2005-02-15 James A. Morrison <phython@gcc.gnu.org>

       PR pch/14940
       PR target/19300
       * config/host-linux.c (linux_gt_pch_use_address): Copy from
       config/pa/pa-host.c:pa_gt_pch_use_address.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@95073 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 66 insertions, 0 deletions

diff --git a/gcc/config/host-linux.c b/gcc/config/host-linux.c
index 717f96cdc66..7683c720c05 100644
--- a/gcc/config/host-linux.c
+++ b/gcc/config/host-linux.c
@@ -61,6 +61,9 @@
 #undef HOST_HOOKS_GT_PCH_GET_ADDRESS
 #define HOST_HOOKS_GT_PCH_GET_ADDRESS linux_gt_pch_get_address
 
+#undef HOST_HOOKS_GT_PCH_USE_ADDRESS
+#define HOST_HOOKS_GT_PCH_USE_ADDRESS linux_gt_pch_use_address
+
 /* For various ports, try to guess a fixed spot in the vm space
    that's probably free.  */
 #if defined(__alpha)
@@ -143,5 +146,68 @@ linux_gt_pch_get_address (size_t size, int fd)
   return addr;
 }
 
+/* Map SIZE bytes of FD+OFFSET at BASE.  Return 1 if we succeeded at
+   mapping the data at BASE, -1 if we couldn't.
+
+   It's not possibly to reliably mmap a file using MAP_PRIVATE to
+   a specific START address on either hpux or linux.  First we see
+   if mmap with MAP_PRIVATE works.  If it does, we are off to the
+   races.  If it doesn't, we try an anonymous private mmap since the
+   kernel is more likely to honor the BASE address in anonymous maps.
+   We then copy the data to the anonymous private map.  This assumes
+   of course that we don't need to change the data in the PCH file
+   after it is created.
+
+   This approach obviously causes a performance penalty but there is
+   little else we can do given the current PCH implementation.  */
+
+static int
+linux_gt_pch_use_address (void *base, size_t size, int fd, size_t offset)
+{
+  void *addr;
+
+  /* We're called with size == 0 if we're not planning to load a PCH
+     file at all.  This allows the hook to free any static space that
+     we might have allocated at link time.  */
+  if (size == 0)
+    return -1;
+
+  /* Try to map the file with MAP_PRIVATE.  */
+  addr = mmap (base, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, offset);
+
+  if (addr == base)
+    return 1;
+
+  if (addr != (void *) MAP_FAILED)
+    munmap (addr, size);
+
+  /* Try to make an anonymous private mmap at the desired location.  */
+  addr = mmap (base, size, PROT_READ | PROT_WRITE,
+	       MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+
+  if (addr != base)
+    {
+      if (addr != (void *) MAP_FAILED)
+        munmap (addr, size);
+      return -1;
+    }
+
+  if (lseek (fd, offset, SEEK_SET) == (off_t)-1)
+    return -1;
+
+  while (size)
+    {
+      ssize_t nbytes;
+
+      nbytes = read (fd, base, MIN (size, SSIZE_MAX));
+      if (nbytes <= 0)
+        return -1;
+      base = (char *) base + nbytes;
+      size -= nbytes;
+    }
+
+  return 1;
+}
+
 
 const struct host_hooks host_hooks = HOST_HOOKS_INITIALIZER;