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author | Mark Wielaard <mark@klomp.org> | 2017-04-07 00:06:30 +0200 |
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committer | Mark Wielaard <mark@klomp.org> | 2017-05-02 15:25:36 +0200 |
commit | aecc2a7052f69386109dcf17d92c8396e9067eec (patch) | |
tree | f34e1b67597bfa047eda6be3b9d1456c7bf553cb /backends/i386_unwind.c | |
parent | a55df2c16721010bf1a9900038c0736bd578c913 (diff) | |
download | elfutils-aecc2a7052f69386109dcf17d92c8396e9067eec.tar.gz |
Add i386 frame pointer unwinder.
Add a simple i386_unwind.c frame pointer unwinder as fallback if DWARF/CFI
unwinding fails.
Signed-off-by: Mark Wielaard <mark@klomp.org>
Diffstat (limited to 'backends/i386_unwind.c')
-rw-r--r-- | backends/i386_unwind.c | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/backends/i386_unwind.c b/backends/i386_unwind.c new file mode 100644 index 00000000..5c9a5de0 --- /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; +} |