore 5
+ .cfi_adjust_cfa_offset -16
sub result, result, r1
- bx lr
+ epilogue push_ip=HAVE_PAC_LEAF
#endif
.endm
+
.text
.p2align 5
-.Lstrcmp_start_addr:
-#ifndef STRCMP_NO_PRECHECK
-.Lfastpath_exit:
- sub r0, r2, r3
- bx lr
- nop
-#endif
def_fn strcmp
+ .fnstart
+ .cfi_sections .debug_frame
+ .cfi_startproc
+ prologue push_ip=HAVE_PAC_LEAF
#ifndef STRCMP_NO_PRECHECK
ldrb r2, [src1]
ldrb r3, [src2]
@@ -136,16 +138,14 @@ 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
- .cfi_offset 4, -16
- .cfi_offset 5, -12
+ .cfi_adjust_cfa_offset 16
+ .cfi_rel_offset 4, 0
+ .cfi_rel_offset 5, 4
orr tmp1, src1, src2
strd r6, r7, [sp, #8]
- .cfi_offset 6, -8
- .cfi_offset 7, -4
+ .cfi_rel_offset 6, 8
+ .cfi_rel_offset 7, 12
mvn const_m1, #0
lsl r2, tmp1, #29
cbz r2, .Lloop_aligned8
@@ -270,7 +270,6 @@ 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
@@ -314,10 +313,19 @@ def_fn strcmp
mov result, tmp1
ldr r4, [sp], #16
.cfi_restore 4
- bx lr
+ .cfi_adjust_cfa_offset -16
+ epilogue push_ip=HAVE_PAC_LEAF
#ifndef STRCMP_NO_PRECHECK
+.Lfastpath_exit:
+ .cfi_restore_state
+ .cfi_remember_state
+ sub r0, r2, r3
+ epilogue push_ip=HAVE_PAC_LEAF
+
.Laligned_m1:
+ .cfi_restore_state
+ .cfi_remember_state
add src2, src2, #4
#endif
.Lsrc1_aligned:
@@ -364,8 +372,9 @@ 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
+ epilogue push_ip=HAVE_PAC_LEAF
6:
.cfi_restore_state
@@ -441,7 +450,8 @@ def_fn strcmp
/* R6/7 not used in this sequence. */
.cfi_restore 6
.cfi_restore 7
- bx lr
+ .cfi_adjust_cfa_offset -16
+ epilogue push_ip=HAVE_PAC_LEAF
.Lstrcmp_tail:
.cfi_restore_state
@@ -463,7 +473,10 @@ 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
+ epilogue push_ip=HAVE_PAC_LEAF
.cfi_endproc
- .size strcmp, . - .Lstrcmp_start_addr
+ .cantunwind
+ .fnend
+ .size strcmp, . - strcmp
diff --git a/newlib/libc/machine/arm/strcmp-armv7m.S b/newlib/libc/machine/arm/strcmp-armv7m.S
index cdb4912df..825b6e77f 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 "arm_asm.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
+ prologue push_ip=HAVE_PAC_LEAF
eor tmp1, src1, src2
tst tmp1, #3
/* Strings not at same byte offset from a word boundary. */
@@ -82,6 +86,7 @@ def_fn strcmp
ldreq data2, [src2], #4
beq 4b
2:
+ .cfi_remember_state
/* There's a zero or a different byte in the word */
S2HI result, data1, #24
S2LO data1, data1, #8
@@ -106,7 +111,7 @@ def_fn strcmp
lsrs result, result, #24
subs result, result, data2
#endif
- bx lr
+ epilogue push_ip=HAVE_PAC_LEAF
#if 0
@@ -205,8 +210,10 @@ def_fn strcmp
/* First of all, compare bytes until src1(sp1) is word-aligned. */
.Lstrcmp_unaligned:
+ .cfi_restore_state
tst src1, #3
beq 2f
+ .cfi_remember_state
ldrb data1, [src1], #1
ldrb data2, [src2], #1
cmp data1, #1
@@ -214,12 +221,13 @@ def_fn strcmp
cmpcs data1, data2
beq .Lstrcmp_unaligned
sub result, data1, data2
- bx lr
+ epilogue push_ip=HAVE_PAC_LEAF
2:
+ .cfi_restore_state
stmfd sp!, {r5}
- .cfi_def_cfa_offset 4
- .cfi_offset 5, -4
+ .cfi_adjust_cfa_offset 4
+ .cfi_rel_offset 5, 0
ldr data1, [src1], #4
and tmp2, src2, #3
@@ -355,8 +363,8 @@ def_fn strcmp
.cfi_remember_state
ldmfd sp!, {r5}
.cfi_restore 5
- .cfi_def_cfa_offset 0
- bx lr
+ .cfi_adjust_cfa_offset -4
+ epilogue push_ip=HAVE_PAC_LEAF
.Lstrcmp_tail:
.cfi_restore_state
@@ -372,7 +380,9 @@ def_fn strcmp
sub result, r2, result
ldmfd sp!, {r5}
.cfi_restore 5
- .cfi_def_cfa_offset 0
- bx lr
+ .cfi_adjust_cfa_offset -4
+ epilogue push_ip=HAVE_PAC_LEAF
.cfi_endproc
+ .cantunwind
+ .fnend
.size strcmp, . - strcmp
--
2.36.1
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