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binutils-gdb/gdb/elf-none-tdep.c

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gdb/riscv: introduce bare metal core dump support This commit adds the ability for bare metal RISC-V target to generate core files from within GDB. The intended use case is that a user will connect to a remote bare metal target, debug up to some error condition, then generate a core file in the normal way using: (gdb) generate-core-file This core file can then be used to revisit the state of the remote target without having to reconnect to the remote target. The core file creation code is split between two new files. In elf-none-tdep.c is code for any architecture with the none ABI (i.e. bare metal) when the BFD library is built with ELF support. In riscv-none-tdep.c are the RISC-V specific parts. This is where the regset and regcache_map_entry structures are defined that control how registers are laid out in the core file. As this file could (in theory at least) be used for a non-ELF bare metal RISC-V target, the calls into elf-none-tdep.c are guarded with '#ifdef HAVE_ELF'. Currently for RISC-V only the x-regs and f-regs (if present) are written out. In future commits I plan to add support for writing out the RISC-V CSRs. The core dump format is based around generating an ELF containing sections for the writable regions of memory that a user could be using. Which regions are dumped rely on GDB's existing common core dumping code, GDB will attempt to figure out the stack and heap as well as copying out writable data sections as identified by the original ELF. Register information is added to the core dump using notes, just as it is for Linux of FreeBSD core dumps. The note types used consist of the 3 basic types you would expect in a OS based core dump, NT_PRPSINFO, NT_PRSTATUS, NT_FPREGSET. The layout of these notes differs slightly (due to field sizes) between RV32 and RV64. Below I describe the data layout for each note. In all cases, all padding fields should be set to zero. Note NT_PRPSINFO is optional. Its data layout is: struct prpsinfo32_t /* For RV32. */ { uint8_t padding[32]; char fname[16]; char psargs[80]; } struct prpsinfo64_t /* For RV64. */ { uint8_t padding[40]; char fname[16]; char psargs[80]; } Field 'fname' - null terminated string consisting of the basename of (up to the fist 15 characters of) the executable. Any additional space should be set to zero. If there's no executable name then this field can be set to all zero. Field 'psargs' - a null terminated string up to 80 characters in length. Any additional space should be filled with zero. This field contains the full executable path and any arguments passed to the executable. If there's nothing sensible to write in this field then fill it with zero. Note NT_PRSTATUS is required, its data layout is: struct prstatus32_t /* For RV32. */ { uint8_t padding_1[12]; uint16_t sig; uint8_t padding_2[10]; uint32_t thread_id; uint8_t padding_3[44]; uint32_t x_regs[32]; uint8_t padding_4[4]; } struct prstatus64_t /* For RV64. */ { uint8_t padding_1[12]; uint16_t sig; uint8_t padding_2[18]; uint32_t thread_id; uint8_t padding_3[76]; uint64_t x_regs[32]; uint8_t padding_4[4]; } Field 'sig' - the signal that stopped this thread. It's implementation defined what this field actually means. Within GDB this will be the signal number that the remote target reports as the stop reason for this thread. Field 'thread_is' - the thread id for this thread. It's implementation defined what this field actually means. Within GDB this will be thread thread-id that is assigned to each remote thread. Field 'x_regs' - at index 0 we store the program counter, and at indices 1 to 31 we store x-registers 1 to 31. x-register 0 is not stored, its value is always zero anyway. Note NT_FPREGSET is optional, its data layout is: fpregset32_t /* For targets with 'F' extension. */ { uint32_t f_regs[32]; uint32_t fcsr; } fpregset64_t /* For targets with 'D' extension . */ { uint64_t f_regs[32]; uint32_t fcsr; } Field 'f_regs' - stores f-registers 0 to 31. Field 'fcsr' - stores the fcsr CSR register, and is always 4-bytes. The rules for ordering the notes is the same as for Linux. The NT_PRSTATUS note must come before any other notes about additional register sets. And for multi-threaded targets all registers for a single thread should be grouped together. This is because only NT_PRSTATUS includes a thread-id, all additional register notes after a NT_PRSTATUS are assumed to belong to the same thread until a different NT_PRSTATUS is seen. gdb/ChangeLog: * Makefile.in (ALL_TARGET_OBS): Add riscv-none-tdep.o. (ALLDEPFILES): Add riscv-none-tdep.c. * configure: Regenerate. * configure.ac (CONFIG_OBS): Add elf-none-tdep.o when BFD has ELF support. * configure.tgt (riscv*-*-*): Include riscv-none-tdep.c. * elf-none-tdep.c: New file. * elf-none-tdep.h: New file. * riscv-none-tdep.c: New file.
2020-11-30 20:15:08 +08:00
/* Common code for targets with the none ABI (bare-metal), but where the
BFD library is build with ELF support.
Copyright (C) 2020-2021 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 "elf-none-tdep.h"
#include "regset.h"
#include "elf-bfd.h" /* for elfcore_write_* */
#include "inferior.h"
#include "regcache.h"
#include "gdbarch.h"
#include "gcore.h"
#include "gcore-elf.h"
/* Build the note section for a corefile, and return it in a malloc
buffer. Currently this just dumps all available registers for each
thread. */
static gdb::unique_xmalloc_ptr<char>
elf_none_make_corefile_notes (struct gdbarch *gdbarch, bfd *obfd,
int *note_size)
{
gdb::unique_xmalloc_ptr<char> note_data;
/* Add note information about the executable and its arguments. */
std::string fname;
std::string psargs;
static const size_t fname_len = 16;
static const size_t psargs_len = 80;
if (get_exec_file (0))
{
const char *exe = get_exec_file (0);
fname = lbasename (exe);
psargs = std::string (exe);
gdb: make inferior::m_args an std::string With the current code, both a NULL pointer and an empty string can mean "no arguments". We don't need this distinction. Changing to a string has the advantage that there is now a single state for that (an empty string), which makes the code a bit simpler in my opinion. Change-Id: Icdc622820f7869478791dbaa84b4a1c7fec21ced
2021-06-26 05:54:55 +08:00
const std::string &infargs = current_inferior ()->args ();
if (!infargs.empty ())
psargs += ' ' + infargs;
gdb/riscv: introduce bare metal core dump support This commit adds the ability for bare metal RISC-V target to generate core files from within GDB. The intended use case is that a user will connect to a remote bare metal target, debug up to some error condition, then generate a core file in the normal way using: (gdb) generate-core-file This core file can then be used to revisit the state of the remote target without having to reconnect to the remote target. The core file creation code is split between two new files. In elf-none-tdep.c is code for any architecture with the none ABI (i.e. bare metal) when the BFD library is built with ELF support. In riscv-none-tdep.c are the RISC-V specific parts. This is where the regset and regcache_map_entry structures are defined that control how registers are laid out in the core file. As this file could (in theory at least) be used for a non-ELF bare metal RISC-V target, the calls into elf-none-tdep.c are guarded with '#ifdef HAVE_ELF'. Currently for RISC-V only the x-regs and f-regs (if present) are written out. In future commits I plan to add support for writing out the RISC-V CSRs. The core dump format is based around generating an ELF containing sections for the writable regions of memory that a user could be using. Which regions are dumped rely on GDB's existing common core dumping code, GDB will attempt to figure out the stack and heap as well as copying out writable data sections as identified by the original ELF. Register information is added to the core dump using notes, just as it is for Linux of FreeBSD core dumps. The note types used consist of the 3 basic types you would expect in a OS based core dump, NT_PRPSINFO, NT_PRSTATUS, NT_FPREGSET. The layout of these notes differs slightly (due to field sizes) between RV32 and RV64. Below I describe the data layout for each note. In all cases, all padding fields should be set to zero. Note NT_PRPSINFO is optional. Its data layout is: struct prpsinfo32_t /* For RV32. */ { uint8_t padding[32]; char fname[16]; char psargs[80]; } struct prpsinfo64_t /* For RV64. */ { uint8_t padding[40]; char fname[16]; char psargs[80]; } Field 'fname' - null terminated string consisting of the basename of (up to the fist 15 characters of) the executable. Any additional space should be set to zero. If there's no executable name then this field can be set to all zero. Field 'psargs' - a null terminated string up to 80 characters in length. Any additional space should be filled with zero. This field contains the full executable path and any arguments passed to the executable. If there's nothing sensible to write in this field then fill it with zero. Note NT_PRSTATUS is required, its data layout is: struct prstatus32_t /* For RV32. */ { uint8_t padding_1[12]; uint16_t sig; uint8_t padding_2[10]; uint32_t thread_id; uint8_t padding_3[44]; uint32_t x_regs[32]; uint8_t padding_4[4]; } struct prstatus64_t /* For RV64. */ { uint8_t padding_1[12]; uint16_t sig; uint8_t padding_2[18]; uint32_t thread_id; uint8_t padding_3[76]; uint64_t x_regs[32]; uint8_t padding_4[4]; } Field 'sig' - the signal that stopped this thread. It's implementation defined what this field actually means. Within GDB this will be the signal number that the remote target reports as the stop reason for this thread. Field 'thread_is' - the thread id for this thread. It's implementation defined what this field actually means. Within GDB this will be thread thread-id that is assigned to each remote thread. Field 'x_regs' - at index 0 we store the program counter, and at indices 1 to 31 we store x-registers 1 to 31. x-register 0 is not stored, its value is always zero anyway. Note NT_FPREGSET is optional, its data layout is: fpregset32_t /* For targets with 'F' extension. */ { uint32_t f_regs[32]; uint32_t fcsr; } fpregset64_t /* For targets with 'D' extension . */ { uint64_t f_regs[32]; uint32_t fcsr; } Field 'f_regs' - stores f-registers 0 to 31. Field 'fcsr' - stores the fcsr CSR register, and is always 4-bytes. The rules for ordering the notes is the same as for Linux. The NT_PRSTATUS note must come before any other notes about additional register sets. And for multi-threaded targets all registers for a single thread should be grouped together. This is because only NT_PRSTATUS includes a thread-id, all additional register notes after a NT_PRSTATUS are assumed to belong to the same thread until a different NT_PRSTATUS is seen. gdb/ChangeLog: * Makefile.in (ALL_TARGET_OBS): Add riscv-none-tdep.o. (ALLDEPFILES): Add riscv-none-tdep.c. * configure: Regenerate. * configure.ac (CONFIG_OBS): Add elf-none-tdep.o when BFD has ELF support. * configure.tgt (riscv*-*-*): Include riscv-none-tdep.c. * elf-none-tdep.c: New file. * elf-none-tdep.h: New file. * riscv-none-tdep.c: New file.
2020-11-30 20:15:08 +08:00
/* All existing targets that handle writing out prpsinfo expect the
fname and psargs strings to be at least 16 and 80 characters long
respectively, including a null terminator at the end. Resize to
the expected length minus one to ensure there is a null within the
required length. */
fname.resize (fname_len - 1);
psargs.resize (psargs_len - 1);
}
/* Resize the buffers up to their required lengths. This will fill any
remaining space with the null character. */
fname.resize (fname_len);
psargs.resize (psargs_len);
/* Now write out the prpsinfo structure. */
note_data.reset (elfcore_write_prpsinfo (obfd, note_data.release (),
note_size, fname.c_str (),
psargs.c_str ()));
if (note_data == nullptr)
return nullptr;
/* Thread register information. */
try
{
update_thread_list ();
}
catch (const gdb_exception_error &e)
{
exception_print (gdb_stderr, e);
}
/* Like the Linux kernel, prefer dumping the signalled thread first.
"First thread" is what tools use to infer the signalled thread. */
thread_info *signalled_thr = gcore_find_signalled_thread ();
/* All threads are reported as having been stopped by the same signal
that stopped SIGNALLED_THR. */
gdb_signal stop_signal;
if (signalled_thr != nullptr)
gdb: make thread_info::suspend private, add getters / setters A following patch will want to take some action when a pending wait status is set on or removed from a thread. Add a getter and a setter on thread_info for the pending waitstatus, so that we can add some code in the setter later. The thing is, the pending wait status field is in the thread_suspend_state, along with other fields that we need to backup before and restore after the thread does an inferior function call. Therefore, make the thread_suspend_state member private (thread_info::suspend becomes thread_info::m_suspend), and add getters / setters for all of its fields: - pending wait status - stop signal - stop reason - stop pc For the pending wait status, add the additional has_pending_waitstatus and clear_pending_waitstatus methods. I think this makes the thread_info interface a bit nicer, because we now access the fields as: thread->stop_pc () rather than thread->suspend.stop_pc The stop_pc field being in the `suspend` structure is an implementation detail of thread_info that callers don't need to be aware of. For the backup / restore of the thread_suspend_state structure, add save_suspend_to and restore_suspend_from methods. You might wonder why `save_suspend_to`, as opposed to a simple getter like thread_suspend_state &suspend (); I want to make it clear that this is to be used only for backing up and restoring the suspend state, _not_ to access fields like: thread->suspend ()->stop_pc Adding some getters / setters allows adding some assertions. I find that this helps understand how things are supposed to work. Add: - When getting the pending status (pending_waitstatus method), ensure that there is a pending status. - When setting a pending status (set_pending_waitstatus method), ensure there is no pending status. There is one case I found where this wasn't true - in remote_target::process_initial_stop_replies - which needed adjustments to respect that contract. I think it's because process_initial_stop_replies is kind of (ab)using the thread_info::suspend::waitstatus to store some statuses temporarily, for its internal use (statuses it doesn't intent on leaving pending). process_initial_stop_replies pulls out stop replies received during the initial connection using target_wait. It always stores the received event in `evthread->suspend.waitstatus`. But it only sets waitstatus_pending_p, if it deems the event interesting enough to leave pending, to be reported to the core: if (ws.kind != TARGET_WAITKIND_STOPPED || ws.value.sig != GDB_SIGNAL_0) evthread->suspend.waitstatus_pending_p = 1; It later uses this flag a bit below, to choose which thread to make the "selected" one: if (selected == NULL && thread->suspend.waitstatus_pending_p) selected = thread; And ultimately that's used if the user-visible mode is all-stop, so that we print the stop for that interesting thread: /* In all-stop, we only print the status of one thread, and leave others with their status pending. */ if (!non_stop) { thread_info *thread = selected; if (thread == NULL) thread = lowest_stopped; if (thread == NULL) thread = first; print_one_stopped_thread (thread); } But in any case (all-stop or non-stop), print_one_stopped_thread needs to access the waitstatus value of these threads that don't have a pending waitstatus (those that had TARGET_WAITKIND_STOPPED + GDB_SIGNAL_0). This doesn't work with the assertions I've put. So, change the code to only set the thread's wait status if it is an interesting one that we are going to leave pending. If the thread stopped due to a non-interesting event (TARGET_WAITKIND_STOPPED + GDB_SIGNAL_0), don't store it. Adjust print_one_stopped_thread to understand that if a thread has no pending waitstatus, it's because it stopped with TARGET_WAITKIND_STOPPED + GDB_SIGNAL_0. The call to set_last_target_status also uses the pending waitstatus. However, given that the pending waitstatus for the thread may have been cleared in print_one_stopped_thread (and that there might not even be a pending waitstatus in the first place, as explained above), it is no longer possible to do it at this point. To fix that, move the call to set_last_target_status in print_one_stopped_thread. I think this will preserve the existing behavior, because set_last_target_status is currently using the current thread's wait status. And the current thread is the last one for which print_one_stopped_thread is called. So by calling set_last_target_status in print_one_stopped_thread, we'll get the same result. set_last_target_status will possibly be called multiple times, but only the last call will matter. It just means possibly more calls to set_last_target_status, but those are cheap. Change-Id: Iedab9653238eaf8231abcf0baa20145acc8b77a7
2021-05-28 11:37:03 +08:00
stop_signal = signalled_thr->stop_signal ();
gdb/riscv: introduce bare metal core dump support This commit adds the ability for bare metal RISC-V target to generate core files from within GDB. The intended use case is that a user will connect to a remote bare metal target, debug up to some error condition, then generate a core file in the normal way using: (gdb) generate-core-file This core file can then be used to revisit the state of the remote target without having to reconnect to the remote target. The core file creation code is split between two new files. In elf-none-tdep.c is code for any architecture with the none ABI (i.e. bare metal) when the BFD library is built with ELF support. In riscv-none-tdep.c are the RISC-V specific parts. This is where the regset and regcache_map_entry structures are defined that control how registers are laid out in the core file. As this file could (in theory at least) be used for a non-ELF bare metal RISC-V target, the calls into elf-none-tdep.c are guarded with '#ifdef HAVE_ELF'. Currently for RISC-V only the x-regs and f-regs (if present) are written out. In future commits I plan to add support for writing out the RISC-V CSRs. The core dump format is based around generating an ELF containing sections for the writable regions of memory that a user could be using. Which regions are dumped rely on GDB's existing common core dumping code, GDB will attempt to figure out the stack and heap as well as copying out writable data sections as identified by the original ELF. Register information is added to the core dump using notes, just as it is for Linux of FreeBSD core dumps. The note types used consist of the 3 basic types you would expect in a OS based core dump, NT_PRPSINFO, NT_PRSTATUS, NT_FPREGSET. The layout of these notes differs slightly (due to field sizes) between RV32 and RV64. Below I describe the data layout for each note. In all cases, all padding fields should be set to zero. Note NT_PRPSINFO is optional. Its data layout is: struct prpsinfo32_t /* For RV32. */ { uint8_t padding[32]; char fname[16]; char psargs[80]; } struct prpsinfo64_t /* For RV64. */ { uint8_t padding[40]; char fname[16]; char psargs[80]; } Field 'fname' - null terminated string consisting of the basename of (up to the fist 15 characters of) the executable. Any additional space should be set to zero. If there's no executable name then this field can be set to all zero. Field 'psargs' - a null terminated string up to 80 characters in length. Any additional space should be filled with zero. This field contains the full executable path and any arguments passed to the executable. If there's nothing sensible to write in this field then fill it with zero. Note NT_PRSTATUS is required, its data layout is: struct prstatus32_t /* For RV32. */ { uint8_t padding_1[12]; uint16_t sig; uint8_t padding_2[10]; uint32_t thread_id; uint8_t padding_3[44]; uint32_t x_regs[32]; uint8_t padding_4[4]; } struct prstatus64_t /* For RV64. */ { uint8_t padding_1[12]; uint16_t sig; uint8_t padding_2[18]; uint32_t thread_id; uint8_t padding_3[76]; uint64_t x_regs[32]; uint8_t padding_4[4]; } Field 'sig' - the signal that stopped this thread. It's implementation defined what this field actually means. Within GDB this will be the signal number that the remote target reports as the stop reason for this thread. Field 'thread_is' - the thread id for this thread. It's implementation defined what this field actually means. Within GDB this will be thread thread-id that is assigned to each remote thread. Field 'x_regs' - at index 0 we store the program counter, and at indices 1 to 31 we store x-registers 1 to 31. x-register 0 is not stored, its value is always zero anyway. Note NT_FPREGSET is optional, its data layout is: fpregset32_t /* For targets with 'F' extension. */ { uint32_t f_regs[32]; uint32_t fcsr; } fpregset64_t /* For targets with 'D' extension . */ { uint64_t f_regs[32]; uint32_t fcsr; } Field 'f_regs' - stores f-registers 0 to 31. Field 'fcsr' - stores the fcsr CSR register, and is always 4-bytes. The rules for ordering the notes is the same as for Linux. The NT_PRSTATUS note must come before any other notes about additional register sets. And for multi-threaded targets all registers for a single thread should be grouped together. This is because only NT_PRSTATUS includes a thread-id, all additional register notes after a NT_PRSTATUS are assumed to belong to the same thread until a different NT_PRSTATUS is seen. gdb/ChangeLog: * Makefile.in (ALL_TARGET_OBS): Add riscv-none-tdep.o. (ALLDEPFILES): Add riscv-none-tdep.c. * configure: Regenerate. * configure.ac (CONFIG_OBS): Add elf-none-tdep.o when BFD has ELF support. * configure.tgt (riscv*-*-*): Include riscv-none-tdep.c. * elf-none-tdep.c: New file. * elf-none-tdep.h: New file. * riscv-none-tdep.c: New file.
2020-11-30 20:15:08 +08:00
else
stop_signal = GDB_SIGNAL_0;
if (signalled_thr != nullptr)
gcore_elf_build_thread_register_notes (gdbarch, signalled_thr,
stop_signal, obfd, &note_data,
note_size);
for (thread_info *thr : current_inferior ()->non_exited_threads ())
{
if (thr == signalled_thr)
continue;
gcore_elf_build_thread_register_notes (gdbarch, thr, stop_signal, obfd,
&note_data, note_size);
}
/* Target description. */
gcore_elf_make_tdesc_note (obfd, &note_data, note_size);
return note_data;
}
/* See none-tdep.h. */
void
elf_none_init_abi (struct gdbarch *gdbarch)
{
/* Default core file support. */
set_gdbarch_make_corefile_notes (gdbarch, elf_none_make_corefile_notes);
}
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