[rfc] Fix pch on sparc-linux.

[James Morrison]

 Hi,

  This patch fixes all the pch failures on sparc-linux, as show here
http://gcc.gnu.org/ml/gcc-testresults/2005-02/msg00458.html, it also fixed
all but one pch failures for me in the gcc.dg/pch testsuite on my initial test.
Christian has already bootstrapped and regtested this patch on sparc-linux,
I'm currently testing it on sparc64-linux to see if it fixes all the libstdc++
failures I got yesterday.

  What I am unsure about as I don't have access to enough linux targets is, is
this good for all linux targets?  Or is it better to copy pa/pa-host.c to
sparc/sparc-linux-host.c and change the function names appropriately?

Jim

2005-02-12  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.

Index: config/host-linux.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/config/host-linux.c,v
retrieving revision 1.6
diff -u -p -r1.6 host-linux.c
--- config/host-linux.c	27 Nov 2004 16:57:06 -0000	1.6
+++ config/host-linux.c	11 Feb 2005 12:34:27 -0000
@@ -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 +154,68 @@ linux_gt_pch_get_address (size_t size, i
   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;