I recently stumbled on this code mentioning Linux kernel 2.6.25, and
thought it could be time for some spring cleaning (newer GDBs probably
don't need to supports 12-year old kernels). I then found that the
"legacy" case is probably broken anyway, which gives an even better
motivation for its removal.
In short, this patch removes the configure checks that check if
user_regs_struct contains the fs_base/gs_base fields and adjusts all
uses of the HAVE_STRUCT_USER_REGS_STRUCT_{FS,GS}_BASE macros. The
longer explanation/rationale follows.
Apparently, Linux kernels since 2.6.25 (that's from 2008) have been
reliably providing fs_base and gs_base as part of user_regs_struct.
Commit df5d438e33d7 in the Linux kernel [1] seems related. This means
that we can get these values by reading registers with PTRACE_GETREGS.
Previously, these values were obtained using a separate
PTRACE_ARCH_PRCTL ptrace call.
First, I'm not even sure the configure check was really right in the
first place.
The user_regs_struct used by GDB comes from
/usr/include/x86_64-linux-gnu/sys/user.h (or equivalent on other
distros) and is provided by glibc. glibc has had the fs_base/gs_base
fields in there for a very long time, at least since this commit from
2001 [2]. The Linux kernel also has its version of user_regs_struct,
which I think was exported to user-space at some point. It included the
fs_base/gs_base fields since at least this 2002 commit [3]. In any
case, my conclusion is that the fields were there long before the
aforementioned Linux kernel commit. The kernel commit didn't add these
fields, it only made sure that they have reliable values when obtained
with PTRACE_GETREGS.
So, checking for the presence of the fs_base/gs_base fields in struct
user_regs_struct doesn't sound like a good way of knowing if we can
reliably get the fs_base/gs_base values from PTRACE_GETREGS. My guess
is that if we were using that strategy on a < 2.6.25 kernel, things
would not work correctly:
- configure would find that the user_regs_struct has the fs_base/gs_base
fields (which are probided by glibc anyway)
- we would be reading the fs_base/gs_base values using PTRACE_GETREGS,
for which the kernel would provide unreliable values
Second, I have tried to see how things worked by forcing GDB to not use
fs_base/gs_base from PTRACE_GETREGS (forcing it to use the "legacy"
code, by configuring with
ac_cv_member_struct_user_regs_struct_gs_base=no ac_cv_member_struct_user_regs_struct_fs_base=no
Doing so breaks writing registers back to the inferior. For example,
calling an inferior functions gives an internal error:
(gdb) p malloc(10)
/home/smarchi/src/binutils-gdb/gdb/i387-tdep.c:1408: internal-error: invalid i387 regnum 152
The relevant last frames where this error happens are:
#8 0x0000563123d262fc in internal_error (file=0x563123e93fd8 "/home/smarchi/src/binutils-gdb/gdb/i387-tdep.c", line=1408, fmt=0x563123e94482 "invalid i387 regnum %d") at /home/smarchi/src/binutils-gdb/gdbsupport/errors.cc:55
#9 0x0000563123047d0d in i387_collect_xsave (regcache=0x5631269453f0, regnum=152, xsave=0x7ffd38402a20, gcore=0) at /home/smarchi/src/binutils-gdb/gdb/i387-tdep.c:1408
#10 0x0000563122c69e8a in amd64_collect_xsave (regcache=0x5631269453f0, regnum=152, xsave=0x7ffd38402a20, gcore=0) at /home/smarchi/src/binutils-gdb/gdb/amd64-tdep.c:3448
#11 0x0000563122c5e94c in amd64_linux_nat_target::store_registers (this=0x56312515fd10 <the_amd64_linux_nat_target>, regcache=0x5631269453f0, regnum=152) at /home/smarchi/src/binutils-gdb/gdb/amd64-linux-nat.c:335
#12 0x00005631234c8c80 in target_store_registers (regcache=0x5631269453f0, regno=152) at /home/smarchi/src/binutils-gdb/gdb/target.c:3485
#13 0x00005631232e8df7 in regcache::raw_write (this=0x5631269453f0, regnum=152, buf=0x56312759e468 "@\225\372\367\377\177") at /home/smarchi/src/binutils-gdb/gdb/regcache.c:765
#14 0x00005631232e8f0c in regcache::cooked_write (this=0x5631269453f0, regnum=152, buf=0x56312759e468 "@\225\372\367\377\177") at /home/smarchi/src/binutils-gdb/gdb/regcache.c:778
#15 0x00005631232e75ec in regcache::restore (this=0x5631269453f0, src=0x5631275eb130) at /home/smarchi/src/binutils-gdb/gdb/regcache.c:283
#16 0x0000563123083fc4 in infcall_suspend_state::restore (this=0x5631273ed930, gdbarch=0x56312718cf20, tp=0x5631270bca90, regcache=0x5631269453f0) at /home/smarchi/src/binutils-gdb/gdb/infrun.c:9103
#17 0x0000563123081eed in restore_infcall_suspend_state (inf_state=0x5631273ed930) at /home/smarchi/src/binutils-gdb/gdb/infrun.c:9151
The problem seems to be that amd64_linux_nat_target::store_registers
calls amd64_native_gregset_supplies_p to know whether gregset provides
fs_base. When !HAVE_STRUCT_USER_REGS_STRUCT_FS_BASE,
amd64_native_gregset_supplies_p returns false. store_registers
therefore assumes that it must be an "xstate" register. This is of
course wrong, and that leads to the failed assertion when
i387_collect_xsave doesn't recognize the register.
amd64_linux_nat_target::store_registers could probably be fixed to
handle this case, but I don't think it's worth it, given that it would
only be to support very old kernels.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=df5d438e33d7fc914ba9b6e0d6b019a8966c5fcc
[2] https://sourceware.org/git/?p=glibc.git;a=commit;h=c9cf6ddeebb7bb
[3] https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=88e4bc32686ebd0b1111a94f93eba2d334241f68
gdb/ChangeLog:
* configure.ac: Remove check for fs_base/gs_base in
user_regs_struct.
* configure: Re-generate.
* config.in: Re-generate.
* amd64-nat.c (amd64_native_gregset_reg_offset): Adjust.
* amd64-linux-nat.c (amd64_linux_nat_target::fetch_registers,
amd64_linux_nat_target::store_registers, ps_get_thread_area, ): Adjust.
gdbserver/ChangeLog:
* configure.ac: Remove check for fs_base/gs_base in
user_regs_struct.
* configure: Re-generate.
* config.in: Re-generate.
* linux-x86-low.cc (x86_64_regmap, x86_fill_gregset,
x86_store_gregset): Adjust.
This changes the gdbserver build to use the gdbsupport that was built
for gdb.
gdbserver and gdbreplay now must use WIN32APILIBS (aka -lws2_32).
Before this change, gdbserver did not define USE_WIN32API when
building gdbsupport, but now this is always done.
ChangeLog
2020-03-12 Tom Tromey <tom@tromey.com>
* Makefile.in: Rebuild.
* Makefile.def (gdbserver): Depend on gdbsupport.
gdbserver/ChangeLog
2020-03-12 Tom Tromey <tom@tromey.com>
* configure: Rebuild.
* configure.ac (GDBSERVER_DEPFILES): Remove srv_selftest_objs.
(WIN32APILIBS): New subst.
* Makefile.in (SFILES, OBS, TAGS, GDBREPLAY_OBS): Remove
gdbsupport files.
(gdbsupport/%.o): Remove target.
(GDBSUPPORT_BUILDDIR, GDBSUPPORT): New variables.
(gdbserver$(EXEEXT), gdbreplay$(EXEEXT)): Add GDBSUPPORT.
(WIN32APILIBS): New variable.
(gdbserver$(EXEEXT)): Add WIN32APILIBS.
(gdbreplay$(EXEEXT)): Likewise.
gdbserver uses gdb's alloc.c, and this in turn can include headers
from intl via gdbsupport/gdb_locale.h. This can cause build failures
in some situations, for example if you build gdb and gdbserver on
mingw.
This patch restores the gdbsupport dependency on intl, and changes
gdbserver to use ZW_GNU_GETTEXT_SISTER_DIR. This fixes this build
problem.
ChangeLog
2020-03-12 Tom Tromey <tom@tromey.com>
* Makefile.in: Rebuild.
* Makefile.def (gdbsupport): Depend on intl.
gdbserver/ChangeLog
2020-03-12 Tom Tromey <tom@tromey.com>
* config.in, configure: Rebuild.
* configure.ac: Call ZW_GNU_GETTEXT_SISTER_DIR.
* acinclude.m4: Include gettext-sister.m4.
* Makefile.in (top_builddir, INTL, INTL_DEPS, INTL_CFLAGS): New
variables.
(INCLUDE_CFLAGS): Add INTL_CFLAGS.
(gdbserver$(EXEEXT), gdbreplay$(EXEEXT)): Use INTL_DEPS, INTL.
The same is done for gdb, gdbserver and gdbsupport. I therefore think
it makes sense to move that to GDB_AC_COMMON.
It is required to move the call to GDB_AC_COMMON so it is before
GDB_AC_SELFTEST in gdbserver/configure.ac, otherwise the $development
variable isn't set when the code behind GDB_AC_SELFTEST executes.
gdb/ChangeLog:
* configure.ac: Don't source bfd/development.sh.
* selftest.m4: Modify comment.
* configure: Re-generate.
gdbserver/ChangeLog:
* configure.ac: Don't source bfd/development.sh, move
GDB_AC_COMMON higher.
* configure: Re-generate.
gdbsupport/ChangeLog:
* configure.ac: Don't source bfd/development.sh.
* common.m4: Source bfd/development.sh.
* configure: Re-generate.
This changes gdbserver so that it no longer builds its own gnulib and
libiberty. Instead, it now relies on the ones that were already built
at the top level.
gdbsupport is still built specially for gdbserver. This is more
complicated and will be tackled in a subsequent patch.
ChangeLog
2020-02-14 Tom Tromey <tom@tromey.com>
* Makefile.in: Rebuild.
* Makefile.def: Make gdbserver require gnulib and libiberty.
gdbserver/ChangeLog
2020-02-14 Tom Tromey <tom@tromey.com>
* acinclude.m4: Don't include acx_configure_dir.m4.
* Makefile.in (LIBIBERTY_BUILDDIR, GNULIB_BUILDDIR): Update.
(SUBDIRS, CLEANDIRS, REQUIRED_SUBDIRS): Remove.
(all, install-only, uninstall, clean-info, clean)
(maintainer-clean): Don't recurse.
(subdir_do, all-lib): Remove.
($(LIBGNU) $(LIBIBERTY) $(GNULIB_H)): Remove rule.
(GNULIB_H): Remove.
(generated_files): Update.
($(GNULIB_BUILDDIR)/Makefile): Remove rule.
* configure: Rebuild.
* configure.ac: Don't configure gnulib or libiberty.
(GNULIB): Update.
gdbsupport/ChangeLog
2020-02-14 Tom Tromey <tom@tromey.com>
* common-defs.h: Change path to gnulib/config.h.
Change-Id: I469cbbf5db2ab37109c058e9e3a1e4f4dabdfc98
For the same reasons outlined in the previous patch, this patch renames
gdbserver source files to .cc.
I have moved the "-x c++" switch to only those rules that require it.
gdbserver/ChangeLog:
* Makefile.in: Rename source files from .c to .cc.
* %.c: Rename to %.cc.
* configure.ac: Rename server.c to server.cc.
* configure: Re-generate.
This patch moves gdbserver to the top level.
This patch is as close to a pure move as possible -- gdbserver still
builds its own variant of gnulib and gdbsupport. Changing this will
be done in a separate patch.
[v2] Note that, per Simon's review comment, this patch changes the
tree so that gdbserver is not built for or1k or score. This makes
sense, because there is apparently not actually a gdbserver port here.
[v3] This version of the patch also splits out some configury into a
new file, gdbserver/configure.host, so that the top-level configure
script can simply rely on it in order to decide whether gdbserver
should be built.
[v4] This version adds documentation and removes some unnecessary
top-level dependencies.
[v5] Update docs to mention "make all-gdbserver" and change how
top-level configure decides whether to build gdbserver, switching to a
single, shared script.
Tested by the buildbot.
ChangeLog
2020-02-07 Tom Tromey <tom@tromey.com>
Pedro Alves <palves@redhat.com>
* src-release.sh (GDB_SUPPORT_DIRS): Add gdbserver.
* gdbserver: New directory, moved from gdb/gdbserver.
* configure.ac (host_tools): Add gdbserver.
Only build gdbserver on certain systems.
* Makefile.in, configure: Rebuild.
* Makefile.def (host_modules, dependencies): Add gdbserver.
* MAINTAINERS: Add gdbserver.
gdb/ChangeLog
2020-02-07 Tom Tromey <tom@tromey.com>
* README: Update gdbserver documentation.
* gdbserver: Move to top level.
* configure.tgt (build_gdbserver): Remove.
* configure.ac: Remove --enable-gdbserver.
* configure: Rebuild.
* Makefile.in (distclean): Don't mention gdbserver.
Change-Id: I826b7565b54604711dc7a11edea0499cd51ff39e
Simon Marchi
Tom Tromey