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| author | Victor Do Nascimento <Victor.DoNascimento@arm.com> | 2022-08-22 12:39:57 +0100 |
|---|---|---|
| committer | Szabolcs Nagy <szabolcs.nagy@arm.com> | 2022-08-22 12:39:57 +0100 |
| commit | ffb6461143e29d34687aca489d9fd8d297dc9920 (patch) | |
| tree | 09118f9a1cb1b8d38904d8289f412420c9e29b51 | |
| parent | 1d89678cd83c42953467c1405bf596362a7c96c0 (diff) | |
| download | arm-optimized-routines-ffb6461143e29d34687aca489d9fd8d297dc9920.tar.gz | |
string: arm: Prevent leaf function unwinding
As leaf functions cannot throw exceptions, with EHABI only supporting
synchronous exceptions, add support for emitting a `.cantunwind'
directive prior to `.fnend' in ARM_FNEND preprocessor macro.
This ensures no personality routine or exception table data is
generated. Existing `.save' directives used in leaf functions are also
removed.
Built w/ arm-none-linux-gnueabihf, ran make check-string w/ qemu-arm-static.
| -rw-r--r-- | string/arm/memchr.S | 2 | ||||
| -rw-r--r-- | string/arm/strcmp.S | 7 | ||||
| -rw-r--r-- | string/arm/strlen-armv6t2.S | 7 | ||||
| -rw-r--r-- | string/asmdefs.h | 6 |
4 files changed, 17 insertions, 5 deletions
diff --git a/string/arm/memchr.S b/string/arm/memchr.S index 77fe569..ddc808b 100644 --- a/string/arm/memchr.S +++ b/string/arm/memchr.S @@ -73,7 +73,6 @@ __memchr_arm: 10: @ At this point, 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 #if HAVE_PAC_LEAF .cfi_offset 4, -20 @@ -169,6 +168,7 @@ __memchr_arm: #endif /* HAVE_PAC_LEAF */ bx lr .cfi_endproc + .cantunwind .fnend .size __memchr_arm, . - __memchr_arm diff --git a/string/arm/strcmp.S b/string/arm/strcmp.S index d891d33..2eb560f 100644 --- a/string/arm/strcmp.S +++ b/string/arm/strcmp.S @@ -27,6 +27,11 @@ #define STRCMP_NO_PRECHECK 0 +/* Ensure the .cantunwind directive is prepended to .fnend. + Leaf functions cannot throw exceptions - EHABI only supports + synchronous exceptions. */ +#define IS_LEAF + /* This version uses Thumb-2 code. */ .thumb .syntax unified @@ -152,7 +157,6 @@ __strcmp_arm: bne L(fastpath_exit) #endif strd r4, r5, [sp, #-16]! - .save {r4, r5} .cfi_adjust_cfa_offset 16 #if HAVE_PAC_LEAF .cfi_offset 4, -20 @@ -163,7 +167,6 @@ __strcmp_arm: #endif /* HAVE_PAC_LEAF */ orr tmp1, src1, src2 strd r6, r7, [sp, #8] - .save {r6, r7} #if HAVE_PAC_LEAF .cfi_offset 6, -12 .cfi_offset 7, -8 diff --git a/string/arm/strlen-armv6t2.S b/string/arm/strlen-armv6t2.S index 2601d03..49ba928 100644 --- a/string/arm/strlen-armv6t2.S +++ b/string/arm/strlen-armv6t2.S @@ -24,6 +24,11 @@ #define S2HI lsl #endif +/* Ensure the .cantunwind directive is prepended to .fnend. + Leaf functions cannot throw exceptions - EHABI only supports + synchronous exceptions. */ +#define IS_LEAF + /* This code requires Thumb. */ .thumb .syntax unified @@ -52,7 +57,6 @@ ENTRY (__strlen_armv6t2) #endif /* __ARM_FEATURE_BTI_DEFAULT */ .cfi_register 143, 12 push {r4, r5, ip} - .save {r4, r5, ra_auth_code} .cfi_def_cfa_offset 12 .cfi_offset 143, -4 .cfi_offset 5, -8 @@ -62,7 +66,6 @@ ENTRY (__strlen_armv6t2) bti #endif /* __ARM_FEATURE_BTI_DEFAULT */ push {r4, r5} - .save {r4, r5} .cfi_def_cfa_offset 8 .cfi_offset 4, -8 .cfi_offset 5, -4 diff --git a/string/asmdefs.h b/string/asmdefs.h index d122b26..eb43836 100644 --- a/string/asmdefs.h +++ b/string/asmdefs.h @@ -10,7 +10,13 @@ #if defined (__arm__) #define ARM_FNSTART .fnstart +#if defined (IS_LEAF) +#define ARM_FNEND \ + .cantunwind \ + .fnend +#else #define ARM_FNEND .fnend +# endif #else #define ARM_FNSTART #define ARM_FNEND |