Expanding the libdwflst support for handling perf sample_regs register
files to other architectures. First, add the pieces for aarch64.
* backends/Makefile.am (aarch64_SRCS): Add aarch64_initreg_sample.c.
* backends/aarch64_init.c (aarch64_init): Add hooks for
set_initial_registers_sample, sample_sp_pc, perf_frame_regs_mask.
* backends/aarch64_initreg_sample.c: New file. Implement
aarch64_set_initial_registers_sample mirroring the ptrace->dwarf_regs
logic in aarch64_initreg.c.
* backends/libebl_PERF_FLAGS.h (PERF_FRAME_REGISTERS_AARCH64): New
constant describing registers needed for aarch64 unwinding.
(generic_sample_sp_pc): New inline function generalizing existing
x86_sample_sp_pc code to any arch given sp_index and pc_index.
* libebl/eblinitreg_sample.c (ebl_sample_perf_regs_mapping): Update
with a default implementation for arches where perf_regs and
dwarf_regs order coincides (we just need the mapping to account for
present/absent registers in perf_regs mask).
* libebl/eblopenbackend.c (__libebl_init_cached_regs_mapping): New
function generalizing a bit of ARCH_init regs_mapping boilerplate.
* libebl/eblopenbackend.c (__libebl_init_cached_regs_mapping):
Implement new function.
---
backends/Makefile.am | 4 +-
backends/aarch64_init.c | 8 ++-
backends/aarch64_initreg_sample.c | 104 ++++++++++++++++++++++++++++++
backends/libebl_PERF_FLAGS.h | 49 ++++++++++++--
libebl/eblinitreg_sample.c | 49 ++++++++++++--
libebl/eblopenbackend.c | 13 +++-
libebl/libeblP.h | 5 +-
7 files changed, 217 insertions(+), 15 deletions(-)
create mode 100644 backends/aarch64_initreg_sample.c
diff --git a/backends/Makefile.am b/backends/Makefile.am
index 7a820df0..bebd990e 100644
--- a/backends/Makefile.am
+++ b/backends/Makefile.am
@@ -1,6 +1,6 @@
## Process this file with automake to create Makefile.in
##
-## Copyright (C) 2000-2010, 2013, 2014, 2025 Red Hat, Inc.
+## Copyright (C) 2000-2010, 2013, 2014, 2025-2026 Red Hat, Inc.
## Copyright (C) 2012 Tilera Corporation
## This file is part of elfutils.
##
@@ -61,7 +61,7 @@ arm_SRCS = arm_init.c arm_symbol.c arm_regs.c arm_corenote.c \
aarch64_SRCS = aarch64_init.c aarch64_regs.c aarch64_symbol.c \
aarch64_corenote.c aarch64_retval.c aarch64_cfi.c \
- aarch64_initreg.c aarch64_unwind.c
+ aarch64_initreg.c aarch64_initreg_sample.c aarch64_unwind.c
sparc_SRCS = sparc_init.c sparc_symbol.c sparc_regs.c sparc_retval.c \
sparc_corenote.c sparc64_corenote.c sparc_auxv.c sparc_attrs.c \
diff --git a/backends/aarch64_init.c b/backends/aarch64_init.c
index c61767d5..f6505bd7 100644
--- a/backends/aarch64_init.c
+++ b/backends/aarch64_init.c
@@ -1,5 +1,5 @@
/* Initialization of AArch64 specific backend library.
- Copyright (C) 2013, 2017 Red Hat, Inc.
+ Copyright (C) 2013, 2017, 2026 Red Hat, Inc.
This file is part of elfutils.
This file is free software; you can redistribute it and/or modify
@@ -33,6 +33,7 @@
#define BACKEND aarch64_
#define RELOC_PREFIX R_AARCH64_
#include "libebl_CPU.h"
+#include "libebl_PERF_FLAGS.h"
/* This defines the common reloc hooks based on aarch64_reloc.def. */
#include "common-reloc.c"
@@ -61,6 +62,11 @@ aarch64_init (Elf *elf __attribute__ ((unused)),
+ ALT_FRAME_RETURN_COLUMN (used when LR isn't used) = 97 DWARF regs. */
eh->frame_nregs = 97;
HOOK (eh, set_initial_registers_tid);
+ HOOK (eh, set_initial_registers_sample);
+ HOOK (eh, sample_sp_pc);
+ /* sample_perf_regs_mapping is default ver */
+ eh->perf_frame_regs_mask = PERF_FRAME_REGISTERS_AARCH64;
+ __libebl_init_cached_regs_mapping (eh);
HOOK (eh, unwind);
return eh;
diff --git a/backends/aarch64_initreg_sample.c
b/backends/aarch64_initreg_sample.c
new file mode 100644
index 00000000..1ea17324
--- /dev/null
+++ b/backends/aarch64_initreg_sample.c
@@ -0,0 +1,104 @@
+/* Populate process registers from a register sample.
+ Copyright (C) 2026 Red Hat Inc.
+ 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 <stdlib.h>
+#include <assert.h>
+
+#define BACKEND aarch64_
+#include "libebl_CPU.h"
+#include "libebl_PERF_FLAGS.h"
+/* TODO libebl_PERF_FLAGS.h now includes generic_sample_sp_pc
+ -- may want to rename the header? */
+
+bool
+aarch64_sample_sp_pc (const Dwarf_Word *regs, uint32_t n_regs,
+ const int *regs_mapping, uint32_t n_regs_mapping,
+ Dwarf_Word *sp, Dwarf_Word *pc)
+{
+ return generic_sample_sp_pc (regs, n_regs, regs_mapping, n_regs_mapping,
+ sp, 31 /* index of sp in dwarf_regs */,
+ pc, 32 /* index of pc in dwarf_regs */);
+}
+
+bool
+aarch64_set_initial_registers_sample (const Dwarf_Word *regs, uint32_t n_regs,
+ const int *regs_mapping, size_t
n_regs_mapping,
+ ebl_tid_registers_t *setfunc,
+ void *arg)
+{
+/* TODO(REVIEW): The #ifdef here seems strictly optional as we don't
+ refer to perf_events or ptrace arch-specific declarations. */
+#if !defined(__aarch64__)
+ (void)regs; (void)n_regs;
+ (void)regs_mapping; (void)n_regs_mapping;
+ (void)setfunc; (void)arg;
+ return false;
+#else
+#define N_GREGS 33
+ Dwarf_Word dwarf_regs[N_GREGS];
+ bool scratch_present = false;
+ size_t i;
+ for (i = 0; i < N_GREGS; i++)
+ dwarf_regs[i] = 0x0;
+ for (i = 0; i < n_regs; i++)
+ {
+ if (i >= n_regs_mapping)
+ break;
+ if (regs_mapping[i] < 0 || regs_mapping[i] >= N_GREGS)
+ continue;
+ if (regs_mapping[i] < 19)
+ scratch_present = true;
+ dwarf_regs[regs_mapping[i]] = regs[i];
+ }
+
+ /* X0..X18 only if present. */
+ if (scratch_present && ! setfunc (0, 19, &dwarf_regs[0], arg))
+ return false;
+
+ /* X19..X29, X30(LR) plus SP. */
+ if (! setfunc (19, 32 - 18, &dwarf_regs[19], arg))
+ return false;
+
+ /* PC. */
+ if (! setfunc (-1, 1, &dwarf_regs[32], arg))
+ return false;
+
+ /* TODO(REVIEW): May need to obtain PAC mask since the unwinder
+ needs to strip it from LR/X30 to handle pointer
+ authentication. */
+
+ /* Skip ELR, RA_SIGN_STATE */
+
+ /* XXX Skip FP registers. */
+ return true;
+#endif /* __aarch64__ */
+}
diff --git a/backends/libebl_PERF_FLAGS.h b/backends/libebl_PERF_FLAGS.h
index 51c20ea6..54eb38a9 100644
--- a/backends/libebl_PERF_FLAGS.h
+++ b/backends/libebl_PERF_FLAGS.h
@@ -1,7 +1,7 @@
/* Linux perf_events sample_regs_user flags required for unwinding.
Internal only; elfutils library users should use ebl_perf_frame_regs_mask().
- Copyright (C) 2025 Red Hat, Inc.
+ Copyright (C) 2025-2026 Red Hat, Inc.
This file is part of elfutils.
This file is free software; you can redistribute it and/or modify
@@ -33,7 +33,7 @@
#if defined(__linux__)
/* XXX Need to exclude __linux__ arches without perf_regs.h. */
-#if defined(__x86_64__) || defined(__i386__)
+#if defined(__x86_64__) || defined(__i386__) || defined(__aarch64__)
/* || defined(other_architecture)... */
# include <asm/perf_regs.h>
#endif
@@ -54,9 +54,50 @@
and note how regs are added in the same order as the perf_regs.h enum. */
#else
/* Since asm/perf_regs.h is absent, or gives the register layout for a
- different arch, we can't unwind i386 and x86_64 frames. */
+ different arch, we can't unwind i386 and x86_64 perf sample frames. */
#define PERF_FRAME_REGISTERS_I386 0
#define PERF_FRAME_REGISTERS_X86_64 0
-#endif
+#endif /* _ASM_X86_PERF_REGS_H */
+
+#if defined(_ASM_ARM64_PERF_REGS_H)
+#define REG(R) (1ULL << PERF_REG_ARM64_ ## R)
+/* Proper unwind set: callee-saved X19..X28, then X29 for FP,
+ LR for return addr, and SP, PC. */
+#define PERF_FRAME_REGISTERS_AARCH64 (REG(X19) | REG(X20) | REG(X21) \
+ | REG(X22) | REG(X23) | REG(X24) | REG(X25) | REG(X26) | REG(X27) \
+ | REG(X28) | REG(X29) /*FP*/ | REG(LR) | REG(SP) | REG(PC))
+/* Register ordering defined in linux arch/arm64/include/uapi/asm/perf_regs.h.
*/
+#else
+/* Since asm/perf_regs.h is absent, or gives the register layout for a
+ different arch, we can't unwind aarch64 perf sample frames. */
+#define PERF_FRAME_REGISTERS_AARCH64 0
+#endif /* _ASM_ARM64_PERF_REGS_H */
+
+static inline bool
+generic_sample_sp_pc (const Dwarf_Word *regs, uint32_t n_regs,
+ const int *regs_mapping, uint32_t n_regs_mapping,
+ Dwarf_Word *sp, uint sp_index /* into dwarf_regs */,
+ Dwarf_Word *pc, uint pc_index /* into dwarf_regs */)
+{
+ if (sp != NULL) *sp = 0;
+ if (pc != NULL) *pc = 0;
+ /* TODO: Register locations could be cached and rechecked on a
+ fastpath without needing to loop, though the overhead reduction
+ is minimal. */
+ int j, need_sp = (sp != NULL), need_pc = (pc != NULL);
+ for (j = 0; (need_sp || need_pc) && n_regs_mapping > (uint32_t)j; j++)
+ {
+ if (n_regs < (uint32_t)j) break;
+ if (need_sp && regs_mapping[j] == (int)sp_index)
+ {
+ *sp = regs[j]; need_sp = false;
+ }
+ if (need_pc && regs_mapping[j] == (int)pc_index)
+ {
+ *pc = regs[j]; need_pc = false;
+ }
+ }
+ return (!need_sp && !need_pc);
+}
#endif /* libebl_PERF_FLAGS.h */
diff --git a/libebl/eblinitreg_sample.c b/libebl/eblinitreg_sample.c
index d5704dfa..0cf264b0 100644
--- a/libebl/eblinitreg_sample.c
+++ b/libebl/eblinitreg_sample.c
@@ -1,6 +1,6 @@
/* Populate process Dwfl_Frame from perf_events sample.
- Copyright (C) 2025 Red Hat, Inc.
+ Copyright (C) 2025-2026 Red Hat, Inc.
This file is part of elfutils.
This file is free software; you can redistribute it and/or modify
@@ -31,9 +31,11 @@
# include <config.h>
#endif
-#include <libeblP.h>
+#include <stdlib.h>
#include <assert.h>
+#include <libeblP.h>
+
bool
ebl_sample_sp_pc (Ebl *ebl,
const Dwarf_Word *regs, uint32_t n_regs,
@@ -83,10 +85,45 @@ ebl_sample_perf_regs_mapping (Ebl *ebl,
uint64_t perf_regs_mask, uint32_t abi,
const int **regs_mapping, size_t *n_regs_mapping)
{
- /* If sample_perf_regs_mapping is unsupported then PERF_FRAME_REGS_MASK is
zero. */
- assert (ebl->sample_perf_regs_mapping != NULL);
- return ebl->sample_perf_regs_mapping (ebl, perf_regs_mask, abi,
- regs_mapping, n_regs_mapping);
+ /* If sample_perf_regs_mapping is unsupported then perf_frame_regs_mask is
zero. */
+ assert (ebl->perf_frame_regs_mask != 0);
+
+ /* If sample_perf_regs_mapping is defined for this arch, use it. */
+ if (ebl->sample_perf_regs_mapping != NULL)
+ return ebl->sample_perf_regs_mapping (ebl, perf_regs_mask, abi,
+ regs_mapping, n_regs_mapping);
+
+ /* If sample_perf_regs_mapping is unspecified, then it is safe
+ to return a linear 1:1 mapping between perf_regs and dwarf_regs. */
+
+ if (perf_regs_mask != 0 && ebl->cached_perf_regs_mask == perf_regs_mask)
+ {
+ *regs_mapping = ebl->cached_regs_mapping;
+ *n_regs_mapping = ebl->cached_n_regs_mapping;
+ return true;
+ }
+
+ /* XXX Unwind-relevant register file should be no bigger than this: */
+ int count = 64;
+
+ ebl->cached_regs_mapping = (int *)calloc (count, sizeof(int));
+ ebl->cached_n_regs_mapping = count;
+
+ int j, k; uint64_t bit;
+ for (j = 0, k = 0, bit = 1;
+ k < count; k++, bit <<= 1)
+ {
+ ebl->cached_regs_mapping[k] = -1;
+ if ((bit & perf_regs_mask)) {
+ ebl->cached_regs_mapping[j] = k;
+ j++;
+ }
+ }
+
+ *regs_mapping = ebl->cached_regs_mapping;
+ *n_regs_mapping = ebl->cached_n_regs_mapping;
+ return true;
+
}
uint64_t
diff --git a/libebl/eblopenbackend.c b/libebl/eblopenbackend.c
index b68dea7a..1be0e5fe 100644
--- a/libebl/eblopenbackend.c
+++ b/libebl/eblopenbackend.c
@@ -1,5 +1,5 @@
/* Generate ELF backend handle.
- Copyright (C) 2000-2017 Red Hat, Inc.
+ Copyright (C) 2000-2017, 2026 Red Hat, Inc.
This file is part of elfutils.
This file is free software; you can redistribute it and/or modify
@@ -271,6 +271,17 @@ fill_defaults (Ebl *result)
result->sysvhash_entrysize = sizeof (Elf32_Word);
}
+/* Called by the initialization functions for backends which support
+ hook sample_perf_regs_mapping(). */
+void
+internal_function
+__libebl_init_cached_regs_mapping (Ebl *eh)
+{
+ eh->cached_perf_regs_mask = 0;
+ eh->cached_regs_mapping = NULL;
+ eh->cached_n_regs_mapping = -1;
+}
+
/* Find an appropriate backend for the file associated with ELF. */
static Ebl *
openbackend (Elf *elf, const char *emulation, GElf_Half machine)
diff --git a/libebl/libeblP.h b/libebl/libeblP.h
index 348da49e..f9b76d4e 100644
--- a/libebl/libeblP.h
+++ b/libebl/libeblP.h
@@ -1,5 +1,5 @@
/* Internal definitions for interface for libebl.
- Copyright (C) 2000-2009, 2013, 2014, 2025 Red Hat, Inc.
+ Copyright (C) 2000-2009, 2013, 2014, 2025-2026 Red Hat, Inc.
This file is part of elfutils.
This file is free software; you can redistribute it and/or modify
@@ -96,6 +96,9 @@ struct ebl
initialize for the given Elf or machine. */
typedef Ebl *(*ebl_bhinit_t) (Elf *, GElf_Half, Ebl *);
+/* Additional helper to init cached perf_events mapping data. */
+void __libebl_init_cached_regs_mapping (Ebl *ebl)
+ internal_function;
/* LEB128 constant helper macros. */
#define ULEB128_7(x) (BUILD_BUG_ON_ZERO ((x) >= (1U << 7)) + (x))
--
2.53.0
