On 13/01/2023 17:44, Srinath Parvathaneni via Gcc-patches wrote:
Hello,
This patch teaches the DWARF support in gcc about RA_AUTH_CODE pseudo
hard-register and also
updates the ".save", ".cfi_register", ".cfi_offset", ".cfi_restore" directives
accordingly.
This patch also adds support to emit ".pacspval" directive when "pac ip, lr,
sp" instruction
in generated in the assembly.
RA_AUTH_CODE register number is 107 and it's dwarf register number is 143.
Applying this patch on top of PACBTI series posted here
https://gcc.gnu.org/pipermail/gcc-patches/2022-August/599658.html and when
compiling the following
test.c with "-march=armv8.1-m.main+mve+pacbti -mbranch-protection=pac-ret
-mthumb -mfloat-abi=hard
fasynchronous-unwind-tables -g -O0 -S" command line options, the assembly
output after this patch
looks like below:
$cat test.c
void fun1(int a);
void fun(int a,...)
{
fun1(a);
}
int main()
{
fun (10);
return 0;
}
$ arm-none-eabi-gcc -march=armv8.1-m.main+mve+pacbti
-mbranch-protection=pac-ret -mthumb -mfloat-abi=hard
-fasynchronous-unwind-tables -g -O0 -S test.s
Assembly output:
...
fun:
...
.pacspval
pac ip, lr, sp
.cfi_register 143, 12
push {r3, r7, ip, lr}
.save {r3, r7, ra_auth_code, lr}
...
.cfi_offset 143, -24
...
.cfi_restore 143
...
aut ip, lr, sp
bx lr
...
main:
...
.pacspval
pac ip, lr, sp
.cfi_register 143, 12
push {r3, r7, ip, lr}
.save {r3, r7, ra_auth_code, lr}
...
.cfi_offset 143, -8
...
.cfi_restore 143
...
aut ip, lr, sp
bx lr
...
Regression tested on arm-none-eabi target and found no regressions.
Ok for master?
Regards,
Srinath.
2023-01-11 Srinath Parvathaneni <srinath.parvathan...@arm.com>
* config/arm/aout.h (ra_auth_code): Add entry in enum.
(emit_multi_reg_push): Add RA_AUTH_CODE register to
dwarf frame expression.
(arm_emit_multi_reg_pop): Restore RA_AUTH_CODE register.
(arm_expand_prologue): Update frame related information and reg notes
for pac/pacbit insn.
(arm_regno_class): Check for pac pseudo reigster.
(arm_dbx_register_number): Assign ra_auth_code register number in
dwarf.
(arm_init_machine_status): Set pacspval_needed to zero.
(arm_debugger_regno): Check for PAC register.
(arm_unwind_emit_sequence): Print .save directive with ra_auth_code
register.
(arm_unwind_emit_set): Add entry for IP_REGNUM in switch case.
(arm_unwind_emit): Update REG_CFA_REGISTER case._
* config/arm/arm.h (FIRST_PSEUDO_REGISTER): Modify.
(DWARF_PAC_REGNUM): Define.
(IS_PAC_REGNUM): Likewise.
(enum reg_class): Add PAC_REG entry.
(machine_function): Add pacbti_needed state to structure.
* config/arm/arm.md (RA_AUTH_CODE): Define.
gcc/testsuite/ChangeLog:
2023-01-11 Srinath Parvathaneni <srinath.parvathan...@arm.com>
* g++.target/arm/pac-1.C: New test.
* gcc.target/arm/pac-15.c: Likewise.
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+ /* NOTE: Dwarf code emitter handle reg-reg copies correctly and in the
+ following example reg-reg copy of SP to IP register is handled
+ through .cfi_def_cfa_register directive and the .cfi_offset
+ directive for IP register is skipped by dwarf code emitter.
+ Example:
+ mov ip, sp
+ .cfi_def_cfa_register 12
+ push {fp, ip, lr, pc}
+ .cfi_offset 11, -16
+ .cfi_offset 13, -12
+ .cfi_offset 14, -8
+
+ Where as Arm-specific .save directive reg-reg copy handling is
+ buggy. After the reg-reg copy, the copied registers need to be
It's not buggy (if it were you'd need to fix it :). It just works in a
different way to the dwarf tracker and doesn't need to handle reg->reg
copies. So please rephrase this.
+ populated in .save directive register list but with the current
+ implementation of .save directive original registers are getting
+ populated in the register list. So to avoid this issue for IP
+ register when PACBTI is enabled we manually updated the .save
+ directive register list to use "ra_auth_code" (pseduo register 143)
+ instead of IP register as shown in following example.
+ Example:
+ pacbti ip, lr, sp
+ .cfi_register 143, 12
+ push {r3, r7, ip, lr}
+ .save {r3, r7, ra_auth_code, lr}
+ */
R.
