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In the context of ROCm-gdb [1], the ROCm target sits on top of the linux-nat target. when a process forks, it needs to carry over some data from the forking inferior to the fork child inferior. Ideally, the ROCm target would implement the follow_fork target_ops method, but there are some small problems. This patch fixes these, which helps the ROCm target, but also makes things more consistent and a bit nicer in general, I believe. The main problem is: when follow-fork-mode is "parent", target_follow_fork is called with the parent as the current inferior. When it's "child", target_follow_fork is called with the child as the current inferior. This means that target_follow_fork is sometimes called on the parent's target stack and sometimes on the child's target stack. The parent's target stack may contain targets above the process target, such as the ROCm target. So if follow-fork-child is "parent", the ROCm target would get notified of the fork and do whatever is needed. But the child's target stack, at that moment, only contains the exec and process target copied over from the parent. The child's target stack is set up by follow_fork_inferior, before calling target_follow_fork. In that case, the ROCm target wouldn't get notified of the fork. For consistency, I think it would be good to always call target_follow_fork on the parent inferior's target stack. I think it makes sense as a way to indicate "this inferior has called fork, do whatever is needed". The desired outcome of the fork (whether an inferior is created for the child, do we need to detach from the child) can be indicated by passed parameter. I therefore propose these changes: - make follow_fork_inferior always call target_follow_fork with the parent as the current inferior. That lets all targets present on the parent's target stack do some fork-related handling and push themselves on the fork child's target stack if needed. For this purpose, pass the child inferior down to target_follow_fork and follow_fork implementations. This is nullptr if no inferior is created for the child, because we want to detach from it. - as a result, in follow_fork_inferior, detach from the parent inferior (if needed) only after the target_follow_fork call. This is needed because we want to call target_follow_fork before the parent's target stack is torn down. - hand over to the targets in the parent's target stack (including the process target) the responsibility to push themselves, if needed, to the child's target stack. Also hand over the responsibility to the process target, at the same time, to create the child's initial thread (just like we do for follow_exec). - pass the child inferior to exec_on_vfork, so we don't need to swap the current inferior between parent and child. Nothing in exec_on_vfork depends on the current inferior, after this change. Although this could perhaps be replaced with just having the exec target implement follow_fork and push itself in the child's target stack, like the process target does... We would just need to make sure the process target calls beneath()->follow_fork(...). I'm not sure about this one. gdb/ChangeLog: * target.h (struct target_ops) <follow_fork>: Add inferior* parameter. (target_follow_fork): Likewise. * target.c (default_follow_fork): Likewise. (target_follow_fork): Likewise. * fbsd-nat.h (class fbsd_nat_target) <follow_fork>: Likewise. (fbsd_nat_target::follow_fork): Likewise, and call inf_ptrace_target::follow_fork. * linux-nat.h (class linux_nat_target) <follow_fork>: Likewise. * linux-nat.c (linux_nat_target::follow_fork): Likewise, and call inf_ptrace_target::follow_fork. * obsd-nat.h (obsd_nat_target) <follow_fork>: Likewise. * obsd-nat.c (obsd_nat_target::follow_fork): Likewise, and call inf_ptrace_target::follow_fork. * remote.c (class remote_target) <follow_fork>: Likewise. (remote_target::follow_fork): Likewise, and call process_stratum_target::follow_fork. * process-stratum-target.h (class process_stratum_target) <follow_fork>: New. * process-stratum-target.c (process_stratum_target::follow_fork): New. * target-delegates.c: Re-generate. [1] https://github.com/ROCm-Developer-Tools/ROCgdb Change-Id: I460bd0af850f0485e8aed4b24c6d8262a4c69929
109 lines
3.9 KiB
C
109 lines
3.9 KiB
C
/* Work with executable files, for GDB, the GNU debugger.
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Copyright (C) 2003-2021 Free Software Foundation, Inc.
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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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#ifndef EXEC_H
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#define EXEC_H
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#include "target.h"
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#include "progspace.h"
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#include "memrange.h"
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#include "symfile-add-flags.h"
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struct target_section;
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struct target_ops;
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struct bfd;
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struct objfile;
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/* Builds a section table, given args BFD. */
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extern target_section_table build_section_table (struct bfd *);
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/* VFORK_CHILD is a child vforked and its program space is shared with its
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parent. This pushes the exec target on that inferior's target stack if
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there are sections in the program space's section table. */
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extern void exec_on_vfork (inferior *vfork_child);
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/* Read from mappable read-only sections of BFD executable files.
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Return TARGET_XFER_OK, if read is successful. Return
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TARGET_XFER_EOF if read is done. Return TARGET_XFER_E_IO
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otherwise. */
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extern enum target_xfer_status
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exec_read_partial_read_only (gdb_byte *readbuf, ULONGEST offset,
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ULONGEST len, ULONGEST *xfered_len);
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/* Read or write from mappable sections of BFD executable files.
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Request to transfer up to LEN 8-bit bytes of the target sections
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defined by SECTIONS and SECTIONS_END. The OFFSET specifies the
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starting address.
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The MATCH_CB predicate is optional; when provided it will be called
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for each section under consideration. When MATCH_CB evaluates as
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true, the section remains under consideration; a false result
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removes it from consideration for performing the memory transfers
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noted above. See memory_xfer_partial_1() in target.c for an
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example.
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Return the number of bytes actually transfered, or zero when no
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data is available for the requested range.
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This function is intended to be used from target_xfer_partial
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implementations. See target_read and target_write for more
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information.
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One, and only one, of readbuf or writebuf must be non-NULL. */
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extern enum target_xfer_status
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section_table_xfer_memory_partial (gdb_byte *,
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const gdb_byte *,
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ULONGEST, ULONGEST, ULONGEST *,
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const target_section_table &,
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gdb::function_view<bool
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(const struct target_section *)> match_cb
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= nullptr);
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/* Read from mappable read-only sections of BFD executable files.
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Similar to exec_read_partial_read_only, but return
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TARGET_XFER_UNAVAILABLE if data is unavailable. */
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extern enum target_xfer_status
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section_table_read_available_memory (gdb_byte *readbuf, ULONGEST offset,
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ULONGEST len, ULONGEST *xfered_len);
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/* Set the loaded address of a section. */
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extern void exec_set_section_address (const char *, int, CORE_ADDR);
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/* Prints info about all sections defined in the TABLE. ABFD is
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special cased --- it's filename is omitted; if it is the executable
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file, its entry point is printed. */
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extern void print_section_info (const target_section_table *table,
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bfd *abfd);
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/* Helper function that attempts to open the symbol file at EXEC_FILE_HOST.
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If successful, it proceeds to add the symbol file as the main symbol file.
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ADD_FLAGS is passed on to the function adding the symbol file. */
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extern void try_open_exec_file (const char *exec_file_host,
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struct inferior *inf,
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symfile_add_flags add_flags);
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#endif
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