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binutils-gdb/gdb/arc-linux-tdep.c
Andrew Burgess 08106042d9 gdb: move the type cast into gdbarch_tdep 
I built GDB for all targets on a x86-64/GNU-Linux system, and
then (accidentally) passed GDB a RISC-V binary, and asked GDB to "run"
the binary on the native target.  I got this error:

  (gdb) show architecture
  The target architecture is set to "auto" (currently "i386").
  (gdb) file /tmp/hello.rv32.exe
  Reading symbols from /tmp/hello.rv32.exe...
  (gdb) show architecture
  The target architecture is set to "auto" (currently "riscv:rv32").
  (gdb) run
  Starting program: /tmp/hello.rv32.exe
  ../../src/gdb/i387-tdep.c:596: internal-error: i387_supply_fxsave: Assertion `tdep->st0_regnum >= I386_ST0_REGNUM' failed.

What's going on here is this; initially the architecture is i386, this
is based on the default architecture, which is set based on the native
target.  After loading the RISC-V executable the architecture of the
current inferior is updated based on the architecture of the
executable.

When we "run", GDB does a fork & exec, with the inferior being
controlled through ptrace.  GDB sees an initial stop from the inferior
as soon as the inferior comes to life.  In response to this stop GDB
ends up calling save_stop_reason (linux-nat.c), which ends up trying
to read register from the inferior, to do this we end up calling
target_ops::fetch_registers, which, for the x86-64 native target,
calls amd64_linux_nat_target::fetch_registers.

After this I eventually end up in i387_supply_fxsave, different x86
based targets will end in different functions to fetch registers, but
it doesn't really matter which function we end up in, the problem is
this line, which is repeated in many places:

  i386_gdbarch_tdep *tdep = (i386_gdbarch_tdep *) gdbarch_tdep (arch);

The problem here is that the ARCH in this line comes from the current
inferior, which, as we discussed above, will be a RISC-V gdbarch, the
tdep field will actually be of type riscv_gdbarch_tdep, not
i386_gdbarch_tdep.  After this cast we are relying on undefined
behaviour, in my case I happen to trigger an assert, but this might
not always be the case.

The thing I tried that exposed this problem was of course, trying to
start an executable of the wrong architecture on a native target.  I
don't think that the correct solution for this problem is to detect,
at the point of cast, that the gdbarch_tdep object is of the wrong
type, but, I did wonder, is there a way that we could protect
ourselves from incorrectly casting the gdbarch_tdep object?

I think that there is something we can do here, and this commit is the
first step in that direction, though no actual check is added by this
commit.

This commit can be split into two parts:

 (1) In gdbarch.h and arch-utils.c.  In these files I have modified
 gdbarch_tdep (the function) so that it now takes a template argument,
 like this:

    template<typename TDepType>
    static inline TDepType *
    gdbarch_tdep (struct gdbarch *gdbarch)
    {
      struct gdbarch_tdep *tdep = gdbarch_tdep_1 (gdbarch);
      return static_cast<TDepType *> (tdep);
    }

  After this change we are no better protected, but the cast is now
  done within the gdbarch_tdep function rather than at the call sites,
  this leads to the second, much larger change in this commit,

  (2) Everywhere gdbarch_tdep is called, we make changes like this:

    -  i386_gdbarch_tdep *tdep = (i386_gdbarch_tdep *) gdbarch_tdep (arch);
    +  i386_gdbarch_tdep *tdep = gdbarch_tdep<i386_gdbarch_tdep> (arch);

There should be no functional change after this commit.

In the next commit I will build on this change to add an assertion in
gdbarch_tdep that checks we are casting to the correct type.
2022-07-21 15:19:42 +01:00

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/* Target dependent code for GNU/Linux ARC.
Copyright 2020-2022 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/>. */
/* GDB header files. */
#include "defs.h"
#include "linux-tdep.h"
#include "objfiles.h"
#include "opcode/arc.h"
#include "osabi.h"
#include "solib-svr4.h"
#include "disasm.h"
/* ARC header files. */
#include "opcodes/arc-dis.h"
#include "arc-linux-tdep.h"
#include "arc-tdep.h"
#include "arch/arc.h"
/* Print an "arc-linux" debug statement. */
#define arc_linux_debug_printf(fmt, ...) \
debug_prefixed_printf_cond (arc_debug, "arc-linux", fmt, ##__VA_ARGS__)
#define REGOFF(offset) (offset * ARC_REGISTER_SIZE)
/* arc_linux_sc_reg_offsets[i] is the offset of register i in the `struct
sigcontext'. Array index is an internal GDB register number, as defined in
arc-tdep.h:arc_regnum.
From <include/uapi/asm/sigcontext.h> and <include/uapi/asm/ptrace.h>.
The layout of this struct is tightly bound to "arc_regnum" enum
in arc-tdep.h. Any change of order in there, must be reflected
here as well. */
static const int arc_linux_sc_reg_offsets[] = {
/* R0 - R12. */
REGOFF (22), REGOFF (21), REGOFF (20), REGOFF (19),
REGOFF (18), REGOFF (17), REGOFF (16), REGOFF (15),
REGOFF (14), REGOFF (13), REGOFF (12), REGOFF (11),
REGOFF (10),
/* R13 - R25. */
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER,
REGOFF (9), /* R26 (GP) */
REGOFF (8), /* FP */
REGOFF (23), /* SP */
ARC_OFFSET_NO_REGISTER, /* ILINK */
ARC_OFFSET_NO_REGISTER, /* R30 */
REGOFF (7), /* BLINK */
/* R32 - R59. */
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER,
REGOFF (4), /* LP_COUNT */
ARC_OFFSET_NO_REGISTER, /* RESERVED */
ARC_OFFSET_NO_REGISTER, /* LIMM */
ARC_OFFSET_NO_REGISTER, /* PCL */
REGOFF (6), /* PC */
REGOFF (5), /* STATUS32 */
REGOFF (2), /* LP_START */
REGOFF (3), /* LP_END */
REGOFF (1), /* BTA */
};
/* arc_linux_core_reg_offsets[i] is the offset in the .reg section of GDB
regnum i. Array index is an internal GDB register number, as defined in
arc-tdep.h:arc_regnum.
From include/uapi/asm/ptrace.h in the ARC Linux sources. */
/* The layout of this struct is tightly bound to "arc_regnum" enum
in arc-tdep.h. Any change of order in there, must be reflected
here as well. */
static const int arc_linux_core_reg_offsets[] = {
/* R0 - R12. */
REGOFF (22), REGOFF (21), REGOFF (20), REGOFF (19),
REGOFF (18), REGOFF (17), REGOFF (16), REGOFF (15),
REGOFF (14), REGOFF (13), REGOFF (12), REGOFF (11),
REGOFF (10),
/* R13 - R25. */
REGOFF (37), REGOFF (36), REGOFF (35), REGOFF (34),
REGOFF (33), REGOFF (32), REGOFF (31), REGOFF (30),
REGOFF (29), REGOFF (28), REGOFF (27), REGOFF (26),
REGOFF (25),
REGOFF (9), /* R26 (GP) */
REGOFF (8), /* FP */
REGOFF (23), /* SP */
ARC_OFFSET_NO_REGISTER, /* ILINK */
ARC_OFFSET_NO_REGISTER, /* R30 */
REGOFF (7), /* BLINK */
/* R32 - R59. */
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
ARC_OFFSET_NO_REGISTER,
REGOFF (4), /* LP_COUNT */
ARC_OFFSET_NO_REGISTER, /* RESERVED */
ARC_OFFSET_NO_REGISTER, /* LIMM */
ARC_OFFSET_NO_REGISTER, /* PCL */
REGOFF (39), /* PC */
REGOFF (5), /* STATUS32 */
REGOFF (2), /* LP_START */
REGOFF (3), /* LP_END */
REGOFF (1), /* BTA */
REGOFF (6) /* ERET */
};
/* Is THIS_FRAME a sigtramp function - the function that returns from
signal handler into normal execution flow? This is the case if the PC is
either at the start of, or in the middle of the two instructions:
mov r8, __NR_rt_sigreturn ; __NR_rt_sigreturn == 139
trap_s 0 ; `swi' for ARC700
On ARC uClibc Linux this function is called __default_rt_sa_restorer.
Returns TRUE if this is a sigtramp frame. */
static bool
arc_linux_is_sigtramp (struct frame_info *this_frame)
{
struct gdbarch *gdbarch = get_frame_arch (this_frame);
CORE_ADDR pc = get_frame_pc (this_frame);
arc_linux_debug_printf ("pc=%s", paddress(gdbarch, pc));
static const gdb_byte insns_be_hs[] = {
0x20, 0x8a, 0x12, 0xc2, /* mov r8,nr_rt_sigreturn */
0x78, 0x1e /* trap_s 0 */
};
static const gdb_byte insns_be_700[] = {
0x20, 0x8a, 0x12, 0xc2, /* mov r8,nr_rt_sigreturn */
0x22, 0x6f, 0x00, 0x3f /* swi */
};
gdb_byte arc_sigtramp_insns[sizeof (insns_be_700)];
size_t insns_sz;
if (arc_mach_is_arcv2 (gdbarch))
{
insns_sz = sizeof (insns_be_hs);
memcpy (arc_sigtramp_insns, insns_be_hs, insns_sz);
}
else
{
insns_sz = sizeof (insns_be_700);
memcpy (arc_sigtramp_insns, insns_be_700, insns_sz);
}
if (gdbarch_byte_order (gdbarch) == BFD_ENDIAN_LITTLE)
{
/* On little endian targets, ARC code section is in what is called
"middle endian", where half-words are in the big-endian order,
only bytes inside the halfwords are in the little endian order.
As a result it is very easy to convert big endian instruction to
little endian, since it is needed to swap bytes in the halfwords,
so there is no need to have information on whether that is a
4-byte instruction or 2-byte. */
gdb_assert ((insns_sz % 2) == 0);
for (int i = 0; i < insns_sz; i += 2)
std::swap (arc_sigtramp_insns[i], arc_sigtramp_insns[i+1]);
}
gdb_byte buf[insns_sz];
/* Read the memory at the PC. Since we are stopped, any breakpoint must
have been removed. */
if (!safe_frame_unwind_memory (this_frame, pc, {buf, insns_sz}))
{
/* Failed to unwind frame. */
return FALSE;
}
/* Is that code the sigtramp instruction sequence? */
if (memcmp (buf, arc_sigtramp_insns, insns_sz) == 0)
return TRUE;
/* No - look one instruction earlier in the code... */
if (!safe_frame_unwind_memory (this_frame, pc - 4, {buf, insns_sz}))
{
/* Failed to unwind frame. */
return FALSE;
}
return (memcmp (buf, arc_sigtramp_insns, insns_sz) == 0);
}
/* Get sigcontext structure of sigtramp frame - it contains saved
registers of interrupted frame.
Stack pointer points to the rt_sigframe structure, and sigcontext can
be found as in:
struct rt_sigframe {
struct siginfo info;
struct ucontext uc;
...
};
struct ucontext {
unsigned long uc_flags;
struct ucontext *uc_link;
stack_t uc_stack;
struct sigcontext uc_mcontext;
sigset_t uc_sigmask;
};
sizeof (struct siginfo) == 0x80
offsetof (struct ucontext, uc_mcontext) == 0x14
GDB cannot include linux headers and use offsetof () because those are
target headers and GDB might be built for a different run host. There
doesn't seem to be an established mechanism to figure out those offsets
via gdbserver, so the only way is to hardcode values in the GDB,
meaning that GDB will be broken if values will change. That seems to
be a very unlikely scenario and other arches (aarch64, alpha, amd64,
etc) in GDB hardcode values. */
static CORE_ADDR
arc_linux_sigcontext_addr (struct frame_info *this_frame)
{
const int ucontext_offset = 0x80;
const int sigcontext_offset = 0x14;
return get_frame_sp (this_frame) + ucontext_offset + sigcontext_offset;
}
/* Implement the "cannot_fetch_register" gdbarch method. */
static int
arc_linux_cannot_fetch_register (struct gdbarch *gdbarch, int regnum)
{
/* Assume that register is readable if it is unknown. */
switch (regnum)
{
case ARC_ILINK_REGNUM:
case ARC_RESERVED_REGNUM:
case ARC_LIMM_REGNUM:
return true;
case ARC_R30_REGNUM:
case ARC_R58_REGNUM:
case ARC_R59_REGNUM:
return !arc_mach_is_arcv2 (gdbarch);
}
return (regnum > ARC_BLINK_REGNUM) && (regnum < ARC_LP_COUNT_REGNUM);
}
/* Implement the "cannot_store_register" gdbarch method. */
static int
arc_linux_cannot_store_register (struct gdbarch *gdbarch, int regnum)
{
/* Assume that register is writable if it is unknown. */
switch (regnum)
{
case ARC_ILINK_REGNUM:
case ARC_RESERVED_REGNUM:
case ARC_LIMM_REGNUM:
case ARC_PCL_REGNUM:
return true;
case ARC_R30_REGNUM:
case ARC_R58_REGNUM:
case ARC_R59_REGNUM:
return !arc_mach_is_arcv2 (gdbarch);
}
return (regnum > ARC_BLINK_REGNUM) && (regnum < ARC_LP_COUNT_REGNUM);
}
/* For ARC Linux, breakpoints use the 16-bit TRAP_S 1 instruction, which
is 0x3e78 (little endian) or 0x783e (big endian). */
static const gdb_byte arc_linux_trap_s_be[] = { 0x78, 0x3e };
static const gdb_byte arc_linux_trap_s_le[] = { 0x3e, 0x78 };
static const int trap_size = 2; /* Number of bytes to insert "trap". */
/* Implement the "breakpoint_kind_from_pc" gdbarch method. */
static int
arc_linux_breakpoint_kind_from_pc (struct gdbarch *gdbarch, CORE_ADDR *pcptr)
{
return trap_size;
}
/* Implement the "sw_breakpoint_from_kind" gdbarch method. */
static const gdb_byte *
arc_linux_sw_breakpoint_from_kind (struct gdbarch *gdbarch,
int kind, int *size)
{
gdb_assert (kind == trap_size);
*size = kind;
return ((gdbarch_byte_order (gdbarch) == BFD_ENDIAN_BIG)
? arc_linux_trap_s_be
: arc_linux_trap_s_le);
}
/* Check for an atomic sequence of instructions beginning with an
LLOCK instruction and ending with a SCOND instruction.
These patterns are hand coded in libc's (glibc and uclibc). Take
a look at [1] for instance:
main+14: llock r2,[r0]
main+18: brne.nt r2,0,main+30
main+22: scond r3,[r0]
main+26: bne main+14
main+30: mov_s r0,0
If such a sequence is found, attempt to step over it.
A breakpoint is placed at the end of the sequence.
This function expects the INSN to be a "llock(d)" instruction.
[1]
https://cgit.uclibc-ng.org/cgi/cgit/uclibc-ng.git/tree/libc/ \
sysdeps/linux/arc/bits/atomic.h#n46
*/
static std::vector<CORE_ADDR>
handle_atomic_sequence (arc_instruction insn, disassemble_info *di)
{
const int atomic_seq_len = 24; /* Instruction sequence length. */
std::vector<CORE_ADDR> next_pcs;
/* Sanity check. */
gdb_assert (insn.insn_class == LLOCK);
/* Data size we are dealing with: LLOCK vs. LLOCKD */
arc_ldst_data_size llock_data_size_mode = insn.data_size_mode;
/* Indicator if any conditional branch is found in the sequence. */
bool found_bc = false;
/* Becomes true if "LLOCK(D) .. SCOND(D)" sequence is found. */
bool is_pattern_valid = false;
for (int insn_count = 0; insn_count < atomic_seq_len; ++insn_count)
{
arc_insn_decode (arc_insn_get_linear_next_pc (insn),
di, arc_delayed_print_insn, &insn);
if (insn.insn_class == BRCC)
{
/* If more than one conditional branch is found, this is not
the pattern we are interested in. */
if (found_bc)
break;
found_bc = true;
continue;
}
/* This is almost a happy ending. */
if (insn.insn_class == SCOND)
{
/* SCOND should match the LLOCK's data size. */
if (insn.data_size_mode == llock_data_size_mode)
is_pattern_valid = true;
break;
}
}
if (is_pattern_valid)
{
/* Get next instruction after scond(d). There is no limm. */
next_pcs.push_back (insn.address + insn.length);
}
return next_pcs;
}
/* Implement the "software_single_step" gdbarch method. */
static std::vector<CORE_ADDR>
arc_linux_software_single_step (struct regcache *regcache)
{
struct gdbarch *gdbarch = regcache->arch ();
arc_gdbarch_tdep *tdep = gdbarch_tdep<arc_gdbarch_tdep> (gdbarch);
struct gdb_non_printing_memory_disassembler dis (gdbarch);
/* Read current instruction. */
struct arc_instruction curr_insn;
arc_insn_decode (regcache_read_pc (regcache), dis.disasm_info (),
arc_delayed_print_insn, &curr_insn);
if (curr_insn.insn_class == LLOCK)
return handle_atomic_sequence (curr_insn, dis.disasm_info ());
CORE_ADDR next_pc = arc_insn_get_linear_next_pc (curr_insn);
std::vector<CORE_ADDR> next_pcs;
/* For instructions with delay slots, the fall thru is not the
instruction immediately after the current instruction, but the one
after that. */
if (curr_insn.has_delay_slot)
{
struct arc_instruction next_insn;
arc_insn_decode (next_pc, dis.disasm_info (), arc_delayed_print_insn,
&next_insn);
next_pcs.push_back (arc_insn_get_linear_next_pc (next_insn));
}
else
next_pcs.push_back (next_pc);
ULONGEST status32;
regcache_cooked_read_unsigned (regcache, gdbarch_ps_regnum (gdbarch),
&status32);
if (curr_insn.is_control_flow)
{
CORE_ADDR branch_pc = arc_insn_get_branch_target (curr_insn);
if (branch_pc != next_pc)
next_pcs.push_back (branch_pc);
}
/* Is current instruction the last in a loop body? */
else if (tdep->has_hw_loops)
{
/* If STATUS32.L is 1, then ZD-loops are disabled. */
if ((status32 & ARC_STATUS32_L_MASK) == 0)
{
ULONGEST lp_end, lp_start, lp_count;
regcache_cooked_read_unsigned (regcache, ARC_LP_START_REGNUM,
&lp_start);
regcache_cooked_read_unsigned (regcache, ARC_LP_END_REGNUM, &lp_end);
regcache_cooked_read_unsigned (regcache, ARC_LP_COUNT_REGNUM,
&lp_count);
arc_linux_debug_printf ("lp_start = %s, lp_end = %s, "
"lp_count = %s, next_pc = %s",
paddress (gdbarch, lp_start),
paddress (gdbarch, lp_end),
pulongest (lp_count),
paddress (gdbarch, next_pc));
if (next_pc == lp_end && lp_count > 1)
{
/* The instruction is in effect a jump back to the start of
the loop. */
next_pcs.push_back (lp_start);
}
}
}
/* Is this a delay slot? Then next PC is in BTA register. */
if ((status32 & ARC_STATUS32_DE_MASK) != 0)
{
ULONGEST bta;
regcache_cooked_read_unsigned (regcache, ARC_BTA_REGNUM, &bta);
next_pcs.push_back (bta);
}
return next_pcs;
}
/* Implement the "skip_solib_resolver" gdbarch method.
See glibc_skip_solib_resolver for details. */
static CORE_ADDR
arc_linux_skip_solib_resolver (struct gdbarch *gdbarch, CORE_ADDR pc)
{
/* For uClibc 0.9.26+.
An unresolved PLT entry points to "__dl_linux_resolve", which calls
"_dl_linux_resolver" to do the resolving and then eventually jumps to
the function.
So we look for the symbol `_dl_linux_resolver', and if we are there,
gdb sets a breakpoint at the return address, and continues. */
struct bound_minimal_symbol resolver
= lookup_minimal_symbol ("_dl_linux_resolver", NULL, NULL);
if (arc_debug)
{
if (resolver.minsym != nullptr)
{
CORE_ADDR res_addr = resolver.value_address ();
arc_linux_debug_printf ("pc = %s, resolver at %s",
print_core_address (gdbarch, pc),
print_core_address (gdbarch, res_addr));
}
else
arc_linux_debug_printf ("pc = %s, no resolver found",
print_core_address (gdbarch, pc));
}
if (resolver.minsym != nullptr && resolver.value_address () == pc)
{
/* Find the return address. */
return frame_unwind_caller_pc (get_current_frame ());
}
else
{
/* No breakpoint required. */
return 0;
}
}
/* Populate REGCACHE with register REGNUM from BUF. */
static void
supply_register (struct regcache *regcache, int regnum, const gdb_byte *buf)
{
/* Skip non-existing registers. */
if ((arc_linux_core_reg_offsets[regnum] == ARC_OFFSET_NO_REGISTER))
return;
regcache->raw_supply (regnum, buf + arc_linux_core_reg_offsets[regnum]);
}
void
arc_linux_supply_gregset (const struct regset *regset,
struct regcache *regcache,
int regnum, const void *gregs, size_t size)
{
gdb_static_assert (ARC_LAST_REGNUM
< ARRAY_SIZE (arc_linux_core_reg_offsets));
const bfd_byte *buf = (const bfd_byte *) gregs;
/* REGNUM == -1 means writing all the registers. */
if (regnum == -1)
for (int reg = 0; reg <= ARC_LAST_REGNUM; reg++)
supply_register (regcache, reg, buf);
else if (regnum <= ARC_LAST_REGNUM)
supply_register (regcache, regnum, buf);
else
gdb_assert_not_reached ("Invalid regnum in arc_linux_supply_gregset.");
}
void
arc_linux_supply_v2_regset (const struct regset *regset,
struct regcache *regcache, int regnum,
const void *v2_regs, size_t size)
{
const bfd_byte *buf = (const bfd_byte *) v2_regs;
/* user_regs_arcv2 is defined in linux arch/arc/include/uapi/asm/ptrace.h. */
if (regnum == -1 || regnum == ARC_R30_REGNUM)
regcache->raw_supply (ARC_R30_REGNUM, buf);
if (regnum == -1 || regnum == ARC_R58_REGNUM)
regcache->raw_supply (ARC_R58_REGNUM, buf + REGOFF (1));
if (regnum == -1 || regnum == ARC_R59_REGNUM)
regcache->raw_supply (ARC_R59_REGNUM, buf + REGOFF (2));
}
/* Populate BUF with register REGNUM from the REGCACHE. */
static void
collect_register (const struct regcache *regcache, struct gdbarch *gdbarch,
int regnum, gdb_byte *buf)
{
int offset;
/* Skip non-existing registers. */
if (arc_linux_core_reg_offsets[regnum] == ARC_OFFSET_NO_REGISTER)
return;
/* The address where the execution has stopped is in pseudo-register
STOP_PC. However, when kernel code is returning from the exception,
it uses the value from ERET register. Since, TRAP_S (the breakpoint
instruction) commits, the ERET points to the next instruction. In
other words: ERET != STOP_PC. To jump back from the kernel code to
the correct address, ERET must be overwritten by GDB's STOP_PC. Else,
the program will continue at the address after the current instruction.
*/
if (regnum == gdbarch_pc_regnum (gdbarch))
offset = arc_linux_core_reg_offsets[ARC_ERET_REGNUM];
else
offset = arc_linux_core_reg_offsets[regnum];
regcache->raw_collect (regnum, buf + offset);
}
void
arc_linux_collect_gregset (const struct regset *regset,
const struct regcache *regcache,
int regnum, void *gregs, size_t size)
{
gdb_static_assert (ARC_LAST_REGNUM
< ARRAY_SIZE (arc_linux_core_reg_offsets));
gdb_byte *buf = (gdb_byte *) gregs;
struct gdbarch *gdbarch = regcache->arch ();
/* REGNUM == -1 means writing all the registers. */
if (regnum == -1)
for (int reg = 0; reg <= ARC_LAST_REGNUM; reg++)
collect_register (regcache, gdbarch, reg, buf);
else if (regnum <= ARC_LAST_REGNUM)
collect_register (regcache, gdbarch, regnum, buf);
else
gdb_assert_not_reached ("Invalid regnum in arc_linux_collect_gregset.");
}
void
arc_linux_collect_v2_regset (const struct regset *regset,
const struct regcache *regcache, int regnum,
void *v2_regs, size_t size)
{
bfd_byte *buf = (bfd_byte *) v2_regs;
if (regnum == -1 || regnum == ARC_R30_REGNUM)
regcache->raw_collect (ARC_R30_REGNUM, buf);
if (regnum == -1 || regnum == ARC_R58_REGNUM)
regcache->raw_collect (ARC_R58_REGNUM, buf + REGOFF (1));
if (regnum == -1 || regnum == ARC_R59_REGNUM)
regcache->raw_collect (ARC_R59_REGNUM, buf + REGOFF (2));
}
/* Linux regset definitions. */
static const struct regset arc_linux_gregset = {
arc_linux_core_reg_offsets,
arc_linux_supply_gregset,
arc_linux_collect_gregset,
};
static const struct regset arc_linux_v2_regset = {
NULL,
arc_linux_supply_v2_regset,
arc_linux_collect_v2_regset,
};
/* Implement the `iterate_over_regset_sections` gdbarch method. */
static void
arc_linux_iterate_over_regset_sections (struct gdbarch *gdbarch,
iterate_over_regset_sections_cb *cb,
void *cb_data,
const struct regcache *regcache)
{
/* There are 40 registers in Linux user_regs_struct, although some of
them are now just a mere paddings, kept to maintain binary
compatibility with older tools. */
const int sizeof_gregset = 40 * ARC_REGISTER_SIZE;
cb (".reg", sizeof_gregset, sizeof_gregset, &arc_linux_gregset, NULL,
cb_data);
cb (".reg-arc-v2", ARC_LINUX_SIZEOF_V2_REGSET, ARC_LINUX_SIZEOF_V2_REGSET,
&arc_linux_v2_regset, NULL, cb_data);
}
/* Implement the `core_read_description` gdbarch method. */
static const struct target_desc *
arc_linux_core_read_description (struct gdbarch *gdbarch,
struct target_ops *target,
bfd *abfd)
{
arc_arch_features features
= arc_arch_features_create (abfd,
gdbarch_bfd_arch_info (gdbarch)->mach);
return arc_lookup_target_description (features);
}
/* Initialization specific to Linux environment. */
static void
arc_linux_init_osabi (struct gdbarch_info info, struct gdbarch *gdbarch)
{
arc_gdbarch_tdep *tdep = gdbarch_tdep<arc_gdbarch_tdep> (gdbarch);
arc_linux_debug_printf ("GNU/Linux OS/ABI initialization.");
/* Fill in target-dependent info in ARC-private structure. */
tdep->is_sigtramp = arc_linux_is_sigtramp;
tdep->sigcontext_addr = arc_linux_sigcontext_addr;
tdep->sc_reg_offset = arc_linux_sc_reg_offsets;
tdep->sc_num_regs = ARRAY_SIZE (arc_linux_sc_reg_offsets);
/* If we are using Linux, we have in uClibc
(libc/sysdeps/linux/arc/bits/setjmp.h):
typedef int __jmp_buf[13+1+1+1]; //r13-r25, fp, sp, blink
Where "blink" is a stored PC of a caller function.
*/
tdep->jb_pc = 15;
linux_init_abi (info, gdbarch, 0);
/* Set up target dependent GDB architecture entries. */
set_gdbarch_cannot_fetch_register (gdbarch, arc_linux_cannot_fetch_register);
set_gdbarch_cannot_store_register (gdbarch, arc_linux_cannot_store_register);
set_gdbarch_breakpoint_kind_from_pc (gdbarch,
arc_linux_breakpoint_kind_from_pc);
set_gdbarch_sw_breakpoint_from_kind (gdbarch,
arc_linux_sw_breakpoint_from_kind);
set_gdbarch_fetch_tls_load_module_address (gdbarch,
svr4_fetch_objfile_link_map);
set_gdbarch_software_single_step (gdbarch, arc_linux_software_single_step);
set_gdbarch_skip_trampoline_code (gdbarch, find_solib_trampoline_target);
set_gdbarch_skip_solib_resolver (gdbarch, arc_linux_skip_solib_resolver);
set_gdbarch_iterate_over_regset_sections
(gdbarch, arc_linux_iterate_over_regset_sections);
set_gdbarch_core_read_description (gdbarch, arc_linux_core_read_description);
/* GNU/Linux uses SVR4-style shared libraries, with 32-bit ints, longs
and pointers (ILP32). */
set_solib_svr4_fetch_link_map_offsets (gdbarch,
linux_ilp32_fetch_link_map_offsets);
}
/* Suppress warning from -Wmissing-prototypes. */
extern initialize_file_ftype _initialize_arc_linux_tdep;
void
_initialize_arc_linux_tdep ()
{
gdbarch_register_osabi (bfd_arch_arc, 0, GDB_OSABI_LINUX,
arc_linux_init_osabi);
}
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