[v1,2/4] aarch64 SFrame: use preferred CFI directive for AArch64 PAC
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| linaro-tcwg-bot/tcwg_binutils_build--master-arm |
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| linaro-tcwg-bot/tcwg_binutils_build--master-aarch64 |
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| linaro-tcwg-bot/tcwg_binutils_check--master-aarch64 |
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| linaro-tcwg-bot/tcwg_binutils_check--master-arm |
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Commit Message
ARMv8.3 addded support for a new security feature named Pointer
Authentication. Support for this feature in SFrame already exists,
but is relying on the deprecated "AArch64" (actually Sparc) CFI
directive .cfi_gnu_window_save. .cfi_negate_ra_state CFI directive
should be used instead to convey this information.
In GCC 14 and older, the Sparc DWARF extension .cfi_gnu_window_save
is emitted instead of .cfi_negate_ra_state.
GCC 15 fixed this issue, but this behavior is preserved for backward
compatibility.
The existing sframe test for AArch64 PAC was using .cfi_gnu_window_save.
This patch replaces this CFI in the existing test by the preferred one,
and adds a new test to check for backward compatibility when using
.cfi_gnu_window_save.
---
.../gas/cfi-sframe/cfi-sframe-aarch64-3.d | 20 ++++++++++++++++++
.../gas/cfi-sframe/cfi-sframe-aarch64-3.s | 21 +++++++++++++++++++
.../cfi-sframe-aarch64-pac-ab-key-1.s | 8 +++----
gas/testsuite/gas/cfi-sframe/cfi-sframe.exp | 1 +
4 files changed, 46 insertions(+), 4 deletions(-)
create mode 100644 gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-3.d
create mode 100644 gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-3.s
Comments
On 11/25/24 8:28 AM, Matthieu Longo wrote:
> ARMv8.3 addded support for a new security feature named Pointer
> Authentication. Support for this feature in SFrame already exists,
> but is relying on the deprecated "AArch64" (actually Sparc) CFI
> directive .cfi_gnu_window_save. .cfi_negate_ra_state CFI directive
> should be used instead to convey this information.
>
> In GCC 14 and older, the Sparc DWARF extension .cfi_gnu_window_save
> is emitted instead of .cfi_negate_ra_state.
> GCC 15 fixed this issue, but this behavior is preserved for backward
> compatibility.
>
> The existing sframe test for AArch64 PAC was using .cfi_gnu_window_save.
> This patch replaces this CFI in the existing test by the preferred one,
> and adds a new test to check for backward compatibility when using
> .cfi_gnu_window_save.
Hi Matthieu,
See one comment inlined below.
Thanks
Indu
> ---
> .../gas/cfi-sframe/cfi-sframe-aarch64-3.d | 20 ++++++++++++++++++
> .../gas/cfi-sframe/cfi-sframe-aarch64-3.s | 21 +++++++++++++++++++
> .../cfi-sframe-aarch64-pac-ab-key-1.s | 8 +++----
> gas/testsuite/gas/cfi-sframe/cfi-sframe.exp | 1 +
> 4 files changed, 46 insertions(+), 4 deletions(-)
> create mode 100644 gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-3.d
> create mode 100644 gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-3.s
>
> diff --git a/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-3.d b/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-3.d
> new file mode 100644
> index 00000000000..f72b70a970a
> --- /dev/null
> +++ b/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-3.d
> @@ -0,0 +1,20 @@
> +#as: --gsframe
> +#objdump: --sframe=.sframe
> +#name: SFrame cfi_negate_ra_state test (using cfi_window_save)
> +#...
> +Contents of the SFrame section .sframe:
> +
> + Header :
> +
> + Version: SFRAME_VERSION_2
> + Flags: NONE
> + Num FDEs: 1
> + Num FREs: 2
> +
> + Function Index :
> + func idx \[0\]: pc = 0x0, size = 8 bytes
> + STARTPC + CFA + FP + RA +
> +#...
> + 0+0004 +sp\+16 +u +u\[s\] +
> +
> +#pass
> diff --git a/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-3.s b/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-3.s
> new file mode 100644
> index 00000000000..df6ff6e8c8f
> --- /dev/null
> +++ b/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-3.s
> @@ -0,0 +1,21 @@
> +## ARMv8.3 addded support a new security feature named Pointer Authentication. The
> +## main idea behind this is to use the unused bits in the pointer values.
> +## Each pointer is patched with a PAC before writing to memory, and is verified
> +## before using it.
> +## When the pointers are mangled, the stack trace generator needs to know so it
> +## can mask off the PAC from the pointer value to recover the return address,
> +## and conversely, skip doing so if the pointers are not mangled.
> +##
> +## .cfi_negate_ra_state CFI directive is usually used to convey this information.
> +## In GCC 14 and older, the Sparc DWARF extension .cfi_window_save is emitted
> +## instead of .cfi_negate_ra_state. GCC 15 fixed this issue, but this behavior
> +## is preserved in binutils for backward compatibility.
> +##
> +## SFrame has support for this. This testcase ensures that the directive
> +## is interpreted successfully.
> + .cfi_startproc
> + .long 0
> + .cfi_def_cfa_offset 16
> + .cfi_window_save
> + .long 0
> + .cfi_endproc
Since the purpose is to ensure that the old behavior is maintained, I am
wondering if it is not better to keep the old test as is (which also
tests the .cfi_window_save *together with* the .cfi_b_key_frame
directives). WDYT ?
> diff --git a/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-pac-ab-key-1.s b/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-pac-ab-key-1.s
> index d9a408c668c..84230a99e3c 100644
> --- a/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-pac-ab-key-1.s
> +++ b/gas/testsuite/gas/cfi-sframe/cfi-sframe-aarch64-pac-ab-key-1.s
> @@ -8,12 +8,12 @@ _Z5foo_av:
> .LFB0:
> .cfi_startproc
> hint 25 // paciasp
> - .cfi_window_save
> + .cfi_negate_ra_state
> stp x29, x30, [sp, -16]!
> .cfi_def_cfa_offset 16
> .cfi_offset 29, -16
> .cfi_offset 30, -8
> - ret
> + ret
> .cfi_endproc
> .LFE0:
> .size _Z5foo_av, .-_Z5foo_av
> @@ -25,12 +25,12 @@ _Z5foo_bv:
> .cfi_startproc
> .cfi_b_key_frame
> hint 27 // pacibsp
> - .cfi_window_save
> + .cfi_negate_ra_state
> stp x29, x30, [sp, -16]!
> .cfi_def_cfa_offset 16
> .cfi_offset 29, -16
> .cfi_offset 30, -8
> nop
> nop
> - ret
> + ret
> .cfi_endproc
> diff --git a/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp b/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp
> index cfae28d39aa..c646b109895 100644
> --- a/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp
> +++ b/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp
> @@ -97,5 +97,6 @@ if { [istarget "x86_64-*-*"] && [gas_sframe_check] } then {
> if { [istarget "aarch64*-*-*"] && [gas_sframe_check] } then {
> run_dump_test "cfi-sframe-aarch64-1"
> run_dump_test "cfi-sframe-aarch64-2"
> + run_dump_test "cfi-sframe-aarch64-3"
> run_dump_test "cfi-sframe-aarch64-pac-ab-key-1"
> }
new file mode 100644
@@ -0,0 +1,20 @@
+#as: --gsframe
+#objdump: --sframe=.sframe
+#name: SFrame cfi_negate_ra_state test (using cfi_window_save)
+#...
+Contents of the SFrame section .sframe:
+
+ Header :
+
+ Version: SFRAME_VERSION_2
+ Flags: NONE
+ Num FDEs: 1
+ Num FREs: 2
+
+ Function Index :
+ func idx \[0\]: pc = 0x0, size = 8 bytes
+ STARTPC + CFA + FP + RA +
+#...
+ 0+0004 +sp\+16 +u +u\[s\] +
+
+#pass
new file mode 100644
@@ -0,0 +1,21 @@
+## ARMv8.3 addded support a new security feature named Pointer Authentication. The
+## main idea behind this is to use the unused bits in the pointer values.
+## Each pointer is patched with a PAC before writing to memory, and is verified
+## before using it.
+## When the pointers are mangled, the stack trace generator needs to know so it
+## can mask off the PAC from the pointer value to recover the return address,
+## and conversely, skip doing so if the pointers are not mangled.
+##
+## .cfi_negate_ra_state CFI directive is usually used to convey this information.
+## In GCC 14 and older, the Sparc DWARF extension .cfi_window_save is emitted
+## instead of .cfi_negate_ra_state. GCC 15 fixed this issue, but this behavior
+## is preserved in binutils for backward compatibility.
+##
+## SFrame has support for this. This testcase ensures that the directive
+## is interpreted successfully.
+ .cfi_startproc
+ .long 0
+ .cfi_def_cfa_offset 16
+ .cfi_window_save
+ .long 0
+ .cfi_endproc
@@ -8,12 +8,12 @@ _Z5foo_av:
.LFB0:
.cfi_startproc
hint 25 // paciasp
- .cfi_window_save
+ .cfi_negate_ra_state
stp x29, x30, [sp, -16]!
.cfi_def_cfa_offset 16
.cfi_offset 29, -16
.cfi_offset 30, -8
- ret
+ ret
.cfi_endproc
.LFE0:
.size _Z5foo_av, .-_Z5foo_av
@@ -25,12 +25,12 @@ _Z5foo_bv:
.cfi_startproc
.cfi_b_key_frame
hint 27 // pacibsp
- .cfi_window_save
+ .cfi_negate_ra_state
stp x29, x30, [sp, -16]!
.cfi_def_cfa_offset 16
.cfi_offset 29, -16
.cfi_offset 30, -8
nop
nop
- ret
+ ret
.cfi_endproc
@@ -97,5 +97,6 @@ if { [istarget "x86_64-*-*"] && [gas_sframe_check] } then {
if { [istarget "aarch64*-*-*"] && [gas_sframe_check] } then {
run_dump_test "cfi-sframe-aarch64-1"
run_dump_test "cfi-sframe-aarch64-2"
+ run_dump_test "cfi-sframe-aarch64-3"
run_dump_test "cfi-sframe-aarch64-pac-ab-key-1"
}