On 11/11/16 18:22, Jiong Wang wrote:
This patch generate DWARF description for pointer authentication. DWARF value
expression is used to describe the authentication action.
Please see the cover letter and AArch64 DWARF specification for the semantics
of AArch64 DWARF operations.
When authentication key index is A key, we use compact DWARF description which
can largely save DWARF frame size, otherwise we fallback to general operator.
Example
===
int
cal (int a, int b, int c)
{
return a + dec (b) + c;
}
Compact DWARF description
(-march=armv8.3-a -msign-return-address)
===
DW_CFA_advance_loc: 4 to 0000000000000004
DW_CFA_val_expression: r30 (x30) (DW_OP_AARCH64_paciasp)
DW_CFA_advance_loc: 4 to 0000000000000008
DW_CFA_val_expression: r30 (x30) (DW_OP_AARCH64_paciasp_deref: -24)
General DWARF description
===
(-march=armv8.3-a -msign-return-address -mpauth-key=b_key)
DW_CFA_advance_loc: 4 to 0000000000000004
DW_CFA_val_expression: r30 (x30) (DW_OP_breg30 (x30): 0;
DW_OP_AARCH64_pauth: 18)
DW_CFA_advance_loc: 4 to 0000000000000008
DW_CFA_val_expression: r30 (x30) (DW_OP_dup; DW_OP_const1s: -24; DW_OP_plus;
DW_OP_deref; DW_OP_AARCH64_pauth: 18)
From Linux kernel testing, -msign-return-address will introduce +24%
.debug_frame size increase when signing all functions and using compact
description, and about +45% .debug_frame size increase if using general
description.
gcc/
2016-11-11 Jiong Wang<jiong.w...@arm.com>
* config/aarch64/aarch64.h (aarch64_pauth_action_type): New enum.
* config/aarch64/aarch64.c (aarch64_attach_ra_auth_dwarf_note): New
function.
(aarch64_attach_ra_auth_dwarf_general): New function.
(aarch64_attach_ra_auth_dwarf_shortcut): New function.
(aarch64_save_callee_saves): Generate dwarf information if LR is
signed.
(aarch64_expand_prologue): Likewise.
(aarch64_expand_epilogue): Likewise.
This patch is an update on DWARF generation for return address signing.
According to new proposal, we simply needs to generate REG_CFA_WINDOW_SAVE
annotation.
gcc/
2017-01-06 Jiong Wang <jiong.w...@arm.com>
* config/aarch64/aarch64.c (aarch64_expand_prologue): Generate dwarf
annotation (REG_CFA_WINDOW_SAVE) for return address signing.
(aarch64_expand_epilogue): Likewise.
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 002895a167ce0deb45a5c1726527651af18bb4df..20ed79e5690f45ec121ef516245c686cc0cc82b5 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -3553,7 +3553,11 @@ aarch64_expand_prologue (void)
/* Sign return address for functions. */
if (aarch64_return_address_signing_enabled ())
- emit_insn (gen_pacisp ());
+ {
+ insn = emit_insn (gen_pacisp ());
+ add_reg_note (insn, REG_CFA_WINDOW_SAVE, const0_rtx);
+ RTX_FRAME_RELATED_P (insn) = 1;
+ }
if (flag_stack_usage_info)
current_function_static_stack_size = frame_size;
@@ -3698,7 +3702,11 @@ aarch64_expand_epilogue (bool for_sibcall)
want to use the CFA of the function which calls eh_return. */
if (aarch64_return_address_signing_enabled ()
&& (for_sibcall || !TARGET_ARMV8_3 || crtl->calls_eh_return))
- emit_insn (gen_autisp ());
+ {
+ insn = emit_insn (gen_autisp ());
+ add_reg_note (insn, REG_CFA_WINDOW_SAVE, const0_rtx);
+ RTX_FRAME_RELATED_P (insn) = 1;
+ }
/* Stack adjustment for exception handler. */
if (crtl->calls_eh_return)
