[binutils-gdb] [aarch64] Add support for pointer authentication B key
Thomas Preud'homme
thopre01@sourceware.org
Wed Dec 5 18:31:00 GMT 2018
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=3a67e1a6b4430374f3073e51bb19347d4c421cfe
commit 3a67e1a6b4430374f3073e51bb19347d4c421cfe
Author: Sam Tebbs <sam.tebbs@arm.com>
Date: Wed Dec 5 18:27:23 2018 +0000
[aarch64] Add support for pointer authentication B key
Armv8.3-A has another key used in pointer authentication called the
B-key (other than the A-key that is already supported). In order for
stack unwinders to work it is necessary to be able to identify frames
that have been signed with the B-key rather than the A-key and it was
felt that keeping this as an augmentation character in the CIE was the
best bet. The DWARF extensions for ARM therefore propose to add a new
augmentation character 'B' to the CIE augmentation string and the
corresponding cfi directive ".cfi_b_key_frame". I've made the relevant
changes to GAS and LD to add support for B-key unwinding, which required
modifying LD to check for 'B' in the augmentation string, adding the
".cfi_b_key_frame" directive to GAS and adding a "pauth_key" field to
GAS's fde_entry and cie_entry structs.
The pointer authentication instructions will behave as NOPs on
architectures that don't support them, and so a check for the
architecture being assembled for is not necessary since there will be no
behavioural difference between augmentation strings with and without the
'B' character on such architectures.
2018-12-05 Sam Tebbs <sam.tebbs@arm.com>
bfd/
* elf-eh-frame.c (_bfd_elf_parse_eh_frame): Add check for 'B'.
gas/
* dw2gencfi.c (struct cie_entry): Add tc_cie_entry_extras invocation.
(alloc_fde_entry): Add tc_fde_entry_init_extra invocation.
(output_cie): Add tc_output_cie_extra invocation.
(select_cie_for_fde): Add tc_cie_fde_equivalent_extra and
tc_cie_entry_init_extra invocation.
(frch_cfi_data, cfa_save_data): Move to dwgencfi.h.
* config/tc-aarch64.c (s_aarch64_cfi_b_key_frame): Declare.
(md_pseudo_table): Add "cfi_b_key_frame".
* config/tc-aarch64.h (tc_fde_entry_extras, tc_cie_entry_extras,
tc_fde_entry_init_extra, tc_output_cie_extra,
tc_cie_fde_equivalent_extra, tc_cie_entry_init_extra): Define.
* dw2gencfi.h (struct fde_entry): Add tc_fde_entry_extras invocation.
(pointer_auth_key): Define.
(frch_cfi_data, cfa_save_data): Move from dwgencfi.c.
* doc/c-aarch64.texi (.cfi_b_key_frame): Add documentation.
* testsuite/gas/aarch64/(pac_ab_key.d, pac_ab_key.s): New file.
Diff:
---
bfd/ChangeLog | 4 +++
bfd/elf-eh-frame.c | 2 ++
gas/ChangeLog | 19 ++++++++++++
gas/config/tc-aarch64.c | 9 ++++++
gas/doc/c-aarch64.texi | 8 +++++
gas/dw2gencfi.c | 22 ++++----------
gas/dw2gencfi.h | 23 +++++++++++++++
gas/testsuite/gas/aarch64/pac_ab_key.d | 54 ++++++++++++++++++++++++++++++++++
gas/testsuite/gas/aarch64/pac_ab_key.s | 31 +++++++++++++++++++
9 files changed, 156 insertions(+), 16 deletions(-)
diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 618126f..de468a4 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,7 @@
+2018-12-05 Sam Tebbs <sam.tebbs@arm.com>
+
+ * elf-eh-frame.c (_bfd_elf_parse_eh_frame): Add check for 'B'.
+
2018-12-04 H.J. Lu <hongjiu.lu@intel.com>
PR ld/23372
diff --git a/bfd/elf-eh-frame.c b/bfd/elf-eh-frame.c
index 12f06ef..b76a657 100644
--- a/bfd/elf-eh-frame.c
+++ b/bfd/elf-eh-frame.c
@@ -797,6 +797,8 @@ _bfd_elf_parse_eh_frame (bfd *abfd, struct bfd_link_info *info,
while (*aug != '\0')
switch (*aug++)
{
+ case 'B':
+ break;
case 'L':
REQUIRE (read_byte (&buf, end, &cie->lsda_encoding));
ENSURE_NO_RELOCS (buf);
diff --git a/gas/ChangeLog b/gas/ChangeLog
index dbb8a37..73cadc7 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,22 @@
+2018-12-05 Sam Tebbs <sam.tebbs@arm.com>
+
+ * dw2gencfi.c (struct cie_entry): Add tc_cie_entry_extras invocation.
+ (alloc_fde_entry): Add tc_fde_entry_init_extra invocation.
+ (output_cie): Add tc_output_cie_extra invocation.
+ (select_cie_for_fde): Add tc_cie_fde_equivalent_extra and
+ tc_cie_entry_init_extra invocation.
+ (frch_cfi_data, cfa_save_data): Move to dwgencfi.h.
+ * config/tc-aarch64.c (s_aarch64_cfi_b_key_frame): Declare.
+ (md_pseudo_table): Add "cfi_b_key_frame".
+ * config/tc-aarch64.h (tc_fde_entry_extras, tc_cie_entry_extras,
+ tc_fde_entry_init_extra, tc_output_cie_extra,
+ tc_cie_fde_equivalent_extra, tc_cie_entry_init_extra): Define.
+ * dw2gencfi.h (struct fde_entry): Add tc_fde_entry_extras invocation.
+ (pointer_auth_key): Define.
+ (frch_cfi_data, cfa_save_data): Move from dwgencfi.c.
+ * doc/c-aarch64.texi (.cfi_b_key_frame): Add documentation.
+ * testsuite/gas/aarch64/(pac_ab_key.d, pac_ab_key.s): New file.
+
2018-12-04 wu.heng <wu.heng@zte.com.cn>
PR 23939
diff --git a/gas/config/tc-aarch64.c b/gas/config/tc-aarch64.c
index 3fed11c..4c97703 100644
--- a/gas/config/tc-aarch64.c
+++ b/gas/config/tc-aarch64.c
@@ -1993,6 +1993,14 @@ s_aarch64_inst (int ignored ATTRIBUTE_UNUSED)
demand_empty_rest_of_line ();
}
+static void
+s_aarch64_cfi_b_key_frame (int ignored ATTRIBUTE_UNUSED)
+{
+ demand_empty_rest_of_line ();
+ struct fde_entry *fde = frchain_now->frch_cfi_data->cur_fde_data;
+ fde->pauth_key = AARCH64_PAUTH_KEY_B;
+}
+
#ifdef OBJ_ELF
/* Emit BFD_RELOC_AARCH64_TLSDESC_ADD on the next ADD instruction. */
@@ -2067,6 +2075,7 @@ const pseudo_typeS md_pseudo_table[] = {
{"arch", s_aarch64_arch, 0},
{"arch_extension", s_aarch64_arch_extension, 0},
{"inst", s_aarch64_inst, 0},
+ {"cfi_b_key_frame", s_aarch64_cfi_b_key_frame, 0},
#ifdef OBJ_ELF
{"tlsdescadd", s_tlsdescadd, 0},
{"tlsdesccall", s_tlsdesccall, 0},
diff --git a/gas/doc/c-aarch64.texi b/gas/doc/c-aarch64.texi
index f38fdf5..ca84c9d 100644
--- a/gas/doc/c-aarch64.texi
+++ b/gas/doc/c-aarch64.texi
@@ -435,6 +435,14 @@ as the @code{.dword} directive.
@c YYYYYYYYYYYYYYYYYYYYYYYYYY
@c ZZZZZZZZZZZZZZZZZZZZZZZZZZ
+@cindex @code{.cfi_b_key_frame} directive, AArch64
+@item @code{.cfi_b_key_frame}
+The @code{.cfi_b_key_frame} directive inserts a 'B' character into the CIE
+corresponding to the current frame's FDE, meaning that its return address has
+been signed with the B-key. If two frames are signed with differing keys then
+they will not share the same CIE. This information is intended to be used by
+the stack unwinder in order to properly authenticate return addresses.
+
@end table
@node AArch64 Opcodes
diff --git a/gas/dw2gencfi.c b/gas/dw2gencfi.c
index 4add173..ff5c0df 100644
--- a/gas/dw2gencfi.c
+++ b/gas/dw2gencfi.c
@@ -403,6 +403,7 @@ struct cie_entry
unsigned char per_encoding;
unsigned char lsda_encoding;
expressionS personality;
+ enum pointer_auth_key pauth_key;
struct cfi_insn_data *first, *last;
};
@@ -414,22 +415,6 @@ static struct fde_entry **last_fde_data = &all_fde_data;
/* List of CIEs so that they could be reused. */
static struct cie_entry *cie_root;
-/* Stack of old CFI data, for save/restore. */
-struct cfa_save_data
-{
- struct cfa_save_data *next;
- offsetT cfa_offset;
-};
-
-/* Current open FDE entry. */
-struct frch_cfi_data
-{
- struct fde_entry *cur_fde_data;
- symbolS *last_address;
- offsetT cur_cfa_offset;
- struct cfa_save_data *cfa_save_stack;
-};
-
/* Construct a new FDE structure and add it to the end of the fde list. */
static struct fde_entry *
@@ -448,6 +433,7 @@ alloc_fde_entry (void)
fde->per_encoding = DW_EH_PE_omit;
fde->lsda_encoding = DW_EH_PE_omit;
fde->eh_header_type = EH_COMPACT_UNKNOWN;
+ fde->pauth_key = AARCH64_PAUTH_KEY_A;
return fde;
}
@@ -1872,6 +1858,8 @@ output_cie (struct cie_entry *cie, bfd_boolean eh_frame, int align)
if (cie->lsda_encoding != DW_EH_PE_omit)
out_one ('L');
out_one ('R');
+ if (cie->pauth_key == AARCH64_PAUTH_KEY_B)
+ out_one ('B');
}
if (cie->signal_frame)
out_one ('S');
@@ -2052,6 +2040,7 @@ select_cie_for_fde (struct fde_entry *fde, bfd_boolean eh_frame,
if (CUR_SEG (cie) != CUR_SEG (fde))
continue;
if (cie->return_column != fde->return_column
+ || cie->pauth_key != fde->pauth_key
|| cie->signal_frame != fde->signal_frame
|| cie->per_encoding != fde->per_encoding
|| cie->lsda_encoding != fde->lsda_encoding)
@@ -2158,6 +2147,7 @@ select_cie_for_fde (struct fde_entry *fde, bfd_boolean eh_frame,
cie->lsda_encoding = fde->lsda_encoding;
cie->personality = fde->personality;
cie->first = fde->data;
+ cie->pauth_key = fde->pauth_key;
for (i = cie->first; i ; i = i->next)
if (i->insn == DW_CFA_advance_loc
diff --git a/gas/dw2gencfi.h b/gas/dw2gencfi.h
index cf534b4..2b1362a 100644
--- a/gas/dw2gencfi.h
+++ b/gas/dw2gencfi.h
@@ -135,6 +135,27 @@ enum {
EH_COMPACT_HAS_LSDA
};
+enum pointer_auth_key {
+ AARCH64_PAUTH_KEY_A,
+ AARCH64_PAUTH_KEY_B
+};
+
+/* Stack of old CFI data, for save/restore. */
+struct cfa_save_data
+{
+ struct cfa_save_data *next;
+ offsetT cfa_offset;
+};
+
+/* Current open FDE entry. */
+struct frch_cfi_data
+{
+ struct fde_entry *cur_fde_data;
+ symbolS *last_address;
+ offsetT cur_cfa_offset;
+ struct cfa_save_data *cfa_save_stack;
+};
+
struct fde_entry
{
struct fde_entry *next;
@@ -162,6 +183,8 @@ struct fde_entry
/* For out of line tables and FDEs. */
symbolS *eh_loc;
int sections;
+ /* The pointer authentication key used. Only used for AArch64. */
+ enum pointer_auth_key pauth_key;
};
/* The list of all FDEs that have been collected. */
diff --git a/gas/testsuite/gas/aarch64/pac_ab_key.d b/gas/testsuite/gas/aarch64/pac_ab_key.d
new file mode 100644
index 0000000..a428633
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/pac_ab_key.d
@@ -0,0 +1,54 @@
+#objdump: --dwarf=frames
+# Test assembling a file with functions signed by two different pointer
+# authentication keys. It must interpret .cfi_b_key_frame properly and emit a
+# 'B' character into the correct CIE's augmentation string.
+
+.+: file .+
+
+Contents of the .eh_frame section:
+
+00000000 0000000000000010 00000000 CIE
+ Version: 1
+ Augmentation: "zR"
+ Code alignment factor: 4
+ Data alignment factor: -8
+ Return address column: 30
+ Augmentation data: 1b
+ DW_CFA_def_cfa: r31 \(sp\) ofs 0
+
+00000014 0000000000000018 00000018 FDE cie=00000000 pc=0000000000000000..0000000000000008
+ DW_CFA_advance_loc: 4 to 0000000000000004
+ DW_CFA_GNU_window_save
+ DW_CFA_advance_loc: 4 to 0000000000000008
+ DW_CFA_def_cfa_offset: 16
+ DW_CFA_offset: r29 \(x29\) at cfa-16
+ DW_CFA_offset: r30 \(x30\) at cfa-8
+ DW_CFA_nop
+ DW_CFA_nop
+
+00000030 0000000000000014 00000000 CIE
+ Version: 1
+ Augmentation: "zRB"
+ Code alignment factor: 4
+ Data alignment factor: -8
+ Return address column: 30
+ Augmentation data: 1b
+ DW_CFA_def_cfa: r31 \(sp\) ofs 0
+ DW_CFA_nop
+ DW_CFA_nop
+ DW_CFA_nop
+
+00000048 000000000000001c 0000001c FDE cie=00000030 pc=0000000000000008..0000000000000010
+ DW_CFA_advance_loc: 4 to 000000000000000c
+ DW_CFA_GNU_window_save
+ DW_CFA_advance_loc: 4 to 0000000000000010
+ DW_CFA_def_cfa_offset: 16
+ DW_CFA_offset: r29 \(x29\) at cfa-16
+ DW_CFA_offset: r30 \(x30\) at cfa-8
+ DW_CFA_nop
+ DW_CFA_nop
+ DW_CFA_nop
+ DW_CFA_nop
+ DW_CFA_nop
+ DW_CFA_nop
+
diff --git a/gas/testsuite/gas/aarch64/pac_ab_key.s b/gas/testsuite/gas/aarch64/pac_ab_key.s
new file mode 100644
index 0000000..4b328e7
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/pac_ab_key.s
@@ -0,0 +1,31 @@
+ .arch armv8-a
+ .text
+ .align 2
+ .global _Z5foo_av
+ .type _Z5foo_av, %function
+_Z5foo_av:
+.LFB0:
+ .cfi_startproc
+ hint 25 // paciasp
+ .cfi_window_save
+ stp x29, x30, [sp, -16]!
+ .cfi_def_cfa_offset 16
+ .cfi_offset 29, -16
+ .cfi_offset 30, -8
+ .cfi_endproc
+.LFE0:
+ .size _Z5foo_av, .-_Z5foo_av
+ .align 2
+ .global _Z5foo_bv
+ .type _Z5foo_bv, %function
+_Z5foo_bv:
+.LFB1:
+ .cfi_startproc
+ .cfi_b_key_frame
+ hint 27 // pacibsp
+ .cfi_window_save
+ stp x29, x30, [sp, -16]!
+ .cfi_def_cfa_offset 16
+ .cfi_offset 29, -16
+ .cfi_offset 30, -8
+ .cfi_endproc
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