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aarch64: Add pac-ret support to assembly files

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Use return address signing in assembly files for functions that save
LR when pac-ret is enabled in the compiler.

The GNU property note for PAC-RET is not meaningful to the dynamic
linker so it is not strictly required, but it may be used to track
the security property of binaries. (The PAC-RET property is only set
if BTI is set too because BTI implies working GNU property support.)

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This commit is contained in:
Szabolcs Nagy 2020-04-29 11:49:20 +01:00
parent 9e1751e6d6
commit 1be3d6eb82
5 changed files with 47 additions and 1 deletions
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8
sysdeps/aarch64/crti.S
View File

@ -75,7 +75,11 @@ call_weak_fn:
.hidden _init
.type _init, %function
_init:
#if HAVE_AARCH64_PAC_RET
PACIASP
#else
BTI_C
#endif
stp x29, x30, [sp, -16]!
mov x29, sp
#if PREINIT_FUNCTION_WEAK
@ -90,6 +94,10 @@ _init:
.hidden _fini
.type _fini, %function
_fini:
#if HAVE_AARCH64_PAC_RET
PACIASP
#else
BTI_C
#endif
stp x29, x30, [sp, -16]!
mov x29, sp

6
sysdeps/aarch64/crtn.S
View File

@ -41,8 +41,14 @@
.section .init,"ax",%progbits
ldp x29, x30, [sp], 16
#if HAVE_AARCH64_PAC_RET
AUTIASP
#endif
RET
.section .fini,"ax",%progbits
ldp x29, x30, [sp], 16
#if HAVE_AARCH64_PAC_RET
AUTIASP
#endif
RET

8
sysdeps/aarch64/dl-tlsdesc.S
View File

@ -183,6 +183,10 @@ _dl_tlsdesc_dynamic:
callee will trash. */
/* Save the remaining registers that we must treat as caller save. */
# if HAVE_AARCH64_PAC_RET
PACIASP
cfi_window_save
# endif
# define NSAVEXREGPAIRS 8
stp x29, x30, [sp,#-16*NSAVEXREGPAIRS]!
cfi_adjust_cfa_offset (16*NSAVEXREGPAIRS)
@ -233,6 +237,10 @@ _dl_tlsdesc_dynamic:
cfi_adjust_cfa_offset (-16*NSAVEXREGPAIRS)
cfi_restore (x29)
cfi_restore (x30)
# if HAVE_AARCH64_PAC_RET
AUTIASP
cfi_window_save
# endif
b 1b
cfi_endproc
.size _dl_tlsdesc_dynamic, .-_dl_tlsdesc_dynamic

18
sysdeps/aarch64/dl-trampoline.S
View File

@ -127,7 +127,12 @@ _dl_runtime_resolve:
cfi_startproc
.align 2
_dl_runtime_profile:
# if HAVE_AARCH64_PAC_RET
PACIASP
cfi_window_save
# else
BTI_C
# endif
/* AArch64 we get called with:
ip0 &PLTGOT[2]
ip1 temp(dl resolver entry point)
@ -239,8 +244,17 @@ _dl_runtime_profile:
cfi_restore(x29)
cfi_restore(x30)
# if HAVE_AARCH64_PAC_RET
add sp, sp, SF_SIZE
cfi_adjust_cfa_offset (-SF_SIZE)
AUTIASP
cfi_window_save
add sp, sp, 16
cfi_adjust_cfa_offset (-16)
# else
add sp, sp, SF_SIZE + 16
cfi_adjust_cfa_offset (- SF_SIZE - 16)
# endif
/* Jump to the newly found address. */
br ip0
@ -287,6 +301,10 @@ _dl_runtime_profile:
/* LR from within La_aarch64_reg */
ldr lr, [x29, #OFFSET_RG + DL_OFFSET_RG_LR]
cfi_restore(lr)
# if HAVE_AARCH64_PAC_RET
/* Note: LR restored from La_aarch64_reg has no PAC. */
cfi_window_save
# endif
mov sp, x29
cfi_def_cfa_register (sp)
ldr x29, [x29, #0]

8
sysdeps/aarch64/sysdep.h
View File

@ -45,6 +45,10 @@
#define BTI_C hint 34
#define BTI_J hint 36
/* Return address signing support (pac-ret). */
#define PACIASP hint 25
#define AUTIASP hint 29
/* GNU_PROPERTY_AARCH64_* macros from elf.h for use in asm code. */
#define FEATURE_1_AND 0xc0000000
#define FEATURE_1_BTI 1
@ -66,7 +70,9 @@
/* Add GNU property note with the supported features to all asm code
where sysdep.h is included. */
#if HAVE_AARCH64_BTI
#if HAVE_AARCH64_BTI && HAVE_AARCH64_PAC_RET
GNU_PROPERTY (FEATURE_1_AND, FEATURE_1_BTI|FEATURE_1_PAC)
#elif HAVE_AARCH64_BTI
GNU_PROPERTY (FEATURE_1_AND, FEATURE_1_BTI)
#endif