2000-04-05 23:38:05 +08:00
|
|
|
/* GNU/Linux on ARM target support.
|
|
|
|
Copyright 1999, 2000 Free Software Foundation, Inc.
|
|
|
|
|
|
|
|
This file is part of GDB.
|
|
|
|
|
|
|
|
This program is free software; you can redistribute it and/or modify
|
|
|
|
it under the terms of 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.
|
|
|
|
|
|
|
|
This program 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 a copy of the GNU General Public License
|
|
|
|
along with this program; if not, write to the Free Software
|
|
|
|
Foundation, Inc., 59 Temple Place - Suite 330,
|
|
|
|
Boston, MA 02111-1307, USA. */
|
|
|
|
|
|
|
|
#include "defs.h"
|
2000-04-06 01:24:08 +08:00
|
|
|
#include "target.h"
|
|
|
|
#include "value.h"
|
2000-04-05 23:38:05 +08:00
|
|
|
#include "gdbtypes.h"
|
2000-04-08 06:26:11 +08:00
|
|
|
#include "floatformat.h"
|
2000-04-05 23:38:05 +08:00
|
|
|
|
|
|
|
#ifdef GET_LONGJMP_TARGET
|
|
|
|
|
|
|
|
/* Figure out where the longjmp will land. We expect that we have
|
|
|
|
just entered longjmp and haven't yet altered r0, r1, so the
|
|
|
|
arguments are still in the registers. (A1_REGNUM) points at the
|
|
|
|
jmp_buf structure from which we extract the pc (JB_PC) that we will
|
|
|
|
land at. The pc is copied into ADDR. This routine returns true on
|
|
|
|
success. */
|
|
|
|
|
|
|
|
#define LONGJMP_TARGET_SIZE sizeof(int)
|
|
|
|
#define JB_ELEMENT_SIZE sizeof(int)
|
|
|
|
#define JB_SL 18
|
|
|
|
#define JB_FP 19
|
|
|
|
#define JB_SP 20
|
|
|
|
#define JB_PC 21
|
|
|
|
|
|
|
|
int
|
|
|
|
arm_get_longjmp_target (CORE_ADDR * pc)
|
|
|
|
{
|
|
|
|
CORE_ADDR jb_addr;
|
|
|
|
char buf[LONGJMP_TARGET_SIZE];
|
|
|
|
|
|
|
|
jb_addr = read_register (A1_REGNUM);
|
|
|
|
|
|
|
|
if (target_read_memory (jb_addr + JB_PC * JB_ELEMENT_SIZE, buf,
|
|
|
|
LONGJMP_TARGET_SIZE))
|
|
|
|
return 0;
|
|
|
|
|
|
|
|
*pc = extract_address (buf, LONGJMP_TARGET_SIZE);
|
|
|
|
return 1;
|
|
|
|
}
|
|
|
|
|
|
|
|
#endif /* GET_LONGJMP_TARGET */
|
|
|
|
|
|
|
|
/* Extract from an array REGBUF containing the (raw) register state
|
|
|
|
a function return value of type TYPE, and copy that, in virtual format,
|
|
|
|
into VALBUF. */
|
|
|
|
|
|
|
|
void
|
|
|
|
arm_linux_extract_return_value (struct type *type,
|
|
|
|
char regbuf[REGISTER_BYTES],
|
|
|
|
char *valbuf)
|
|
|
|
{
|
|
|
|
/* ScottB: This needs to be looked at to handle the different
|
|
|
|
floating point emulators on ARM Linux. Right now the code
|
|
|
|
assumes that fetch inferior registers does the right thing for
|
|
|
|
GDB. I suspect this won't handle NWFPE registers correctly, nor
|
|
|
|
will the default ARM version (arm_extract_return_value()). */
|
|
|
|
|
|
|
|
int regnum = (TYPE_CODE_FLT == TYPE_CODE (type)) ? F0_REGNUM : A1_REGNUM;
|
|
|
|
memcpy (valbuf, ®buf[REGISTER_BYTE (regnum)], TYPE_LENGTH (type));
|
|
|
|
}
|
|
|
|
|
2000-04-08 06:26:11 +08:00
|
|
|
/* Note: ScottB
|
|
|
|
|
|
|
|
This function does not support passing parameters using the FPA
|
|
|
|
variant of the APCS. It passes any floating point arguments in the
|
|
|
|
general registers and/or on the stack.
|
|
|
|
|
|
|
|
FIXME: This and arm_push_arguments should be merged. However this
|
|
|
|
function breaks on a little endian host, big endian target
|
|
|
|
using the COFF file format. ELF is ok.
|
|
|
|
|
|
|
|
ScottB. */
|
|
|
|
|
|
|
|
/* Addresses for calling Thumb functions have the bit 0 set.
|
|
|
|
Here are some macros to test, set, or clear bit 0 of addresses. */
|
|
|
|
#define IS_THUMB_ADDR(addr) ((addr) & 1)
|
|
|
|
#define MAKE_THUMB_ADDR(addr) ((addr) | 1)
|
|
|
|
#define UNMAKE_THUMB_ADDR(addr) ((addr) & ~1)
|
|
|
|
|
|
|
|
CORE_ADDR
|
|
|
|
arm_linux_push_arguments (int nargs, value_ptr * args, CORE_ADDR sp,
|
|
|
|
int struct_return, CORE_ADDR struct_addr)
|
|
|
|
{
|
|
|
|
char *fp;
|
|
|
|
int argnum, argreg, nstack_size;
|
|
|
|
|
|
|
|
/* Walk through the list of args and determine how large a temporary
|
|
|
|
stack is required. Need to take care here as structs may be
|
|
|
|
passed on the stack, and we have to to push them. */
|
|
|
|
nstack_size = -4 * REGISTER_SIZE; /* Some arguments go into A1-A4. */
|
|
|
|
|
|
|
|
if (struct_return) /* The struct address goes in A1. */
|
|
|
|
nstack_size += REGISTER_SIZE;
|
|
|
|
|
|
|
|
/* Walk through the arguments and add their size to nstack_size. */
|
|
|
|
for (argnum = 0; argnum < nargs; argnum++)
|
|
|
|
{
|
|
|
|
int len;
|
|
|
|
struct type *arg_type;
|
|
|
|
|
|
|
|
arg_type = check_typedef (VALUE_TYPE (args[argnum]));
|
|
|
|
len = TYPE_LENGTH (arg_type);
|
|
|
|
|
|
|
|
/* ANSI C code passes float arguments as integers, K&R code
|
|
|
|
passes float arguments as doubles. Correct for this here. */
|
|
|
|
if (TYPE_CODE_FLT == TYPE_CODE (arg_type) && REGISTER_SIZE == len)
|
|
|
|
nstack_size += FP_REGISTER_VIRTUAL_SIZE;
|
|
|
|
else
|
|
|
|
nstack_size += len;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Allocate room on the stack, and initialize our stack frame
|
|
|
|
pointer. */
|
|
|
|
fp = NULL;
|
|
|
|
if (nstack_size > 0)
|
|
|
|
{
|
|
|
|
sp -= nstack_size;
|
|
|
|
fp = (char *) sp;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Initialize the integer argument register pointer. */
|
|
|
|
argreg = A1_REGNUM;
|
|
|
|
|
|
|
|
/* The struct_return pointer occupies the first parameter passing
|
|
|
|
register. */
|
|
|
|
if (struct_return)
|
|
|
|
write_register (argreg++, struct_addr);
|
|
|
|
|
|
|
|
/* Process arguments from left to right. Store as many as allowed
|
|
|
|
in the parameter passing registers (A1-A4), and save the rest on
|
|
|
|
the temporary stack. */
|
|
|
|
for (argnum = 0; argnum < nargs; argnum++)
|
|
|
|
{
|
|
|
|
int len;
|
|
|
|
char *val;
|
|
|
|
double dbl_arg;
|
|
|
|
CORE_ADDR regval;
|
|
|
|
enum type_code typecode;
|
|
|
|
struct type *arg_type, *target_type;
|
|
|
|
|
|
|
|
arg_type = check_typedef (VALUE_TYPE (args[argnum]));
|
|
|
|
target_type = TYPE_TARGET_TYPE (arg_type);
|
|
|
|
len = TYPE_LENGTH (arg_type);
|
|
|
|
typecode = TYPE_CODE (arg_type);
|
|
|
|
val = (char *) VALUE_CONTENTS (args[argnum]);
|
|
|
|
|
|
|
|
/* ANSI C code passes float arguments as integers, K&R code
|
|
|
|
passes float arguments as doubles. The .stabs record for
|
|
|
|
for ANSI prototype floating point arguments records the
|
|
|
|
type as FP_INTEGER, while a K&R style (no prototype)
|
|
|
|
.stabs records the type as FP_FLOAT. In this latter case
|
|
|
|
the compiler converts the float arguments to double before
|
|
|
|
calling the function. */
|
|
|
|
if (TYPE_CODE_FLT == typecode && REGISTER_SIZE == len)
|
|
|
|
{
|
|
|
|
/* Float argument in buffer is in host format. Read it and
|
|
|
|
convert to DOUBLEST, and store it in target double. */
|
|
|
|
DOUBLEST dblval;
|
|
|
|
|
|
|
|
len = TARGET_DOUBLE_BIT / TARGET_CHAR_BIT;
|
|
|
|
floatformat_to_doublest (HOST_FLOAT_FORMAT, val, &dblval);
|
|
|
|
store_floating (&dbl_arg, len, dblval);
|
|
|
|
val = (char *) &dbl_arg;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* If the argument is a pointer to a function, and it is a Thumb
|
|
|
|
function, set the low bit of the pointer. */
|
|
|
|
if (TYPE_CODE_PTR == typecode
|
|
|
|
&& NULL != target_type
|
|
|
|
&& TYPE_CODE_FUNC == TYPE_CODE (target_type))
|
|
|
|
{
|
|
|
|
CORE_ADDR regval = extract_address (val, len);
|
|
|
|
if (arm_pc_is_thumb (regval))
|
|
|
|
store_address (val, len, MAKE_THUMB_ADDR (regval));
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Copy the argument to general registers or the stack in
|
|
|
|
register-sized pieces. Large arguments are split between
|
|
|
|
registers and stack. */
|
|
|
|
while (len > 0)
|
|
|
|
{
|
|
|
|
int partial_len = len < REGISTER_SIZE ? len : REGISTER_SIZE;
|
|
|
|
|
|
|
|
if (argreg <= ARM_LAST_ARG_REGNUM)
|
|
|
|
{
|
|
|
|
/* It's an argument being passed in a general register. */
|
|
|
|
regval = extract_address (val, partial_len);
|
|
|
|
write_register (argreg++, regval);
|
|
|
|
}
|
|
|
|
else
|
|
|
|
{
|
|
|
|
/* Push the arguments onto the stack. */
|
|
|
|
write_memory ((CORE_ADDR) fp, val, REGISTER_SIZE);
|
|
|
|
fp += REGISTER_SIZE;
|
|
|
|
}
|
|
|
|
|
|
|
|
len -= partial_len;
|
|
|
|
val += partial_len;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Return adjusted stack pointer. */
|
|
|
|
return sp;
|
|
|
|
}
|
|
|
|
|
2000-04-11 05:02:33 +08:00
|
|
|
/*
|
|
|
|
Dynamic Linking on ARM Linux
|
|
|
|
----------------------------
|
|
|
|
|
|
|
|
Note: PLT = procedure linkage table
|
|
|
|
GOT = global offset table
|
|
|
|
|
|
|
|
As much as possible, ELF dynamic linking defers the resolution of
|
|
|
|
jump/call addresses until the last minute. The technique used is
|
|
|
|
inspired by the i386 ELF design, and is based on the following
|
|
|
|
constraints.
|
|
|
|
|
|
|
|
1) The calling technique should not force a change in the assembly
|
|
|
|
code produced for apps; it MAY cause changes in the way assembly
|
|
|
|
code is produced for position independent code (i.e. shared
|
|
|
|
libraries).
|
|
|
|
|
|
|
|
2) The technique must be such that all executable areas must not be
|
|
|
|
modified; and any modified areas must not be executed.
|
|
|
|
|
|
|
|
To do this, there are three steps involved in a typical jump:
|
|
|
|
|
|
|
|
1) in the code
|
|
|
|
2) through the PLT
|
|
|
|
3) using a pointer from the GOT
|
|
|
|
|
|
|
|
When the executable or library is first loaded, each GOT entry is
|
|
|
|
initialized to point to the code which implements dynamic name
|
|
|
|
resolution and code finding. This is normally a function in the
|
|
|
|
program interpreter (on ARM Linux this is usually ld-linux.so.2,
|
|
|
|
but it does not have to be). On the first invocation, the function
|
|
|
|
is located and the GOT entry is replaced with the real function
|
|
|
|
address. Subsequent calls go through steps 1, 2 and 3 and end up
|
|
|
|
calling the real code.
|
|
|
|
|
|
|
|
1) In the code:
|
|
|
|
|
|
|
|
b function_call
|
|
|
|
bl function_call
|
|
|
|
|
|
|
|
This is typical ARM code using the 26 bit relative branch or branch
|
|
|
|
and link instructions. The target of the instruction
|
|
|
|
(function_call is usually the address of the function to be called.
|
|
|
|
In position independent code, the target of the instruction is
|
|
|
|
actually an entry in the PLT when calling functions in a shared
|
|
|
|
library. Note that this call is identical to a normal function
|
|
|
|
call, only the target differs.
|
|
|
|
|
|
|
|
2) In the PLT:
|
|
|
|
|
|
|
|
The PLT is a synthetic area, created by the linker. It exists in
|
|
|
|
both executables and libraries. It is an array of stubs, one per
|
|
|
|
imported function call. It looks like this:
|
|
|
|
|
|
|
|
PLT[0]:
|
|
|
|
str lr, [sp, #-4]! @push the return address (lr)
|
|
|
|
ldr lr, [pc, #16] @load from 6 words ahead
|
|
|
|
add lr, pc, lr @form an address for GOT[0]
|
|
|
|
ldr pc, [lr, #8]! @jump to the contents of that addr
|
|
|
|
|
|
|
|
The return address (lr) is pushed on the stack and used for
|
|
|
|
calculations. The load on the second line loads the lr with
|
|
|
|
&GOT[3] - . - 20. The addition on the third leaves:
|
|
|
|
|
|
|
|
lr = (&GOT[3] - . - 20) + (. + 8)
|
|
|
|
lr = (&GOT[3] - 12)
|
|
|
|
lr = &GOT[0]
|
|
|
|
|
|
|
|
On the fourth line, the pc and lr are both updated, so that:
|
|
|
|
|
|
|
|
pc = GOT[2]
|
|
|
|
lr = &GOT[0] + 8
|
|
|
|
= &GOT[2]
|
|
|
|
|
|
|
|
NOTE: PLT[0] borrows an offset .word from PLT[1]. This is a little
|
|
|
|
"tight", but allows us to keep all the PLT entries the same size.
|
|
|
|
|
|
|
|
PLT[n+1]:
|
|
|
|
ldr ip, [pc, #4] @load offset from gotoff
|
|
|
|
add ip, pc, ip @add the offset to the pc
|
|
|
|
ldr pc, [ip] @jump to that address
|
|
|
|
gotoff: .word GOT[n+3] - .
|
|
|
|
|
|
|
|
The load on the first line, gets an offset from the fourth word of
|
|
|
|
the PLT entry. The add on the second line makes ip = &GOT[n+3],
|
|
|
|
which contains either a pointer to PLT[0] (the fixup trampoline) or
|
|
|
|
a pointer to the actual code.
|
|
|
|
|
|
|
|
3) In the GOT:
|
|
|
|
|
|
|
|
The GOT contains helper pointers for both code (PLT) fixups and
|
|
|
|
data fixups. The first 3 entries of the GOT are special. The next
|
|
|
|
M entries (where M is the number of entries in the PLT) belong to
|
|
|
|
the PLT fixups. The next D (all remaining) entries belong to
|
|
|
|
various data fixups. The actual size of the GOT is 3 + M + D.
|
|
|
|
|
|
|
|
The GOT is also a synthetic area, created by the linker. It exists
|
|
|
|
in both executables and libraries. When the GOT is first
|
|
|
|
initialized , all the GOT entries relating to PLT fixups are
|
|
|
|
pointing to code back at PLT[0].
|
|
|
|
|
|
|
|
The special entries in the GOT are:
|
|
|
|
|
|
|
|
GOT[0] = linked list pointer used by the dynamic loader
|
|
|
|
GOT[1] = pointer to the reloc table for this module
|
|
|
|
GOT[2] = pointer to the fixup/resolver code
|
|
|
|
|
|
|
|
The first invocation of function call comes through and uses the
|
|
|
|
fixup/resolver code. On the entry to the fixup/resolver code:
|
|
|
|
|
|
|
|
ip = &GOT[n+3]
|
|
|
|
lr = &GOT[2]
|
|
|
|
stack[0] = return address (lr) of the function call
|
|
|
|
[r0, r1, r2, r3] are still the arguments to the function call
|
|
|
|
|
|
|
|
This is enough information for the fixup/resolver code to work
|
|
|
|
with. Before the fixup/resolver code returns, it actually calls
|
|
|
|
the requested function and repairs &GOT[n+3]. */
|
|
|
|
|
|
|
|
CORE_ADDR
|
|
|
|
arm_skip_solib_resolver (CORE_ADDR pc)
|
|
|
|
{
|
|
|
|
/* FIXME */
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2000-04-05 23:38:05 +08:00
|
|
|
void
|
|
|
|
_initialize_arm_linux_tdep (void)
|
|
|
|
{
|
|
|
|
}
|