/* GNU/Linux on ARM target support.
Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,
2009, 2010 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 3 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, see . */
#include "defs.h"
#include "target.h"
#include "value.h"
#include "gdbtypes.h"
#include "floatformat.h"
#include "gdbcore.h"
#include "frame.h"
#include "regcache.h"
#include "doublest.h"
#include "solib-svr4.h"
#include "osabi.h"
#include "regset.h"
#include "trad-frame.h"
#include "tramp-frame.h"
#include "breakpoint.h"
#include "arm-tdep.h"
#include "arm-linux-tdep.h"
#include "linux-tdep.h"
#include "glibc-tdep.h"
#include "arch-utils.h"
#include "inferior.h"
#include "gdbthread.h"
#include "symfile.h"
#include "gdb_string.h"
extern int arm_apcs_32;
/* Under ARM GNU/Linux the traditional way of performing a breakpoint
is to execute a particular software interrupt, rather than use a
particular undefined instruction to provoke a trap. Upon exection
of the software interrupt the kernel stops the inferior with a
SIGTRAP, and wakes the debugger. */
static const char arm_linux_arm_le_breakpoint[] = { 0x01, 0x00, 0x9f, 0xef };
static const char arm_linux_arm_be_breakpoint[] = { 0xef, 0x9f, 0x00, 0x01 };
/* However, the EABI syscall interface (new in Nov. 2005) does not look at
the operand of the swi if old-ABI compatibility is disabled. Therefore,
use an undefined instruction instead. This is supported as of kernel
version 2.5.70 (May 2003), so should be a safe assumption for EABI
binaries. */
static const char eabi_linux_arm_le_breakpoint[] = { 0xf0, 0x01, 0xf0, 0xe7 };
static const char eabi_linux_arm_be_breakpoint[] = { 0xe7, 0xf0, 0x01, 0xf0 };
/* All the kernels which support Thumb support using a specific undefined
instruction for the Thumb breakpoint. */
static const char arm_linux_thumb_be_breakpoint[] = {0xde, 0x01};
static const char arm_linux_thumb_le_breakpoint[] = {0x01, 0xde};
/* Because the 16-bit Thumb breakpoint is affected by Thumb-2 IT blocks,
we must use a length-appropriate breakpoint for 32-bit Thumb
instructions. See also thumb_get_next_pc. */
static const char arm_linux_thumb2_be_breakpoint[] = { 0xf7, 0xf0, 0xa0, 0x00 };
static const char arm_linux_thumb2_le_breakpoint[] = { 0xf0, 0xf7, 0x00, 0xa0 };
/* Description of the longjmp buffer. The buffer is treated as an array of
elements of size ARM_LINUX_JB_ELEMENT_SIZE.
The location of saved registers in this buffer (in particular the PC
to use after longjmp is called) varies depending on the ABI (in
particular the FP model) and also (possibly) the C Library.
For glibc, eglibc, and uclibc the following holds: If the FP model is
SoftVFP or VFP (which implies EABI) then the PC is at offset 9 in the
buffer. This is also true for the SoftFPA model. However, for the FPA
model the PC is at offset 21 in the buffer. */
#define ARM_LINUX_JB_ELEMENT_SIZE INT_REGISTER_SIZE
#define ARM_LINUX_JB_PC_FPA 21
#define ARM_LINUX_JB_PC_EABI 9
/*
Dynamic Linking on ARM GNU/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 GNU/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]. */
/* The constants below were determined by examining the following files
in the linux kernel sources:
arch/arm/kernel/signal.c
- see SWI_SYS_SIGRETURN and SWI_SYS_RT_SIGRETURN
include/asm-arm/unistd.h
- see __NR_sigreturn, __NR_rt_sigreturn, and __NR_SYSCALL_BASE */
#define ARM_LINUX_SIGRETURN_INSTR 0xef900077
#define ARM_LINUX_RT_SIGRETURN_INSTR 0xef9000ad
/* For ARM EABI, the syscall number is not in the SWI instruction
(instead it is loaded into r7). We recognize the pattern that
glibc uses... alternatively, we could arrange to do this by
function name, but they are not always exported. */
#define ARM_SET_R7_SIGRETURN 0xe3a07077
#define ARM_SET_R7_RT_SIGRETURN 0xe3a070ad
#define ARM_EABI_SYSCALL 0xef000000
/* OABI syscall restart trampoline, used for EABI executables too
whenever OABI support has been enabled in the kernel. */
#define ARM_OABI_SYSCALL_RESTART_SYSCALL 0xef900000
#define ARM_LDR_PC_SP_12 0xe49df00c
static void
arm_linux_sigtramp_cache (struct frame_info *this_frame,
struct trad_frame_cache *this_cache,
CORE_ADDR func, int regs_offset)
{
CORE_ADDR sp = get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);
CORE_ADDR base = sp + regs_offset;
int i;
for (i = 0; i < 16; i++)
trad_frame_set_reg_addr (this_cache, i, base + i * 4);
trad_frame_set_reg_addr (this_cache, ARM_PS_REGNUM, base + 16 * 4);
/* The VFP or iWMMXt registers may be saved on the stack, but there's
no reliable way to restore them (yet). */
/* Save a frame ID. */
trad_frame_set_id (this_cache, frame_id_build (sp, func));
}
/* There are a couple of different possible stack layouts that
we need to support.
Before version 2.6.18, the kernel used completely independent
layouts for non-RT and RT signals. For non-RT signals the stack
began directly with a struct sigcontext. For RT signals the stack
began with two redundant pointers (to the siginfo and ucontext),
and then the siginfo and ucontext.
As of version 2.6.18, the non-RT signal frame layout starts with
a ucontext and the RT signal frame starts with a siginfo and then
a ucontext. Also, the ucontext now has a designated save area
for coprocessor registers.
For RT signals, it's easy to tell the difference: we look for
pinfo, the pointer to the siginfo. If it has the expected
value, we have an old layout. If it doesn't, we have the new
layout.
For non-RT signals, it's a bit harder. We need something in one
layout or the other with a recognizable offset and value. We can't
use the return trampoline, because ARM usually uses SA_RESTORER,
in which case the stack return trampoline is not filled in.
We can't use the saved stack pointer, because sigaltstack might
be in use. So for now we guess the new layout... */
/* There are three words (trap_no, error_code, oldmask) in
struct sigcontext before r0. */
#define ARM_SIGCONTEXT_R0 0xc
/* There are five words (uc_flags, uc_link, and three for uc_stack)
in the ucontext_t before the sigcontext. */
#define ARM_UCONTEXT_SIGCONTEXT 0x14
/* There are three elements in an rt_sigframe before the ucontext:
pinfo, puc, and info. The first two are pointers and the third
is a struct siginfo, with size 128 bytes. We could follow puc
to the ucontext, but it's simpler to skip the whole thing. */
#define ARM_OLD_RT_SIGFRAME_SIGINFO 0x8
#define ARM_OLD_RT_SIGFRAME_UCONTEXT 0x88
#define ARM_NEW_RT_SIGFRAME_UCONTEXT 0x80
#define ARM_NEW_SIGFRAME_MAGIC 0x5ac3c35a
static void
arm_linux_sigreturn_init (const struct tramp_frame *self,
struct frame_info *this_frame,
struct trad_frame_cache *this_cache,
CORE_ADDR func)
{
struct gdbarch *gdbarch = get_frame_arch (this_frame);
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
CORE_ADDR sp = get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);
ULONGEST uc_flags = read_memory_unsigned_integer (sp, 4, byte_order);
if (uc_flags == ARM_NEW_SIGFRAME_MAGIC)
arm_linux_sigtramp_cache (this_frame, this_cache, func,
ARM_UCONTEXT_SIGCONTEXT
+ ARM_SIGCONTEXT_R0);
else
arm_linux_sigtramp_cache (this_frame, this_cache, func,
ARM_SIGCONTEXT_R0);
}
static void
arm_linux_rt_sigreturn_init (const struct tramp_frame *self,
struct frame_info *this_frame,
struct trad_frame_cache *this_cache,
CORE_ADDR func)
{
struct gdbarch *gdbarch = get_frame_arch (this_frame);
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
CORE_ADDR sp = get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);
ULONGEST pinfo = read_memory_unsigned_integer (sp, 4, byte_order);
if (pinfo == sp + ARM_OLD_RT_SIGFRAME_SIGINFO)
arm_linux_sigtramp_cache (this_frame, this_cache, func,
ARM_OLD_RT_SIGFRAME_UCONTEXT
+ ARM_UCONTEXT_SIGCONTEXT
+ ARM_SIGCONTEXT_R0);
else
arm_linux_sigtramp_cache (this_frame, this_cache, func,
ARM_NEW_RT_SIGFRAME_UCONTEXT
+ ARM_UCONTEXT_SIGCONTEXT
+ ARM_SIGCONTEXT_R0);
}
static void
arm_linux_restart_syscall_init (const struct tramp_frame *self,
struct frame_info *this_frame,
struct trad_frame_cache *this_cache,
CORE_ADDR func)
{
CORE_ADDR sp = get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);
trad_frame_set_reg_addr (this_cache, ARM_PC_REGNUM, sp);
trad_frame_set_reg_value (this_cache, ARM_SP_REGNUM, sp + 12);
/* Save a frame ID. */
trad_frame_set_id (this_cache, frame_id_build (sp, func));
}
static struct tramp_frame arm_linux_sigreturn_tramp_frame = {
SIGTRAMP_FRAME,
4,
{
{ ARM_LINUX_SIGRETURN_INSTR, -1 },
{ TRAMP_SENTINEL_INSN }
},
arm_linux_sigreturn_init
};
static struct tramp_frame arm_linux_rt_sigreturn_tramp_frame = {
SIGTRAMP_FRAME,
4,
{
{ ARM_LINUX_RT_SIGRETURN_INSTR, -1 },
{ TRAMP_SENTINEL_INSN }
},
arm_linux_rt_sigreturn_init
};
static struct tramp_frame arm_eabi_linux_sigreturn_tramp_frame = {
SIGTRAMP_FRAME,
4,
{
{ ARM_SET_R7_SIGRETURN, -1 },
{ ARM_EABI_SYSCALL, -1 },
{ TRAMP_SENTINEL_INSN }
},
arm_linux_sigreturn_init
};
static struct tramp_frame arm_eabi_linux_rt_sigreturn_tramp_frame = {
SIGTRAMP_FRAME,
4,
{
{ ARM_SET_R7_RT_SIGRETURN, -1 },
{ ARM_EABI_SYSCALL, -1 },
{ TRAMP_SENTINEL_INSN }
},
arm_linux_rt_sigreturn_init
};
static struct tramp_frame arm_linux_restart_syscall_tramp_frame = {
NORMAL_FRAME,
4,
{
{ ARM_OABI_SYSCALL_RESTART_SYSCALL, -1 },
{ ARM_LDR_PC_SP_12, -1 },
{ TRAMP_SENTINEL_INSN }
},
arm_linux_restart_syscall_init
};
/* Core file and register set support. */
#define ARM_LINUX_SIZEOF_GREGSET (18 * INT_REGISTER_SIZE)
void
arm_linux_supply_gregset (const struct regset *regset,
struct regcache *regcache,
int regnum, const void *gregs_buf, size_t len)
{
struct gdbarch *gdbarch = get_regcache_arch (regcache);
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
const gdb_byte *gregs = gregs_buf;
int regno;
CORE_ADDR reg_pc;
gdb_byte pc_buf[INT_REGISTER_SIZE];
for (regno = ARM_A1_REGNUM; regno < ARM_PC_REGNUM; regno++)
if (regnum == -1 || regnum == regno)
regcache_raw_supply (regcache, regno,
gregs + INT_REGISTER_SIZE * regno);
if (regnum == ARM_PS_REGNUM || regnum == -1)
{
if (arm_apcs_32)
regcache_raw_supply (regcache, ARM_PS_REGNUM,
gregs + INT_REGISTER_SIZE * ARM_CPSR_GREGNUM);
else
regcache_raw_supply (regcache, ARM_PS_REGNUM,
gregs + INT_REGISTER_SIZE * ARM_PC_REGNUM);
}
if (regnum == ARM_PC_REGNUM || regnum == -1)
{
reg_pc = extract_unsigned_integer (gregs
+ INT_REGISTER_SIZE * ARM_PC_REGNUM,
INT_REGISTER_SIZE, byte_order);
reg_pc = gdbarch_addr_bits_remove (gdbarch, reg_pc);
store_unsigned_integer (pc_buf, INT_REGISTER_SIZE, byte_order, reg_pc);
regcache_raw_supply (regcache, ARM_PC_REGNUM, pc_buf);
}
}
void
arm_linux_collect_gregset (const struct regset *regset,
const struct regcache *regcache,
int regnum, void *gregs_buf, size_t len)
{
gdb_byte *gregs = gregs_buf;
int regno;
for (regno = ARM_A1_REGNUM; regno < ARM_PC_REGNUM; regno++)
if (regnum == -1 || regnum == regno)
regcache_raw_collect (regcache, regno,
gregs + INT_REGISTER_SIZE * regno);
if (regnum == ARM_PS_REGNUM || regnum == -1)
{
if (arm_apcs_32)
regcache_raw_collect (regcache, ARM_PS_REGNUM,
gregs + INT_REGISTER_SIZE * ARM_CPSR_GREGNUM);
else
regcache_raw_collect (regcache, ARM_PS_REGNUM,
gregs + INT_REGISTER_SIZE * ARM_PC_REGNUM);
}
if (regnum == ARM_PC_REGNUM || regnum == -1)
regcache_raw_collect (regcache, ARM_PC_REGNUM,
gregs + INT_REGISTER_SIZE * ARM_PC_REGNUM);
}
/* Support for register format used by the NWFPE FPA emulator. */
#define typeNone 0x00
#define typeSingle 0x01
#define typeDouble 0x02
#define typeExtended 0x03
void
supply_nwfpe_register (struct regcache *regcache, int regno,
const gdb_byte *regs)
{
const gdb_byte *reg_data;
gdb_byte reg_tag;
gdb_byte buf[FP_REGISTER_SIZE];
reg_data = regs + (regno - ARM_F0_REGNUM) * FP_REGISTER_SIZE;
reg_tag = regs[(regno - ARM_F0_REGNUM) + NWFPE_TAGS_OFFSET];
memset (buf, 0, FP_REGISTER_SIZE);
switch (reg_tag)
{
case typeSingle:
memcpy (buf, reg_data, 4);
break;
case typeDouble:
memcpy (buf, reg_data + 4, 4);
memcpy (buf + 4, reg_data, 4);
break;
case typeExtended:
/* We want sign and exponent, then least significant bits,
then most significant. NWFPE does sign, most, least. */
memcpy (buf, reg_data, 4);
memcpy (buf + 4, reg_data + 8, 4);
memcpy (buf + 8, reg_data + 4, 4);
break;
default:
break;
}
regcache_raw_supply (regcache, regno, buf);
}
void
collect_nwfpe_register (const struct regcache *regcache, int regno,
gdb_byte *regs)
{
gdb_byte *reg_data;
gdb_byte reg_tag;
gdb_byte buf[FP_REGISTER_SIZE];
regcache_raw_collect (regcache, regno, buf);
/* NOTE drow/2006-06-07: This code uses the tag already in the
register buffer. I've preserved that when moving the code
from the native file to the target file. But this doesn't
always make sense. */
reg_data = regs + (regno - ARM_F0_REGNUM) * FP_REGISTER_SIZE;
reg_tag = regs[(regno - ARM_F0_REGNUM) + NWFPE_TAGS_OFFSET];
switch (reg_tag)
{
case typeSingle:
memcpy (reg_data, buf, 4);
break;
case typeDouble:
memcpy (reg_data, buf + 4, 4);
memcpy (reg_data + 4, buf, 4);
break;
case typeExtended:
memcpy (reg_data, buf, 4);
memcpy (reg_data + 4, buf + 8, 4);
memcpy (reg_data + 8, buf + 4, 4);
break;
default:
break;
}
}
void
arm_linux_supply_nwfpe (const struct regset *regset,
struct regcache *regcache,
int regnum, const void *regs_buf, size_t len)
{
const gdb_byte *regs = regs_buf;
int regno;
if (regnum == ARM_FPS_REGNUM || regnum == -1)
regcache_raw_supply (regcache, ARM_FPS_REGNUM,
regs + NWFPE_FPSR_OFFSET);
for (regno = ARM_F0_REGNUM; regno <= ARM_F7_REGNUM; regno++)
if (regnum == -1 || regnum == regno)
supply_nwfpe_register (regcache, regno, regs);
}
void
arm_linux_collect_nwfpe (const struct regset *regset,
const struct regcache *regcache,
int regnum, void *regs_buf, size_t len)
{
gdb_byte *regs = regs_buf;
int regno;
for (regno = ARM_F0_REGNUM; regno <= ARM_F7_REGNUM; regno++)
if (regnum == -1 || regnum == regno)
collect_nwfpe_register (regcache, regno, regs);
if (regnum == ARM_FPS_REGNUM || regnum == -1)
regcache_raw_collect (regcache, ARM_FPS_REGNUM,
regs + INT_REGISTER_SIZE * ARM_FPS_REGNUM);
}
/* Return the appropriate register set for the core section identified
by SECT_NAME and SECT_SIZE. */
static const struct regset *
arm_linux_regset_from_core_section (struct gdbarch *gdbarch,
const char *sect_name, size_t sect_size)
{
struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
if (strcmp (sect_name, ".reg") == 0
&& sect_size == ARM_LINUX_SIZEOF_GREGSET)
{
if (tdep->gregset == NULL)
tdep->gregset = regset_alloc (gdbarch, arm_linux_supply_gregset,
arm_linux_collect_gregset);
return tdep->gregset;
}
if (strcmp (sect_name, ".reg2") == 0
&& sect_size == ARM_LINUX_SIZEOF_NWFPE)
{
if (tdep->fpregset == NULL)
tdep->fpregset = regset_alloc (gdbarch, arm_linux_supply_nwfpe,
arm_linux_collect_nwfpe);
return tdep->fpregset;
}
return NULL;
}
/* Insert a single step breakpoint at the next executed instruction. */
static int
arm_linux_software_single_step (struct frame_info *frame)
{
struct gdbarch *gdbarch = get_frame_arch (frame);
struct address_space *aspace = get_frame_address_space (frame);
CORE_ADDR next_pc = arm_get_next_pc (frame, get_frame_pc (frame));
/* The Linux kernel offers some user-mode helpers in a high page. We can
not read this page (as of 2.6.23), and even if we could then we couldn't
set breakpoints in it, and even if we could then the atomic operations
would fail when interrupted. They are all called as functions and return
to the address in LR, so step to there instead. */
if (next_pc > 0xffff0000)
next_pc = get_frame_register_unsigned (frame, ARM_LR_REGNUM);
insert_single_step_breakpoint (gdbarch, aspace, next_pc);
return 1;
}
/* Support for displaced stepping of Linux SVC instructions. */
static void
arm_linux_cleanup_svc (struct gdbarch *gdbarch ATTRIBUTE_UNUSED,
struct regcache *regs,
struct displaced_step_closure *dsc)
{
CORE_ADDR from = dsc->insn_addr;
ULONGEST apparent_pc;
int within_scratch;
regcache_cooked_read_unsigned (regs, ARM_PC_REGNUM, &apparent_pc);
within_scratch = (apparent_pc >= dsc->scratch_base
&& apparent_pc < (dsc->scratch_base
+ DISPLACED_MODIFIED_INSNS * 4 + 4));
if (debug_displaced)
{
fprintf_unfiltered (gdb_stdlog, "displaced: PC is apparently %.8lx after "
"SVC step ", (unsigned long) apparent_pc);
if (within_scratch)
fprintf_unfiltered (gdb_stdlog, "(within scratch space)\n");
else
fprintf_unfiltered (gdb_stdlog, "(outside scratch space)\n");
}
if (within_scratch)
displaced_write_reg (regs, dsc, ARM_PC_REGNUM, from + 4, BRANCH_WRITE_PC);
}
static int
arm_linux_copy_svc (struct gdbarch *gdbarch, uint32_t insn, CORE_ADDR to,
struct regcache *regs, struct displaced_step_closure *dsc)
{
CORE_ADDR from = dsc->insn_addr;
struct frame_info *frame;
unsigned int svc_number = displaced_read_reg (regs, from, 7);
if (debug_displaced)
fprintf_unfiltered (gdb_stdlog, "displaced: copying Linux svc insn %.8lx\n",
(unsigned long) insn);
frame = get_current_frame ();
/* Is this a sigreturn or rt_sigreturn syscall? Note: these are only useful
for EABI. */
if (svc_number == 119 || svc_number == 173)
{
if (get_frame_type (frame) == SIGTRAMP_FRAME)
{
CORE_ADDR return_to;
struct symtab_and_line sal;
if (debug_displaced)
fprintf_unfiltered (gdb_stdlog, "displaced: found "
"sigreturn/rt_sigreturn SVC call. PC in frame = %lx\n",
(unsigned long) get_frame_pc (frame));
return_to = frame_unwind_caller_pc (frame);
if (debug_displaced)
fprintf_unfiltered (gdb_stdlog, "displaced: unwind pc = %lx. "
"Setting momentary breakpoint.\n", (unsigned long) return_to);
gdb_assert (inferior_thread ()->step_resume_breakpoint == NULL);
sal = find_pc_line (return_to, 0);
sal.pc = return_to;
sal.section = find_pc_overlay (return_to);
sal.explicit_pc = 1;
frame = get_prev_frame (frame);
if (frame)
{
inferior_thread ()->step_resume_breakpoint
= set_momentary_breakpoint (gdbarch, sal, get_frame_id (frame),
bp_step_resume);
/* We need to make sure we actually insert the momentary
breakpoint set above. */
insert_breakpoints ();
}
else if (debug_displaced)
fprintf_unfiltered (gdb_stderr, "displaced: couldn't find previous "
"frame to set momentary breakpoint for "
"sigreturn/rt_sigreturn\n");
}
else if (debug_displaced)
fprintf_unfiltered (gdb_stdlog, "displaced: sigreturn/rt_sigreturn "
"SVC call not in signal trampoline frame\n");
}
/* Preparation: If we detect sigreturn, set momentary breakpoint at resume
location, else nothing.
Insn: unmodified svc.
Cleanup: if pc lands in scratch space, pc <- insn_addr + 4
else leave pc alone. */
dsc->modinsn[0] = insn;
dsc->cleanup = &arm_linux_cleanup_svc;
/* Pretend we wrote to the PC, so cleanup doesn't set PC to the next
instruction. */
dsc->wrote_to_pc = 1;
return 0;
}
/* The following two functions implement single-stepping over calls to Linux
kernel helper routines, which perform e.g. atomic operations on architecture
variants which don't support them natively.
When this function is called, the PC will be pointing at the kernel helper
(at an address inaccessible to GDB), and r14 will point to the return
address. Displaced stepping always executes code in the copy area:
so, make the copy-area instruction branch back to the kernel helper (the
"from" address), and make r14 point to the breakpoint in the copy area. In
that way, we regain control once the kernel helper returns, and can clean
up appropriately (as if we had just returned from the kernel helper as it
would have been called from the non-displaced location). */
static void
cleanup_kernel_helper_return (struct gdbarch *gdbarch ATTRIBUTE_UNUSED,
struct regcache *regs,
struct displaced_step_closure *dsc)
{
displaced_write_reg (regs, dsc, ARM_LR_REGNUM, dsc->tmp[0], CANNOT_WRITE_PC);
displaced_write_reg (regs, dsc, ARM_PC_REGNUM, dsc->tmp[0], BRANCH_WRITE_PC);
}
static void
arm_catch_kernel_helper_return (struct gdbarch *gdbarch, CORE_ADDR from,
CORE_ADDR to, struct regcache *regs,
struct displaced_step_closure *dsc)
{
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
dsc->numinsns = 1;
dsc->insn_addr = from;
dsc->cleanup = &cleanup_kernel_helper_return;
/* Say we wrote to the PC, else cleanup will set PC to the next
instruction in the helper, which isn't helpful. */
dsc->wrote_to_pc = 1;
/* Preparation: tmp[0] <- r14
r14 <- +4
*(+8) <- from
Insn: ldr pc, [r14, #4]
Cleanup: r14 <- tmp[0], pc <- tmp[0]. */
dsc->tmp[0] = displaced_read_reg (regs, from, ARM_LR_REGNUM);
displaced_write_reg (regs, dsc, ARM_LR_REGNUM, (ULONGEST) to + 4,
CANNOT_WRITE_PC);
write_memory_unsigned_integer (to + 8, 4, byte_order, from);
dsc->modinsn[0] = 0xe59ef004; /* ldr pc, [lr, #4]. */
}
/* Linux-specific displaced step instruction copying function. Detects when
the program has stepped into a Linux kernel helper routine (which must be
handled as a special case), falling back to arm_displaced_step_copy_insn()
if it hasn't. */
static struct displaced_step_closure *
arm_linux_displaced_step_copy_insn (struct gdbarch *gdbarch,
CORE_ADDR from, CORE_ADDR to,
struct regcache *regs)
{
struct displaced_step_closure *dsc
= xmalloc (sizeof (struct displaced_step_closure));
/* Detect when we enter an (inaccessible by GDB) Linux kernel helper, and
stop at the return location. */
if (from > 0xffff0000)
{
if (debug_displaced)
fprintf_unfiltered (gdb_stdlog, "displaced: detected kernel helper "
"at %.8lx\n", (unsigned long) from);
arm_catch_kernel_helper_return (gdbarch, from, to, regs, dsc);
}
else
{
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
uint32_t insn = read_memory_unsigned_integer (from, 4, byte_order);
if (debug_displaced)
fprintf_unfiltered (gdb_stdlog, "displaced: stepping insn %.8lx "
"at %.8lx\n", (unsigned long) insn,
(unsigned long) from);
/* Override the default handling of SVC instructions. */
dsc->u.svc.copy_svc_os = arm_linux_copy_svc;
arm_process_displaced_insn (gdbarch, insn, from, to, regs, dsc);
}
arm_displaced_init_closure (gdbarch, from, to, dsc);
return dsc;
}
static void
arm_linux_init_abi (struct gdbarch_info info,
struct gdbarch *gdbarch)
{
struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
tdep->lowest_pc = 0x8000;
if (info.byte_order == BFD_ENDIAN_BIG)
{
if (tdep->arm_abi == ARM_ABI_AAPCS)
tdep->arm_breakpoint = eabi_linux_arm_be_breakpoint;
else
tdep->arm_breakpoint = arm_linux_arm_be_breakpoint;
tdep->thumb_breakpoint = arm_linux_thumb_be_breakpoint;
tdep->thumb2_breakpoint = arm_linux_thumb2_be_breakpoint;
}
else
{
if (tdep->arm_abi == ARM_ABI_AAPCS)
tdep->arm_breakpoint = eabi_linux_arm_le_breakpoint;
else
tdep->arm_breakpoint = arm_linux_arm_le_breakpoint;
tdep->thumb_breakpoint = arm_linux_thumb_le_breakpoint;
tdep->thumb2_breakpoint = arm_linux_thumb2_le_breakpoint;
}
tdep->arm_breakpoint_size = sizeof (arm_linux_arm_le_breakpoint);
tdep->thumb_breakpoint_size = sizeof (arm_linux_thumb_le_breakpoint);
tdep->thumb2_breakpoint_size = sizeof (arm_linux_thumb2_le_breakpoint);
if (tdep->fp_model == ARM_FLOAT_AUTO)
tdep->fp_model = ARM_FLOAT_FPA;
switch (tdep->fp_model)
{
case ARM_FLOAT_FPA:
tdep->jb_pc = ARM_LINUX_JB_PC_FPA;
break;
case ARM_FLOAT_SOFT_FPA:
case ARM_FLOAT_SOFT_VFP:
case ARM_FLOAT_VFP:
tdep->jb_pc = ARM_LINUX_JB_PC_EABI;
break;
default:
internal_error
(__FILE__, __LINE__,
_("arm_linux_init_abi: Floating point model not supported"));
break;
}
tdep->jb_elt_size = ARM_LINUX_JB_ELEMENT_SIZE;
set_solib_svr4_fetch_link_map_offsets
(gdbarch, svr4_ilp32_fetch_link_map_offsets);
/* Single stepping. */
set_gdbarch_software_single_step (gdbarch, arm_linux_software_single_step);
/* Shared library handling. */
set_gdbarch_skip_trampoline_code (gdbarch, find_solib_trampoline_target);
set_gdbarch_skip_solib_resolver (gdbarch, glibc_skip_solib_resolver);
/* Enable TLS support. */
set_gdbarch_fetch_tls_load_module_address (gdbarch,
svr4_fetch_objfile_link_map);
tramp_frame_prepend_unwinder (gdbarch,
&arm_linux_sigreturn_tramp_frame);
tramp_frame_prepend_unwinder (gdbarch,
&arm_linux_rt_sigreturn_tramp_frame);
tramp_frame_prepend_unwinder (gdbarch,
&arm_eabi_linux_sigreturn_tramp_frame);
tramp_frame_prepend_unwinder (gdbarch,
&arm_eabi_linux_rt_sigreturn_tramp_frame);
tramp_frame_prepend_unwinder (gdbarch,
&arm_linux_restart_syscall_tramp_frame);
/* Core file support. */
set_gdbarch_regset_from_core_section (gdbarch,
arm_linux_regset_from_core_section);
set_gdbarch_get_siginfo_type (gdbarch, linux_get_siginfo_type);
/* Displaced stepping. */
set_gdbarch_displaced_step_copy_insn (gdbarch,
arm_linux_displaced_step_copy_insn);
set_gdbarch_displaced_step_fixup (gdbarch, arm_displaced_step_fixup);
set_gdbarch_displaced_step_free_closure (gdbarch,
simple_displaced_step_free_closure);
set_gdbarch_displaced_step_location (gdbarch, displaced_step_at_entry_point);
}
/* Provide a prototype to silence -Wmissing-prototypes. */
extern initialize_file_ftype _initialize_arm_linux_tdep;
void
_initialize_arm_linux_tdep (void)
{
gdbarch_register_osabi (bfd_arch_arm, 0, GDB_OSABI_LINUX,
arm_linux_init_abi);
}