Describe the default CFI for the alpha ABI: the CFA is $sp, the return
address is in $ra ($26), and $9-$15 and $f2-$f9 are callee-saved.
Set frame_nregs to 65. GCC's DWARF_ALT_FRAME_RETURN_COLUMN on alpha is
64, and glibc's signal trampolines use it as the return address column
(cfi_return_column (64)), so the unwinder needs a slot for it after
$0-$31 and $f0-$f31.
Together with the prstatus fix this makes eu-stack --core work on
alpha core files.
* backends/alpha_cfi.c: New file.
* backends/Makefile.am (alpha_SRCS): Add alpha_cfi.c.
* backends/alpha_init.c (alpha_init): Hook abi_cfi and set
frame_nregs.
---
backends/Makefile.am | 2 +-
backends/alpha_cfi.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++
backends/alpha_init.c | 5 ++++
3 files changed, 75 insertions(+), 1 deletion(-)
diff --git a/backends/Makefile.am b/backends/Makefile.am
index d7dfc7bc..604673b6 100644
--- a/backends/Makefile.am
+++ b/backends/Makefile.am
@@ -53,7 +53,7 @@ x86_64_SRCS = x86_64_init.c x86_64_symbol.c x86_64_corenote.c
x86_64_cfi.c \
ia64_SRCS = ia64_init.c ia64_symbol.c ia64_regs.c ia64_retval.c
alpha_SRCS = alpha_init.c alpha_symbol.c alpha_retval.c alpha_regs.c \
- alpha_corenote.c alpha_auxv.c
+ alpha_corenote.c alpha_auxv.c alpha_cfi.c
arm_SRCS = arm_init.c arm_symbol.c arm_regs.c arm_corenote.c \
arm_auxv.c arm_attrs.c arm_retval.c arm_cfi.c arm_initreg.c \
diff --git a/backends/alpha_cfi.c b/backends/alpha_cfi.c
new file mode 100644
index 00000000..bb7de1da
--- /dev/null
+++ b/backends/alpha_cfi.c
@@ -0,0 +1,69 @@
+/* Alpha ABI-specified defaults for DWARF CFI.
+ Copyright (C) 2026 Matt Turner
+ This file is part of elfutils.
+
+ This file is free software; you can redistribute it and/or modify
+ it under the terms of either
+
+ * the GNU Lesser General Public License as published by the Free
+ Software Foundation; either version 3 of the License, or (at
+ your option) any later version
+
+ or
+
+ * the GNU General Public License as published by the Free
+ Software Foundation; either version 2 of the License, or (at
+ your option) any later version
+
+ or both in parallel, as here.
+
+ elfutils 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 copies of the GNU General Public License and
+ the GNU Lesser General Public License along with this program. If
+ not, see <http://www.gnu.org/licenses/>. */
+
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <dwarf.h>
+
+#define BACKEND alpha_
+#include "libebl_CPU.h"
+
+int
+alpha_abi_cfi (Ebl *ebl __attribute__ ((unused)), Dwarf_CIE *abi_info)
+{
+ static const uint8_t abi_cfi[] =
+ {
+ /* The CFA is the value of $sp ($30) in the previous frame. */
+ DW_CFA_def_cfa, ULEB128_7 (30), ULEB128_7 (0),
+
+ /* $sp is restored from the CFA. */
+ DW_CFA_val_offset, ULEB128_7 (30), ULEB128_7 (0),
+
+#define SV(n) DW_CFA_same_value, ULEB128_7 (n)
+ /* The return address in $ra ($26) is set up by the caller. */
+ SV (26),
+
+ /* Callee-saved registers $s0-$s5 ($9-$14) and $fp ($15). */
+ SV (9), SV (10), SV (11), SV (12), SV (13), SV (14), SV (15),
+
+ /* Callee-saved registers $f2-$f9. */
+ SV (34), SV (35), SV (36), SV (37), SV (38), SV (39), SV (40), SV (41),
+#undef SV
+ };
+
+ abi_info->initial_instructions = abi_cfi;
+ abi_info->initial_instructions_end = &abi_cfi[sizeof abi_cfi];
+ abi_info->data_alignment_factor = -8;
+
+ abi_info->return_address_register = 26; /* $ra */
+
+ return 0;
+}
diff --git a/backends/alpha_init.c b/backends/alpha_init.c
index c69aec6d..229c5beb 100644
--- a/backends/alpha_init.c
+++ b/backends/alpha_init.c
@@ -57,6 +57,11 @@ alpha_init (Elf *elf __attribute__ ((unused)),
HOOK (eh, register_info);
HOOK (eh, core_note);
HOOK (eh, auxv_info);
+ HOOK (eh, abi_cfi);
+ /* $0-$31, $f0-$f31, and column 64 for the PC, which gcc's
+ DWARF_ALT_FRAME_RETURN_COLUMN and glibc's signal trampolines use
+ as the return address column. */
+ eh->frame_nregs = 65;
eh->sysvhash_entrysize = sizeof (Elf64_Xword);
return eh;
--
2.55.0
