[PATCH] Cygwin: mmap: use 64K pages for bookkeeping

[Ken Brown]

On 1/15/2025 8:17 AM, Takashi Yano wrote:
> With this patch, gdb no longer works in my environment:
> 
> $ gdb
> Pre-boot error; key: system-error, args: ("load-thunk-from-memory" "~A" ("Invalid argument") (22))
> 
> Fatal signal: Aborted
> ----- Backtrace -----
> ---------------------
> A fatal error internal to GDB has been detected, further
> debugging is not possible.  GDB will now terminate.
> 
> This is a bug, please report it.  For instructions, see:
> <https://www.gnu.org/software/gdb/bugs/>.
> 
> Abort
> $
> 
> Any idea?

I ran gdb under strace and saw the following:


   125 6200747 [main] gdb 25844 mprotect: mprotect (addr: 
0x6FFFFFA50000, len 7584, prot 0x3)
   122 6200869 [main] gdb 25844 seterrno_from_win_error: 
../../../../winsup/cygwin/mm/mmap.cc:1290 windows error 487
   141 6201010 [main] gdb 25844 geterrno_from_win_error: windows error 
487 == errno 22
   133 6201143 [main] gdb 25844 mprotect: -1 = mprotect (), errno 22
[...]
    65 6237537 [main] gdb 25844 mmap_record::unmap_pages: VirtualProtect 
in unmap_pages () failed, Win32 error 487

Windows error 487 is ERROR_INVALID_ADDRESS.

I'll try to figure out what's going on.  In the meantime, I've reverted 
the commit.

Thanks for reporting this, and sorry for the inconvenience.

Ken