[PATCH 2/2] gdb: Add native support for ARC in GNU/Linux
Shahab Vahedi
shahab.vahedi@gmail.com
Thu Nov 12 13:48:11 GMT 2020
From: Anton Kolesov <anton.kolesov@synopsys.com>
With this patch in place it is possible to build a GDB that
can run on ARC (GNU/Linux) hosts for debugging ARC targets.
The "arc-linux-nat.c" is a rather small one that mostly deals
with registers and a few thread related hooks.
gdb/ChangeLog:
* Makefile.in (ALLDEPFILES): Add arc-linux-nat.c.
* configure.host (host to gdb names): Add arc*-*-linux*.
* configure.nat (gdb_host_cpu): Add arc.
* arc-linux-nat.c: New.
---
gdb/Makefile.in | 1 +
gdb/arc-linux-nat.c | 321 ++++++++++++++++++++++++++++++++++++++++++++
gdb/configure.host | 3 +
gdb/configure.nat | 4 +
4 files changed, 329 insertions(+)
create mode 100644 gdb/arc-linux-nat.c
diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index c46935efafa..44ba2f04ac9 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -2144,6 +2144,7 @@ ALLDEPFILES = \
amd64-ravenscar-thread.c \
amd64-sol2-tdep.c \
amd64-tdep.c \
+ arc-linux-nat.c \
arc-tdep.c \
arm.c \
arm-bsd-tdep.c \
diff --git a/gdb/arc-linux-nat.c b/gdb/arc-linux-nat.c
new file mode 100644
index 00000000000..365cc88477b
--- /dev/null
+++ b/gdb/arc-linux-nat.c
@@ -0,0 +1,321 @@
+/* Native-dependent code for GNU/Linux ARC.
+
+ Copyright 2020 Free Software Foundation, Inc.
+
+ This file is part of GDB.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#include "defs.h"
+#include "frame.h"
+#include "inferior.h"
+#include "gdbcore.h"
+#include "regcache.h"
+#include "gdbsupport/gdb_assert.h"
+#include "target.h"
+#include "linux-nat.h"
+#include "nat/gdb_ptrace.h"
+
+#include <stdint.h>
+#include <sys/types.h>
+#include <sys/param.h>
+#include <signal.h>
+#include <sys/user.h>
+#include <sys/ioctl.h>
+#include "gdbsupport/gdb_wait.h"
+#include <fcntl.h>
+#include <sys/procfs.h>
+#include <linux/elf.h>
+
+#include "gregset.h"
+#include "arc-tdep.h"
+#include "arc-linux-tdep.h"
+#include "arch/arc.h"
+
+/* Defines ps_err_e, struct ps_prochandle. */
+#include "gdb_proc_service.h"
+
+/* Linux starting with 4.12 supports NT_ARC_V2 note type, which adds R30,
+ R58 and R59 registers, which are specific to ARC HS and aren't
+ available in ARC 700. */
+#if defined (NT_ARC_V2) && defined (__ARCHS__)
+#define ARC_HAS_V2_REGSET
+#endif
+
+class arc_linux_nat_target final : public linux_nat_target
+{
+public:
+ /* Add ARC register access methods. */
+ void fetch_registers (struct regcache *, int) override;
+ void store_registers (struct regcache *, int) override;
+
+ const struct target_desc *read_description () override;
+
+ /* Handle threads */
+ void low_prepare_to_resume (struct lwp_info *lp) override;
+};
+
+static arc_linux_nat_target the_arc_linux_nat_target;
+
+/* Read general registers from target process/thread (via ptrace)
+ into REGCACHE. */
+
+static void
+fetch_gregs (struct regcache *regcache, int regnum)
+{
+ const int tid = get_ptrace_pid (regcache->ptid ());
+ struct iovec iov;
+ gdb_gregset_t regs;
+
+ iov.iov_base = ®s;
+ iov.iov_len = sizeof (gdb_gregset_t);
+
+ if (ptrace (PTRACE_GETREGSET, tid, NT_PRSTATUS, (void *) &iov) < 0)
+ perror_with_name (_("Couldn't get general registers"));
+ else
+ arc_linux_supply_gregset (NULL, regcache, regnum, ®s, 0);
+}
+
+#ifdef ARC_HAS_V2_REGSET
+/* Read ARC v2 registers from target process/thread (via ptrace)
+ into REGCACHE. */
+
+static void
+fetch_v2_regs (struct regcache *regcache, int regnum)
+{
+ const int tid = get_ptrace_pid (regcache->ptid ());
+ struct iovec iov;
+ bfd_byte v2_buffer[ARC_LINUX_SIZEOF_V2_REGSET];
+
+ iov.iov_base = &v2_buffer;
+ iov.iov_len = ARC_LINUX_SIZEOF_V2_REGSET;
+
+ if (ptrace (PTRACE_GETREGSET, tid, NT_ARC_V2, (void *) &iov) < 0)
+ perror_with_name (_("Couldn't get ARC HS registers"));
+ else
+ arc_linux_supply_v2_regset (NULL, regcache, regnum, v2_buffer, 0);
+}
+#endif
+
+/* Store general registers from REGCACHE into the target process/thread. */
+
+static void
+store_gregs (const struct regcache *regcache, int regnum)
+{
+ const int tid = get_ptrace_pid (regcache->ptid ());
+ struct iovec iov;
+ gdb_gregset_t regs;
+
+ iov.iov_base = ®s;
+ iov.iov_len = sizeof (gdb_gregset_t);
+
+ if (ptrace (PTRACE_GETREGSET, tid, NT_PRSTATUS, (void *) &iov) < 0)
+ perror_with_name (_("Couldn't get general registers"));
+ else
+ {
+ arc_linux_collect_gregset (NULL, regcache, regnum, regs, 0);
+
+ if (ptrace (PTRACE_SETREGSET, tid, NT_PRSTATUS, (void *) &iov) < 0)
+ perror_with_name (_("Couldn't write general registers"));
+ }
+}
+
+#ifdef ARC_HAS_V2_REGSET
+/* Store ARC v2 registers from REGCACHE into the target process/thread. */
+
+static void
+store_v2_regs (const struct regcache *regcache, int regnum)
+{
+ const int tid = get_ptrace_pid (regcache->ptid ());
+ struct iovec iov;
+ bfd_byte v2_buffer[ARC_LINUX_SIZEOF_V2_REGSET];
+
+ iov.iov_base = &v2_buffer;
+ iov.iov_len = ARC_LINUX_SIZEOF_V2_REGSET;
+
+ if (ptrace (PTRACE_GETREGSET, tid, NT_ARC_V2, (void *) &iov) < 0)
+ perror_with_name (_("Couldn't get ARC HS registers"));
+ else
+ {
+ arc_linux_collect_v2_regset (NULL, regcache, regnum, v2_buffer, 0);
+
+ if (ptrace (PTRACE_SETREGSET, tid, NT_ARC_V2, (void *) &iov) < 0)
+ perror_with_name (_("Couldn't write ARC HS registers"));
+ }
+}
+#endif
+
+/* Target operation: Read REGNUM register (all registers if REGNUM == -1)
+ from target process into REGCACHE. */
+
+void
+arc_linux_nat_target::fetch_registers (struct regcache *regcache, int regnum)
+{
+
+ if (regnum == -1 || regnum <= ARC_LAST_REGNUM)
+ fetch_gregs (regcache, regnum);
+
+#ifdef ARC_HAS_V2_REGSET
+ if (regnum == -1
+ || regnum == ARC_R30_REGNUM
+ || regnum == ARC_R58_REGNUM
+ || regnum == ARC_R59_REGNUM)
+ fetch_v2_regs (regcache, regnum);
+#endif
+}
+
+/* Target operation: Store REGNUM register (all registers if REGNUM == -1)
+ to the target process from REGCACHE. */
+
+void
+arc_linux_nat_target::store_registers (struct regcache *regcache, int regnum)
+{
+ if (regnum == -1 || regnum <= ARC_LAST_REGNUM)
+ store_gregs (regcache, regnum);
+
+#ifdef ARC_HAS_V2_REGSET
+ if (regnum == -1
+ || regnum == ARC_R30_REGNUM
+ || regnum == ARC_R58_REGNUM
+ || regnum == ARC_R59_REGNUM)
+ store_v2_regs (regcache, regnum);
+#endif
+}
+
+/* Copy general purpose register(s) from REGCACHE into regset GREGS.
+ This function is exported to proc-service.c */
+
+void
+fill_gregset (const struct regcache *regcache,
+ gdb_gregset_t *gregs, int regnum)
+{
+ arc_linux_collect_gregset (NULL, regcache, regnum, gregs, 0);
+}
+
+/* Copy all the general purpose registers from regset GREGS into REGCACHE.
+ This function is exported to proc-service.c. */
+
+void
+supply_gregset (struct regcache *regcache, const gdb_gregset_t *gregs)
+{
+ arc_linux_supply_gregset (NULL, regcache, -1, gregs, 0);
+}
+
+/* ARC doesn't have separate FP registers. This function is exported
+ to proc-service.c. */
+
+void
+fill_fpregset (const struct regcache *regcache,
+ gdb_fpregset_t *fpregsetp, int regnum)
+{
+ if (arc_debug)
+ debug_printf ("arc-linux-nat: fill_fpregset called.");
+ return;
+}
+
+/* ARC doesn't have separate FP registers. This function is exported
+ to proc-service.c. */
+
+void
+supply_fpregset (struct regcache *regcache, const gdb_fpregset_t *fpregsetp)
+{
+ if (arc_debug)
+ debug_printf ("arc-linux-nat: supply_fpregset called.");
+ return;
+}
+
+/* Implement the "read_description" method of linux_nat_target. */
+
+const struct target_desc *
+arc_linux_nat_target::read_description ()
+{
+ /* This is a native target, hence description is hardcoded. */
+#ifdef __ARCHS__
+ arc_arch_features features (4, ARC_ISA_ARCV2);
+#else
+ arc_arch_features features (4, ARC_ISA_ARCV1);
+#endif
+ return arc_lookup_target_description (features);
+}
+
+/* As described in arc_linux_collect_gregset(), we need to write resume-PC
+ to ERET. However by default GDB for native targets doesn't write
+ registers if they haven't been changed. This is a callback called by
+ generic GDB, and in this callback we have to rewrite PC value so it
+ would force rewrite of register on target. It seems that the only
+ other arch that utilizes this hook is x86/x86-64 for HW breakpoint
+ support. But then, AFAIK no other arch has this stop_pc/eret
+ complexity.
+
+ No better way was found, other than this fake write of register value,
+ to force GDB into writing register to target. Is there any? */
+
+void
+arc_linux_nat_target::low_prepare_to_resume (struct lwp_info *lwp)
+{
+ /* When new processes and threads are created we do not have the address
+ space for them and calling get_thread_regcache will cause an internal
+ error in GDB. It looks like that checking for last_resume_kind is the
+ sensible way to determine processes for which we cannot get regcache.
+ Ultimately, a better way would be removing the need for
+ low_prepare_to_resume in the first place. */
+ if (lwp->last_resume_kind == resume_stop)
+ return;
+
+ struct regcache *regcache = get_thread_regcache (this, lwp->ptid);
+ struct gdbarch *gdbarch = regcache->arch ();
+
+ /* Read current PC value, then write it back. It is required to call
+ invalidate(), otherwise GDB will note that new value is equal to old
+ value and will skip write. */
+ ULONGEST new_pc;
+ regcache_cooked_read_unsigned (regcache, gdbarch_pc_regnum (gdbarch),
+ &new_pc);
+ regcache->invalidate (gdbarch_pc_regnum (gdbarch));
+ regcache_cooked_write_unsigned (regcache, gdbarch_pc_regnum (gdbarch),
+ new_pc);
+}
+
+/* Fetch the thread-local storage pointer for libthread_db. Note that
+ this function is not called from GDB, but is called from libthread_db.
+ This is required to debug multithreaded applications with NPTL. */
+
+ps_err_e
+ps_get_thread_area (struct ps_prochandle *ph, lwpid_t lwpid, int idx,
+ void **base)
+{
+ if (arc_debug >= 2)
+ debug_printf ("arc-linux-nat: ps_get_thread_area called");
+
+ if (ptrace (PTRACE_GET_THREAD_AREA, lwpid, NULL, base) != 0)
+ return PS_ERR;
+
+ /* IDX is the bias from the thread pointer to the beginning of the
+ thread descriptor. It has to be subtracted due to implementation
+ quirks in libthread_db. */
+ *base = (void *) ((char *) *base - idx);
+
+ return PS_OK;
+}
+
+/* Suppress warning from -Wmissing-prototypes. */
+void _initialize_arc_linux_nat (void);
+
+void
+_initialize_arc_linux_nat (void)
+{
+ /* Register the target. */
+ linux_target = &the_arc_linux_nat_target;
+ add_inf_child_target (&the_arc_linux_nat_target);
+}
diff --git a/gdb/configure.host b/gdb/configure.host
index ce528237291..e94a19b0332 100644
--- a/gdb/configure.host
+++ b/gdb/configure.host
@@ -60,6 +60,7 @@ case "${host_cpu}" in
aarch64*) gdb_host_cpu=aarch64 ;;
alpha*) gdb_host_cpu=alpha ;;
+arc*) gdb_host_cpu=arc ;;
arm*) gdb_host_cpu=arm ;;
hppa*) gdb_host_cpu=pa ;;
i[34567]86*) gdb_host_cpu=i386 ;;
@@ -91,6 +92,8 @@ alpha*-*-netbsd* | alpha*-*-knetbsd*-gnu)
gdb_host=nbsd ;;
alpha*-*-openbsd*) gdb_host=nbsd ;;
+arc*-*-linux*) gdb_host=linux ;;
+
arm*-*-freebsd*) gdb_host=fbsd ;;
arm*-*-linux*) gdb_host=linux ;;
arm*-*-netbsdelf* | arm*-*-knetbsd*-gnu)
diff --git a/gdb/configure.nat b/gdb/configure.nat
index ef2218f0b8d..0e36e09b692 100644
--- a/gdb/configure.nat
+++ b/gdb/configure.nat
@@ -238,6 +238,10 @@ case ${gdb_host} in
nat/aarch64-linux.o \
nat/aarch64-sve-linux-ptrace.o"
;;
+ arc)
+ # Host: ARC based machine running GNU/Linux
+ NATDEPFILES="${NATDEPFILES} arc-linux-nat.o"
+ ;;
arm)
# Host: ARM based machine running GNU/Linux
NATDEPFILES="${NATDEPFILES} arm-linux-nat.o \
--
2.29.2
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