https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=fd57eea5617a33a09d2b9e4d1b132339c4260026
commit fd57eea5617a33a09d2b9e4d1b132339c4260026
Author: Ken Brown <kbr...@cornell.edu>
Date: Wed Jan 15 11:04:03 2025 -0500
Revert "Cygwin: mmap: use 64K pages for bookkeeping"
This reverts commit 74017d229d5e46867c8a3ec01bf653e4392bf14c.
After this commit, gdb exits with a fatal error on startup.
Addresses: https://cygwin.com/pipermail/cygwin-patches/2025q1/013240.html
Fixes: 74017d229d5e ("Cygwin: mmap: use 64K pages for bookkeeping")
Signed-off-by: Ken Brown <kbr...@cornell.edu>
Diff:
---
winsup/cygwin/mm/mmap.cc | 29 +++++++++++++----------------
1 file changed, 13 insertions(+), 16 deletions(-)
diff --git a/winsup/cygwin/mm/mmap.cc b/winsup/cygwin/mm/mmap.cc
index 9c10d5e2a..501d37bb2 100644
--- a/winsup/cygwin/mm/mmap.cc
+++ b/winsup/cygwin/mm/mmap.cc
@@ -28,8 +28,8 @@ details. */
to mapping length (POSIX semantics). */
#define __PROT_ATTACH 0x8000000
-/* Use 64K pages throughout. */
-#define PAGE_CNT(bytes) howmany((bytes), wincap.allocation_granularity())
+/* Stick with 4K pages for bookkeeping. */
+#define PAGE_CNT(bytes) howmany((bytes), wincap.page_size())
#define PGBITS (sizeof (DWORD)*8)
#define MAPSIZE(pages) howmany ((pages), PGBITS)
@@ -418,7 +418,7 @@ mmap_record::match (caddr_t addr, SIZE_T len, caddr_t
&m_addr, SIZE_T &m_len,
bool &contains)
{
contains = false;
- SIZE_T rec_len = PAGE_CNT (get_len ()) * wincap.allocation_granularity ();
+ SIZE_T rec_len = PAGE_CNT (get_len ()) * wincap.page_size ();
caddr_t low = MAX (addr, get_address ());
caddr_t high = MIN (addr + len, get_address () + rec_len);
if (low < high)
@@ -470,9 +470,8 @@ mmap_record::map_pages (SIZE_T len, int new_prot, off_t off)
len = PAGE_CNT (len);
if (!noreserve ()
- && !VirtualProtect (get_address ()
- + off * wincap.allocation_granularity (),
- len * wincap.allocation_granularity (),
+ && !VirtualProtect (get_address () + off * wincap.page_size (),
+ len * wincap.page_size (),
::gen_protect (new_prot, get_flags ()),
&old_prot))
{
@@ -492,7 +491,7 @@ mmap_record::map_pages (caddr_t addr, SIZE_T len, int
new_prot)
new_prot);
DWORD old_prot;
off_t off = addr - get_address ();
- off /= wincap.allocation_granularity ();
+ off /= wincap.page_size ();
len = PAGE_CNT (len);
/* VirtualProtect can only be called on committed pages, so it's not
clear how to change protection in the noreserve case. In this
@@ -508,9 +507,8 @@ mmap_record::map_pages (caddr_t addr, SIZE_T len, int
new_prot)
return false;
}
}
- else if (!VirtualProtect (get_address ()
- + off * wincap.allocation_granularity (),
- len * wincap.allocation_granularity (),
+ else if (!VirtualProtect (get_address () + off * wincap.page_size (),
+ len * wincap.page_size (),
::gen_protect (new_prot, get_flags ()),
&old_prot))
{
@@ -534,7 +532,7 @@ mmap_record::unmap_pages (caddr_t addr, SIZE_T len)
&old_prot))
debug_printf ("VirtualProtect in unmap_pages () failed, %E");
- off /= wincap.allocation_granularity ();
+ off /= wincap.page_size ();
len = PAGE_CNT (len);
for (; len-- > 0; ++off)
MAP_CLR (off);
@@ -551,7 +549,7 @@ mmap_record::access (caddr_t address)
{
if (address < get_address () || address >= get_address () + get_len ())
return 0;
- SIZE_T off = (address - get_address ()) / wincap.allocation_granularity ();
+ SIZE_T off = (address - get_address ()) / wincap.page_size ();
return MAP_ISSET (off);
}
@@ -644,8 +642,7 @@ mmap_list::try_map (void *addr, size_t len, int new_prot,
int flags, off_t off)
{
if (!rec->map_pages (len, new_prot, off))
return (caddr_t) MAP_FAILED;
- return (caddr_t) rec->get_address ()
- + off * wincap.allocation_granularity ();
+ return (caddr_t) rec->get_address () + off * wincap.page_size ();
}
}
else if (fixed (flags))
@@ -882,8 +879,8 @@ mmap (void *addr, size_t len, int prot, int flags, int fd,
off_t off)
/* The autoconf mmap test maps a file of size 1 byte. It then tests
every byte of the entire mapped page of 64K for 0-bytes since that's
what POSIX requires. The problem is, we can't create that mapping.
- The file mapping will be only a single Windows page, 4K, and the
- remainder of the 64K slot will result in a SEGV when accessed.
+ The file mapping will be only a single page, 4K, and the remainder
+ of the 64K slot will result in a SEGV when accessed.
So, what we do here is cheating for the sake of the autoconf test.
The justification is that there's very likely no application actually
