Squashed 'third_party/elfutils/' content from commit 555e15e
Change-Id: I61cde98949e47e5c8c09c33260de17f30921be79
git-subtree-dir: third_party/elfutils
git-subtree-split: 555e15ebe8bf1eb33d00747173cfc80cc65648a4
diff --git a/backends/i386_unwind.c b/backends/i386_unwind.c
new file mode 100644
index 0000000..5c9a5de
--- /dev/null
+++ b/backends/i386_unwind.c
@@ -0,0 +1,84 @@
+/* Get previous frame state for an existing frame state using frame pointers.
+ Copyright (C) 2017 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 i386_
+#include "libebl_CPU.h"
+
+/* Register numbers for frame and stack pointers. We take advantage of
+ them being next to each other when calling getfunc and setfunc. */
+#define ESP 4
+#define EBP (ESP + 1)
+
+/* Most basic frame pointer chasing with EBP as frame pointer.
+ PC = *(FP + 4), SP = FP + 8, FP = *FP. */
+bool
+i386_unwind (Ebl *ebl __attribute__ ((unused)),
+ Dwarf_Addr pc __attribute__ ((unused)),
+ ebl_tid_registers_t *setfunc, ebl_tid_registers_get_t *getfunc,
+ ebl_pid_memory_read_t *readfunc, void *arg,
+ bool *signal_framep __attribute__ ((unused)))
+{
+ /* sp = 0, fp = 1 */
+ Dwarf_Word regs[2];
+
+ /* Get current stack and frame pointers. */
+ if (! getfunc (ESP, 2, regs, arg))
+ return false;
+
+ Dwarf_Word sp = regs[0];
+ Dwarf_Word fp = regs[1];
+
+ /* Sanity check. We only support traditional stack frames. */
+ if (fp == 0 || sp == 0 || fp < sp)
+ return false;
+
+ /* Get the return address from the stack, it is our new pc. */
+ Dwarf_Word ret_addr;
+ if (! readfunc (fp + 4, &ret_addr, arg) || ret_addr == 0)
+ return false;
+
+ /* Get new sp and fp. Sanity check again. */
+ sp = fp + 8;
+ if (! readfunc (fp, &fp, arg) || fp == 0 || sp >= fp)
+ return false;
+
+ /* Set new sp, fp and pc. */
+ regs[0] = sp;
+ regs[1] = fp;
+ if (! setfunc (ESP, 2, regs, arg) || ! setfunc (-1, 1, &ret_addr, arg))
+ return false;
+
+ return true;
+}