mirror of
https://sourceware.org/git/binutils-gdb.git
synced 2024-12-09 04:21:49 +08:00
e7ee86a99a
(LINUX_SIGTRAMP_INSN0, LINUX_SIGTRAMP_OFFSET0, LINUX_SIGTRAMP_INSN1, LINUX_SIGTRAMP_OFFSET1, LINUX_SIGTRAMP_INSN2, LINUX_SIGTRAMP_OFFSET2, linux_sigtramp_code, LINUX_SIGTRAMP_LEN, i386_linux_sigtramp_start, LINUX_RT_SIGTRAMP_INSN0, LINUX_RT_SIGTRAMP_OFFSET0, LINUX_RT_SIGTRAMP_INSN1, LINUX_RT_SIGTRAMP_OFFSET1, linux_rt_sigtramp_code, LINUX_RT_SIGTRAMP_LEN, i386_linux_rt_sigtramp_start, i386_linux_in_sigtramp, i386_linux_sigcontext_addr, LINUX_SIGCONTEXT_PC_OFFSET, i386_linux_sigtramp_saved_pc, LINUX_SIGCONTEXT_SP_OFFSET, i386_linux_sigtramp_saved_sp): Deleted. Folks rightly pointed out that these are target-dependent, and useful in non-native configurations. Moved to... * i386-linux-tdep.c: ... Here, a new file. * Makefile.in (ALLDEPFILES): Add i386-linux-tdep.c. (i386-linux-tdep.o): New rule. (i386-linux-nat.o): We no longer depend on frame.h. * config/i386/linux.mt (TDEPFILES): Add i386-linux-tdep.o.
282 lines
8.9 KiB
C
282 lines
8.9 KiB
C
/* Target-dependent code for Linux running on i386's, for GDB.
|
||
Copyright (C) 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"
|
||
#include "gdbcore.h"
|
||
#include "frame.h"
|
||
#include "value.h"
|
||
|
||
|
||
/* Recognizing signal handler frames. */
|
||
|
||
/* Linux has two flavors of signals. Normal signal handlers, and
|
||
"realtime" (RT) signals. The RT signals can provide additional
|
||
information to the signal handler if the SA_SIGINFO flag is set
|
||
when establishing a signal handler using `sigaction'. It is not
|
||
unlikely that future versions of Linux will support SA_SIGINFO for
|
||
normal signals too. */
|
||
|
||
/* When the i386 Linux kernel calls a signal handler and the
|
||
SA_RESTORER flag isn't set, the return address points to a bit of
|
||
code on the stack. This function returns whether the PC appears to
|
||
be within this bit of code.
|
||
|
||
The instruction sequence for normal signals is
|
||
pop %eax
|
||
mov $0x77,%eax
|
||
int $0x80
|
||
or 0x58 0xb8 0x77 0x00 0x00 0x00 0xcd 0x80.
|
||
|
||
Checking for the code sequence should be somewhat reliable, because
|
||
the effect is to call the system call sigreturn. This is unlikely
|
||
to occur anywhere other than a signal trampoline.
|
||
|
||
It kind of sucks that we have to read memory from the process in
|
||
order to identify a signal trampoline, but there doesn't seem to be
|
||
any other way. The IN_SIGTRAMP macro in tm-linux.h arranges to
|
||
only call us if no function name could be identified, which should
|
||
be the case since the code is on the stack.
|
||
|
||
Detection of signal trampolines for handlers that set the
|
||
SA_RESTORER flag is in general not possible. Unfortunately this is
|
||
what the GNU C Library has been doing for quite some time now.
|
||
However, as of version 2.1.2, the GNU C Library uses signal
|
||
trampolines (named __restore and __restore_rt) that are identical
|
||
to the ones used by the kernel. Therefore, these trampolines are
|
||
supported too. */
|
||
|
||
#define LINUX_SIGTRAMP_INSN0 (0x58) /* pop %eax */
|
||
#define LINUX_SIGTRAMP_OFFSET0 (0)
|
||
#define LINUX_SIGTRAMP_INSN1 (0xb8) /* mov $NNNN,%eax */
|
||
#define LINUX_SIGTRAMP_OFFSET1 (1)
|
||
#define LINUX_SIGTRAMP_INSN2 (0xcd) /* int */
|
||
#define LINUX_SIGTRAMP_OFFSET2 (6)
|
||
|
||
static const unsigned char linux_sigtramp_code[] =
|
||
{
|
||
LINUX_SIGTRAMP_INSN0, /* pop %eax */
|
||
LINUX_SIGTRAMP_INSN1, 0x77, 0x00, 0x00, 0x00, /* mov $0x77,%eax */
|
||
LINUX_SIGTRAMP_INSN2, 0x80 /* int $0x80 */
|
||
};
|
||
|
||
#define LINUX_SIGTRAMP_LEN (sizeof linux_sigtramp_code)
|
||
|
||
/* If PC is in a sigtramp routine, return the address of the start of
|
||
the routine. Otherwise, return 0. */
|
||
|
||
static CORE_ADDR
|
||
i386_linux_sigtramp_start (CORE_ADDR pc)
|
||
{
|
||
unsigned char buf[LINUX_SIGTRAMP_LEN];
|
||
|
||
/* We only recognize a signal trampoline if PC is at the start of
|
||
one of the three instructions. We optimize for finding the PC at
|
||
the start, as will be the case when the trampoline is not the
|
||
first frame on the stack. We assume that in the case where the
|
||
PC is not at the start of the instruction sequence, there will be
|
||
a few trailing readable bytes on the stack. */
|
||
|
||
if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0)
|
||
return 0;
|
||
|
||
if (buf[0] != LINUX_SIGTRAMP_INSN0)
|
||
{
|
||
int adjust;
|
||
|
||
switch (buf[0])
|
||
{
|
||
case LINUX_SIGTRAMP_INSN1:
|
||
adjust = LINUX_SIGTRAMP_OFFSET1;
|
||
break;
|
||
case LINUX_SIGTRAMP_INSN2:
|
||
adjust = LINUX_SIGTRAMP_OFFSET2;
|
||
break;
|
||
default:
|
||
return 0;
|
||
}
|
||
|
||
pc -= adjust;
|
||
|
||
if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0)
|
||
return 0;
|
||
}
|
||
|
||
if (memcmp (buf, linux_sigtramp_code, LINUX_SIGTRAMP_LEN) != 0)
|
||
return 0;
|
||
|
||
return pc;
|
||
}
|
||
|
||
/* This function does the same for RT signals. Here the instruction
|
||
sequence is
|
||
mov $0xad,%eax
|
||
int $0x80
|
||
or 0xb8 0xad 0x00 0x00 0x00 0xcd 0x80.
|
||
|
||
The effect is to call the system call rt_sigreturn. */
|
||
|
||
#define LINUX_RT_SIGTRAMP_INSN0 (0xb8) /* mov $NNNN,%eax */
|
||
#define LINUX_RT_SIGTRAMP_OFFSET0 (0)
|
||
#define LINUX_RT_SIGTRAMP_INSN1 (0xcd) /* int */
|
||
#define LINUX_RT_SIGTRAMP_OFFSET1 (5)
|
||
|
||
static const unsigned char linux_rt_sigtramp_code[] =
|
||
{
|
||
LINUX_RT_SIGTRAMP_INSN0, 0xad, 0x00, 0x00, 0x00, /* mov $0xad,%eax */
|
||
LINUX_RT_SIGTRAMP_INSN1, 0x80 /* int $0x80 */
|
||
};
|
||
|
||
#define LINUX_RT_SIGTRAMP_LEN (sizeof linux_rt_sigtramp_code)
|
||
|
||
/* If PC is in a RT sigtramp routine, return the address of the start
|
||
of the routine. Otherwise, return 0. */
|
||
|
||
static CORE_ADDR
|
||
i386_linux_rt_sigtramp_start (CORE_ADDR pc)
|
||
{
|
||
unsigned char buf[LINUX_RT_SIGTRAMP_LEN];
|
||
|
||
/* We only recognize a signal trampoline if PC is at the start of
|
||
one of the two instructions. We optimize for finding the PC at
|
||
the start, as will be the case when the trampoline is not the
|
||
first frame on the stack. We assume that in the case where the
|
||
PC is not at the start of the instruction sequence, there will be
|
||
a few trailing readable bytes on the stack. */
|
||
|
||
if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0)
|
||
return 0;
|
||
|
||
if (buf[0] != LINUX_RT_SIGTRAMP_INSN0)
|
||
{
|
||
if (buf[0] != LINUX_RT_SIGTRAMP_INSN1)
|
||
return 0;
|
||
|
||
pc -= LINUX_RT_SIGTRAMP_OFFSET1;
|
||
|
||
if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0)
|
||
return 0;
|
||
}
|
||
|
||
if (memcmp (buf, linux_rt_sigtramp_code, LINUX_RT_SIGTRAMP_LEN) != 0)
|
||
return 0;
|
||
|
||
return pc;
|
||
}
|
||
|
||
/* Return whether PC is in a Linux sigtramp routine. */
|
||
|
||
int
|
||
i386_linux_in_sigtramp (CORE_ADDR pc, char *name)
|
||
{
|
||
if (name)
|
||
return STREQ ("__restore", name) || STREQ ("__restore_rt", name);
|
||
|
||
return (i386_linux_sigtramp_start (pc) != 0
|
||
|| i386_linux_rt_sigtramp_start (pc) != 0);
|
||
}
|
||
|
||
/* Assuming FRAME is for a Linux sigtramp routine, return the address
|
||
of the associated sigcontext structure. */
|
||
|
||
CORE_ADDR
|
||
i386_linux_sigcontext_addr (struct frame_info *frame)
|
||
{
|
||
CORE_ADDR pc;
|
||
|
||
pc = i386_linux_sigtramp_start (frame->pc);
|
||
if (pc)
|
||
{
|
||
CORE_ADDR sp;
|
||
|
||
if (frame->next)
|
||
/* If this isn't the top frame, the next frame must be for the
|
||
signal handler itself. The sigcontext structure lives on
|
||
the stack, right after the signum argument. */
|
||
return frame->next->frame + 12;
|
||
|
||
/* This is the top frame. We'll have to find the address of the
|
||
sigcontext structure by looking at the stack pointer. Keep
|
||
in mind that the first instruction of the sigtramp code is
|
||
"pop %eax". If the PC is at this instruction, adjust the
|
||
returned value accordingly. */
|
||
sp = read_register (SP_REGNUM);
|
||
if (pc == frame->pc)
|
||
return sp + 4;
|
||
return sp;
|
||
}
|
||
|
||
pc = i386_linux_rt_sigtramp_start (frame->pc);
|
||
if (pc)
|
||
{
|
||
if (frame->next)
|
||
/* If this isn't the top frame, the next frame must be for the
|
||
signal handler itself. The sigcontext structure is part of
|
||
the user context. A pointer to the user context is passed
|
||
as the third argument to the signal handler. */
|
||
return read_memory_integer (frame->next->frame + 16, 4) + 20;
|
||
|
||
/* This is the top frame. Again, use the stack pointer to find
|
||
the address of the sigcontext structure. */
|
||
return read_memory_integer (read_register (SP_REGNUM) + 8, 4) + 20;
|
||
}
|
||
|
||
error ("Couldn't recognize signal trampoline.");
|
||
return 0;
|
||
}
|
||
|
||
/* Offset to saved PC in sigcontext, from <asm/sigcontext.h>. */
|
||
#define LINUX_SIGCONTEXT_PC_OFFSET (56)
|
||
|
||
/* Assuming FRAME is for a Linux sigtramp routine, return the saved
|
||
program counter. */
|
||
|
||
CORE_ADDR
|
||
i386_linux_sigtramp_saved_pc (struct frame_info *frame)
|
||
{
|
||
CORE_ADDR addr;
|
||
addr = i386_linux_sigcontext_addr (frame);
|
||
return read_memory_integer (addr + LINUX_SIGCONTEXT_PC_OFFSET, 4);
|
||
}
|
||
|
||
/* Offset to saved SP in sigcontext, from <asm/sigcontext.h>. */
|
||
#define LINUX_SIGCONTEXT_SP_OFFSET (28)
|
||
|
||
/* Assuming FRAME is for a Linux sigtramp routine, return the saved
|
||
stack pointer. */
|
||
|
||
CORE_ADDR
|
||
i386_linux_sigtramp_saved_sp (struct frame_info *frame)
|
||
{
|
||
CORE_ADDR addr;
|
||
addr = i386_linux_sigcontext_addr (frame);
|
||
return read_memory_integer (addr + LINUX_SIGCONTEXT_SP_OFFSET, 4);
|
||
}
|
||
|
||
/* Immediately after a function call, return the saved pc. */
|
||
|
||
CORE_ADDR
|
||
i386_linux_saved_pc_after_call (struct frame_info *frame)
|
||
{
|
||
if (frame->signal_handler_caller)
|
||
return i386_linux_sigtramp_saved_pc (frame);
|
||
|
||
return read_memory_integer (read_register (SP_REGNUM), 4);
|
||
}
|