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/* Common target dependent code for GNU/Linux on ARM systems.
Copyright (C) 1999-2020 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 <http://www.gnu.org/licenses/>. */
#include "gdbsupport/common-defs.h"
#include "gdbsupport/common-regcache.h"
#include "arch/arm.h"
#include "arm-linux.h"
#include "arch/arm-get-next-pcs.h"
/* Calculate the offset from stack pointer of the pc register on the stack
in the case of a sigreturn or sigreturn_rt syscall. */
int
arm_linux_sigreturn_next_pc_offset (unsigned long sp,
unsigned long sp_data,
unsigned long svc_number,
int is_sigreturn)
{
/* Offset of R0 register. */
int r0_offset = 0;
/* Offset of PC register. */
int pc_offset = 0;
if (is_sigreturn)
{
if (sp_data == ARM_NEW_SIGFRAME_MAGIC)
r0_offset = ARM_UCONTEXT_SIGCONTEXT + ARM_SIGCONTEXT_R0;
else
r0_offset = ARM_SIGCONTEXT_R0;
}
else
{
if (sp_data == sp + ARM_OLD_RT_SIGFRAME_SIGINFO)
r0_offset = ARM_OLD_RT_SIGFRAME_UCONTEXT;
else
r0_offset = ARM_NEW_RT_SIGFRAME_UCONTEXT;
r0_offset += ARM_UCONTEXT_SIGCONTEXT + ARM_SIGCONTEXT_R0;
}
pc_offset = r0_offset + ARM_INT_REGISTER_SIZE * ARM_PC_REGNUM;
return pc_offset;
}
/* Implementation of "fixup" method of struct arm_get_next_pcs_ops
for arm-linux. */
CORE_ADDR
arm_linux_get_next_pcs_fixup (struct arm_get_next_pcs *self,
CORE_ADDR nextpc)
{
/* 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 (tail) called
as functions and return to the address in LR. However, when GDB single
step this instruction, this instruction isn't executed yet, and LR
may not be updated yet. In other words, GDB can get the target
address from LR if this instruction isn't BL or BLX. */
if (nextpc > 0xffff0000)
{
int bl_blx_p = 0;
CORE_ADDR pc = regcache_read_pc (self->regcache);
int pc_incr = 0;
if (self->ops->is_thumb (self))
{
unsigned short inst1
= self->ops->read_mem_uint (pc, 2, self->byte_order_for_code);
if (bits (inst1, 8, 15) == 0x47 && bit (inst1, 7))
{
/* BLX Rm */
bl_blx_p = 1;
pc_incr = 2;
}
else if (thumb_insn_size (inst1) == 4)
{
unsigned short inst2;
inst2 = self->ops->read_mem_uint (pc + 2, 2,
self->byte_order_for_code);
if ((inst1 & 0xf800) == 0xf000 && bits (inst2, 14, 15) == 0x3)
{
/* BL <label> and BLX <label> */
bl_blx_p = 1;
pc_incr = 4;
}
}
pc_incr = MAKE_THUMB_ADDR (pc_incr);
}
else
{
unsigned int insn
= self->ops->read_mem_uint (pc, 4, self->byte_order_for_code);
if (bits (insn, 28, 31) == INST_NV)
{
if (bits (insn, 25, 27) == 0x5) /* BLX <label> */
bl_blx_p = 1;
}
else
{
if (bits (insn, 24, 27) == 0xb /* BL <label> */
|| bits (insn, 4, 27) == 0x12fff3 /* BLX Rm */)
bl_blx_p = 1;
}
pc_incr = 4;
}
/* If the instruction BL or BLX, the target address is the following
instruction of BL or BLX, otherwise, the target address is in LR
already. */
if (bl_blx_p)
nextpc = pc + pc_incr;
else
nextpc = regcache_raw_get_unsigned (self->regcache, ARM_LR_REGNUM);
}
return nextpc;
}
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