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binutils-gdb/gdb/aarch64-linux-nat.c
Tom de Vries fbf3c4b979 [gdb/tdep] Use pid to choose process 64/32-bitness 
In a linux kernel mailing list discussion, it was mentioned that "gdb has
this odd thing where it takes the 64-bit vs 32-bit data for the whole process
from one thread, and picks the worst possible thread to do it (ie explicitly
not even the main thread, ...)" [1].

The picking of the thread is done here in
x86_linux_nat_target::read_description:
...
  /* GNU/Linux LWP ID's are process ID's.  */
  tid = inferior_ptid.lwp ();
  if (tid == 0)
    tid = inferior_ptid.pid (); /* Not a threaded program.  */
...

To understand what this code does, let's investigate a scenario in which
inferior_ptid.lwp () != inferior_ptid.pid ().

Say we start exec jit-attach-pie, identified with pid x.  The main thread
starts another thread that sleeps, and then the main thread waits for the
sleeping thread.  So we have two threads, identified with LWP IDs x and x+1:
...
PID  LWP  CMD
x    x    ./jit-attach-pie
x    x+1  ./jit-attach-pie
...
[ The thread with LWP x is known as the thread group leader. ]

When attaching to this exec using the pid, gdb does a stop_all_threads which
iterates over all the threads, first LWP x, and then LWP x+1.

So the state we arrive with at x86_linux_nat_target::read_description is:
...
(gdb) p inferior_ptid
$1 = {m_pid = x, m_lwp = x+1, m_tid = 0}
...
and consequently we probe 64/32-bitness from thread LWP x+1.

[ Note that this is different from when gdb doesn't attach but instead
launches the exec itself, in which case there's just one thread to begin with,
and consequently the probed thread is LWP x. ]

According to aforementioned remark, a better choice would have been the main
thread, that is, LWP x.

This patch implement that choice, by simply doing:
...
  tid = inferior_ptid.pid ();
...

The fact that gdb makes a per-process permanent choice for 64/32-bitness is a
problem in itself: each thread can be in either 64 or 32 bit mode, and change
forth and back.  That is a problem that this patch doesn't fix.

Now finally: why does this matter in the context of the linux kernel
discussion?  The discussion was related to a patch that exposed io_uring
threads to user-space.  This made it possible that one of those threads would
be picked out to select 64/32-bitness.  Given that such threads are atypical
user-space threads in the sense that they don't return to user-space and don't
have a userspace register state, reading their registers returns garbage, and
so it could f.i. occur that in a 64-bit process with all normal user-space
threads in 64-bit mode, the probing would return 32-bit.

It may be that this is worked-around on the kernel side by providing userspace
register state in those threads such that current gdb is happy.  Nevertheless,
it seems prudent to fix this on the gdb size as well.

Tested on x86_64-linux.

[1] https://lore.kernel.org/io-uring/CAHk-=wh0KoEZXPYMGkfkeVEerSCEF1AiCZSvz9TRrx=Kj74D+Q@mail.gmail.com/

gdb/ChangeLog:

2021-05-23  Tom de Vries  <tdevries@suse.de>

	PR tdep/27822
	* target.h (struct target_ops): Mention target_thread_architecture in
	read_description comment.
	* x86-linux-nat.c (x86_linux_nat_target::read_description): Use
	pid to determine if process is 64-bit or 32-bit.
	* aarch64-linux-nat.c (aarch64_linux_nat_target::read_description):
	Same.
	* ppc-linux-nat.c (ppc_linux_nat_target::read_description): Same.
        * riscv-linux-nat.c (riscv_linux_nat_target::read_description): Same.
	* s390-linux-nat.c (s390_linux_nat_target::read_description): Same.
	* arm-linux-nat.c (arm_linux_nat_target::read_description): Same.
	Likewise, use pid to determine if kernel supports reading VFP
	registers.
2021-05-23 10:08:45 +02:00

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/* Native-dependent code for GNU/Linux AArch64.
Copyright (C) 2011-2021 Free Software Foundation, Inc.
Contributed by ARM Ltd.
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 "defs.h"
#include "inferior.h"
#include "gdbcore.h"
#include "regcache.h"
#include "linux-nat.h"
#include "target-descriptions.h"
#include "auxv.h"
#include "gdbcmd.h"
#include "aarch64-tdep.h"
#include "aarch64-linux-tdep.h"
#include "aarch32-linux-nat.h"
#include "aarch32-tdep.h"
#include "arch/arm.h"
#include "nat/aarch64-linux.h"
#include "nat/aarch64-linux-hw-point.h"
#include "nat/aarch64-sve-linux-ptrace.h"
#include "elf/external.h"
#include "elf/common.h"
#include "nat/gdb_ptrace.h"
#include <sys/utsname.h>
#include <asm/ptrace.h>
#include "gregset.h"
#include "linux-tdep.h"
/* Defines ps_err_e, struct ps_prochandle. */
#include "gdb_proc_service.h"
#include "arch-utils.h"
#include "arch/aarch64-mte-linux.h"
#include "nat/aarch64-mte-linux-ptrace.h"
#ifndef TRAP_HWBKPT
#define TRAP_HWBKPT 0x0004
#endif
class aarch64_linux_nat_target final : public linux_nat_target
{
public:
/* Add our register access methods. */
void fetch_registers (struct regcache *, int) override;
void store_registers (struct regcache *, int) override;
const struct target_desc *read_description () override;
/* Add our hardware breakpoint and watchpoint implementation. */
int can_use_hw_breakpoint (enum bptype, int, int) override;
int insert_hw_breakpoint (struct gdbarch *, struct bp_target_info *) override;
int remove_hw_breakpoint (struct gdbarch *, struct bp_target_info *) override;
int region_ok_for_hw_watchpoint (CORE_ADDR, int) override;
int insert_watchpoint (CORE_ADDR, int, enum target_hw_bp_type,
struct expression *) override;
int remove_watchpoint (CORE_ADDR, int, enum target_hw_bp_type,
struct expression *) override;
bool stopped_by_watchpoint () override;
bool stopped_data_address (CORE_ADDR *) override;
bool watchpoint_addr_within_range (CORE_ADDR, CORE_ADDR, int) override;
int can_do_single_step () override;
/* Override the GNU/Linux inferior startup hook. */
void post_startup_inferior (ptid_t) override;
/* Override the GNU/Linux post attach hook. */
void post_attach (int pid) override;
/* These three defer to common nat/ code. */
void low_new_thread (struct lwp_info *lp) override
{ aarch64_linux_new_thread (lp); }
void low_delete_thread (struct arch_lwp_info *lp) override
{ aarch64_linux_delete_thread (lp); }
void low_prepare_to_resume (struct lwp_info *lp) override
{ aarch64_linux_prepare_to_resume (lp); }
void low_new_fork (struct lwp_info *parent, pid_t child_pid) override;
void low_forget_process (pid_t pid) override;
/* Add our siginfo layout converter. */
bool low_siginfo_fixup (siginfo_t *ptrace, gdb_byte *inf, int direction)
override;
struct gdbarch *thread_architecture (ptid_t) override;
bool supports_memory_tagging () override;
/* Read memory allocation tags from memory via PTRACE. */
bool fetch_memtags (CORE_ADDR address, size_t len,
gdb::byte_vector &tags, int type) override;
/* Write allocation tags to memory via PTRACE. */
bool store_memtags (CORE_ADDR address, size_t len,
const gdb::byte_vector &tags, int type) override;
};
static aarch64_linux_nat_target the_aarch64_linux_nat_target;
/* Per-process data. We don't bind this to a per-inferior registry
because of targets like x86 GNU/Linux that need to keep track of
processes that aren't bound to any inferior (e.g., fork children,
checkpoints). */
struct aarch64_process_info
{
/* Linked list. */
struct aarch64_process_info *next;
/* The process identifier. */
pid_t pid;
/* Copy of aarch64 hardware debug registers. */
struct aarch64_debug_reg_state state;
};
static struct aarch64_process_info *aarch64_process_list = NULL;
/* Find process data for process PID. */
static struct aarch64_process_info *
aarch64_find_process_pid (pid_t pid)
{
struct aarch64_process_info *proc;
for (proc = aarch64_process_list; proc; proc = proc->next)
if (proc->pid == pid)
return proc;
return NULL;
}
/* Add process data for process PID. Returns newly allocated info
object. */
static struct aarch64_process_info *
aarch64_add_process (pid_t pid)
{
struct aarch64_process_info *proc;
proc = XCNEW (struct aarch64_process_info);
proc->pid = pid;
proc->next = aarch64_process_list;
aarch64_process_list = proc;
return proc;
}
/* Get data specific info for process PID, creating it if necessary.
Never returns NULL. */
static struct aarch64_process_info *
aarch64_process_info_get (pid_t pid)
{
struct aarch64_process_info *proc;
proc = aarch64_find_process_pid (pid);
if (proc == NULL)
proc = aarch64_add_process (pid);
return proc;
}
/* Called whenever GDB is no longer debugging process PID. It deletes
data structures that keep track of debug register state. */
void
aarch64_linux_nat_target::low_forget_process (pid_t pid)
{
struct aarch64_process_info *proc, **proc_link;
proc = aarch64_process_list;
proc_link = &aarch64_process_list;
while (proc != NULL)
{
if (proc->pid == pid)
{
*proc_link = proc->next;
xfree (proc);
return;
}
proc_link = &proc->next;
proc = *proc_link;
}
}
/* Get debug registers state for process PID. */
struct aarch64_debug_reg_state *
aarch64_get_debug_reg_state (pid_t pid)
{
return &aarch64_process_info_get (pid)->state;
}
/* Fill GDB's register array with the general-purpose register values
from the current thread. */
static void
fetch_gregs_from_thread (struct regcache *regcache)
{
int ret, tid;
struct gdbarch *gdbarch = regcache->arch ();
elf_gregset_t regs;
struct iovec iovec;
/* Make sure REGS can hold all registers contents on both aarch64
and arm. */
gdb_static_assert (sizeof (regs) >= 18 * 4);
tid = regcache->ptid ().lwp ();
iovec.iov_base = &regs;
if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
iovec.iov_len = 18 * 4;
else
iovec.iov_len = sizeof (regs);
ret = ptrace (PTRACE_GETREGSET, tid, NT_PRSTATUS, &iovec);
if (ret < 0)
perror_with_name (_("Unable to fetch general registers."));
if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
aarch32_gp_regcache_supply (regcache, (uint32_t *) regs, 1);
else
{
int regno;
for (regno = AARCH64_X0_REGNUM; regno <= AARCH64_CPSR_REGNUM; regno++)
regcache->raw_supply (regno, &regs[regno - AARCH64_X0_REGNUM]);
}
}
/* Store to the current thread the valid general-purpose register
values in the GDB's register array. */
static void
store_gregs_to_thread (const struct regcache *regcache)
{
int ret, tid;
elf_gregset_t regs;
struct iovec iovec;
struct gdbarch *gdbarch = regcache->arch ();
/* Make sure REGS can hold all registers contents on both aarch64
and arm. */
gdb_static_assert (sizeof (regs) >= 18 * 4);
tid = regcache->ptid ().lwp ();
iovec.iov_base = &regs;
if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
iovec.iov_len = 18 * 4;
else
iovec.iov_len = sizeof (regs);
ret = ptrace (PTRACE_GETREGSET, tid, NT_PRSTATUS, &iovec);
if (ret < 0)
perror_with_name (_("Unable to fetch general registers."));
if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
aarch32_gp_regcache_collect (regcache, (uint32_t *) regs, 1);
else
{
int regno;
for (regno = AARCH64_X0_REGNUM; regno <= AARCH64_CPSR_REGNUM; regno++)
if (REG_VALID == regcache->get_register_status (regno))
regcache->raw_collect (regno, &regs[regno - AARCH64_X0_REGNUM]);
}
ret = ptrace (PTRACE_SETREGSET, tid, NT_PRSTATUS, &iovec);
if (ret < 0)
perror_with_name (_("Unable to store general registers."));
}
/* Fill GDB's register array with the fp/simd register values
from the current thread. */
static void
fetch_fpregs_from_thread (struct regcache *regcache)
{
int ret, tid;
elf_fpregset_t regs;
struct iovec iovec;
struct gdbarch *gdbarch = regcache->arch ();
/* Make sure REGS can hold all VFP registers contents on both aarch64
and arm. */
gdb_static_assert (sizeof regs >= ARM_VFP3_REGS_SIZE);
tid = regcache->ptid ().lwp ();
iovec.iov_base = &regs;
if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
{
iovec.iov_len = ARM_VFP3_REGS_SIZE;
ret = ptrace (PTRACE_GETREGSET, tid, NT_ARM_VFP, &iovec);
if (ret < 0)
perror_with_name (_("Unable to fetch VFP registers."));
aarch32_vfp_regcache_supply (regcache, (gdb_byte *) &regs, 32);
}
else
{
int regno;
iovec.iov_len = sizeof (regs);
ret = ptrace (PTRACE_GETREGSET, tid, NT_FPREGSET, &iovec);
if (ret < 0)
perror_with_name (_("Unable to fetch vFP/SIMD registers."));
for (regno = AARCH64_V0_REGNUM; regno <= AARCH64_V31_REGNUM; regno++)
regcache->raw_supply (regno, &regs.vregs[regno - AARCH64_V0_REGNUM]);
regcache->raw_supply (AARCH64_FPSR_REGNUM, &regs.fpsr);
regcache->raw_supply (AARCH64_FPCR_REGNUM, &regs.fpcr);
}
}
/* Store to the current thread the valid fp/simd register
values in the GDB's register array. */
static void
store_fpregs_to_thread (const struct regcache *regcache)
{
int ret, tid;
elf_fpregset_t regs;
struct iovec iovec;
struct gdbarch *gdbarch = regcache->arch ();
/* Make sure REGS can hold all VFP registers contents on both aarch64
and arm. */
gdb_static_assert (sizeof regs >= ARM_VFP3_REGS_SIZE);
tid = regcache->ptid ().lwp ();
iovec.iov_base = &regs;
if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
{
iovec.iov_len = ARM_VFP3_REGS_SIZE;
ret = ptrace (PTRACE_GETREGSET, tid, NT_ARM_VFP, &iovec);
if (ret < 0)
perror_with_name (_("Unable to fetch VFP registers."));
aarch32_vfp_regcache_collect (regcache, (gdb_byte *) &regs, 32);
}
else
{
int regno;
iovec.iov_len = sizeof (regs);
ret = ptrace (PTRACE_GETREGSET, tid, NT_FPREGSET, &iovec);
if (ret < 0)
perror_with_name (_("Unable to fetch FP/SIMD registers."));
for (regno = AARCH64_V0_REGNUM; regno <= AARCH64_V31_REGNUM; regno++)
if (REG_VALID == regcache->get_register_status (regno))
regcache->raw_collect
(regno, (char *) &regs.vregs[regno - AARCH64_V0_REGNUM]);
if (REG_VALID == regcache->get_register_status (AARCH64_FPSR_REGNUM))
regcache->raw_collect (AARCH64_FPSR_REGNUM, (char *) &regs.fpsr);
if (REG_VALID == regcache->get_register_status (AARCH64_FPCR_REGNUM))
regcache->raw_collect (AARCH64_FPCR_REGNUM, (char *) &regs.fpcr);
}
if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
{
ret = ptrace (PTRACE_SETREGSET, tid, NT_ARM_VFP, &iovec);
if (ret < 0)
perror_with_name (_("Unable to store VFP registers."));
}
else
{
ret = ptrace (PTRACE_SETREGSET, tid, NT_FPREGSET, &iovec);
if (ret < 0)
perror_with_name (_("Unable to store FP/SIMD registers."));
}
}
/* Fill GDB's register array with the sve register values
from the current thread. */
static void
fetch_sveregs_from_thread (struct regcache *regcache)
{
std::unique_ptr<gdb_byte[]> base
= aarch64_sve_get_sveregs (regcache->ptid ().lwp ());
aarch64_sve_regs_copy_to_reg_buf (regcache, base.get ());
}
/* Store to the current thread the valid sve register
values in the GDB's register array. */
static void
store_sveregs_to_thread (struct regcache *regcache)
{
int ret;
struct iovec iovec;
int tid = regcache->ptid ().lwp ();
/* First store vector length to the thread. This is done first to ensure the
ptrace buffers read from the kernel are the correct size. */
if (!aarch64_sve_set_vq (tid, regcache))
perror_with_name (_("Unable to set VG register."));
/* Obtain a dump of SVE registers from ptrace. */
std::unique_ptr<gdb_byte[]> base = aarch64_sve_get_sveregs (tid);
/* Overwrite with regcache state. */
aarch64_sve_regs_copy_from_reg_buf (regcache, base.get ());
/* Write back to the kernel. */
iovec.iov_base = base.get ();
iovec.iov_len = ((struct user_sve_header *) base.get ())->size;
ret = ptrace (PTRACE_SETREGSET, tid, NT_ARM_SVE, &iovec);
if (ret < 0)
perror_with_name (_("Unable to store sve registers"));
}
/* Fill GDB's register array with the pointer authentication mask values from
the current thread. */
static void
fetch_pauth_masks_from_thread (struct regcache *regcache)
{
struct gdbarch_tdep *tdep = gdbarch_tdep (regcache->arch ());
int ret;
struct iovec iovec;
uint64_t pauth_regset[2] = {0, 0};
int tid = regcache->ptid ().lwp ();
iovec.iov_base = &pauth_regset;
iovec.iov_len = sizeof (pauth_regset);
ret = ptrace (PTRACE_GETREGSET, tid, NT_ARM_PAC_MASK, &iovec);
if (ret != 0)
perror_with_name (_("unable to fetch pauth registers."));
regcache->raw_supply (AARCH64_PAUTH_DMASK_REGNUM (tdep->pauth_reg_base),
&pauth_regset[0]);
regcache->raw_supply (AARCH64_PAUTH_CMASK_REGNUM (tdep->pauth_reg_base),
&pauth_regset[1]);
}
/* Fill GDB's register array with the MTE register values from
the current thread. */
static void
fetch_mteregs_from_thread (struct regcache *regcache)
{
struct gdbarch_tdep *tdep = gdbarch_tdep (regcache->arch ());
int regno = tdep->mte_reg_base;
gdb_assert (regno != -1);
uint64_t tag_ctl = 0;
struct iovec iovec;
iovec.iov_base = &tag_ctl;
iovec.iov_len = sizeof (tag_ctl);
int tid = get_ptrace_pid (regcache->ptid ());
if (ptrace (PTRACE_GETREGSET, tid, NT_ARM_TAGGED_ADDR_CTRL, &iovec) != 0)
perror_with_name (_("unable to fetch MTE registers."));
regcache->raw_supply (regno, &tag_ctl);
}
/* Store to the current thread the valid MTE register set in the GDB's
register array. */
static void
store_mteregs_to_thread (struct regcache *regcache)
{
struct gdbarch_tdep *tdep = gdbarch_tdep (regcache->arch ());
int regno = tdep->mte_reg_base;
gdb_assert (regno != -1);
uint64_t tag_ctl = 0;
if (REG_VALID != regcache->get_register_status (regno))
return;
regcache->raw_collect (regno, (char *) &tag_ctl);
struct iovec iovec;
iovec.iov_base = &tag_ctl;
iovec.iov_len = sizeof (tag_ctl);
int tid = get_ptrace_pid (regcache->ptid ());
if (ptrace (PTRACE_SETREGSET, tid, NT_ARM_TAGGED_ADDR_CTRL, &iovec) != 0)
perror_with_name (_("unable to store MTE registers."));
}
/* Implement the "fetch_registers" target_ops method. */
void
aarch64_linux_nat_target::fetch_registers (struct regcache *regcache,
int regno)
{
struct gdbarch_tdep *tdep = gdbarch_tdep (regcache->arch ());
if (regno == -1)
{
fetch_gregs_from_thread (regcache);
if (tdep->has_sve ())
fetch_sveregs_from_thread (regcache);
else
fetch_fpregs_from_thread (regcache);
if (tdep->has_pauth ())
fetch_pauth_masks_from_thread (regcache);
if (tdep->has_mte ())
fetch_mteregs_from_thread (regcache);
}
else if (regno < AARCH64_V0_REGNUM)
fetch_gregs_from_thread (regcache);
else if (tdep->has_sve ())
fetch_sveregs_from_thread (regcache);
else
fetch_fpregs_from_thread (regcache);
if (tdep->has_pauth ())
{
if (regno == AARCH64_PAUTH_DMASK_REGNUM (tdep->pauth_reg_base)
|| regno == AARCH64_PAUTH_CMASK_REGNUM (tdep->pauth_reg_base))
fetch_pauth_masks_from_thread (regcache);
}
/* Fetch individual MTE registers. */
if (tdep->has_mte ()
&& (regno == tdep->mte_reg_base))
fetch_mteregs_from_thread (regcache);
}
/* Implement the "store_registers" target_ops method. */
void
aarch64_linux_nat_target::store_registers (struct regcache *regcache,
int regno)
{
struct gdbarch_tdep *tdep = gdbarch_tdep (regcache->arch ());
if (regno == -1)
{
store_gregs_to_thread (regcache);
if (tdep->has_sve ())
store_sveregs_to_thread (regcache);
else
store_fpregs_to_thread (regcache);
if (tdep->has_mte ())
store_mteregs_to_thread (regcache);
}
else if (regno < AARCH64_V0_REGNUM)
store_gregs_to_thread (regcache);
else if (tdep->has_sve ())
store_sveregs_to_thread (regcache);
else
store_fpregs_to_thread (regcache);
/* Store MTE registers. */
if (tdep->has_mte ()
&& (regno == tdep->mte_reg_base))
store_mteregs_to_thread (regcache);
}
/* Fill register REGNO (if it is a general-purpose register) in
*GREGSETPS with the value in GDB's register array. If REGNO is -1,
do this for all registers. */
void
fill_gregset (const struct regcache *regcache,
gdb_gregset_t *gregsetp, int regno)
{
regcache_collect_regset (&aarch64_linux_gregset, regcache,
regno, (gdb_byte *) gregsetp,
AARCH64_LINUX_SIZEOF_GREGSET);
}
/* Fill GDB's register array with the general-purpose register values
in *GREGSETP. */
void
supply_gregset (struct regcache *regcache, const gdb_gregset_t *gregsetp)
{
regcache_supply_regset (&aarch64_linux_gregset, regcache, -1,
(const gdb_byte *) gregsetp,
AARCH64_LINUX_SIZEOF_GREGSET);
}
/* Fill register REGNO (if it is a floating-point register) in
*FPREGSETP with the value in GDB's register array. If REGNO is -1,
do this for all registers. */
void
fill_fpregset (const struct regcache *regcache,
gdb_fpregset_t *fpregsetp, int regno)
{
regcache_collect_regset (&aarch64_linux_fpregset, regcache,
regno, (gdb_byte *) fpregsetp,
AARCH64_LINUX_SIZEOF_FPREGSET);
}
/* Fill GDB's register array with the floating-point register values
in *FPREGSETP. */
void
supply_fpregset (struct regcache *regcache, const gdb_fpregset_t *fpregsetp)
{
regcache_supply_regset (&aarch64_linux_fpregset, regcache, -1,
(const gdb_byte *) fpregsetp,
AARCH64_LINUX_SIZEOF_FPREGSET);
}
/* linux_nat_new_fork hook. */
void
aarch64_linux_nat_target::low_new_fork (struct lwp_info *parent,
pid_t child_pid)
{
pid_t parent_pid;
struct aarch64_debug_reg_state *parent_state;
struct aarch64_debug_reg_state *child_state;
/* NULL means no watchpoint has ever been set in the parent. In
that case, there's nothing to do. */
if (parent->arch_private == NULL)
return;
/* GDB core assumes the child inherits the watchpoints/hw
breakpoints of the parent, and will remove them all from the
forked off process. Copy the debug registers mirrors into the
new process so that all breakpoints and watchpoints can be
removed together. */
parent_pid = parent->ptid.pid ();
parent_state = aarch64_get_debug_reg_state (parent_pid);
child_state = aarch64_get_debug_reg_state (child_pid);
*child_state = *parent_state;
}
/* Called by libthread_db. Returns a pointer to the thread local
storage (or its descriptor). */
ps_err_e
ps_get_thread_area (struct ps_prochandle *ph,
lwpid_t lwpid, int idx, void **base)
{
int is_64bit_p
= (gdbarch_bfd_arch_info (target_gdbarch ())->bits_per_word == 64);
return aarch64_ps_get_thread_area (ph, lwpid, idx, base, is_64bit_p);
}
/* Implement the "post_startup_inferior" target_ops method. */
void
aarch64_linux_nat_target::post_startup_inferior (ptid_t ptid)
{
low_forget_process (ptid.pid ());
aarch64_linux_get_debug_reg_capacity (ptid.pid ());
linux_nat_target::post_startup_inferior (ptid);
}
/* Implement the "post_attach" target_ops method. */
void
aarch64_linux_nat_target::post_attach (int pid)
{
low_forget_process (pid);
/* Set the hardware debug register capacity. If
aarch64_linux_get_debug_reg_capacity is not called
(as it is in aarch64_linux_child_post_startup_inferior) then
software watchpoints will be used instead of hardware
watchpoints when attaching to a target. */
aarch64_linux_get_debug_reg_capacity (pid);
linux_nat_target::post_attach (pid);
}
/* Implement the "read_description" target_ops method. */
const struct target_desc *
aarch64_linux_nat_target::read_description ()
{
int ret, tid;
gdb_byte regbuf[ARM_VFP3_REGS_SIZE];
struct iovec iovec;
tid = inferior_ptid.pid ();
iovec.iov_base = regbuf;
iovec.iov_len = ARM_VFP3_REGS_SIZE;
ret = ptrace (PTRACE_GETREGSET, tid, NT_ARM_VFP, &iovec);
if (ret == 0)
return aarch32_read_description ();
CORE_ADDR hwcap = linux_get_hwcap (this);
CORE_ADDR hwcap2 = linux_get_hwcap2 (this);
bool pauth_p = hwcap & AARCH64_HWCAP_PACA;
bool mte_p = hwcap2 & HWCAP2_MTE;
return aarch64_read_description (aarch64_sve_get_vq (tid), pauth_p, mte_p);
}
/* Convert a native/host siginfo object, into/from the siginfo in the
layout of the inferiors' architecture. Returns true if any
conversion was done; false otherwise. If DIRECTION is 1, then copy
from INF to NATIVE. If DIRECTION is 0, copy from NATIVE to
INF. */
bool
aarch64_linux_nat_target::low_siginfo_fixup (siginfo_t *native, gdb_byte *inf,
int direction)
{
struct gdbarch *gdbarch = get_frame_arch (get_current_frame ());
/* Is the inferior 32-bit? If so, then do fixup the siginfo
object. */
if (gdbarch_bfd_arch_info (gdbarch)->bits_per_word == 32)
{
if (direction == 0)
aarch64_compat_siginfo_from_siginfo ((struct compat_siginfo *) inf,
native);
else
aarch64_siginfo_from_compat_siginfo (native,
(struct compat_siginfo *) inf);
return true;
}
return false;
}
/* Returns the number of hardware watchpoints of type TYPE that we can
set. Value is positive if we can set CNT watchpoints, zero if
setting watchpoints of type TYPE is not supported, and negative if
CNT is more than the maximum number of watchpoints of type TYPE
that we can support. TYPE is one of bp_hardware_watchpoint,
bp_read_watchpoint, bp_write_watchpoint, or bp_hardware_breakpoint.
CNT is the number of such watchpoints used so far (including this
one). OTHERTYPE is non-zero if other types of watchpoints are
currently enabled. */
int
aarch64_linux_nat_target::can_use_hw_breakpoint (enum bptype type,
int cnt, int othertype)
{
if (type == bp_hardware_watchpoint || type == bp_read_watchpoint
|| type == bp_access_watchpoint || type == bp_watchpoint)
{
if (aarch64_num_wp_regs == 0)
return 0;
}
else if (type == bp_hardware_breakpoint)
{
if (aarch64_num_bp_regs == 0)
return 0;
}
else
gdb_assert_not_reached ("unexpected breakpoint type");
/* We always return 1 here because we don't have enough information
about possible overlap of addresses that they want to watch. As an
extreme example, consider the case where all the watchpoints watch
the same address and the same region length: then we can handle a
virtually unlimited number of watchpoints, due to debug register
sharing implemented via reference counts. */
return 1;
}
/* Insert a hardware-assisted breakpoint at BP_TGT->reqstd_address.
Return 0 on success, -1 on failure. */
int
aarch64_linux_nat_target::insert_hw_breakpoint (struct gdbarch *gdbarch,
struct bp_target_info *bp_tgt)
{
int ret;
CORE_ADDR addr = bp_tgt->placed_address = bp_tgt->reqstd_address;
int len;
const enum target_hw_bp_type type = hw_execute;
struct aarch64_debug_reg_state *state
= aarch64_get_debug_reg_state (inferior_ptid.pid ());
gdbarch_breakpoint_from_pc (gdbarch, &addr, &len);
if (show_debug_regs)
fprintf_unfiltered
(gdb_stdlog,
"insert_hw_breakpoint on entry (addr=0x%08lx, len=%d))\n",
(unsigned long) addr, len);
ret = aarch64_handle_breakpoint (type, addr, len, 1 /* is_insert */, state);
if (show_debug_regs)
{
aarch64_show_debug_reg_state (state,
"insert_hw_breakpoint", addr, len, type);
}
return ret;
}
/* Remove a hardware-assisted breakpoint at BP_TGT->placed_address.
Return 0 on success, -1 on failure. */
int
aarch64_linux_nat_target::remove_hw_breakpoint (struct gdbarch *gdbarch,
struct bp_target_info *bp_tgt)
{
int ret;
CORE_ADDR addr = bp_tgt->placed_address;
int len = 4;
const enum target_hw_bp_type type = hw_execute;
struct aarch64_debug_reg_state *state
= aarch64_get_debug_reg_state (inferior_ptid.pid ());
gdbarch_breakpoint_from_pc (gdbarch, &addr, &len);
if (show_debug_regs)
fprintf_unfiltered
(gdb_stdlog, "remove_hw_breakpoint on entry (addr=0x%08lx, len=%d))\n",
(unsigned long) addr, len);
ret = aarch64_handle_breakpoint (type, addr, len, 0 /* is_insert */, state);
if (show_debug_regs)
{
aarch64_show_debug_reg_state (state,
"remove_hw_watchpoint", addr, len, type);
}
return ret;
}
/* Implement the "insert_watchpoint" target_ops method.
Insert a watchpoint to watch a memory region which starts at
address ADDR and whose length is LEN bytes. Watch memory accesses
of the type TYPE. Return 0 on success, -1 on failure. */
int
aarch64_linux_nat_target::insert_watchpoint (CORE_ADDR addr, int len,
enum target_hw_bp_type type,
struct expression *cond)
{
int ret;
struct aarch64_debug_reg_state *state
= aarch64_get_debug_reg_state (inferior_ptid.pid ());
if (show_debug_regs)
fprintf_unfiltered (gdb_stdlog,
"insert_watchpoint on entry (addr=0x%08lx, len=%d)\n",
(unsigned long) addr, len);
gdb_assert (type != hw_execute);
ret = aarch64_handle_watchpoint (type, addr, len, 1 /* is_insert */, state);
if (show_debug_regs)
{
aarch64_show_debug_reg_state (state,
"insert_watchpoint", addr, len, type);
}
return ret;
}
/* Implement the "remove_watchpoint" target_ops method.
Remove a watchpoint that watched the memory region which starts at
address ADDR, whose length is LEN bytes, and for accesses of the
type TYPE. Return 0 on success, -1 on failure. */
int
aarch64_linux_nat_target::remove_watchpoint (CORE_ADDR addr, int len,
enum target_hw_bp_type type,
struct expression *cond)
{
int ret;
struct aarch64_debug_reg_state *state
= aarch64_get_debug_reg_state (inferior_ptid.pid ());
if (show_debug_regs)
fprintf_unfiltered (gdb_stdlog,
"remove_watchpoint on entry (addr=0x%08lx, len=%d)\n",
(unsigned long) addr, len);
gdb_assert (type != hw_execute);
ret = aarch64_handle_watchpoint (type, addr, len, 0 /* is_insert */, state);
if (show_debug_regs)
{
aarch64_show_debug_reg_state (state,
"remove_watchpoint", addr, len, type);
}
return ret;
}
/* Implement the "region_ok_for_hw_watchpoint" target_ops method. */
int
aarch64_linux_nat_target::region_ok_for_hw_watchpoint (CORE_ADDR addr, int len)
{
return aarch64_linux_region_ok_for_watchpoint (addr, len);
}
/* Implement the "stopped_data_address" target_ops method. */
bool
aarch64_linux_nat_target::stopped_data_address (CORE_ADDR *addr_p)
{
siginfo_t siginfo;
int i;
struct aarch64_debug_reg_state *state;
if (!linux_nat_get_siginfo (inferior_ptid, &siginfo))
return false;
/* This must be a hardware breakpoint. */
if (siginfo.si_signo != SIGTRAP
|| (siginfo.si_code & 0xffff) != TRAP_HWBKPT)
return false;
/* Make sure to ignore the top byte, otherwise we may not recognize a
hardware watchpoint hit. The stopped data addresses coming from the
kernel can potentially be tagged addresses. */
struct gdbarch *gdbarch = thread_architecture (inferior_ptid);
const CORE_ADDR addr_trap
= address_significant (gdbarch, (CORE_ADDR) siginfo.si_addr);
/* Check if the address matches any watched address. */
state = aarch64_get_debug_reg_state (inferior_ptid.pid ());
for (i = aarch64_num_wp_regs - 1; i >= 0; --i)
{
const unsigned int offset
= aarch64_watchpoint_offset (state->dr_ctrl_wp[i]);
const unsigned int len = aarch64_watchpoint_length (state->dr_ctrl_wp[i]);
const CORE_ADDR addr_watch = state->dr_addr_wp[i] + offset;
const CORE_ADDR addr_watch_aligned = align_down (state->dr_addr_wp[i], 8);
const CORE_ADDR addr_orig = state->dr_addr_orig_wp[i];
if (state->dr_ref_count_wp[i]
&& DR_CONTROL_ENABLED (state->dr_ctrl_wp[i])
&& addr_trap >= addr_watch_aligned
&& addr_trap < addr_watch + len)
{
/* ADDR_TRAP reports the first address of the memory range
accessed by the CPU, regardless of what was the memory
range watched. Thus, a large CPU access that straddles
the ADDR_WATCH..ADDR_WATCH+LEN range may result in an
ADDR_TRAP that is lower than the
ADDR_WATCH..ADDR_WATCH+LEN range. E.g.:
addr: | 4 | 5 | 6 | 7 | 8 |
|---- range watched ----|
|----------- range accessed ------------|
In this case, ADDR_TRAP will be 4.
To match a watchpoint known to GDB core, we must never
report *ADDR_P outside of any ADDR_WATCH..ADDR_WATCH+LEN
range. ADDR_WATCH <= ADDR_TRAP < ADDR_ORIG is a false
positive on kernels older than 4.10. See PR
external/20207. */
*addr_p = addr_orig;
return true;
}
}
return false;
}
/* Implement the "stopped_by_watchpoint" target_ops method. */
bool
aarch64_linux_nat_target::stopped_by_watchpoint ()
{
CORE_ADDR addr;
return stopped_data_address (&addr);
}
/* Implement the "watchpoint_addr_within_range" target_ops method. */
bool
aarch64_linux_nat_target::watchpoint_addr_within_range (CORE_ADDR addr,
CORE_ADDR start, int length)
{
return start <= addr && start + length - 1 >= addr;
}
/* Implement the "can_do_single_step" target_ops method. */
int
aarch64_linux_nat_target::can_do_single_step ()
{
return 1;
}
/* Implement the "thread_architecture" target_ops method. */
struct gdbarch *
aarch64_linux_nat_target::thread_architecture (ptid_t ptid)
{
/* Return the gdbarch for the current thread. If the vector length has
changed since the last time this was called, then do a further lookup. */
uint64_t vq = aarch64_sve_get_vq (ptid.lwp ());
/* Find the current gdbarch the same way as process_stratum_target. Only
return it if the current vector length matches the one in the tdep. */
inferior *inf = find_inferior_ptid (this, ptid);
gdb_assert (inf != NULL);
if (vq == gdbarch_tdep (inf->gdbarch)->vq)
return inf->gdbarch;
/* We reach here if the vector length for the thread is different from its
value at process start. Lookup gdbarch via info (potentially creating a
new one), stashing the vector length inside id. Use -1 for when SVE
unavailable, to distinguish from an unset value of 0. */
struct gdbarch_info info;
gdbarch_info_init (&info);
info.bfd_arch_info = bfd_lookup_arch (bfd_arch_aarch64, bfd_mach_aarch64);
info.id = (int *) (vq == 0 ? -1 : vq);
return gdbarch_find_by_info (info);
}
/* Implement the "supports_memory_tagging" target_ops method. */
bool
aarch64_linux_nat_target::supports_memory_tagging ()
{
return (linux_get_hwcap2 (this) & HWCAP2_MTE) != 0;
}
/* Implement the "fetch_memtags" target_ops method. */
bool
aarch64_linux_nat_target::fetch_memtags (CORE_ADDR address, size_t len,
gdb::byte_vector &tags, int type)
{
int tid = get_ptrace_pid (inferior_ptid);
/* Allocation tags? */
if (type == static_cast<int> (aarch64_memtag_type::mte_allocation))
return aarch64_mte_fetch_memtags (tid, address, len, tags);
return false;
}
/* Implement the "store_memtags" target_ops method. */
bool
aarch64_linux_nat_target::store_memtags (CORE_ADDR address, size_t len,
const gdb::byte_vector &tags, int type)
{
int tid = get_ptrace_pid (inferior_ptid);
/* Allocation tags? */
if (type == static_cast<int> (aarch64_memtag_type::mte_allocation))
return aarch64_mte_store_memtags (tid, address, len, tags);
return false;
}
/* Define AArch64 maintenance commands. */
static void
add_show_debug_regs_command (void)
{
/* A maintenance command to enable printing the internal DRi mirror
variables. */
add_setshow_boolean_cmd ("show-debug-regs", class_maintenance,
&show_debug_regs, _("\
Set whether to show variables that mirror the AArch64 debug registers."), _("\
Show whether to show variables that mirror the AArch64 debug registers."), _("\
Use \"on\" to enable, \"off\" to disable.\n\
If enabled, the debug registers values are shown when GDB inserts\n\
or removes a hardware breakpoint or watchpoint, and when the inferior\n\
triggers a breakpoint or watchpoint."),
NULL,
NULL,
&maintenance_set_cmdlist,
&maintenance_show_cmdlist);
}
void _initialize_aarch64_linux_nat ();
void
_initialize_aarch64_linux_nat ()
{
add_show_debug_regs_command ();
/* Register the target. */
linux_target = &the_aarch64_linux_nat_target;
add_inf_child_target (&the_aarch64_linux_nat_target);
}
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