[newlib-cygwin] Cygwin: mmap: use extended memory API if available

[newlib-cygwin] Cygwin: mmap: use extended memory API if available

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=8d0a7701aa9e98bda511ba55f5f2dc210722d3e9

commit 8d0a7701aa9e98bda511ba55f5f2dc210722d3e9
Author: Corinna Vinschen <corinna@vinschen.de>
Date:   Tue Apr 7 14:16:09 2020 +0200

    Cygwin: mmap: use extended memory API if available
    
    So far Cygwin was jumping through hoops to restrict memory
    allocation to specific regions.  With the advent of VirtualAlloc2
    and MapViewOfFile3 (and it's NT counterpart NtMapViewOfSectionEx),
    we can skip searching for free space in the specific regions
    and just call these functions and let the OS do the job more
    efficiently and less racy.
    
    Use the new functions on W10 1803 and later in mmap.
    
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 winsup/cygwin/mmap.cc | 84 +++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 74 insertions(+), 10 deletions(-)

diff --git a/winsup/cygwin/mmap.cc b/winsup/cygwin/mmap.cc
index 662489c8c..feb9e5d0e 100644
--- a/winsup/cygwin/mmap.cc
+++ b/winsup/cygwin/mmap.cc
@@ -188,13 +188,12 @@ CreateMapping (HANDLE fhdl, size_t len, off_t off, DWORD openflags,
 
 static void *
 MapView (HANDLE h, void *addr, size_t len, DWORD openflags,
-	 int prot, int flags, off_t off)
+	 int prot, int flags, off_t off, bool from_fixup_after_fork)
 {
   NTSTATUS status;
   LARGE_INTEGER offset = { QuadPart:off };
   DWORD protect = gen_create_protect (openflags, flags);
   void *base = addr;
-  SIZE_T commitsize = attached (prot) ? 0 : len;
   SIZE_T viewsize = len;
 #ifdef __x86_64__ /* AT_ROUND_TO_PAGE isn't supported on 64 bit systems. */
   ULONG alloc_type = MEM_TOP_DOWN;
@@ -203,12 +202,51 @@ MapView (HANDLE h, void *addr, size_t len, DWORD openflags,
 		     | MEM_TOP_DOWN;
 #endif
 
+#ifdef __x86_64__
+  /* Don't call NtMapViewOfSectionEx during fork.  It requires autoloading
+     a function under loader lock (STATUS_DLL_INIT_FAILED). */
+  if (!from_fixup_after_fork && wincap.has_extended_mem_api ())
+    {
+      MEM_ADDRESS_REQUIREMENTS mmap_req = {
+	(PVOID) MMAP_STORAGE_LOW,
+	(PVOID) (MMAP_STORAGE_HIGH - 1),
+	0
+      };
+      MEM_EXTENDED_PARAMETER mmap_ext = {
+	.Type = MemExtendedParameterAddressRequirements,
+	.Pointer = (PVOID) &mmap_req
+      };
+
+      alloc_type |= attached (prot) ? MEM_RESERVE : 0;
+      status = NtMapViewOfSectionEx (h, NtCurrentProcess (), &base, &offset,
+				     &viewsize, alloc_type, protect,
+				     addr ? NULL : &mmap_ext, addr ? 0 : 1);
+      if (!NT_SUCCESS (status) && addr && !fixed (flags))
+	{
+	  base = NULL;
+	  status = NtMapViewOfSectionEx (h, NtCurrentProcess (), &base,
+					 &offset, &viewsize, alloc_type,
+					 protect, &mmap_ext, 1);
+	}
+      if (!NT_SUCCESS (status))
+	{
+	  base = NULL;
+	  SetLastError (RtlNtStatusToDosError (status));
+	}
+      debug_printf ("%p (status %p) = NtMapViewOfSectionEx (h:%p, addr:%p, "
+		    "off:%Y, viewsize:%U, alloc_type:%y, protect:%y",
+		    base, status, h, addr, off, viewsize, alloc_type, protect);
+      return base;
+    }
+#endif
+
   /* Try mapping using the given address first, even if it's NULL.
      If it failed, and addr was not NULL and flags is not MAP_FIXED,
      try again with NULL address.
 
      Note: Retrying the mapping might be unnecessary, now that mmap64 checks
 	   for a valid memory area first. */
+  SIZE_T commitsize = attached (prot) ? 0 : len;
   status = NtMapViewOfSection (h, NtCurrentProcess (), &base, 0, commitsize,
 			       &offset, &viewsize, ViewShare, alloc_type,
 			       protect);
@@ -1051,7 +1089,8 @@ go_ahead:
     }
 
 #ifdef __x86_64__
-  addr = mmap_alloc.alloc (addr, orig_len ?: len, fixed (flags));
+  if (!wincap.has_extended_mem_api ())
+    addr = mmap_alloc.alloc (addr, orig_len ?: len, fixed (flags));
 #else
   if (orig_len)
     {
@@ -1637,9 +1676,33 @@ fhandler_dev_zero::mmap (caddr_t *addr, size_t len, int prot,
       DWORD protect = gen_protect (prot, flags);
       DWORD alloc_type = MEM_TOP_DOWN | MEM_RESERVE
 			 | (noreserve (flags) ? 0 : MEM_COMMIT);
-      base = VirtualAlloc (*addr, len, alloc_type, protect);
-      if (!base && addr && !fixed (flags))
-	base = VirtualAlloc (NULL, len, alloc_type, protect);
+#ifdef __x86_64__
+      if (wincap.has_extended_mem_api ())
+	{
+	  MEM_ADDRESS_REQUIREMENTS mmap_req = {
+	    (PVOID) MMAP_STORAGE_LOW,
+	    (PVOID) (MMAP_STORAGE_HIGH - 1),
+	    0
+	  };
+	  MEM_EXTENDED_PARAMETER mmap_ext = {
+	    .Type = MemExtendedParameterAddressRequirements,
+	    .Pointer = (PVOID) &mmap_req
+	  };
+
+	  base = VirtualAlloc2 (GetCurrentProcess(), *addr, len, alloc_type,
+				protect, *addr ? NULL : &mmap_ext,
+				*addr ? 0 : 1);
+	  if (!base && addr && !fixed (flags))
+	    base = VirtualAlloc2 (GetCurrentProcess(), NULL, len, alloc_type,
+				  protect, &mmap_ext, 1);
+	}
+      else
+#endif
+	{
+	  base = VirtualAlloc (*addr, len, alloc_type, protect);
+	  if (!base && addr && !fixed (flags))
+	    base = VirtualAlloc (NULL, len, alloc_type, protect);
+	}
       if (!base || (fixed (flags) && base != *addr))
 	{
 	  if (!base)
@@ -1664,7 +1727,7 @@ fhandler_dev_zero::mmap (caddr_t *addr, size_t len, int prot,
 	  return INVALID_HANDLE_VALUE;
 	}
 
-      base = MapView (h, *addr, len, get_access(), prot, flags, off);
+      base = MapView (h, *addr, len, get_access(), prot, flags, off, false);
       if (!base || (fixed (flags) && base != *addr))
 	{
 	  if (!base)
@@ -1718,7 +1781,7 @@ fhandler_dev_zero::fixup_mmap_after_fork (HANDLE h, int prot, int flags,
       base = VirtualAlloc (address, size, alloc_type, PAGE_READWRITE);
     }
   else
-    base = MapView (h, address, size, get_access (), prot, flags, offset);
+    base = MapView (h, address, size, get_access (), prot, flags, offset, true);
   if (base != address)
     {
       MEMORY_BASIC_INFORMATION m;
@@ -1744,7 +1807,7 @@ fhandler_disk_file::mmap (caddr_t *addr, size_t len, int prot,
       return INVALID_HANDLE_VALUE;
     }
 
-  void *base = MapView (h, *addr, len, get_access (), prot, flags, off);
+  void *base = MapView (h, *addr, len, get_access (), prot, flags, off, false);
   if (!base || (fixed (flags) && base != *addr))
     {
       if (!base)
@@ -1804,7 +1867,8 @@ fhandler_disk_file::fixup_mmap_after_fork (HANDLE h, int prot, int flags,
 					   void *address)
 {
   /* Re-create the map */
-  void *base = MapView (h, address, size, get_access (), prot, flags, offset);
+  void *base = MapView (h, address, size, get_access (), prot, flags,
+			offset, true);
   if (base != address)
     {
       MEMORY_BASIC_INFORMATION m;