[aarch64] Add TPIDR2 register support for Linux

With the AArch64 Scalable Matrix Extension we have a new TPIDR2 register, and
it will be added to the existing NT_ARM_TLS register set. Kernel patches are
being reviewed here:

https://lore.kernel.org/linux-arm-kernel/20220818170111.351889-1-broonie@kernel.org/

From GDB's perspective, we handle it in a similar way to the existing TPIDR
register. But we need to consider cases of systems that only have TPIDR and
systems that have both TPIDR and TPIDR2.

With that in mind, the following patch adds the required code to support
TPIDR2 and turns the org.gnu.gdb.aarch64.tls feature into a
dynamically-generated target description as opposed to a static target
description containing only TPIDR.

That means we can remove the gdb/features/aarch64-tls.xml file and replace the
existing gdb/features/aarch64-tls.c auto-generated file with a new file that
dynamically generates the target description containing either TPIDR alone or
TPIDR and TPIDR2.

In the future, when *BSD's start to support this register, they can just
enable it as is being done for the AArch64 Linux target.

The core file read/write code has been updated to support TPIDR2 as well.

On GDBserver's side, there is a small change to the find_regno function to
expose a non-throwing version of it.

It always seemed strange to me how find_regno causes the whole operation to
abort if it doesn't find a particular register name. The patch moves code
from find_regno into find_regno_no_throw and makes find_regno call
find_regno_no_throw instead.

This allows us to do register name lookups to find a particular register
number without risking erroring out if nothing is found.

The patch also adjusts the feature detection code for aarch64-fbsd, since
the infrastructure is shared amongst all aarch64 targets. I haven't added
code to support TPIDR2 in aarch64-fbsd though, as I'm not sure when/if
that will happen.
This commit is contained in:
Luis Machado 2022-08-22 17:04:41 +01:00
parent 73425813c1
commit ba60b96371
17 changed files with 215 additions and 81 deletions

View File

@ -93,7 +93,7 @@ aarch64_fbsd_nat_target::fetch_registers (struct regcache *regcache,
aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
if (tdep->has_tls ())
fetch_regset<uint64_t> (regcache, regnum, NT_ARM_TLS,
&aarch64_fbsd_tls_regset, tdep->tls_regnum);
&aarch64_fbsd_tls_regset, tdep->tls_regnum_base);
}
/* Store register REGNUM back into the inferior. If REGNUM is -1, do
@ -112,7 +112,7 @@ aarch64_fbsd_nat_target::store_registers (struct regcache *regcache,
aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
if (tdep->has_tls ())
store_regset<uint64_t> (regcache, regnum, NT_ARM_TLS,
&aarch64_fbsd_tls_regset, tdep->tls_regnum);
&aarch64_fbsd_tls_regset, tdep->tls_regnum_base);
}
/* Implement the target read_description method. */
@ -121,7 +121,7 @@ const struct target_desc *
aarch64_fbsd_nat_target::read_description ()
{
aarch64_features features;
features.tls = have_regset (inferior_ptid, NT_ARM_TLS) != 0;
features.tls = have_regset (inferior_ptid, NT_ARM_TLS)? 1 : 0;
return aarch64_read_description (features);
}

View File

@ -50,7 +50,7 @@ static const struct regcache_map_entry aarch64_fbsd_fpregmap[] =
{ 0 }
};
/* Register numbers are relative to tdep->tls_regnum. */
/* Register numbers are relative to tdep->tls_regnum_base. */
static const struct regcache_map_entry aarch64_fbsd_tls_regmap[] =
{
@ -151,7 +151,7 @@ aarch64_fbsd_supply_tls_regset (const struct regset *regset,
struct gdbarch *gdbarch = regcache->arch ();
aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
regcache->supply_regset (regset, tdep->tls_regnum, regnum, buf, size);
regcache->supply_regset (regset, tdep->tls_regnum_base, regnum, buf, size);
}
static void
@ -162,7 +162,7 @@ aarch64_fbsd_collect_tls_regset (const struct regset *regset,
struct gdbarch *gdbarch = regcache->arch ();
aarch64_gdbarch_tdep *tdep = gdbarch_tdep<aarch64_gdbarch_tdep> (gdbarch);
regcache->collect_regset (regset, tdep->tls_regnum, regnum, buf, size);
regcache->collect_regset (regset, tdep->tls_regnum_base, regnum, buf, size);
}
const struct regset aarch64_fbsd_tls_regset =
@ -201,7 +201,7 @@ aarch64_fbsd_core_read_description (struct gdbarch *gdbarch,
asection *tls = bfd_get_section_by_name (abfd, ".reg-aarch-tls");
aarch64_features features;
features.tls = tls != nullptr;
features.tls = tls != nullptr? 1 : 0;
return aarch64_read_description (features);
}
@ -218,10 +218,10 @@ aarch64_fbsd_get_thread_local_address (struct gdbarch *gdbarch, ptid_t ptid,
regcache = get_thread_arch_regcache (current_inferior ()->process_target (),
ptid, gdbarch);
target_fetch_registers (regcache, tdep->tls_regnum);
target_fetch_registers (regcache, tdep->tls_regnum_base);
ULONGEST tpidr;
if (regcache->cooked_read (tdep->tls_regnum, &tpidr) != REG_VALID)
if (regcache->cooked_read (tdep->tls_regnum_base, &tpidr) != REG_VALID)
error (_("Unable to fetch %%tpidr"));
/* %tpidr points to the TCB whose first member is the dtv

View File

@ -440,21 +440,22 @@ fetch_tlsregs_from_thread (struct regcache *regcache)
{
aarch64_gdbarch_tdep *tdep
= gdbarch_tdep<aarch64_gdbarch_tdep> (regcache->arch ());
int regno = tdep->tls_regnum;
int regno = tdep->tls_regnum_base;
gdb_assert (regno != -1);
gdb_assert (tdep->tls_register_count > 0);
uint64_t tpidr = 0;
uint64_t tpidrs[tdep->tls_register_count] = { 0 };
struct iovec iovec;
iovec.iov_base = &tpidr;
iovec.iov_len = sizeof (tpidr);
iovec.iov_base = tpidrs;
iovec.iov_len = sizeof (tpidrs);
int tid = get_ptrace_pid (regcache->ptid ());
if (ptrace (PTRACE_GETREGSET, tid, NT_ARM_TLS, &iovec) != 0)
perror_with_name (_("unable to fetch TLS register"));
perror_with_name (_("unable to fetch TLS registers"));
regcache->raw_supply (regno, &tpidr);
for (int i = 0; i < tdep->tls_register_count; i++)
regcache->raw_supply (regno + i, &tpidrs[i]);
}
/* Store to the current thread the valid TLS register set in GDB's
@ -465,21 +466,24 @@ store_tlsregs_to_thread (struct regcache *regcache)
{
aarch64_gdbarch_tdep *tdep
= gdbarch_tdep<aarch64_gdbarch_tdep> (regcache->arch ());
int regno = tdep->tls_regnum;
int regno = tdep->tls_regnum_base;
gdb_assert (regno != -1);
gdb_assert (tdep->tls_register_count > 0);
uint64_t tpidr = 0;
uint64_t tpidrs[tdep->tls_register_count] = { 0 };
if (REG_VALID != regcache->get_register_status (regno))
return;
for (int i = 0; i < tdep->tls_register_count; i++)
{
if (REG_VALID != regcache->get_register_status (regno + i))
continue;
regcache->raw_collect (regno, (char *) &tpidr);
regcache->raw_collect (regno + i, (char *) &tpidrs[i]);
}
struct iovec iovec;
iovec.iov_base = &tpidr;
iovec.iov_len = sizeof (tpidr);
iovec.iov_base = &tpidrs;
iovec.iov_len = sizeof (tpidrs);
int tid = get_ptrace_pid (regcache->ptid ());
if (ptrace (PTRACE_SETREGSET, tid, NT_ARM_TLS, &iovec) != 0)
@ -531,7 +535,9 @@ aarch64_fetch_registers (struct regcache *regcache, int regno)
&& (regno == tdep->mte_reg_base))
fetch_mteregs_from_thread (regcache);
if (tdep->has_tls () && regno == tdep->tls_regnum)
if (tdep->has_tls ()
&& regno >= tdep->tls_regnum_base
&& regno < tdep->tls_regnum_base + tdep->tls_register_count)
fetch_tlsregs_from_thread (regcache);
}
@ -607,7 +613,9 @@ aarch64_store_registers (struct regcache *regcache, int regno)
&& (regno == tdep->mte_reg_base))
store_mteregs_to_thread (regcache);
if (tdep->has_tls () && regno == tdep->tls_regnum)
if (tdep->has_tls ()
&& regno >= tdep->tls_regnum_base
&& regno < tdep->tls_regnum_base + tdep->tls_register_count)
store_tlsregs_to_thread (regcache);
}
@ -788,7 +796,7 @@ aarch64_linux_nat_target::read_description ()
features.vq = aarch64_sve_get_vq (tid);
features.pauth = hwcap & AARCH64_HWCAP_PACA;
features.mte = hwcap2 & HWCAP2_MTE;
features.tls = true;
features.tls = aarch64_tls_register_count (tid);
return aarch64_read_description (features);
}

View File

@ -754,22 +754,30 @@ aarch64_linux_iterate_over_regset_sections (struct gdbarch *gdbarch,
"MTE registers", cb_data);
}
/* Handle the TLS registers. */
if (tdep->has_tls ())
{
gdb_assert (tdep->tls_regnum_base != -1);
gdb_assert (tdep->tls_register_count > 0);
int sizeof_tls_regset
= AARCH64_TLS_REGISTER_SIZE * tdep->tls_register_count;
const struct regcache_map_entry tls_regmap[] =
{
{ 1, tdep->tls_regnum, 8 },
{ tdep->tls_register_count, tdep->tls_regnum_base,
AARCH64_TLS_REGISTER_SIZE },
{ 0 }
};
const struct regset aarch64_linux_tls_regset =
{
tls_regmap, regcache_supply_regset, regcache_collect_regset
tls_regmap, regcache_supply_regset, regcache_collect_regset,
REGSET_VARIABLE_SIZE
};
cb (".reg-aarch-tls", AARCH64_LINUX_SIZEOF_TLSREGSET,
AARCH64_LINUX_SIZEOF_TLSREGSET, &aarch64_linux_tls_regset,
"TLS register", cb_data);
cb (".reg-aarch-tls", sizeof_tls_regset, sizeof_tls_regset,
&aarch64_linux_tls_regset, "TLS register", cb_data);
}
}
@ -779,7 +787,6 @@ static const struct target_desc *
aarch64_linux_core_read_description (struct gdbarch *gdbarch,
struct target_ops *target, bfd *abfd)
{
asection *tls = bfd_get_section_by_name (abfd, ".reg-aarch-tls");
gdb::optional<gdb::byte_vector> auxv = target_read_auxv_raw (target);
CORE_ADDR hwcap = linux_get_hwcap (auxv, target, gdbarch);
CORE_ADDR hwcap2 = linux_get_hwcap2 (auxv, target, gdbarch);
@ -788,7 +795,16 @@ aarch64_linux_core_read_description (struct gdbarch *gdbarch,
features.vq = aarch64_linux_core_read_vq (gdbarch, abfd);
features.pauth = hwcap & AARCH64_HWCAP_PACA;
features.mte = hwcap2 & HWCAP2_MTE;
features.tls = tls != nullptr;
/* Handle the TLS section. */
asection *tls = bfd_get_section_by_name (abfd, ".reg-aarch-tls");
if (tls != nullptr)
{
size_t size = bfd_section_size (tls);
/* Convert the size to the number of actual registers, by
dividing by 8. */
features.tls = size / AARCH64_TLS_REGISTER_SIZE;
}
return aarch64_read_description (features);
}

View File

@ -39,9 +39,6 @@
/* The MTE regset consists of a 64-bit register. */
#define AARCH64_LINUX_SIZEOF_MTE_REGSET (8)
/* The TLS regset consists of a single register. */
#define AARCH64_LINUX_SIZEOF_TLSREGSET (X_REGISTER_SIZE)
extern const struct regset aarch64_linux_gregset;
extern const struct regset aarch64_linux_fpregset;

View File

@ -3465,8 +3465,18 @@ aarch64_features_from_target_desc (const struct target_desc *tdesc)
= (tdesc_find_feature (tdesc, "org.gnu.gdb.aarch64.pauth") != nullptr);
features.mte
= (tdesc_find_feature (tdesc, "org.gnu.gdb.aarch64.mte") != nullptr);
features.tls
= (tdesc_find_feature (tdesc, "org.gnu.gdb.aarch64.tls") != nullptr);
const struct tdesc_feature *tls_feature
= tdesc_find_feature (tdesc, "org.gnu.gdb.aarch64.tls");
if (tls_feature != nullptr)
{
/* We have TLS registers. Find out how many. */
if (tdesc_unnumbered_register (tls_feature, "tpidr2"))
features.tls = 2;
else
features.tls = 1;
}
return features;
}
@ -3526,7 +3536,7 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
bool valid_p = true;
int i, num_regs = 0, num_pseudo_regs = 0;
int first_pauth_regnum = -1, ra_sign_state_offset = -1;
int first_mte_regnum = -1, tls_regnum = -1;
int first_mte_regnum = -1, first_tls_regnum = -1;
uint64_t vq = aarch64_get_tdesc_vq (info.target_desc);
if (vq > AARCH64_MAX_SVE_VQ)
@ -3614,15 +3624,38 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
}
/* Add the TLS register. */
int tls_register_count = 0;
if (feature_tls != nullptr)
{
tls_regnum = num_regs;
/* Validate the descriptor provides the mandatory TLS register
and allocate its number. */
valid_p = tdesc_numbered_register (feature_tls, tdesc_data.get (),
tls_regnum, "tpidr");
first_tls_regnum = num_regs;
num_regs++;
/* Look for the TLS registers. tpidr is required, but tpidr2 is
optional. */
valid_p
= tdesc_numbered_register (feature_tls, tdesc_data.get (),
first_tls_regnum, "tpidr");
if (valid_p)
{
tls_register_count++;
bool has_tpidr2
= tdesc_numbered_register (feature_tls, tdesc_data.get (),
first_tls_regnum + tls_register_count,
"tpidr2");
/* Figure out how many TLS registers we have. */
if (has_tpidr2)
tls_register_count++;
num_regs += tls_register_count;
}
else
{
warning (_("Provided TLS register feature doesn't contain "
"required tpidr register."));
return nullptr;
}
}
/* Add the pauth registers. */
@ -3675,7 +3708,8 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
tdep->pauth_reg_base = first_pauth_regnum;
tdep->ra_sign_state_regnum = -1;
tdep->mte_reg_base = first_mte_regnum;
tdep->tls_regnum = tls_regnum;
tdep->tls_regnum_base = first_tls_regnum;
tdep->tls_register_count = tls_register_count;
set_gdbarch_push_dummy_call (gdbarch, aarch64_push_dummy_call);
set_gdbarch_frame_align (gdbarch, aarch64_frame_align);

View File

@ -111,12 +111,13 @@ struct aarch64_gdbarch_tdep : gdbarch_tdep_base
return mte_reg_base != -1;
}
/* TLS register. This is -1 if the TLS register is not available. */
int tls_regnum = 0;
/* TLS registers. This is -1 if the TLS registers are not available. */
int tls_regnum_base = 0;
int tls_register_count = 0;
bool has_tls() const
{
return tls_regnum != -1;
return tls_regnum_base != -1;
}
/* The W pseudo-registers. */

View File

@ -53,8 +53,9 @@ aarch64_create_target_description (const aarch64_features &features)
if (features.mte)
regnum = create_feature_aarch64_mte (tdesc.get (), regnum);
if (features.tls)
regnum = create_feature_aarch64_tls (tdesc.get (), regnum);
/* TLS registers. */
if (features.tls > 0)
regnum = create_feature_aarch64_tls (tdesc.get (), regnum, features.tls);
return tdesc.release ();
}

View File

@ -33,7 +33,9 @@ struct aarch64_features
bool pauth = false;
bool mte = false;
bool tls = false;
/* A positive TLS value indicates the number of TLS registers available. */
uint8_t tls = 0;
};
inline bool operator==(const aarch64_features &lhs, const aarch64_features &rhs)
@ -56,7 +58,9 @@ namespace std
h = features.vq;
h = h << 1 | features.pauth;
h = h << 1 | features.mte;
h = h << 1 | features.tls;
/* Shift by two bits for now. We may need to increase this in the future
if more TLS registers get added. */
h = h << 2 | features.tls;
return h;
}
};
@ -96,7 +100,9 @@ enum aarch64_regnum
AARCH64_LAST_V_ARG_REGNUM = AARCH64_V0_REGNUM + 7
};
#define V_REGISTER_SIZE 16
/* Sizes of various AArch64 registers. */
#define AARCH64_TLS_REGISTER_SIZE 8
#define V_REGISTER_SIZE 16
/* Pseudo register base numbers. */
#define AARCH64_Q0_REGNUM 0
@ -117,8 +123,6 @@ enum aarch64_regnum
#define AARCH64_NUM_REGS AARCH64_FPCR_REGNUM + 1
#define AARCH64_SVE_NUM_REGS AARCH64_SVE_VG_REGNUM + 1
#define AARCH64_TLS_REGS_SIZE (8)
/* There are a number of ways of expressing the current SVE vector size:
VL : Vector Length.

View File

@ -202,7 +202,6 @@ FEATURE_XMLFILES = aarch64-core.xml \
aarch64-fpu.xml \
aarch64-pauth.xml \
aarch64-mte.xml \
aarch64-tls.xml \
arc/v1-core.xml \
arc/v1-aux.xml \
arc/v2-core.xml \

View File

@ -1,14 +1,43 @@
/* THIS FILE IS GENERATED. -*- buffer-read-only: t -*- vi:set ro:
Original: aarch64-tls.xml */
/* Copyright (C) 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/>. */
#include "gdbsupport/tdesc.h"
/* This function is NOT auto generated from xml.
Create the aarch64 description containing the TLS registers. TPIDR is
always available, but TPIDR2 is only available on some systems.
COUNT is the number of registers in this set. The minimum is 1. */
static int
create_feature_aarch64_tls (struct target_desc *result, long regnum)
create_feature_aarch64_tls (struct target_desc *result, long regnum, int count)
{
/* TPIDR is always present. */
gdb_assert (count >= 1);
struct tdesc_feature *feature;
feature = tdesc_create_feature (result, "org.gnu.gdb.aarch64.tls");
tdesc_create_reg (feature, "tpidr", regnum++, 1, NULL, 64, "data_ptr");
/* Add TPIDR2. */
if (count > 1)
tdesc_create_reg (feature, "tpidr2", regnum++, 1, NULL, 64, "data_ptr");
return regnum;
}

View File

@ -1,11 +0,0 @@
<?xml version="1.0"?>
<!-- Copyright (C) 2022 Free Software Foundation, Inc.
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved. -->
<!DOCTYPE feature SYSTEM "gdb-target.dtd">
<feature name="org.gnu.gdb.aarch64.tls">
<reg name="tpidr" bitsize="64" type="data_ptr"/>
</feature>

View File

@ -250,3 +250,24 @@ aarch64_ps_get_thread_area (struct ps_prochandle *ph,
return PS_OK;
}
/* See nat/aarch64-linux.h. */
int
aarch64_tls_register_count (int tid)
{
uint64_t tls_regs[2];
struct iovec iovec;
iovec.iov_base = tls_regs;
iovec.iov_len = sizeof (tls_regs);
/* Attempt to read both TPIDR and TPIDR2. If the request fails, it means
the Linux Kernel does not support TPIDR2.
Otherwise the Linux Kernel supports both TPIDR and TPIDR2. */
if (ptrace (PTRACE_GETREGSET, tid, NT_ARM_TLS, &iovec) != 0)
return 1;
/* TPIDR2 is available as well. */
return 2;
}

View File

@ -129,4 +129,8 @@ ps_err_e aarch64_ps_get_thread_area (struct ps_prochandle *ph,
lwpid_t lwpid, int idx, void **base,
int is_64bit_p);
/* Return the number of TLS registers in the NT_ARM_TLS set. This is only
used for aarch64 state. */
int aarch64_tls_register_count (int tid);
#endif /* NAT_AARCH64_LINUX_H */

View File

@ -292,9 +292,16 @@ aarch64_store_mteregset (struct regcache *regcache, const void *buf)
static void
aarch64_fill_tlsregset (struct regcache *regcache, void *buf)
{
gdb_byte *tls_buf = (gdb_byte *) buf;
int tls_regnum = find_regno (regcache->tdesc, "tpidr");
collect_register (regcache, tls_regnum, buf);
collect_register (regcache, tls_regnum, tls_buf);
/* Read TPIDR2, if it exists. */
gdb::optional<int> regnum = find_regno_no_throw (regcache->tdesc, "tpidr2");
if (regnum.has_value ())
collect_register (regcache, *regnum, tls_buf + sizeof (uint64_t));
}
/* Store TLS register to regcache. */
@ -302,9 +309,16 @@ aarch64_fill_tlsregset (struct regcache *regcache, void *buf)
static void
aarch64_store_tlsregset (struct regcache *regcache, const void *buf)
{
gdb_byte *tls_buf = (gdb_byte *) buf;
int tls_regnum = find_regno (regcache->tdesc, "tpidr");
supply_register (regcache, tls_regnum, buf);
supply_register (regcache, tls_regnum, tls_buf);
/* Write TPIDR2, if it exists. */
gdb::optional<int> regnum = find_regno_no_throw (regcache->tdesc, "tpidr2");
if (regnum.has_value ())
supply_register (regcache, *regnum, tls_buf + sizeof (uint64_t));
}
bool
@ -795,8 +809,8 @@ aarch64_adjust_register_sets (const struct aarch64_features &features)
regset->size = AARCH64_LINUX_SIZEOF_MTE;
break;
case NT_ARM_TLS:
if (features.tls)
regset->size = AARCH64_TLS_REGS_SIZE;
if (features.tls > 0)
regset->size = AARCH64_TLS_REGISTER_SIZE * features.tls;
break;
default:
gdb_assert_not_reached ("Unknown register set found.");
@ -829,7 +843,7 @@ aarch64_target::low_arch_setup ()
features.pauth = linux_get_hwcap (8) & AARCH64_HWCAP_PACA;
/* A-profile MTE is 64-bit only. */
features.mte = linux_get_hwcap2 (8) & HWCAP2_MTE;
features.tls = true;
features.tls = aarch64_tls_register_count (tid);
current_process ()->tdesc = aarch64_linux_read_description (features);

View File

@ -244,16 +244,28 @@ registers_from_string (struct regcache *regcache, char *buf)
hex2bin (buf, registers, len / 2);
}
int
find_regno (const struct target_desc *tdesc, const char *name)
/* See regcache.h */
gdb::optional<int>
find_regno_no_throw (const struct target_desc *tdesc, const char *name)
{
for (int i = 0; i < tdesc->reg_defs.size (); ++i)
{
if (strcmp (name, find_register_by_number (tdesc, i).name) == 0)
return i;
}
internal_error ("Unknown register %s requested",
name);
return {};
}
int
find_regno (const struct target_desc *tdesc, const char *name)
{
gdb::optional<int> regnum = find_regno_no_throw (tdesc, name);
if (regnum.has_value ())
return *regnum;
internal_error ("Unknown register %s requested", name);
}
static void

View File

@ -110,6 +110,11 @@ int register_cache_size (const struct target_desc *tdesc);
int register_size (const struct target_desc *tdesc, int n);
/* No throw version of find_regno. If NAME is not a known register, return
an empty value. */
gdb::optional<int> find_regno_no_throw (const struct target_desc *tdesc,
const char *name);
int find_regno (const struct target_desc *tdesc, const char *name);
void supply_register (struct regcache *regcache, int n, const void *buf);