aarch64: Add SFrame support for aarch64 architecture

    The SFrame is supported for AArch64 architecture.
    Enable SFrame stack tracer for AArch64 too.

Signed-off-by: Claudiu Zissulescu <claudiu.zissulescu-ianculescu@oracle.com>
Reviewed-by: DJ Delorie <dj@redhat.com>

diff --git a/sysdeps/unix/sysv/linux/aarch64/uw-sigframe.h b/sysdeps/unix/sysv/linux/aarch64/uw-sigframe.h
new file mode 100644 (file)
index 0000000..3a77c23
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/aarch64/uw-sigframe.h
@@ -0,0 +1,78 @@
+/* Signal frame backtracing support for SFrame on AARCH64.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public License
+   as published by the Free Software Foundation; either version 2.1 of
+   the License, or (at your option) any later version.
+
+   The GNU C Library 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 Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* This code is inspired from libgcc's MD_FALLBACK_FRAME_STATE_FOR
+   implementation.  See libgcc/config/aarch64/linux-unwind.h  */
+
+#include <signal.h>
+#include <sys/ucontext.h>
+#include <kernel_rt_sigframe.h>
+
+#if __AARCH64EL__
+#define MOVZ_X8_8B      0xd2801168
+#define SVC_0           0xd4000001
+#else
+#define MOVZ_X8_8B      0x681180d2
+#define SVC_0           0x010000d4
+#endif
+
+#define MD_DECODE_SIGNAL_FRAME aarch64_decode_signal_frame
+
+static _Unwind_Reason_Code
+aarch64_decode_signal_frame (frame *frame)
+{
+  unsigned int *pc = (unsigned int *) frame->pc;
+  mcontext_t *mt;
+  struct kernel_rt_sigframe *rt_;
+
+  if ((frame->pc & 3) != 0)
+    return _URC_END_OF_STACK;
+
+  /* A signal frame will have a return address pointing to
+     __kernel_rt_sigreturn.  This code is hardwired as:
+
+     0xd2801168         movz x8, #0x8b
+     0xd4000001         svc  0x0
+   */
+  if (pc[0] != MOVZ_X8_8B || pc[1] != SVC_0)
+    return _URC_END_OF_STACK;
+
+  rt_ = (struct kernel_rt_sigframe *) frame->sp;
+  mt = &rt_->uc.uc_mcontext;
+
+  /* Frame pointer register number.  */
+#define FP_REGNUM 30
+
+  frame->pc = (_Unwind_Ptr) mt->pc;
+  frame->sp = (_Unwind_Ptr) mt->sp;
+  frame->fp = (_Unwind_Ptr) mt->regs[FP_REGNUM];
+  return _URC_NO_REASON;
+}
+
+#define MD_DETECT_OUTERMOST_FRAME aarch64_detect_outermost_frame
+
+static _Unwind_Reason_Code
+aarch64_detect_outermost_frame (frame *frame)
+{
+  /* Initial frame has LR and FP set to zero.  We track only FP.  */
+  if (frame->fp == 0)
+    return _URC_END_OF_STACK;
+
+  return _URC_NO_REASON;
+}