saveargs.c revision 702941cd97e30d600c2c1275823bc58231b2c361
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2007 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
/*
* The Sun Studio and GCC (patched for opensolaris/illumos) compilers
* implement a argument saving scheme on amd64 via the -Wu,save-args or
* options. When the option is specified, INTEGER type function arguments
* passed via registers will be saved on the stack immediately after %rbp, and
* will not be modified through out the life of the routine.
*
* +--------+
* %rbp --> | %rbp |
* +--------+
* -0x8(%rbp) | %rdi |
* +--------+
* -0x10(%rbp) | %rsi |
* +--------+
* -0x18(%rbp) | %rdx |
* +--------+
* -0x20(%rbp) | %rcx |
* +--------+
* -0x28(%rbp) | %r8 |
* +--------+
* -0x30(%rbp) | %r9 |
* +--------+
*
*
* For example, for the following function,
*
* void
* foo(int a1, int a2, int a3, int a4, int a5, int a6, int a7)
* {
* ...
* }
*
* Disassembled code will look something like the following:
*
* pushq %rbp
* movq %rsp, %rbp
* subq $imm8, %rsp **
* movq %rdi, -0x8(%rbp)
* movq %rsi, -0x10(%rbp)
* movq %rdx, -0x18(%rbp)
* movq %rcx, -0x20(%rbp)
* movq %r8, -0x28(%rbp)
* movq %r9, -0x30(%rbp)
* ...
* or
* pushq %rbp
* movq %rsp, %rbp
* subq $imm8, %rsp **
* movq %r9, -0x30(%rbp)
* movq %r8, -0x28(%rbp)
* movq %rcx, -0x20(%rbp)
* movq %rdx, -0x18(%rbp)
* movq %rsi, -0x10(%rbp)
* movq %rdi, -0x8(%rbp)
* ...
* or
* pushq %rbp
* movq %rsp, %rbp
* pushq %rdi
* pushq %rsi
* pushq %rdx
* pushq %rcx
* pushq %r8
* pushq %r9
*
* **: The space being reserved is in addition to what the current
* function prolog already reserves.
*
* We loop through the first SAVEARGS_INSN_SEQ_LEN bytes of the function
* looking for each argument saving instruction we would expect to see.
*
* If there are odd number of arguments to a function, additional space is
* reserved on the stack to maintain 16-byte alignment. For example,
*
* argc == 0: no argument saving.
* argc == 3: save 3, but space for 4 is reserved
* argc == 7: save 6.
*/
#include <sys/sysmacros.h>
#include <sys/types.h>
#include <libdisasm.h>
#include <string.h>
#include <saveargs.h>
/*
* Size of the instruction sequence arrays. It should correspond to
* the maximum number of arguments passed via registers.
*/
#define INSTR_ARRAY_SIZE 6
#define INSTR1(ins, off) (ins[(off)])
#define INSTR2(ins, off) (ins[(off)] + (ins[(off) + 1] << 8))
#define INSTR3(ins, off) \
(ins[(off)] + (ins[(off) + 1] << 8) + (ins[(off + 2)] << 16))
#define INSTR4(ins, off) \
(ins[(off)] + (ins[(off) + 1] << 8) + (ins[(off + 2)] << 16) + \
(ins[(off) + 3] << 24))
/*
* Sun Studio 10 patch implementation saves %rdi first;
* GCC 3.4.3 Sun branch implementation saves them in reverse order.
*/
static const uint32_t save_instr[INSTR_ARRAY_SIZE] = {
0xf87d8948, /* movq %rdi, -0x8(%rbp) */
0xf0758948, /* movq %rsi, -0x10(%rbp) */
0xe8558948, /* movq %rdx, -0x18(%rbp) */
0xe04d8948, /* movq %rcx, -0x20(%rbp) */
0xd845894c, /* movq %r8, -0x28(%rbp) */
0xd04d894c /* movq %r9, -0x30(%rbp) */
};
static const uint16_t save_instr_push[] = {
0x57, /* pushq %rdi */
0x56, /* pushq %rsi */
0x52, /* pushq %rdx */
0x51, /* pushq %rcx */
0x5041, /* pushq %r8 */
0x5141 /* pushq %r9 */
};
/*
* If the return type of a function is a structure greater than 16 bytes in
* size, %rdi will contain the address to which it should be stored, and
* arguments will begin at %rsi. Studio will push all of the normal argument
* registers anyway, GCC will start pushing at %rsi, so we need a separate
* pattern.
*/
static const uint32_t save_instr_sr[INSTR_ARRAY_SIZE-1] = {
0xf8758948, /* movq %rsi,-0x8(%rbp) */
0xf0558948, /* movq %rdx,-0x10(%rbp) */
0xe84d8948, /* movq %rcx,-0x18(%rbp) */
0xe045894c, /* movq %r8,-0x20(%rbp) */
0xd84d894c /* movq %r9,-0x28(%rbp) */
};
static const uint8_t save_fp_pushes[] = {
0x55, /* pushq %rbp */
0xcc /* int $0x3 */
};
#define NUM_FP_PUSHES (sizeof (save_fp_pushes) / sizeof (save_fp_pushes[0]))
static const uint32_t save_fp_movs[] = {
0x00e58948, /* movq %rsp,%rbp, encoding 1 */
0x00ec8b48, /* movq %rsp,%rbp, encoding 2 */
};
#define NUM_FP_MOVS (sizeof (save_fp_movs) / sizeof (save_fp_movs[0]))
typedef struct {
uint8_t *data;
size_t size;
} text_t;
static int
do_read(void *data, uint64_t addr, void *buf, size_t len)
{
text_t *t = data;
if (addr >= t->size)
return (-1);
len = MIN(len, t->size - addr);
(void) memcpy(buf, (char *)t->data + addr, len);
return (len);
}
/* ARGSUSED */
int
do_lookup(void *data, uint64_t addr, char *buf, size_t buflen, uint64_t *start,
size_t *symlen)
{
/* We don't actually need lookup info */
return (-1);
}
static int
instr_size(dis_handle_t *dhp, uint8_t *ins, unsigned int i, size_t size)
{
text_t t;
t.data = ins;
t.size = size;
dis_set_data(dhp, &t);
return (dis_instrlen(dhp, i));
}
static boolean_t
has_saved_fp(dis_handle_t *dhp, uint8_t *ins, int size)
{
int i, j;
uint32_t n;
boolean_t found_push = B_FALSE;
ssize_t sz = 0;
for (i = 0; i < size; i += sz) {
if ((sz = instr_size(dhp, ins, i, size)) < 1)
return (B_FALSE);
if (found_push == B_FALSE) {
if (sz != 1)
continue;
n = INSTR1(ins, i);
for (j = 0; j <= NUM_FP_PUSHES; j++)
if (save_fp_pushes[j] == n) {
found_push = B_TRUE;
break;
}
} else {
if (sz != 3)
continue;
n = INSTR3(ins, i);
for (j = 0; j <= NUM_FP_MOVS; j++)
if (save_fp_movs[j] == n)
return (B_TRUE);
}
}
return (B_FALSE);
}
int
saveargs_has_args(uint8_t *ins, size_t size, uint_t argc, int start_index)
{
int i, j;
uint32_t n;
uint8_t found = 0;
ssize_t sz = 0;
dis_handle_t *dhp = NULL;
int ret = SAVEARGS_NO_ARGS;
argc = MIN((start_index + argc), INSTR_ARRAY_SIZE);
if ((dhp = dis_handle_create(DIS_X86_SIZE64, NULL, do_lookup,
do_read)) == NULL)
return (SAVEARGS_NO_ARGS);
if (!has_saved_fp(dhp, ins, size)) {
dis_handle_destroy(dhp);
return (SAVEARGS_NO_ARGS);
}
/*
* For each possible style of argument saving, walk the insn stream as
* we've been given it, and set bit N in 'found' if we find the
* instruction saving the Nth argument.
*/
/*
* Compare against regular implementation
*/
found = 0;
for (i = 0; i < size; i += sz) {
sz = instr_size(dhp, ins, i, size);
if (sz < 1)
break;
else if (sz != 4)
continue;
n = INSTR4(ins, i);
for (j = 0; j < argc; j++) {
if (n == save_instr[j]) {
found |= (1 << j);
if (found == ((1 << argc) - 1)) {
ret = start_index ?
SAVEARGS_STRUCT_ARGS :
SAVEARGS_TRAD_ARGS;
goto done;
}
break;
}
}
}
/*
* Compare against GCC push-based implementation
*/
found = 0;
for (i = 0; i < size; i += sz) {
if ((sz = instr_size(dhp, ins, i, size)) < 1)
break;
for (j = start_index; j < argc; j++) {
if (sz == 2) /* Two byte */
n = INSTR2(ins, i);
else if (sz == 1)
n = INSTR1(ins, i);
else
continue;
if (n == save_instr_push[j]) {
found |= (1 << (j - start_index));
if (found ==
((1 << (argc - start_index)) - 1)) {
ret = SAVEARGS_TRAD_ARGS;
goto done;
}
break;
}
}
}
/*
* Look for a GCC-style returned structure.
*/
found = 0;
if (start_index != 0) {
for (i = 0; i < size; i += sz) {
sz = instr_size(dhp, ins, i, size);
if (sz < 1)
break;
else if (sz != 4)
continue;
n = INSTR4(ins, i);
/* argc is inclusive of start_index, allow for that */
for (j = 0; j < (argc - start_index); j++) {
if (n == save_instr_sr[j]) {
found |= (1 << j);
if (found ==
((1 << (argc - start_index)) - 1)) {
ret = SAVEARGS_TRAD_ARGS;
goto done;
}
break;
}
}
}
}
done:
dis_handle_destroy(dhp);
return (ret);
}