[PATCH v3] Return the regnum for PC (32) on aarch64
Yichao Yu
yyc1992@gmail.com
Tue May 17 14:41:43 GMT 2022
This will allow the unwind info to explicitly specify a different value
for the return address from the link register.
Such usage, although uncommon, is valid and useful for signal frames.
It is also endorsed by aadwarf64 from ARM (Note 9 in [1]).
Ref https://sourceware.org/pipermail/gdb/2022-May/050091.html
[1] https://github.com/ARM-software/abi-aa/blob/2022Q1/aadwarf64/aadwarf64.rst#dwarf-register-names
---
gdb/aarch64-tdep.c | 3 +
gdb/aarch64-tdep.h | 1 +
gdb/testsuite/gdb.arch/aarch64-unwind-pc.S | 48 ++++++++++++++
gdb/testsuite/gdb.arch/aarch64-unwind-pc.exp | 70 ++++++++++++++++++++
4 files changed, 122 insertions(+)
create mode 100644 gdb/testsuite/gdb.arch/aarch64-unwind-pc.S
create mode 100644 gdb/testsuite/gdb.arch/aarch64-unwind-pc.exp
diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index 9d06ebfe27c..f9eb455232f 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -2219,6 +2219,9 @@ aarch64_dwarf_reg_to_regnum (struct gdbarch *gdbarch, int reg)
if (reg == AARCH64_DWARF_SP)
return AARCH64_SP_REGNUM;
+ if (reg == AARCH64_DWARF_PC)
+ return AARCH64_PC_REGNUM;
+
if (reg >= AARCH64_DWARF_V0 && reg <= AARCH64_DWARF_V0 + 31)
return AARCH64_V0_REGNUM + reg - AARCH64_DWARF_V0;
diff --git a/gdb/aarch64-tdep.h b/gdb/aarch64-tdep.h
index e4cdebb6311..aa1bedbdac6 100644
--- a/gdb/aarch64-tdep.h
+++ b/gdb/aarch64-tdep.h
@@ -34,6 +34,7 @@ struct regset;
/* AArch64 Dwarf register numbering. */
#define AARCH64_DWARF_X0 0
#define AARCH64_DWARF_SP 31
+#define AARCH64_DWARF_PC 32
#define AARCH64_DWARF_PAUTH_RA_STATE 34
#define AARCH64_DWARF_PAUTH_DMASK 35
#define AARCH64_DWARF_PAUTH_CMASK 36
diff --git a/gdb/testsuite/gdb.arch/aarch64-unwind-pc.S b/gdb/testsuite/gdb.arch/aarch64-unwind-pc.S
new file mode 100644
index 00000000000..6cc4f80e349
--- /dev/null
+++ b/gdb/testsuite/gdb.arch/aarch64-unwind-pc.S
@@ -0,0 +1,48 @@
+/* Copyright 2022 Free Software Foundation, Inc.
+
+ This file is part of GDB.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+ .text
+ .globl main
+ .type main,#function
+main:
+ .cfi_startproc
+ stp x29, x30, [sp, -16]!
+ .cfi_def_cfa sp, 16
+ .cfi_offset x29, 0
+ .cfi_offset x30, 8
+ bl test_func
+ ldp x29, x30, [sp], 16
+ .cfi_restore x29
+ .cfi_restore x30
+ .cfi_def_cfa sp, 0
+ mov x0, 0
+ ret
+ .cfi_endproc
+
+ .globl test_func
+test_func:
+ .cfi_startproc
+ // Unwind x30 to a different value
+ // CFA_val_expression x30 const2u 0x1234
+ .cfi_escape 0x16, 30, 0x03, 0x0a, 0x34, 0x12
+ // CFA_val_expression pc breg30 0
+ .cfi_escape 0x16, 32, 0x02, 0x8e, 0x00
+ mov x0, x30
+ .cfi_register 32, x0
+ mov x30, 0x1234
+ ret x0
+ .cfi_endproc
diff --git a/gdb/testsuite/gdb.arch/aarch64-unwind-pc.exp b/gdb/testsuite/gdb.arch/aarch64-unwind-pc.exp
new file mode 100644
index 00000000000..105b9a9cc3a
--- /dev/null
+++ b/gdb/testsuite/gdb.arch/aarch64-unwind-pc.exp
@@ -0,0 +1,70 @@
+# Copyright 2022 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# This file is part of the gdb testsuite.
+
+# Test explicitly unwinding the PC DWARF register on aarch64
+
+if {![is_aarch64_target]} then {
+ verbose "Skipping ${gdb_test_file_name}."
+ return
+}
+
+standard_testfile .S
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {
+ return -1
+}
+
+if ![runto_main] {
+ return -1
+}
+
+proc test_reg_vals {} {
+ gdb_test "p \$pc - &main" "= 8" "p \$pc"
+ gdb_test "p/x \$x30" "= 0x1234" "p \$x30"
+}
+
+proc test_unwind_pc { inst } {
+ gdb_test "si" "$inst" "single step"
+ gdb_test "backtrace" \
+ ".*#1.*in main ().*" \
+ "backtrace"
+ gdb_test "up" "in main ().*" "parent frame"
+ test_reg_vals
+}
+
+# Ready to enter the function
+gdb_test "si" "bl test_func" "call site"
+# Step through the 3 instructions in the function to make sure that
+# we have the same unwind info throughout.
+with_test_prefix "1st stepi" {
+ test_unwind_pc "mov x0, x30"
+}
+with_test_prefix "2nd stepi" {
+ test_unwind_pc "mov x30, 0x1234"
+}
+with_test_prefix "3rd stepi" {
+ test_unwind_pc "ret x0"
+}
+# Check again after we returned
+with_test_prefix "final" {
+ # Check that we've stepped out (si prints out the new function name)
+ gdb_test "si" ".*main *().*" "single step out"
+ gdb_test "backtrace" \
+ "#0\[\t \]+main ().*" \
+ "backtrace"
+ test_reg_vals
+}
--
2.36.1
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