Only required for Windows 7.
This in turn allows to drop the helper_pid and related
methods from fhandler_pty_common.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Only required for Windows 7.
This allows to remove fhandler_pipe::get_query_hdl_per_system(),
too.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Originally the code was written to allow three ways of prefixing
accounts and to freely define a domain/account separator. This code
has been disabled even before being officially released, and it was
never re-enabled. Given there has been no complaints for eight years
now, drop this code eventually. Just add a macro to define the
domain/account separator statically.
Fixes: cc332c9e27 ("(cygheap_pwdgrp::nss_init_line): Disable db_prefix
and db_separator settings. Add comment")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
- The codes related to pty and console in spawn.cc have been moved
into the new class fhandler_termios::spawn_worker, and make spawn.cc
call them. The functionality has not been changed at all.
Every time the cygheap is initialized, that is, on each fork
or exec, cygheap_init() *again* computes the bucket size values
and stores them in the cgyheap, albeit they are always the
same values anyway.
Make bucket_val a local const array, statically initialized
instead.
Fixes: 61522196c7 ("* Merge in cygwin-64bit-branch.)"
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Another reason ASLR may fail is the coupling of the standard shared
mem regions (global, userinfo, process info, shared console) to the
address of the Cygwin DLL. They are always placed in fixed addresses
preceeding the Cygwin DLL's address. With ASLR this is bound to fail.
Use a fixed, unused memory area to place the shared mem regions.
This also allows to simplify the shared memory creation. There's
no reason anymore to rebase the regions and rather than offsets,
just use the addresses directly.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
One reason that ASLR is tricky is the fact that the cygheap
is placed at the end of the DLL and especially that it's expected
to be growable. To support ASLR, this construct must go.
Define dedicated cygheap memory region and reserve entire region.
Commit 3 Megs, as was the default size of the cygheap before.
Fix linker script accordingly, drop a now useless version check
in get_cygwin_startup_info().
Collect all info about memory layout in one header file, so
the mem layout is documented in one logical place and not
in heap.cc arbitrarily.
Use info from this file throughout.
This is to prepare for ASLR support.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
According to POSIX and the Linux man page, select(2) is supposed to
report read ready if a file is at EOF. In the case of a FIFO, this
means that the pipe is empty and there are no writers. But there
seems to be an undocumented exception, observed on Linux and other
platforms: If no writer has ever been opened, then select(2) does not
report read ready. This can happen if a reader is opened with
O_NONBLOCK before any writers have opened.
This commit makes Cygwin consistent with those other platforms by
introducing a special EOF test, fhandler_fifo::select_hit_eof, which
returns false if there's never been a writer opened.
To implement this we use a new variable '_writer_opened' in the FIFO's
shared memory, which is set to 1 the first time a writer opens. New
methods writer_opened() and set_writer_opened() are used to test and
set this variable.
Addresses: https://cygwin.com/pipermail/cygwin/2022-September/252223.html
The patch fixing the alignment of _cygtls::context accidentally
pushed the desperate attempt to automate the alignment by using
another, non-working variation of attribute((aligned)). Drop it.
Fixes: dcab768cb9 ("Cygwin: cygtls: fix context alignment")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
A hang was encountered, apparently triggered by commit 63b503916d,
changing tls_pathbufs from malloc'ed to HeapAlloc'ed memory. After
lengthy debugging it transpired that adding the heap handle to the
tls_pathbuf struct added 8 bytes to the cygtls area, thus moving
the "context" member by 8 bytes, too, so it was suddently unaligned.
Fix this for now by changing the alignment.
Fix this once and for all, by adding code to the gentls_offsets script
to check if the alignment of the "context" member is 16 bytes. If not,
print a matching error message, remove the just generated file, and exit
with error.
FIXME: It would be really nice to find a way to auomate the correct
alignment of the "context" member, but I don't see any way to use
alignment attributes to get what we need here.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
while debugging a problem introduced in commit
63b503916d ("Cygwin: tls_pathbuf: Use Windows heap")
a hang in fork was encountered using the original implementation
of tls_pathbuf:
Using tmp_pathbuf inside the code block guarded by __malloc_trylock
may call malloc from tmp_pathbuf::w_get and thus trying to lock an
exclusive SRW lock recursively, which results in a deadlock.
Allocate a small SECURITY_ATTRIBUTES block on the stack rather than
allocating a 64K tmp_pathbuf. This avoids the potential malloc call.
Drop the __malloc_trylock call entirely. There must not be a malloc
call inside the frok::parent block guarded by __malloc_lock, and
just trying to lock is too dangerous inside fork while other threads
might actually chage the content of the heap. Additionally, add a
comment frowning on malloc usage inside tis code block.
Fixes: 44a79a6eca ("Cygwin: convert malloc lock to SRWLOCK")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Rather than using malloc/free for the buffers, we're now using
HeapAlloc/HeapFree on a HEAP_NO_SERIALIZE heap created for this
thread.
Advantages:
- Less contention. Our malloc/free doesn't scale well in
multithreaded scenarios
- Even faster heap allocation by using a non serialized heap.
- Internal, local, temporary data not cluttering the user heap.
- Internal, local, temporary data not copied over to child process
at fork().
Disadvantage:
- A forked process has to start allocating temporary buffers from
scratch. However, this should be alleviated by the fact that
buffer allocation usually reaches its peak very early in process
runtime, so the longer the proceess runs, the less buffers have
to allocated, and, only few processes don't exec after fork
anyway.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Rename CygwinCreateThread to create_posix_thread and move
from miscfuncs.cc to create_posix_thread.cc, inbcluding all
related functions. Analogue for the prototypes.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Corinna Vinschen
Takashi Yano
Ken Brown