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108 lines
3.7 KiB
108 lines
3.7 KiB
1 month ago
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commit 9de9cd17e73db0ba9af9ef11dc12d490fb59720c
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Author: sayan paul <saypaul@redhat.com>
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Date: Wed May 29 15:31:04 2024 +0530
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malloc: New test to check malloc alternate path using memory obstruction
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The test aims to ensure that malloc uses the alternate path to
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allocate memory when sbrk() or brk() fails.To achieve this,
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the test first creates an obstruction at current program break,
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tests that obstruction with a failing sbrk(), then checks if malloc
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is still returning a valid ptr thus inferring that malloc() used
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mmap() instead of brk() or sbrk() to allocate the memory.
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Reviewed-by: Arjun Shankar <arjun@redhat.com>
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Reviewed-by: Zack Weinberg <zack@owlfolio.org>
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(cherry picked from commit 127fc56152347d73cb7c1c283e60e1cb1f15e9f9)
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diff --git a/malloc/Makefile b/malloc/Makefile
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index c1a03f3cb02c464d..cc14cf66c9661f99 100644
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--- a/malloc/Makefile
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+++ b/malloc/Makefile
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@@ -34,6 +34,7 @@ tests := \
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tst-interpose-nothread \
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tst-interpose-thread \
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tst-malloc \
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+ tst-malloc-alternate-path \
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tst-malloc-backtrace \
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tst-malloc-check \
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tst-malloc-fork-deadlock \
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diff --git a/malloc/tst-malloc-alternate-path.c b/malloc/tst-malloc-alternate-path.c
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new file mode 100644
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index 0000000000000000..43ae916815d6ff47
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--- /dev/null
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+++ b/malloc/tst-malloc-alternate-path.c
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@@ -0,0 +1,72 @@
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+/* Test that malloc uses mmap when sbrk or brk fails.
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+ Copyright (C) 2024 Free Software Foundation, Inc.
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+ This file is part of the GNU C Library.
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+
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+ The GNU C Library is free software; you can redistribute it and/or
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+ modify it under the terms of the GNU Lesser General Public
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+ License as published by the Free Software Foundation; either
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+ version 2.1 of the License, or (at your option) any later version.
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+
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+ The GNU C Library is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+ Lesser General Public License for more details.
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+
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+ You should have received a copy of the GNU Lesser General Public
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+ License along with the GNU C Library; if not, see
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+ <https://www.gnu.org/licenses/>. */
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+
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+/* This test sets up an obstruction to ensure that brk/sbrk fails to
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+ grow the heap, then verifies that malloc uses mmap for allocations
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+ instead. */
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+
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+#include <unistd.h>
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+#include <sys/mman.h>
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+#include <stdlib.h>
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+#include <libc-pointer-arith.h>
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+#include <support/check.h>
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+#include <stddef.h>
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+#include <stdalign.h>
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+
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+#define LARGE_SIZE (10 * (1 << 20)) // 10 MB
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+static long page_size;
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+
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+static int
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+do_test (void)
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+{
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+ /* Get current program break. */
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+ void *current_brk = sbrk (0);
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+
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+ page_size = sysconf (_SC_PAGESIZE);
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+
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+ /* Round up to the next page boundary. */
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+ void *next_page_boundary = PTR_ALIGN_UP (current_brk, page_size);
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+
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+ /* Place a mapping using mmap at the next page boundary. */
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+ void *obstruction_addr
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+ = mmap (next_page_boundary, page_size, PROT_READ,
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+ MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
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+
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+ /* Check if memory obstruction is set up correctly. */
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+ TEST_VERIFY_EXIT (obstruction_addr == next_page_boundary);
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+
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+ /* Try to extend the heap beyond the obstruction using sbrk */
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+ int *ptr = sbrk (page_size);
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+ TEST_VERIFY_EXIT (ptr == (void *) -1);
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+
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+ /* Attempt multiple small allocations using malloc. */
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+ for (size_t i = 0; i < page_size / alignof (max_align_t); i++)
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+ {
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+ TEST_VERIFY (malloc (alignof (max_align_t)));
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+ }
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+
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+ /* Attempt to allocate a large block of memory using malloc. */
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+ TEST_VERIFY_EXIT (malloc (LARGE_SIZE) != NULL);
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+
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+ /* Check if malloc changed current program break. */
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+ TEST_VERIFY_EXIT (current_brk == sbrk (0));
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+
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+ return 0;
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+}
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+
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+#include <support/test-driver.c>
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