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Replace core.fsyncObjectFiles with two new configuration variables,
core.fsync and core.fsyncMethod.
* ns/core-fsyncmethod:
core.fsync: documentation and user-friendly aggregate options
core.fsync: new option to harden the index
core.fsync: add configuration parsing
core.fsync: introduce granular fsync control infrastructure
core.fsyncmethod: add writeout-only mode
wrapper: make inclusion of Windows csprng header tightly scoped
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The single-key interactive operation used by "git add -p" has been
made more robust.
* pw/single-key-interactive:
add -p: disable stdin buffering when interactive.singlekey is set
terminal: set VMIN and VTIME in non-canonical mode
terminal: pop signal handler when terminal is restored
terminal: always reset terminal when reading without echo
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This commit introduces the `core.fsyncMethod` configuration
knob, which can currently be set to `fsync` or `writeout-only`.
The new writeout-only mode attempts to tell the operating system to
flush its in-memory page cache to the storage hardware without issuing a
CACHE_FLUSH command to the storage controller.
Writeout-only fsync is significantly faster than a vanilla fsync on
common hardware, since data is written to a disk-side cache rather than
all the way to a durable medium. Later changes in this patch series will
take advantage of this primitive to implement batching of hardware
flushes.
When git_fsync is called with FSYNC_WRITEOUT_ONLY, it may fail and the
caller is expected to do an ordinary fsync as needed.
On Apple platforms, the fsync system call does not issue a CACHE_FLUSH
directive to the storage controller. This change updates fsync to do
fcntl(F_FULLFSYNC) to make fsync actually durable. We maintain parity
with existing behavior on Apple platforms by setting the default value
of the new core.fsyncMethod option.
Signed-off-by: Neeraj Singh <neerajsi@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Including NTSecAPI.h in git-compat-util.h causes build errors in any
other file that includes winternl.h. NTSecAPI.h was included in order to
get access to the RtlGenRandom cryptographically secure PRNG. This
change scopes the inclusion of ntsecapi.h to wrapper.c, which is the only
place that it's actually needed.
The build breakage is due to the definition of UNICODE_STRING in
NtSecApi.h:
#ifndef _NTDEF_
typedef LSA_UNICODE_STRING UNICODE_STRING, *PUNICODE_STRING;
typedef LSA_STRING STRING, *PSTRING ;
#endif
LsaLookup.h:
typedef struct _LSA_UNICODE_STRING {
USHORT Length;
USHORT MaximumLength;
#ifdef MIDL_PASS
[size_is(MaximumLength/2), length_is(Length/2)]
#endif // MIDL_PASS
PWSTR Buffer;
} LSA_UNICODE_STRING, *PLSA_UNICODE_STRING;
winternl.h also defines UNICODE_STRING:
typedef struct _UNICODE_STRING {
USHORT Length;
USHORT MaximumLength;
PWSTR Buffer;
} UNICODE_STRING;
typedef UNICODE_STRING *PUNICODE_STRING;
Both definitions have equivalent layouts. Apparently these internal
Windows headers aren't designed to be included together. This is
an oversight in the headers and does not represent an incompatibility
between the APIs.
Signed-off-by: Neeraj Singh <neerajsi@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The mingw_utime implementation in mingw.c does not support
directories. This means that "test-tool chmtime" fails on Windows when
targeting directories. This has previously been noted and sidestepped
temporarily by Jeff Hostetler, in "t/helper/test-chmtime: skip
directories on Windows" in the "Builtin FSMonitor Part 2" work, but
not yet fixed.
It would make sense to backdate file and folder changes in untracked
cache tests, to avoid needing to insert explicit delays/pauses in the
tests.
Add support for directory date manipulation in mingw_utime by
replacing the file-oriented _wopen() call with the
directory-supporting CreateFileW() windows API explicitly.
Signed-off-by: Tao Klerks <tao@klerks.biz>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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If VMIN and VTIME are both set to zero then the terminal performs
non-blocking reads which means that read_key_without_echo() returns
EOF if there is no key press pending. This results in the user being
unable to select anything when running "git add -p". Fix this by
explicitly setting VMIN and VTIME when enabling non-canonical mode.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When disable_bits() changes the terminal attributes it uses
sigchain_push_common() to restore the terminal if a signal is received
before restore_term() is called. However there is no corresponding
call to sigchain_pop_common() when the settings are restored so the
signal handler is left on the sigchain stack. This leaves the stack
unbalanced so code such as
sigchain_push_common(my_handler);
...
read_key_without_echo(...);
...
sigchain_pop_common();
pops the handler pushed by disable_bits() rather than the one it
intended to. Additionally "git add -p" changes the terminal settings
every time it reads a key press so the stack can grow significantly.
In order to fix this save_term() now sets up the signal handler so
restore_term() can unconditionally call sigchain_pop_common(). There
are no callers of save_term() outside of terminal.c as the only
external caller was removed by e3f7e01b50 ("Revert "editor: save and
reset terminal after calling EDITOR"", 2021-11-22). Any future callers
of save_term() should benefit from having the signal handler set up
for them.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Break out of the loop to ensure restore_term() is called before
returning.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The build procedure has been taught to notice older version of zlib
and enable our replacement uncompress2() automatically.
* ab/auto-detect-zlib-compress2:
compat: auto-detect if zlib has uncompress2()
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Pick a better random number generator and use it when we prepare
temporary filenames.
* bc/csprng-mktemps:
wrapper: use a CSPRNG to generate random file names
wrapper: add a helper to generate numbers from a CSPRNG
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Fix a hand-rolled alloca() imitation that may have violated
alignment requirement of data being sorted in compatibility
implementation of qsort_s() and stable qsort().
* jc/qsort-s-alignment-fix:
stable-qsort: avoid using potentially unaligned access
compat/qsort_s.c: avoid using potentially unaligned access
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We have a copy of uncompress2() implementation in compat/ so that we
can build with an older version of zlib that lack the function, and
the build procedure selects if it is used via the NO_UNCOMPRESS2
$(MAKE) variable. This is yet another "annoying" knob the porters
need to tweak on platforms that are not common enough to have the
default set in the config.mak.uname file.
Attempt to instead ask the system header <zlib.h> to decide if we
need the compatibility implementation. This is a deviation from the
way we have been handling the "compatiblity" features so far, and if
it can be done cleanly enough, it could work as a model for features
that need compatibility definition we discover in the future. With
that goal in mind, avoid expedient but ugly hacks, like shoving the
code that is conditionally compiled into an unrelated .c file, which
may not work in future cases---instead, take an approach that uses a
file that is independently compiled and stands on its own.
Compile and link compat/zlib-uncompress2.c file unconditionally, but
conditionally hide the implementation behind #if/#endif when zlib
version is 1.2.9 or newer, and unconditionally archive the resulting
object file in the libgit.a to be picked up by the linker.
There are a few things to note in the shape of the code base after
this change:
- We no longer use NO_UNCOMPRESS2 knob; if the system header
<zlib.h> claims a version that is more cent than the library
actually is, this would break, but it is easy to add it back when
we find such a system.
- The object file compat/zlib-uncompress2.o is always compiled and
archived in libgit.a, just like a few other compat/ object files
already are.
- The inclusion of <zlib.h> is done in <git-compat-util.h>; we used
to do so from <cache.h> which includes <git-compat-util.h> as the
first thing it does, so from the *.c codes, there is no practical
change.
- Until objects in libgit.a that is already used gains a reference
to the function, the reftable code will be the only one that
wants it, so libgit.a on the linker command line needs to appear
once more at the end to satisify the mutual dependency.
- Beat found a trick used by OpenSSL to avoid making the
conditionally-compiled object truly empty (apparently because
they had to deal with compilers that do not want to see an
effectively empty input file). Our compat/zlib-uncompress2.c
file borrows the same trick for portabilty.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Helped-by: Beat Bolli <dev+git@drbeat.li>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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A recent upstream topic introduced checks for certain Git commands that
prevent them from deleting the current working directory, introducing
also a regression test that ensures that commands such as `git version`
_can_ run without a current working directory.
While technically not possible on Windows via the regular Win32 API, we
do run the regression tests in an MSYS2 Bash which uses a POSIX
emulation layer (the MSYS2/Cygwin runtime) where a really evil hack
_does_ allow to delete a directory even if it is the current working
directory.
Therefore, Git needs to be prepared for a missing working directory,
even on Windows.
This issue was not noticed in upstream Git because there was no caller
that tried to discover a Git directory with a deleted current working
directory in the test suite. But in the microsoft/git fork, we do want
to run `pre-command`/`post-command` hooks for every command, even for
`git version`, which means that we make precisely such a call. The bug
is not in that `pre-command`/`post-command` feature, though, but in
`mingw_getcwd()` and needs to be addressed there.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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There are many situations in which having access to a cryptographically
secure pseudorandom number generator (CSPRNG) is helpful. In the
future, we'll encounter one of these when dealing with temporary files.
To make this possible, let's add a function which reads from a system
CSPRNG and returns some bytes.
We know that all systems will have such an interface. A CSPRNG is
required for a secure TLS or SSH implementation and a Git implementation
which provided neither would be of little practical use. In addition,
POSIX is set to standardize getentropy(2) in the next version, so in the
(potentially distant) future we can rely on that.
For systems which lack one of the other interfaces, we provide the
ability to use OpenSSL's CSPRNG. OpenSSL is highly portable and
functions on practically every known OS, and we know it will have access
to some source of cryptographically secure randomness. We also provide
support for the arc4random in libbsd for folks who would prefer to use
that.
Because this is a security sensitive interface, we take some
precautions. We either succeed by filling the buffer completely as we
requested, or we fail. We don't return partial data because the caller
will almost never find that to be a useful behavior.
Specify a makefile knob which users can use to specify one or more
suitable CSPRNGs, and turn the multiple string options into a set of
defines, since we cannot match on strings in the preprocessor. We allow
multiple options to make the job of handling this in autoconf easier.
The order of options is important here. On systems with arc4random,
which is most of the BSDs, we use that, since, except on MirBSD and
macOS, it uses ChaCha20, which is extremely fast, and sits entirely in
userspace, avoiding a system call. We then prefer getrandom over
getentropy, because the former has been available longer on Linux, and
then OpenSSL. Finally, if none of those are available, we use
/dev/urandom, because most Unix-like operating systems provide that API.
We prefer options that don't involve device files when possible because
those work in some restricted environments where device files may not be
available.
Set the configuration variables appropriately for Linux and the BSDs,
including macOS, as well as Windows and NonStop. We specifically only
consider versions which receive publicly available security support
here. For the same reason, we don't specify getrandom(2) on Linux,
because CentOS 7 doesn't support it in glibc (although its kernel does)
and we don't want to resort to making syscalls.
Finally, add a test helper to allow this to be tested by hand and in
tests. We don't add any tests, since invoking the CSPRNG is not likely
to produce interesting, reproducible results.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Fix calling dynamically loaded functions on Windows.
* ma/windows-dynload-fix:
lazyload: use correct calling conventions
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Christoph Reiter reported on the Git for Windows issue tracker[1], that
mingw_strftime() imports strftime() from ucrtbase.dll with the wrong
calling convention. It should be __cdecl instead of WINAPI, which we
always use in DECLARE_PROC_ADDR().
The MSYS2 project encountered cmake sefaults on x86 Windows caused by
the same issue in the cmake source. [2] There are no known git crashes
that where caused by this, yet, but we should try to prevent them.
We import two other non-WINAPI functions via DECLARE_PROC_ADDR(), too.
* NtSetSystemInformation() (NTAPI)
* GetUserNameExW() (SEC_ENTRY)
NTAPI, SEC_ENTRY and WINAPI are all ususally defined as __stdcall,
but there are circumstances where they're defined differently.
Teach DECLARE_PROC_ADDR() about calling conventions and be explicit
about when we want to use which calling convention.
Import winnt.h for the definition of NTAPI and sspi.h for SEC_ENTRY
near their respective only users.
[1] https://github.com/git-for-windows/git/issues/3560
[2] https://github.com/msys2/MINGW-packages/issues/10152
Reported-By: Christoph Reiter <reiter.christoph@gmail.com>
Signed-off-by: Matthias Aßhauer <mha1993@live.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The compatibility definition for qsort_s() uses "char buffer[1024]"
on the stack to avoid making malloc() calls for small temporary
space, which essentially hand-rolls alloca().
But the elements of the array being sorted may have alignment needs
more strict than what an array of bytes may have. &buf[0] may be
word aligned, but using the address as if it stores the first
element of an array of a struct, whose first member may need to be
aligned on double-word boundary, would be a no-no.
We could use xalloca() from git-compat-util.h, or alloca() directly
on platforms with HAVE_ALLOCA_H, but let's try using unconditionally
xmalloc() before we know the performance characteristics of the
callers.
It may not make much of an argument to inspect the current callers
and say "it shouldn't matter to any of them", but anyway:
* The one in object-name.c is used to sort potential matches to a
given ambiguous object name prefix in the error path;
* The one in pack-write.c is done once per a pack .idx file being
written to create the reverse index, so (1) the cost of malloc()
overhead is dwarfed by the cost of the packing operation, and (2)
the number of entries being sorted is the number of objects in a
pack;
* The one in ref-filter.c is used by "branch --list", "tag --list",
and "for-each-ref", only once per operation. We sort an array of
pointers with entries, each corresponding to a ref that is shown.
* The one in string-list.c is used by sort_string_list(), which is
way too generic to assume any access patterns, so it may or may
not matter, but I do not care too much ;-)
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The "reftable" backend for the refs API, without integrating into
the refs subsystem, has been added.
* hn/reftable:
Add "test-tool dump-reftable" command.
reftable: add dump utility
reftable: implement stack, a mutable database of reftable files.
reftable: implement refname validation
reftable: add merged table view
reftable: add a heap-based priority queue for reftable records
reftable: reftable file level tests
reftable: read reftable files
reftable: generic interface to tables
reftable: write reftable files
reftable: a generic binary tree implementation
reftable: reading/writing blocks
Provide zlib's uncompress2 from compat/zlib-compat.c
reftable: (de)serialization for the polymorphic record type.
reftable: add blocksource, an abstraction for random access reads
reftable: utility functions
reftable: add error related functionality
reftable: add LICENSE
hash.h: provide constants for the hash IDs
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Build fix on Windows.
* cb/mingw-gmtime-r:
mingw: avoid fallback for {local,gm}time_r()
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The compatibility implementation for unsetenv(3) were written to
mimic ancient, non-POSIX, variant seen in an old glibc; it has been
changed to return an integer to match the more modern era.
* jc/unsetenv-returns-an-int:
unsetenv(3) returns int, not void
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mingw-w64's pthread_unistd.h had a bug that mistakenly (because there is
no support for the *lockfile() functions required[1]) defined
_POSIX_THREAD_SAFE_FUNCTIONS and that was being worked around since
3ecd153a3b (compat/mingw: support MSys2-based MinGW build, 2016-01-14).
The bug was fixed in winphtreads, but as a side effect, leaves the
reentrant functions from time.h no longer visible and therefore breaks
the build.
Since the intention all along was to avoid using the fallback functions,
formalize the use of POSIX by setting the corresponding feature flag and
compile out the implementation for the fallback functions.
[1] https://unix.org/whitepapers/reentrant.html
Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
Acked-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Cygwin emulates Unix sockets by writing files with custom contents and
then marking them as system files.
The tricky problem is that while the file is written and its `system`
bit is set, it is still identified as a file. This caused test failures
when Git is too fast looking for the Unix sockets and then complains
that there is a plain file in the way.
Let's work around this by adding a delayed retry loop, specifically for
Cygwin.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Tested-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This compatilibity implementation has been returning a wrong type,
ever since 731043fd (Add compat/unsetenv.c ., 2006-01-25) added to
the system, yet nobody noticed it in the past 16 years, presumably
because no code checks failures in their unsetenv() calls. Sigh.
For now, make it always succeed.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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An editor session launched during a Git operation (e.g. during 'git
commit') can leave the terminal in a funny state. The code path
has updated to save the terminal state before, and restore it
after, it spawns an editor.
* cm/save-restore-terminal:
editor: save and reset terminal after calling EDITOR
terminal: teach git how to save/restore its terminal settings
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Built-in fsmonitor (part 1).
* jh/builtin-fsmonitor-part1:
t/helper/simple-ipc: convert test-simple-ipc to use start_bg_command
run-command: create start_bg_command
simple-ipc/ipc-win32: add Windows ACL to named pipe
simple-ipc/ipc-win32: add trace2 debugging
simple-ipc: move definition of ipc_active_state outside of ifdef
simple-ipc: preparations for supporting binary messages.
trace2: add trace2_child_ready() to report on background children
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Mostly preliminary clean-up in the hook API.
* ab/config-based-hooks-1:
hook-list.h: add a generated list of hooks, like config-list.h
hook.c users: use "hook_exists()" instead of "find_hook()"
hook.c: add a hook_exists() wrapper and use it in bugreport.c
hook.[ch]: move find_hook() from run-command.c to hook.c
Makefile: remove an out-of-date comment
Makefile: don't perform "mv $@+ $@" dance for $(GENERATED_H)
Makefile: stop hardcoding {command,config}-list.h
Makefile: mark "check" target as .PHONY
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mmap() imitation used to call xmalloc() that dies upon malloc()
failure, which has been corrected to just return an error to the
caller to be handled.
* rs/git-mmap-uses-malloc:
compat: let git_mmap use malloc(3) directly
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This will be needed for reading reflog blocks in reftable.
Helped-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Currently, git will share its console with all its children (unless
they create their own), and is therefore possible that any of them
that might change the settings for it could affect its operations once
completed.
Refactor the platform specific functionality to save the terminal
settings and expand it to also do so for the output handler.
This will allow for the state of the terminal to be saved and
restored around a child that might misbehave (ex vi) which will
be implemented next.
Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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gcc will helpfully raise a -Wcast-function-type warning when casting
between functions that might have incompatible return types
(ex: GetUserNameExW returns bool which is only half the size of the
return type from FARPROC which is long long), so create a new type that
could be used as a completely generic function pointer and cast through
it instead.
Additionaly remove the -Wno-incompatible-pointer-types temporary
flag added in 27e0c3c (win32: allow building with pedantic mode
enabled, 2021-09-03), as it will be no longer needed.
Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Here, GCC warns about every use of the INIT_PROC_ADDR macro, for example:
In file included from compat/mingw.c:8:
compat/mingw.c: In function 'mingw_strftime':
compat/win32/lazyload.h:38:12: warning: assignment to
'size_t (*)(char *, size_t, const char *, const struct tm *)'
{aka 'long long unsigned int (*)(char *, long long unsigned int,
const char *, const struct tm *)'} from incompatible pointer type
'FARPROC' {aka 'long long int (*)()'} [-Wincompatible-pointer-types]
38 | (function = get_proc_addr(&proc_addr_##function))
| ^
compat/mingw.c:1014:6: note: in expansion of macro 'INIT_PROC_ADDR'
1014 | if (INIT_PROC_ADDR(strftime))
| ^~~~~~~~~~~~~~
(message wrapped for convenience). Insert a cast to keep the compiler
happy. A cast is fine in these cases because they are generic function
pointer values that have been looked up in a DLL.
Helped-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Change various places that hardcode the names of these two files to
refer to either $(GENERATED_H), or to a new generated-hdrs
target. That target is consistent with the *-objs targets I recently
added in 029bac01a8 (Makefile: add {program,xdiff,test,git,fuzz}-objs
& objects targets, 2021-02-23).
A subsequent commit will add a new generated hook-list.h. By doing
this refactoring we'll only need to add the new file to the
GENERATED_H variable, not EXCEPT_HDRS, the vcbuild/README etc.
Hardcoding command-list.h there seems to have been a case of
copy/paste programming in 976aaedca0 (msvc: add a Makefile target to
pre-generate the Visual Studio solution, 2019-07-29). The
config-list.h was added later in 709df95b78 (help: move
list_config_help to builtin/help, 2020-04-16).
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Update the build procedure to use the "-pedantic" build when
DEVELOPER makefile macro is in effect.
* cb/pedantic-build-for-developers:
developer: enable pedantic by default
win32: allow building with pedantic mode enabled
gettext: remove optional non-standard parens in N_() definition
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The tracing of process ancestry information has been enhanced.
* ab/tr2-leaks-and-fixes:
tr2: log N parent process names on Linux
tr2: do compiler enum check in trace2_collect_process_info()
tr2: leave the parent list empty upon failure & don't leak memory
tr2: stop leaking "thread_name" memory
tr2: clarify TRACE2_PROCESS_INFO_EXIT comment under Linux
tr2: remove NEEDSWORK comment for "non-procfs" implementations
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Set an ACL on the named pipe to allow the well-known group EVERYONE
to read and write to the IPC server's named pipe. In the event that
the daemon was started with elevation, allow non-elevated clients
to communicate with the daemon.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Create "ipc-debug" category events to log unexpected errors
when creating Simple-IPC connections.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Add `command_len` argument to the Simple IPC API.
In my original Simple IPC API, I assumed that the request would always
be a null-terminated string of text characters. The `command`
argument was just a `const char *`.
I found a caller that would like to pass a binary command to the
daemon, so I am amending the Simple IPC API to receive `const char
*command, size_t command_len` arguments.
I considered changing the `command` argument to be a `void *`, but the
IPC layer simply passes it to the pkt-line layer which takes a `const
char *`, so to avoid confusion I left it as is.
Note, the response side has always been a `struct strbuf` which
includes the buffer and length, so we already support returning a
binary answer. (Yes, it feels a little weird returning a binary
buffer in a `strbuf`, but it works.)
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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mmap() imitation used to call xmalloc() that dies upon malloc()
failure, which has been corrected to just return an error to the
caller to be handled.
* rs/git-mmap-uses-malloc:
compat: let git_mmap use malloc(3) directly
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In 2f732bf15e6 (tr2: log parent process name, 2021-07-21) we started
logging parent process names, but only logged all parents on Windows.
on Linux only the name of the immediate parent process was logged.
Extend the functionality added there to also log full parent chain on
Linux.
This requires us to lookup "/proc/<getppid()>/stat" instead of
"/proc/<getppid()>/comm". The "comm" file just contains the name of the
process, but the "stat" file has both that information, and the parent
PID of that process, see procfs(5). We parse out the parent PID of our
own parent, and recursively walk the chain of "/proc/*/stat" files all
the way up the chain. A parent PID of 0 indicates the end of the
chain.
It's possible given the semantics of Linux's PID files that we end up
getting an entirely nonsensical chain of processes. It could happen if
e.g. we have a chain of processes like:
1 (init) => 321 (bash) => 123 (git)
Let's assume that "bash" was started a while ago, and that as shown
the OS has already cycled back to using a lower PID for us than our
parent process. In the time it takes us to start up and get to
trace2_collect_process_info(TRACE2_PROCESS_INFO_STARTUP) our parent
process might exit, and be replaced by an entirely different process!
We'd racily look up our own getppid(), but in the meantime our parent
would exit, and Linux would have cycled all the way back to starting
an entirely unrelated process as PID 321.
If that happens we'll just silently log incorrect data in our ancestry
chain. Luckily we don't need to worry about this except in this
specific cycling scenario, as Linux does not have PID
randomization. It appears it once did through a third-party feature,
but that it was removed around 2006[1]. For anyone worried about this
edge case raising PID_MAX via "/proc/sys/kernel/pid_max" will mitigate
it, but not eliminate it.
One thing we don't need to worry about is getting into an infinite
loop when walking "/proc/*/stat". See 353d3d77f4f (trace2: collect
Windows-specific process information, 2019-02-22) for the related
Windows code that needs to deal with that, and [2] for an explanation
of that edge case.
Aside from potential race conditions it's also a bit painful to
correctly parse the process name out of "/proc/*/stat". A simpler
approach is to use fscanf(), see [3] for an implementation of that,
but as noted in the comment being added here it would fail in the face
of some weird process names, so we need our own parse_proc_stat() to
parse it out.
With this patch the "ancestry" chain for a trace2 event might look
like this:
$ GIT_TRACE2_EVENT=/dev/stdout ~/g/git/git version | grep ancestry | jq -r .ancestry
[
"bash",
"screen",
"systemd"
]
And in the case of naughty process names like the following. This uses
perl's ability to use prctl(PR_SET_NAME, ...). See
Perl/perl5@7636ea95c5 (Set the legacy process name with prctl() on
assignment to $0 on Linux, 2010-04-15)[4]:
$ perl -e '$0 = "(naughty\nname)"; system "GIT_TRACE2_EVENT=/dev/stdout ~/g/git/git version"' | grep ancestry | jq -r .ancestry
[
"sh",
"(naughty\nname)",
"bash",
"screen",
"systemd"
]
1. https://grsecurity.net/news#grsec2110
2. https://lore.kernel.org/git/48a62d5e-28e2-7103-a5bb-5db7e197a4b9@jeffhostetler.com/
3. https://lore.kernel.org/git/87o8agp29o.fsf@evledraar.gmail.com/
4. https://github.com/Perl/perl5/commit/7636ea95c57762930accf4358f7c0c2dec086b5e
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Acked-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Change code added in 2f732bf15e6 (tr2: log parent process name,
2021-07-21) to use a switch statement without a "default" branch to
have the compiler error if this code ever drifts out of sync with the
members of the "enum trace2_process_info_reason".
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Acked-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In a subsequent commit I'll be replacing most of this code to log N
parents, but let's first fix bugs introduced in the recent
2f732bf15e6 (tr2: log parent process name, 2021-07-21).
It was using the strbuf_read_file() in the wrong way, its return value
is either a length or a negative value on error. If we didn't have a
procfs, or otherwise couldn't access it we'd end up pushing an empty
string to the trace2 ancestry array.
It was also using the strvec_push() API the wrong way. That API always
does an xstrdup(), so by detaching the strbuf here we'd leak
memory. Let's instead pass in our pointer for strvec_push() to
xstrdup(), and then free our own strbuf. I do have some WIP changes to
make strvec_push_nodup() non-static, which makes this and some other
callsites nicer, but let's just follow the prevailing pattern of using
strvec_push() for now.
We'll also need to free that "procfs_path" strbuf whether or not
strbuf_read_file() succeeds, which was another source of memory leaks
in 2f732bf15e6, i.e. we'd leak that memory as well if we weren't on a
system where we could read the file from procfs.
Let's move all the freeing of the memory to the end of the
function. If we're still at STRBUF_INIT with "name" due to not having
taken the branch where the strbuf_read_file() succeeds freeing it is
redundant. So we could move it into the body of the "if", but just
handling freeing the same way for all branches of the function makes
it more readable.
In combination with the preceding commit this makes all of
t[0-9]*trace2*.sh pass under SANITIZE=leak on Linux.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Acked-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Rewrite a comment added in 2f732bf15e6 (tr2: log parent process name,
2021-07-21) to describe what we might do under
TRACE2_PROCESS_INFO_EXIT in the future, instead of vaguely referring
to "something extra".
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Acked-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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I'm fairly sure that there is no way on Linux to inspect the process
tree without using procfs, any tool such as ps(1), top(1) etc. that
shows this sort of information ultimately looks the information up in
procfs.
So let's remove this comment added in 2f732bf15e6 (tr2: log parent
process name, 2021-07-21), it's setting us up for an impossible task.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Acked-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In preparation to building with pedantic mode enabled, change a couple
of places where the current mingw gcc compiler provided with the SDK
reports issues.
A full fix for the incompatible use of (void *) to store function
pointers has been punted, with the minimal change to instead use a
generic function pointer (FARPROC), and therefore the (hopefully)
temporary need to disable incompatible pointer warnings.
Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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trace2 logs learned to show parent process name to see in what
context Git was invoked.
* es/trace2-log-parent-process-name:
tr2: log parent process name
tr2: make process info collection platform-generic
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xmalloc() dies on error, allows zero-sized allocations and enforces
GIT_ALLOC_LIMIT for testing. Our mmap replacement doesn't need any of
that. Let's cut out the wrapper, reject zero-sized requests as required
by POSIX and use malloc(3) directly. Allocation errors were needlessly
handled by git_mmap() before; this code becomes reachable now.
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When performing a rebase, rmdir() is called on the folder .git/logs. On
Unix rmdir() exits without deleting anything in case .git/logs is a
symbolic link but the equivalent functions on Windows (_rmdir, _wrmdir
and RemoveDirectoryW) do not behave the same and remove the folder if it
is symlinked even if it is not empty.
This creates issues when folders in .git/ are symlinks which is
especially the case when git-repo[1] is used: It replaces `.git/logs/`
with a symlink.
One such issue is that the _target_ of that symlink is removed e.g.
during a `git rebase`, where `delete_reflog("REBASE_HEAD")` will not
only try to remove `.git/logs/REBASE_HEAD` but then recursively try to
remove the parent directories until an error occurs, a technique that
obviously relies on `rmdir()` refusing to remove a symlink.
This was reported in https://github.com/git-for-windows/git/issues/2967.
This commit updates mingw_rmdir() so that its behavior is the same as
Linux rmdir() in case of symbolic links.
To verify that Git does not regress on the reported issue, this patch
adds a regression test for the `git rebase` symptom, even if the same
`rmdir()` behavior is quite likely to cause potential problems in other
Git commands as well.
[1]: git-repo is a python tool built on top of Git which helps manage
many Git repositories. It stores all the .git/ folders in a central
place by taking advantage of symbolic links.
More information: https://gerrit.googlesource.com/git-repo/
Signed-off-by: Thomas Bétous <tomspycell@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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It can be useful to tell who invoked Git - was it invoked manually by a
user via CLI or script? By an IDE? In some cases - like 'repo' tool -
we can influence the source code and set the GIT_TRACE2_PARENT_SID
environment variable from the caller process. In 'repo''s case, that
parent SID is manipulated to include the string "repo", which means we
can positively identify when Git was invoked by 'repo' tool. However,
identifying parents that way requires both that we know which tools
invoke Git and that we have the ability to modify the source code of
those tools. It cannot scale to keep up with the various IDEs and
wrappers which use Git, most of which we don't know about. Learning
which tools and wrappers invoke Git, and how, would give us insight to
decide where to improve Git's usability and performance.
Unfortunately, there's no cross-platform reliable way to gather the name
of the parent process. If procfs is present, we can use that; otherwise
we will need to discover the name another way. However, the process ID
should be sufficient to look up the process name on most platforms, so
that code may be shareable.
Git for Windows gathers similar information and logs it as a "data_json"
event. However, since "data_json" has a variable format, it is difficult
to parse effectively in some languages; instead, let's pursue a
dedicated "cmd_ancestry" event to record information about the ancestry
of the current process and a consistent, parseable way.
Git for Windows also gathers information about more than one generation
of parent. In Linux further ancestry info can be gathered with procfs,
but it's unwieldy to do so. In the interest of later moving Git for
Windows ancestry logging to the 'cmd_ancestry' event, and in the
interest of later adding more ancestry to the Linux implementation - or
of adding this functionality to other platforms which have an easier
time walking the process tree - let's make 'cmd_ancestry' accept an
array of parentage.
Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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To pave the way for non-Windows platforms to define
trace2_collect_process_info(), reorganize the stub-or-definition schema
to something which doesn't directly reference Windows.
Platforms which want to collect parent process information in the
future should:
1. Add an implementation to compat/ (e.g. compat/somearch/procinfo.c)
2. Add that object to COMPAT_OBJS to config.mak.uname
(e.g. COMPAT_OBJS += compat/somearch/procinfo.o)
3. Define HAVE_PLATFORM_PROCINFO in config.mak.uname
In the Windows case, this definition lives in
compat/win32/trace2_win32_process_info.c, which is already conditionally
added to COMPAT_OBJS; so let's add HAVE_PLATFORM_PROCINFO to hint to the
build that compat/stub/procinfo.c should not be used.
Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Helped-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The "simple-ipc" did not compile without pthreads support, but the
build procedure was not properly account for it.
* jh/simple-ipc-sans-pthread:
simple-ipc: correct ifdefs when NO_PTHREADS is defined
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Junio C Hamano
Neeraj Singh
Tao Klerks
Phillip Wood
Ævar Arnfjörð Bjarmason
Johannes Schindelin
brian m. carlson
Matthias Aßhauer
Carlo Marcelo Arenas Belón
Han-Wen Nienhuys
Johannes Sixt
Jeff Hostetler
René Scharfe
Thomas Bétous
Emily Shaffer