The new loop in open_shared has a subtil performance problem.
Next_address is bumped only if mapping at this address
failed. Every subsequent call to open_shared has a high probability
having to call MapViewOfFileEx twice, because next_address is still
set to the address of the last successful mapping.
Avoid this by bumping next_address every time.
While at it, fix a comment.
Conflict: Missing backport of 31302b267b86 ("Cygwin: drop fixed addresses for standard shared regions")
Fixes: dc0fe7742b8c ("Cygwin: open_shared: try harder allocating a shared region")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
For fixed regions (cygwin/user/myself/shared console), try fixed
address first. Fallback to non-fixed region. Don't even try fixed
address if the Cygwin DLL gets dynamically loaded.
For non-fixed regions, try to allocate in a loop within the area
from SHARED_REGIONS_ADDRESS_LOW to SHARED_REGIONS_ADDRESS_HIGH.
Fixes: 60675f1a7eb2 ("Cygwin: decouple shared mem regions from Cygwin DLL")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Fix comments accordingly.
This is in preparation for a change in open_shared, handling shared
regions more cleanly.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
For ages, open_shared uses the shared_locations parameter as
output to indicate if the mapping for a shared region has been
created or just opened. Split this into two parameters. Use
the shared_locations parameter as input only, return the creation
state of the mapping in a bool reference parameter.
Conflict: Simple collision due to missing backport of
3721a756b0d8 ("Cygwin: console: Make the console accessible from other terminals.")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
After the commit 30add3e6b3e3, the problem:
https://cygwin.com/pipermail/cygwin/2022-December/252759.html
occurs rarely. It seems that myself_pinfo should be initialized
where the timing before child_copy() and after cygheap allocation.
This patch moves the initialization there.
Fixes: 30add3e6b3e3 ("Cygwin: exec: don't access cygheap before it's
initialized")
Reported-by: Brian Inglis <Brian.Inglis@Shaw.ca>
Reviewed-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
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: 61522196c715 ("* 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>
