[v3,11/13] aarch64: Add pac-ret support to assembly files
Commit Message
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.)
---
sysdeps/aarch64/crti.S | 8 ++++++++
sysdeps/aarch64/crtn.S | 6 ++++++
sysdeps/aarch64/dl-tlsdesc.S | 8 ++++++++
sysdeps/aarch64/dl-trampoline.S | 18 ++++++++++++++++++
sysdeps/aarch64/sysdep.h | 8 +++++++-
5 files changed, 47 insertions(+), 1 deletion(-)
Comments
On 15/05/2020 11:40, Szabolcs Nagy wrote:
> 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.)
With the suggestion from previous HAVE_AARCH64_PAC_RET patch,
these tests could be used as #if HAVE_AARCH64_PAC_RET.
Besides that, LGTM.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> ---
> sysdeps/aarch64/crti.S | 8 ++++++++
> sysdeps/aarch64/crtn.S | 6 ++++++
> sysdeps/aarch64/dl-tlsdesc.S | 8 ++++++++
> sysdeps/aarch64/dl-trampoline.S | 18 ++++++++++++++++++
> sysdeps/aarch64/sysdep.h | 8 +++++++-
> 5 files changed, 47 insertions(+), 1 deletion(-)
>
> diff --git a/sysdeps/aarch64/crti.S b/sysdeps/aarch64/crti.S
> index c346bcad72..02ec7d015e 100644
> --- a/sysdeps/aarch64/crti.S
> +++ b/sysdeps/aarch64/crti.S
> @@ -75,7 +75,11 @@ call_weak_fn:
> .hidden _init
> .type _init, %function
> _init:
> +#ifdef 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:
> +#ifdef HAVE_AARCH64_PAC_RET
> + PACIASP
> +#else
> BTI_C
> +#endif
> stp x29, x30, [sp, -16]!
> mov x29, sp
Ok.
> diff --git a/sysdeps/aarch64/crtn.S b/sysdeps/aarch64/crtn.S
> index 0c1ef112c2..4b93b90411 100644
> --- a/sysdeps/aarch64/crtn.S
> +++ b/sysdeps/aarch64/crtn.S
> @@ -41,8 +41,14 @@
>
> .section .init,"ax",%progbits
> ldp x29, x30, [sp], 16
> +#ifdef HAVE_AARCH64_PAC_RET
> + AUTIASP
> +#endif
> RET
>
> .section .fini,"ax",%progbits
> ldp x29, x30, [sp], 16
> +#ifdef HAVE_AARCH64_PAC_RET
> + AUTIASP
> +#endif
> RET
Ok.
> diff --git a/sysdeps/aarch64/dl-tlsdesc.S b/sysdeps/aarch64/dl-tlsdesc.S
> index 9d96c8632a..3746dbec17 100644
> --- a/sysdeps/aarch64/dl-tlsdesc.S
> +++ b/sysdeps/aarch64/dl-tlsdesc.S
> @@ -183,6 +183,10 @@ _dl_tlsdesc_dynamic:
> callee will trash. */
>
> /* Save the remaining registers that we must treat as caller save. */
> +# ifdef 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)
> +# ifdef HAVE_AARCH64_PAC_RET
> + AUTIASP
> + cfi_window_save
> +# endif
> b 1b
> cfi_endproc
> .size _dl_tlsdesc_dynamic, .-_dl_tlsdesc_dynamic
Ok.
> diff --git a/sysdeps/aarch64/dl-trampoline.S b/sysdeps/aarch64/dl-trampoline.S
> index 2cbfa81434..53f92d68bf 100644
> --- a/sysdeps/aarch64/dl-trampoline.S
> +++ b/sysdeps/aarch64/dl-trampoline.S
> @@ -127,7 +127,12 @@ _dl_runtime_resolve:
> cfi_startproc
> .align 2
> _dl_runtime_profile:
> +# ifdef 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)
>
> +# ifdef 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)
> +# ifdef 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]
Ok.
> diff --git a/sysdeps/aarch64/sysdep.h b/sysdeps/aarch64/sysdep.h
> index 086fc84b53..c51572a690 100644
> --- a/sysdeps/aarch64/sysdep.h
> +++ b/sysdeps/aarch64/sysdep.h
> @@ -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 defined HAVE_AARCH64_BTI
> +#if defined HAVE_AARCH64_BTI && defined HAVE_AARCH64_PAC_RET
> +GNU_PROPERTY (FEATURE_1_AND, FEATURE_1_BTI|FEATURE_1_PAC)
> +#elif defined HAVE_AARCH64_BTI
> GNU_PROPERTY (FEATURE_1_AND, FEATURE_1_BTI)
> #endif
>
>
Ok.
@@ -75,7 +75,11 @@ call_weak_fn:
.hidden _init
.type _init, %function
_init:
+#ifdef 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:
+#ifdef HAVE_AARCH64_PAC_RET
+ PACIASP
+#else
BTI_C
+#endif
stp x29, x30, [sp, -16]!
mov x29, sp
@@ -41,8 +41,14 @@
.section .init,"ax",%progbits
ldp x29, x30, [sp], 16
+#ifdef HAVE_AARCH64_PAC_RET
+ AUTIASP
+#endif
RET
.section .fini,"ax",%progbits
ldp x29, x30, [sp], 16
+#ifdef HAVE_AARCH64_PAC_RET
+ AUTIASP
+#endif
RET
@@ -183,6 +183,10 @@ _dl_tlsdesc_dynamic:
callee will trash. */
/* Save the remaining registers that we must treat as caller save. */
+# ifdef 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)
+# ifdef HAVE_AARCH64_PAC_RET
+ AUTIASP
+ cfi_window_save
+# endif
b 1b
cfi_endproc
.size _dl_tlsdesc_dynamic, .-_dl_tlsdesc_dynamic
@@ -127,7 +127,12 @@ _dl_runtime_resolve:
cfi_startproc
.align 2
_dl_runtime_profile:
+# ifdef 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)
+# ifdef 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)
+# ifdef 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]
@@ -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 defined HAVE_AARCH64_BTI
+#if defined HAVE_AARCH64_BTI && defined HAVE_AARCH64_PAC_RET
+GNU_PROPERTY (FEATURE_1_AND, FEATURE_1_BTI|FEATURE_1_PAC)
+#elif defined HAVE_AARCH64_BTI
GNU_PROPERTY (FEATURE_1_AND, FEATURE_1_BTI)
#endif