Prepare for radical source tree reorganization. zack/build-layout-experiment

All top-level files and directories are moved into a temporary storage
directory, REORG.TODO, except for files that will certainly still
exist in their current form at top level when we're done (COPYING,
COPYING.LIB, LICENSES, NEWS, README), all old ChangeLog files (which
are moved to the new directory OldChangeLogs, instead), and the
generated file INSTALL (which is just deleted; in the new order, there
will be no generated files checked into version control).

1 files changed, 298 insertions, 0 deletions

diff --git a/REORG.TODO/string/tst-xbzero-opt.c b/REORG.TODO/string/tst-xbzero-opt.c
new file mode 100644
index 0000000000..7c25632724
--- /dev/null
+++ b/REORG.TODO/string/tst-xbzero-opt.c
@@ -0,0 +1,298 @@
+/* Test that explicit_bzero block clears are not optimized out.
+   Copyright (C) 2016-2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* This test is conceptually based on a test designed by Matthew
+   Dempsky for the OpenBSD regression suite:
+   <openbsd>/src/regress/lib/libc/explicit_bzero/explicit_bzero.c.
+   The basic idea is, we have a function that contains a
+   block-clearing operation (not necessarily explicit_bzero), after
+   which the block is dead, in the compiler-jargon sense.  Execute
+   that function while running on a user-allocated alternative
+   stack. Then we have another pointer to the memory region affected
+   by the block clear -- namely, the original allocation for the
+   alternative stack -- and can find out whether it actually happened.
+
+   The OpenBSD test uses sigaltstack and SIGUSR1 to get onto an
+   alternative stack.  This causes a number of awkward problems; some
+   operating systems (e.g. Solaris and OSX) wipe the signal stack upon
+   returning to the normal stack, there's no way to be sure that other
+   processes running on the same system will not interfere, and the
+   signal stack is very small so it's not safe to call printf there.
+   This implementation instead uses the <ucontext.h> coroutine
+   interface.  The coroutine stack is still too small to safely use
+   printf, but we know the OS won't erase it, so we can do all the
+   checks and printing from the normal stack.  */
+
+#define _GNU_SOURCE 1
+
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ucontext.h>
+#include <unistd.h>
+
+/* A byte pattern that is unlikely to occur by chance: the first 16
+   prime numbers (OEIS A000040).  */
+static const unsigned char test_pattern[16] =
+{
+  2, 3, 5, 7,  11, 13, 17, 19,  23, 29, 31, 37,  41, 43, 47, 53
+};
+
+/* Immediately after each subtest returns, we call swapcontext to get
+   back onto the main stack.  That call might itself overwrite the
+   test pattern, so we fill a modest-sized buffer with copies of it
+   and check whether any of them survived.  */
+
+#define PATTERN_SIZE (sizeof test_pattern)
+#define PATTERN_REPS 32
+#define TEST_BUFFER_SIZE (PATTERN_SIZE * PATTERN_REPS)
+
+/* There are three subtests, two of which are sanity checks.
+   Each test follows this sequence:
+
+     main                      coroutine
+     ----                      --------
+     advance cur_subtest
+     swap
+                               call setup function
+                                 prepare test buffer
+                                 swap
+     verify that buffer
+     was filled in
+     swap
+                                 possibly clear buffer
+                                 return
+                               swap
+     check buffer again,
+     according to test
+     expectation
+
+   In the "no_clear" case, we don't do anything to the test buffer
+   between preparing it and letting it go out of scope, and we expect
+   to find it.  This confirms that the test buffer does get filled in
+   and we can find it from the stack buffer.  In the "ordinary_clear"
+   case, we clear it using memset.  Depending on the target, the
+   compiler may not be able to apply dead store elimination to the
+   memset call, so the test does not fail if the memset is not
+   eliminated.  Finally, the "explicit_clear" case uses explicit_bzero
+   and expects _not_ to find the test buffer, which is the real
+   test.  */
+
+static ucontext_t uc_main, uc_co;
+
+/* Always check the test buffer immediately after filling it; this
+   makes externally visible side effects depend on the buffer existing
+   and having been filled in.  */
+static inline __attribute__  ((always_inline)) void
+prepare_test_buffer (unsigned char *buf)
+{
+  for (unsigned int i = 0; i < PATTERN_REPS; i++)
+    memcpy (buf + i*PATTERN_SIZE, test_pattern, PATTERN_SIZE);
+
+  if (swapcontext (&uc_co, &uc_main))
+    abort ();
+}
+
+static void
+setup_no_clear (void)
+{
+  unsigned char buf[TEST_BUFFER_SIZE];
+  prepare_test_buffer (buf);
+}
+
+static void
+setup_ordinary_clear (void)
+{
+  unsigned char buf[TEST_BUFFER_SIZE];
+  prepare_test_buffer (buf);
+  memset (buf, 0, TEST_BUFFER_SIZE);
+}
+
+static void
+setup_explicit_clear (void)
+{
+  unsigned char buf[TEST_BUFFER_SIZE];
+  prepare_test_buffer (buf);
+  explicit_bzero (buf, TEST_BUFFER_SIZE);
+}
+
+enum test_expectation
+  {
+    EXPECT_NONE, EXPECT_SOME, EXPECT_ALL, NO_EXPECTATIONS
+  };
+struct subtest
+{
+  void (*setup_subtest) (void);
+  const char *label;
+  enum test_expectation expected;
+};
+static const struct subtest *cur_subtest;
+
+static const struct subtest subtests[] =
+{
+  { setup_no_clear,       "no clear",       EXPECT_SOME },
+  /* The memset may happen or not, depending on compiler
+     optimizations.  */
+  { setup_ordinary_clear, "ordinary clear", NO_EXPECTATIONS },
+  { setup_explicit_clear, "explicit clear", EXPECT_NONE },
+  { 0,                    0,                -1          }
+};
+
+static void
+test_coroutine (void)
+{
+  while (cur_subtest->setup_subtest)
+    {
+      cur_subtest->setup_subtest ();
+      if (swapcontext (&uc_co, &uc_main))
+	abort ();
+    }
+}
+
+/* All the code above this point runs on the coroutine stack.
+   All the code below this point runs on the main stack.  */
+
+static int test_status;
+static unsigned char *co_stack_buffer;
+static size_t co_stack_size;
+
+static unsigned int
+count_test_patterns (unsigned char *buf, size_t bufsiz)
+{
+  unsigned char *first = memmem (buf, bufsiz, test_pattern, PATTERN_SIZE);
+  if (!first)
+    return 0;
+  unsigned int cnt = 0;
+  for (unsigned int i = 0; i < PATTERN_REPS; i++)
+    {
+      unsigned char *p = first + i*PATTERN_SIZE;
+      if (p + PATTERN_SIZE - buf > bufsiz)
+	break;
+      if (memcmp (p, test_pattern, PATTERN_SIZE) == 0)
+	cnt++;
+    }
+  return cnt;
+}
+
+static void
+check_test_buffer (enum test_expectation expected,
+		   const char *label, const char *stage)
+{
+  unsigned int cnt = count_test_patterns (co_stack_buffer, co_stack_size);
+  switch (expected)
+    {
+    case EXPECT_NONE:
+      if (cnt == 0)
+	printf ("PASS: %s/%s: expected 0 got %d\n", label, stage, cnt);
+      else
+	{
+	  printf ("FAIL: %s/%s: expected 0 got %d\n", label, stage, cnt);
+	  test_status = 1;
+	}
+      break;
+
+    case EXPECT_SOME:
+      if (cnt > 0)
+	printf ("PASS: %s/%s: expected some got %d\n", label, stage, cnt);
+      else
+	{
+	  printf ("FAIL: %s/%s: expected some got 0\n", label, stage);
+	  test_status = 1;
+	}
+      break;
+
+     case EXPECT_ALL:
+      if (cnt == PATTERN_REPS)
+	printf ("PASS: %s/%s: expected %d got %d\n", label, stage,
+		PATTERN_REPS, cnt);
+      else
+	{
+	  printf ("FAIL: %s/%s: expected %d got %d\n", label, stage,
+		  PATTERN_REPS, cnt);
+	  test_status = 1;
+	}
+      break;
+
+    case NO_EXPECTATIONS:
+      printf ("INFO: %s/%s: found %d patterns%s\n", label, stage, cnt,
+	      cnt == 0 ? " (memset not eliminated)" : "");
+      break;
+
+    default:
+      printf ("ERROR: %s/%s: invalid value for 'expected' = %d\n",
+	      label, stage, (int)expected);
+      test_status = 1;
+    }
+}
+
+static void
+test_loop (void)
+{
+  cur_subtest = subtests;
+  while (cur_subtest->setup_subtest)
+    {
+      if (swapcontext (&uc_main, &uc_co))
+	abort ();
+      check_test_buffer (EXPECT_ALL, cur_subtest->label, "prepare");
+      if (swapcontext (&uc_main, &uc_co))
+	abort ();
+      check_test_buffer (cur_subtest->expected, cur_subtest->label, "test");
+      cur_subtest++;
+    }
+  /* Terminate the coroutine.  */
+  if (swapcontext (&uc_main, &uc_co))
+    abort ();
+}
+
+int
+do_test (void)
+{
+  size_t page_alignment = sysconf (_SC_PAGESIZE);
+  if (page_alignment < sizeof (void *))
+    page_alignment = sizeof (void *);
+
+  co_stack_size = SIGSTKSZ + TEST_BUFFER_SIZE;
+  if (co_stack_size < page_alignment * 4)
+    co_stack_size = page_alignment * 4;
+
+  void *p;
+  int err = posix_memalign (&p, page_alignment, co_stack_size);
+  if (err || !p)
+    {
+      printf ("ERROR: allocating alt stack: %s\n", strerror (err));
+      return 2;
+    }
+  co_stack_buffer = p;
+
+  if (getcontext (&uc_co))
+    {
+      printf ("ERROR: allocating coroutine context: %s\n", strerror (err));
+      return 2;
+    }
+  uc_co.uc_stack.ss_sp   = co_stack_buffer;
+  uc_co.uc_stack.ss_size = co_stack_size;
+  uc_co.uc_link          = &uc_main;
+  makecontext (&uc_co, test_coroutine, 0);
+
+  test_loop ();
+  return test_status;
+}
+
+#include <support/test-driver.c>