Add support for fast tracepoints
This patch adds support for fast tracepoints for aarch64-linux. With this
implementation, a tracepoint can only be placed in a +/- 128MB range of
the jump pad. This is due to the unconditional branch instruction
being limited to a (26 bit << 2) offset from the current PC.
Three target operations are implemented:
- target_install_fast_tracepoint_jump_pad
Building the jump pad the biggest change of this patch. We need to add
functions to emit all instructions needed to save and restore the
current state when the tracepoint is hit. As well as implementing a
lock and creating a collecting_t object identifying the current thread.
Steps performed by the jump pad:
* Save the current state on the stack.
* Push a collecting_t object on the stack. We read the special
tpidr_el0 system register to get the thread ID.
* Spin-lock on the shared memory location of all tracing threads. We
write the address of our collecting_t object there once we have the
lock.
* Call gdb_collect.
* Release the lock.
* Restore the state.
* Execute the replaced instruction which will have been relocated.
* Jump back to the program.
- target_get_thread_area
As implemented in ps_get_thread_area, target_get_thread_area uses ptrace
to fetch the NT_ARM_TLS register. At the architecture level, NT_ARM_TLS
represents the tpidr_el0 system register.
So this ptrace call (if lwpid is the current thread):
~~~
ptrace (PTRACE_GETREGSET, lwpid, NT_ARM_TLS, &iovec);
~~~
Is equivalent to the following instruction:
~~~
msr x0, tpidr_el0
~~~
This instruction is used when creating the collecting_t object that
GDBserver can read to know if a given thread is currently tracing.
So target_get_thread_area must get the same thread IDs as what the jump
pad writes into its collecting_t object.
- target_get_min_fast_tracepoint_insn_len
This just returns 4.
gdb/gdbserver/ChangeLog:
* Makefile.in (linux-aarch64-ipa.o, aarch64-ipa.o): New rules.
* configure.srv (aarch64*-*-linux*): Add linux-aarch64-ipa.o and
aarch64-ipa.o.
* linux-aarch64-ipa.c: New file.
* linux-aarch64-low.c: Include arch/aarch64-insn.h, inttypes.h
and endian.h.
(aarch64_get_thread_area): New target method.
(extract_signed_bitfield): New helper function.
(aarch64_decode_ldr_literal): New function.
(enum aarch64_opcodes): New enum.
(struct aarch64_register): New struct.
(struct aarch64_operand): New struct.
(x0): New static global.
(x1): Likewise.
(x2): Likewise.
(x3): Likewise.
(x4): Likewise.
(w2): Likewise.
(ip0): Likewise.
(sp): Likewise.
(xzr): Likewise.
(aarch64_register): New helper function.
(register_operand): Likewise.
(immediate_operand): Likewise.
(struct aarch64_memory_operand): New struct.
(offset_memory_operand): New helper function.
(preindex_memory_operand): Likewise.
(enum aarch64_system_control_registers): New enum.
(ENCODE): New macro.
(emit_insn): New helper function.
(emit_b): New function.
(emit_bcond): Likewise.
(emit_cb): Likewise.
(emit_tb): Likewise.
(emit_blr): Likewise.
(emit_stp): Likewise.
(emit_ldp_q_offset): Likewise.
(emit_stp_q_offset): Likewise.
(emit_load_store): Likewise.
(emit_ldr): Likewise.
(emit_ldrsw): Likewise.
(emit_str): Likewise.
(emit_ldaxr): Likewise.
(emit_stxr): Likewise.
(emit_stlr): Likewise.
(emit_data_processing_reg): Likewise.
(emit_data_processing): Likewise.
(emit_add): Likewise.
(emit_sub): Likewise.
(emit_mov): Likewise.
(emit_movk): Likewise.
(emit_mov_addr): Likewise.
(emit_mrs): Likewise.
(emit_msr): Likewise.
(emit_sevl): Likewise.
(emit_wfe): Likewise.
(append_insns): Likewise.
(can_encode_int32_in): New helper function.
(aarch64_relocate_instruction): New function.
(aarch64_install_fast_tracepoint_jump_pad): Likewise.
(aarch64_get_min_fast_tracepoint_insn_len): Likewise.
(struct linux_target_ops): Install aarch64_get_thread_area,
aarch64_install_fast_tracepoint_jump_pad and
aarch64_get_min_fast_tracepoint_insn_len.
2015-09-21 14:01:04 +00:00
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/* GNU/Linux/AArch64 specific low level interface, for the in-process
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agent library for GDB.
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2016-01-01 04:33:14 +00:00
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Copyright (C) 2015-2016 Free Software Foundation, Inc.
|
Add support for fast tracepoints
This patch adds support for fast tracepoints for aarch64-linux. With this
implementation, a tracepoint can only be placed in a +/- 128MB range of
the jump pad. This is due to the unconditional branch instruction
being limited to a (26 bit << 2) offset from the current PC.
Three target operations are implemented:
- target_install_fast_tracepoint_jump_pad
Building the jump pad the biggest change of this patch. We need to add
functions to emit all instructions needed to save and restore the
current state when the tracepoint is hit. As well as implementing a
lock and creating a collecting_t object identifying the current thread.
Steps performed by the jump pad:
* Save the current state on the stack.
* Push a collecting_t object on the stack. We read the special
tpidr_el0 system register to get the thread ID.
* Spin-lock on the shared memory location of all tracing threads. We
write the address of our collecting_t object there once we have the
lock.
* Call gdb_collect.
* Release the lock.
* Restore the state.
* Execute the replaced instruction which will have been relocated.
* Jump back to the program.
- target_get_thread_area
As implemented in ps_get_thread_area, target_get_thread_area uses ptrace
to fetch the NT_ARM_TLS register. At the architecture level, NT_ARM_TLS
represents the tpidr_el0 system register.
So this ptrace call (if lwpid is the current thread):
~~~
ptrace (PTRACE_GETREGSET, lwpid, NT_ARM_TLS, &iovec);
~~~
Is equivalent to the following instruction:
~~~
msr x0, tpidr_el0
~~~
This instruction is used when creating the collecting_t object that
GDBserver can read to know if a given thread is currently tracing.
So target_get_thread_area must get the same thread IDs as what the jump
pad writes into its collecting_t object.
- target_get_min_fast_tracepoint_insn_len
This just returns 4.
gdb/gdbserver/ChangeLog:
* Makefile.in (linux-aarch64-ipa.o, aarch64-ipa.o): New rules.
* configure.srv (aarch64*-*-linux*): Add linux-aarch64-ipa.o and
aarch64-ipa.o.
* linux-aarch64-ipa.c: New file.
* linux-aarch64-low.c: Include arch/aarch64-insn.h, inttypes.h
and endian.h.
(aarch64_get_thread_area): New target method.
(extract_signed_bitfield): New helper function.
(aarch64_decode_ldr_literal): New function.
(enum aarch64_opcodes): New enum.
(struct aarch64_register): New struct.
(struct aarch64_operand): New struct.
(x0): New static global.
(x1): Likewise.
(x2): Likewise.
(x3): Likewise.
(x4): Likewise.
(w2): Likewise.
(ip0): Likewise.
(sp): Likewise.
(xzr): Likewise.
(aarch64_register): New helper function.
(register_operand): Likewise.
(immediate_operand): Likewise.
(struct aarch64_memory_operand): New struct.
(offset_memory_operand): New helper function.
(preindex_memory_operand): Likewise.
(enum aarch64_system_control_registers): New enum.
(ENCODE): New macro.
(emit_insn): New helper function.
(emit_b): New function.
(emit_bcond): Likewise.
(emit_cb): Likewise.
(emit_tb): Likewise.
(emit_blr): Likewise.
(emit_stp): Likewise.
(emit_ldp_q_offset): Likewise.
(emit_stp_q_offset): Likewise.
(emit_load_store): Likewise.
(emit_ldr): Likewise.
(emit_ldrsw): Likewise.
(emit_str): Likewise.
(emit_ldaxr): Likewise.
(emit_stxr): Likewise.
(emit_stlr): Likewise.
(emit_data_processing_reg): Likewise.
(emit_data_processing): Likewise.
(emit_add): Likewise.
(emit_sub): Likewise.
(emit_mov): Likewise.
(emit_movk): Likewise.
(emit_mov_addr): Likewise.
(emit_mrs): Likewise.
(emit_msr): Likewise.
(emit_sevl): Likewise.
(emit_wfe): Likewise.
(append_insns): Likewise.
(can_encode_int32_in): New helper function.
(aarch64_relocate_instruction): New function.
(aarch64_install_fast_tracepoint_jump_pad): Likewise.
(aarch64_get_min_fast_tracepoint_insn_len): Likewise.
(struct linux_target_ops): Install aarch64_get_thread_area,
aarch64_install_fast_tracepoint_jump_pad and
aarch64_get_min_fast_tracepoint_insn_len.
2015-09-21 14:01:04 +00:00
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include "server.h"
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#include "tracepoint.h"
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/* Defined in auto-generated file aarch64.c. */
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void init_registers_aarch64 (void);
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extern const struct target_desc *tdesc_aarch64;
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/* Each register saved by the jump pad is in a 16 byte cell. */
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#define FT_CR_SIZE 16
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#define FT_CR_FPCR 0
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#define FT_CR_FPSR 1
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#define FT_CR_CPSR 2
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#define FT_CR_PC 3
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#define FT_CR_SP 4
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#define FT_CR_X0 5
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#define FT_CR_GPR(n) (FT_CR_X0 + (n))
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#define FT_CR_FPR(n) (FT_CR_GPR (31) + (n))
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/* Mapping between registers collected by the jump pad and GDB's register
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array layout used by regcache.
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See linux-aarch64-low.c (aarch64_install_fast_tracepoint_jump_pad) for
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more details. */
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static const int aarch64_ft_collect_regmap[] = {
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FT_CR_GPR (0),
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FT_CR_GPR (1),
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FT_CR_GPR (2),
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FT_CR_GPR (3),
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FT_CR_GPR (4),
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FT_CR_GPR (5),
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FT_CR_GPR (6),
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FT_CR_GPR (7),
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FT_CR_GPR (8),
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FT_CR_GPR (9),
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FT_CR_GPR (10),
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FT_CR_GPR (11),
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FT_CR_GPR (12),
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FT_CR_GPR (13),
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FT_CR_GPR (14),
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FT_CR_GPR (15),
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FT_CR_GPR (16),
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FT_CR_GPR (17),
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FT_CR_GPR (18),
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FT_CR_GPR (19),
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FT_CR_GPR (20),
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FT_CR_GPR (21),
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FT_CR_GPR (22),
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FT_CR_GPR (23),
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FT_CR_GPR (24),
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FT_CR_GPR (25),
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FT_CR_GPR (26),
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FT_CR_GPR (27),
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FT_CR_GPR (28),
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/* FP */
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FT_CR_GPR (29),
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/* LR */
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FT_CR_GPR (30),
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FT_CR_SP,
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FT_CR_PC,
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FT_CR_CPSR,
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FT_CR_FPR (0),
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FT_CR_FPR (1),
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FT_CR_FPR (2),
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FT_CR_FPR (3),
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FT_CR_FPR (4),
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FT_CR_FPR (5),
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FT_CR_FPR (6),
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FT_CR_FPR (7),
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FT_CR_FPR (8),
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FT_CR_FPR (9),
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FT_CR_FPR (10),
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FT_CR_FPR (11),
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FT_CR_FPR (12),
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FT_CR_FPR (13),
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FT_CR_FPR (14),
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FT_CR_FPR (15),
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FT_CR_FPR (16),
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FT_CR_FPR (17),
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FT_CR_FPR (18),
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FT_CR_FPR (19),
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FT_CR_FPR (20),
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FT_CR_FPR (21),
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FT_CR_FPR (22),
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FT_CR_FPR (23),
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FT_CR_FPR (24),
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FT_CR_FPR (25),
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FT_CR_FPR (26),
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FT_CR_FPR (27),
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FT_CR_FPR (28),
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FT_CR_FPR (29),
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FT_CR_FPR (30),
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FT_CR_FPR (31),
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FT_CR_FPSR,
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FT_CR_FPCR
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};
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#define AARCH64_NUM_FT_COLLECT_GREGS \
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(sizeof (aarch64_ft_collect_regmap) / sizeof(aarch64_ft_collect_regmap[0]))
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/* Fill in REGCACHE with registers saved by the jump pad in BUF. */
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void
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supply_fast_tracepoint_registers (struct regcache *regcache,
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const unsigned char *buf)
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{
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int i;
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for (i = 0; i < AARCH64_NUM_FT_COLLECT_GREGS; i++)
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supply_register (regcache, i,
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((char *) buf)
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+ (aarch64_ft_collect_regmap[i] * FT_CR_SIZE));
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}
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IP_AGENT_EXPORT_FUNC ULONGEST
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gdb_agent_get_raw_reg (const unsigned char *raw_regs, int regnum)
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{
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if (regnum >= AARCH64_NUM_FT_COLLECT_GREGS)
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return 0;
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return *(ULONGEST *) (raw_regs
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+ aarch64_ft_collect_regmap[regnum] * FT_CR_SIZE);
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}
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[PR gdb/13808] gdb.trace: Pass tdesc selected in gdbserver to IPA.
If gdbserver and IPA are using different tdesc, they will disagree
about 'R' trace packet size. This results in mangled traces.
To make sure they pick the same tdesc, gdbserver pokes the tdesc
(specified as an index in a target-specific list) into a global
variable in IPA. In theory, IPA could find out the tdesc on its
own, but that may be complex (in particular, I don't know how to
tell whether we have LAST_BREAK on s390 without messing with ptrace),
and we'd have to duplicate the logic.
Tested on i386 and x86_64. On i386, it fixes two FAILs in ftrace.exp.
On x86_64, these failures have been KFAILed - one of them works now,
but the other now fails due to an unrelated reason (ugh).
gdb/gdbserver/ChangeLog:
PR gdb/13808
* Makefile.in: Add i386-*-linux-ipa.o and amd64-*-linux-ipa.o.
* configure.srv: Ditto.
* linux-aarch64-ipa.c (get_ipa_tdesc): New function.
(initialize_low_tracepoint): Remove ipa_tdesc assignment.
* linux-amd64-ipa.c: Add "linux-x86-tdesc.h" include.
(init_registers_amd64_linux): Remove prototype.
(tdesc_amd64_linux): Remove declaration.
(get_ipa_tdesc): New function.
(initialize_low_tracepoint): Remove ipa_tdesc assignment,
initialize remaining tdescs.
* linux-i386-ipa.c: Add "linux-x86-tdesc.h" include.
(init_registers_i386_linux): Remove prototype.
(tdesc_i386_linux): Remove declaration.
(get_ipa_tdesc): New function.
(initialize_low_tracepoint): Remove ipa_tdesc assignment,
initialize remaining tdescs.
* linux-low.c (linux_get_ipa_tdesc_idx): New function.
(linux_target_ops): wire in linux_get_ipa_tdesc_idx.
* linux-low.h (struct linux_target_ops): Add get_ipa_tdesc_idx.
* linux-x86-low.c: Move tdesc declarations to linux-x86-tdesc.h.
(x86_get_ipa_tdesc_idx): New function.
(the_low_target): Wire in x86_get_ipa_tdesc_idx.
* linux-x86-tdesc.h: New file.
* target.h (struct target_ops): Add get_ipa_tdesc_idx.
(target_get_ipa_tdesc_idx): New macro.
* tracepoint.c (ipa_tdesc_idx): New macro.
(struct ipa_sym_addresses): Add addr_ipa_tdesc_idx.
(symbol_list): Add ipa_tdesc_idx.
(cmd_qtstart): Write ipa_tdesc_idx in the target.
(ipa_tdesc): Remove.
(ipa_tdesc_idx): New variable.
(get_context_regcache): Use get_ipa_tdesc.
(gdb_collect): Ditto.
(gdb_probe): Ditto.
* tracepoint.h (get_ipa_tdesc): New prototype.
(ipa_tdesc): Remove.
gdb/testsuite/ChangeLog:
PR gdb/13808
* gdb.trace/ftrace.exp (test_fast_tracepoints): Remove kfail.
2016-02-21 20:44:48 +00:00
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/* Return target_desc to use for IPA, given the tdesc index passed by
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gdbserver. Index is ignored, since we have only one tdesc
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at the moment. */
|
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const struct target_desc *
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get_ipa_tdesc (int idx)
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{
|
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return tdesc_aarch64;
|
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}
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|
|
Add support for fast tracepoints
This patch adds support for fast tracepoints for aarch64-linux. With this
implementation, a tracepoint can only be placed in a +/- 128MB range of
the jump pad. This is due to the unconditional branch instruction
being limited to a (26 bit << 2) offset from the current PC.
Three target operations are implemented:
- target_install_fast_tracepoint_jump_pad
Building the jump pad the biggest change of this patch. We need to add
functions to emit all instructions needed to save and restore the
current state when the tracepoint is hit. As well as implementing a
lock and creating a collecting_t object identifying the current thread.
Steps performed by the jump pad:
* Save the current state on the stack.
* Push a collecting_t object on the stack. We read the special
tpidr_el0 system register to get the thread ID.
* Spin-lock on the shared memory location of all tracing threads. We
write the address of our collecting_t object there once we have the
lock.
* Call gdb_collect.
* Release the lock.
* Restore the state.
* Execute the replaced instruction which will have been relocated.
* Jump back to the program.
- target_get_thread_area
As implemented in ps_get_thread_area, target_get_thread_area uses ptrace
to fetch the NT_ARM_TLS register. At the architecture level, NT_ARM_TLS
represents the tpidr_el0 system register.
So this ptrace call (if lwpid is the current thread):
~~~
ptrace (PTRACE_GETREGSET, lwpid, NT_ARM_TLS, &iovec);
~~~
Is equivalent to the following instruction:
~~~
msr x0, tpidr_el0
~~~
This instruction is used when creating the collecting_t object that
GDBserver can read to know if a given thread is currently tracing.
So target_get_thread_area must get the same thread IDs as what the jump
pad writes into its collecting_t object.
- target_get_min_fast_tracepoint_insn_len
This just returns 4.
gdb/gdbserver/ChangeLog:
* Makefile.in (linux-aarch64-ipa.o, aarch64-ipa.o): New rules.
* configure.srv (aarch64*-*-linux*): Add linux-aarch64-ipa.o and
aarch64-ipa.o.
* linux-aarch64-ipa.c: New file.
* linux-aarch64-low.c: Include arch/aarch64-insn.h, inttypes.h
and endian.h.
(aarch64_get_thread_area): New target method.
(extract_signed_bitfield): New helper function.
(aarch64_decode_ldr_literal): New function.
(enum aarch64_opcodes): New enum.
(struct aarch64_register): New struct.
(struct aarch64_operand): New struct.
(x0): New static global.
(x1): Likewise.
(x2): Likewise.
(x3): Likewise.
(x4): Likewise.
(w2): Likewise.
(ip0): Likewise.
(sp): Likewise.
(xzr): Likewise.
(aarch64_register): New helper function.
(register_operand): Likewise.
(immediate_operand): Likewise.
(struct aarch64_memory_operand): New struct.
(offset_memory_operand): New helper function.
(preindex_memory_operand): Likewise.
(enum aarch64_system_control_registers): New enum.
(ENCODE): New macro.
(emit_insn): New helper function.
(emit_b): New function.
(emit_bcond): Likewise.
(emit_cb): Likewise.
(emit_tb): Likewise.
(emit_blr): Likewise.
(emit_stp): Likewise.
(emit_ldp_q_offset): Likewise.
(emit_stp_q_offset): Likewise.
(emit_load_store): Likewise.
(emit_ldr): Likewise.
(emit_ldrsw): Likewise.
(emit_str): Likewise.
(emit_ldaxr): Likewise.
(emit_stxr): Likewise.
(emit_stlr): Likewise.
(emit_data_processing_reg): Likewise.
(emit_data_processing): Likewise.
(emit_add): Likewise.
(emit_sub): Likewise.
(emit_mov): Likewise.
(emit_movk): Likewise.
(emit_mov_addr): Likewise.
(emit_mrs): Likewise.
(emit_msr): Likewise.
(emit_sevl): Likewise.
(emit_wfe): Likewise.
(append_insns): Likewise.
(can_encode_int32_in): New helper function.
(aarch64_relocate_instruction): New function.
(aarch64_install_fast_tracepoint_jump_pad): Likewise.
(aarch64_get_min_fast_tracepoint_insn_len): Likewise.
(struct linux_target_ops): Install aarch64_get_thread_area,
aarch64_install_fast_tracepoint_jump_pad and
aarch64_get_min_fast_tracepoint_insn_len.
2015-09-21 14:01:04 +00:00
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void
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initialize_low_tracepoint (void)
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{
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init_registers_aarch64 ();
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}
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