Move to gawk-3.1.7.

1 files changed, 275 insertions, 0 deletions

diff --git a/libsigsegv/src/stackvma-mincore.c b/libsigsegv/src/stackvma-mincore.c
new file mode 100644
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+++ b/libsigsegv/src/stackvma-mincore.c
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+/* Determine the virtual memory area of a given address.
+   Copyright (C) 2006, 2008  Bruno Haible <bruno@clisp.org>
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* mincore() is a system call that allows to inquire the status of a
+   range of pages of virtual memory.  In particular, it allows to inquire
+   whether a page is mapped at all.
+   As of 2006, mincore() is supported by:        possible bits:
+     - Linux,   since Linux 2.4 and glibc 2.2,   1
+     - Solaris, since Solaris 9,                 1
+     - MacOS X, since MacOS X 10.3 (at least),   1
+     - FreeBSD, since FreeBSD 6.0,               MINCORE_{INCORE,REFERENCED,MODIFIED}
+     - NetBSD,  since NetBSD 3.0 (at least),     1
+     - OpenBSD, since OpenBSD 2.6 (at least),    1
+   However, while the API allows to easily determine the bounds of mapped
+   virtual memory, it does not make it easy the bounds of _unmapped_ virtual
+   memory ranges.  We try to work around this, but it may still be slow.  */
+
+#include "stackvma.h"
+#include <limits.h>
+#ifdef HAVE_UNISTD_H
+# include <unistd.h>
+#endif
+#include <sys/types.h>
+#include <sys/mman.h>
+
+/* Cache for getpagesize().  */
+static unsigned long pagesize;
+
+/* Initialize pagesize.  */
+static void
+init_pagesize (void)
+{
+#if HAVE_GETPAGESIZE
+  pagesize = getpagesize ();
+#elif HAVE_SYSCONF_PAGESIZE
+  pagesize = sysconf (_SC_PAGESIZE);
+#else
+  pagesize = PAGESIZE;
+#endif
+}
+
+/* Test whether the page starting at ADDR is among the address range.
+   ADDR must be a multiple of pagesize.  */
+static int
+is_mapped (unsigned long addr)
+{
+  char vec[1];
+  return mincore ((void *) addr, pagesize, vec) >= 0;
+}
+
+/* Assuming that the page starting at ADDR is among the address range,
+   return the start of its virtual memory range.
+   ADDR must be a multiple of pagesize.  */
+static unsigned long
+mapped_range_start (unsigned long addr)
+{
+  /* Use a moderately sized VEC here, small enough that it fits on the stack
+     (without requiring malloc).  */
+  char vec[2048];
+  unsigned long stepsize = sizeof (vec);
+
+  for (;;)
+    {
+      unsigned long max_remaining;
+
+      if (addr == 0)
+        return addr;
+
+      max_remaining = addr / pagesize;
+      if (stepsize > max_remaining)
+        stepsize = max_remaining;
+      if (mincore ((void *) (addr - stepsize * pagesize),
+                   stepsize * pagesize, vec) < 0)
+        /* Time to search in smaller steps.  */
+        break;
+      /* The entire range exists.  Continue searching in large steps.  */
+      addr -= stepsize * pagesize;
+    }
+  for (;;)
+    {
+      unsigned long halfstepsize1;
+      unsigned long halfstepsize2;
+
+      if (stepsize == 1)
+        return addr;
+
+      /* Here we know that less than stepsize pages exist starting at addr.  */
+      halfstepsize1 = (stepsize + 1) / 2;
+      halfstepsize2 = stepsize / 2;
+      /* halfstepsize1 + halfstepsize2 = stepsize.  */
+
+      if (mincore ((void *) (addr - halfstepsize1 * pagesize),
+                   halfstepsize1 * pagesize, vec) < 0)
+        stepsize = halfstepsize1;
+      else
+        {
+          addr -= halfstepsize1 * pagesize;
+          stepsize = halfstepsize2;
+        }
+    }
+}
+
+/* Assuming that the page starting at ADDR is among the address range,
+   return the end of its virtual memory range + 1.
+   ADDR must be a multiple of pagesize.  */
+static unsigned long
+mapped_range_end (unsigned long addr)
+{
+  /* Use a moderately sized VEC here, small enough that it fits on the stack
+     (without requiring malloc).  */
+  char vec[2048];
+  unsigned long stepsize = sizeof (vec);
+
+  addr += pagesize;
+  for (;;)
+    {
+      unsigned long max_remaining;
+
+      if (addr == 0) /* wrapped around? */
+        return addr;
+
+      max_remaining = (- addr) / pagesize;
+      if (stepsize > max_remaining)
+        stepsize = max_remaining;
+      if (mincore ((void *) addr, stepsize * pagesize, vec) < 0)
+        /* Time to search in smaller steps.  */
+        break;
+      /* The entire range exists.  Continue searching in large steps.  */
+      addr += stepsize * pagesize;
+    }
+  for (;;)
+    {
+      unsigned long halfstepsize1;
+      unsigned long halfstepsize2;
+
+      if (stepsize == 1)
+        return addr;
+
+      /* Here we know that less than stepsize pages exist starting at addr.  */
+      halfstepsize1 = (stepsize + 1) / 2;
+      halfstepsize2 = stepsize / 2;
+      /* halfstepsize1 + halfstepsize2 = stepsize.  */
+
+      if (mincore ((void *) addr, halfstepsize1 * pagesize, vec) < 0)
+        stepsize = halfstepsize1;
+      else
+        {
+          addr += halfstepsize1 * pagesize;
+          stepsize = halfstepsize2;
+        }
+    }
+}
+
+/* Determine whether an address range [ADDR1..ADDR2] is completely unmapped.
+   ADDR1 must be <= ADDR2.  */
+static int
+is_unmapped (unsigned long addr1, unsigned long addr2)
+{
+  unsigned long count;
+  unsigned long stepsize;
+
+  /* Round addr1 down.  */
+  addr1 = (addr1 / pagesize) * pagesize;
+  /* Round addr2 up and turn it into an exclusive bound.  */
+  addr2 = ((addr2 / pagesize) + 1) * pagesize;
+
+  /* This is slow: mincore() does not provide a way to determine the bounds
+     of the gaps directly.  So we have to use mincore() on individual pages
+     over and over again.  Only after we've verified that all pages are
+     unmapped, we know that the range is completely unmapped.
+     If we were to traverse the pages from bottom to top or from top to bottom,
+     it would be slow even in the average case.  To speed up the search, we
+     exploit the fact that mapped memory ranges are larger than one page on
+     average, therefore we have good chances of hitting a mapped area if we
+     traverse only every second, or only fourth page, etc.  This doesn't
+     decrease the worst-case runtime, only the average runtime.  */
+  count = (addr2 - addr1) / pagesize;
+  /* We have to test is_mapped (addr1 + i * pagesize) for 0 <= i < count.  */
+  for (stepsize = 1; stepsize < count; )
+    stepsize = 2 * stepsize;
+  for (;;)
+    {
+      unsigned long addr_stepsize;
+      unsigned long i;
+      unsigned long addr;
+
+      stepsize = stepsize / 2;
+      if (stepsize == 0)
+        break;
+      addr_stepsize = stepsize * pagesize;
+      for (i = stepsize, addr = addr1 + addr_stepsize;
+           i < count;
+           i += 2 * stepsize, addr += 2 * addr_stepsize)
+        /* Here addr = addr1 + i * pagesize.  */
+        if (is_mapped (addr))
+          return 0;
+    }
+  return 1;
+}
+
+#if STACK_DIRECTION < 0
+
+/* Info about the gap between this VMA and the previous one.
+   addr must be < vma->start.  */
+static int
+mincore_is_near_this (unsigned long addr, struct vma_struct *vma)
+{
+  /*   vma->start - addr <= (vma->start - vma->prev_end) / 2
+     is mathematically equivalent to
+       vma->prev_end <= 2 * addr - vma->start
+     <==> is_unmapped (2 * addr - vma->start, vma->start - 1).
+     But be careful about overflow: if 2 * addr - vma->start is negative,
+     we consider a tiny "guard page" mapping [0, 0] to be present around
+     NULL; it intersects the range (2 * addr - vma->start, vma->start - 1),
+     therefore return false.  */
+  unsigned long testaddr = addr - (vma->start - addr);
+  if (testaddr > addr) /* overflow? */
+    return 0;
+  /* Here testaddr <= addr < vma->start.  */
+  return is_unmapped (testaddr, vma->start - 1);
+}
+
+#endif
+#if STACK_DIRECTION > 0
+
+/* Info about the gap between this VMA and the next one.
+   addr must be > vma->end - 1.  */
+static int
+mincore_is_near_this (unsigned long addr, struct vma_struct *vma)
+{
+  /*   addr - vma->end < (vma->next_start - vma->end) / 2
+     is mathematically equivalent to
+       vma->next_start > 2 * addr - vma->end
+     <==> is_unmapped (vma->end, 2 * addr - vma->end).
+     But be careful about overflow: if 2 * addr - vma->end is > ~0UL,
+     we consider a tiny "guard page" mapping [0, 0] to be present around
+     NULL; it intersects the range (vma->end, 2 * addr - vma->end),
+     therefore return false.  */
+  unsigned long testaddr = addr + (addr - vma->end);
+  if (testaddr < addr) /* overflow? */
+    return 0;
+  /* Here vma->end - 1 < addr <= testaddr.  */
+  return is_unmapped (vma->end, testaddr);
+}
+
+#endif
+
+#ifdef STATIC
+STATIC
+#endif
+int
+sigsegv_get_vma (unsigned long address, struct vma_struct *vma)
+{
+  if (pagesize == 0)
+    init_pagesize ();
+  address = (address / pagesize) * pagesize;
+  vma->start = mapped_range_start (address);
+  vma->end = mapped_range_end (address);
+  vma->is_near_this = mincore_is_near_this;
+  return 0;
+}