Merge patch series "mcheck implementation for U-Boot"

Eugene Uriev <eugeneuriev@gmail.com> says:

There was no "mcheck" for U-Boot before.

Since U-Boot has only 1 thread, and normally makes 4000+ - 6000+
mallocs, it's better to use havier canaries to protect heap-chunks.
My variant uses 2x8 = 16byte-long protector. And
the multiplier could be changed to tune speed/protection tradeoff.
This protects not only against memset()-s, but against "near" wild
pointers too, and makes more probable to catch "distant" ones.

The core file of the set is included into the C-file, not complied
separately in order to enable (potential) coexisting of
mcheck-protectors, e.g. malloc_simple(.) and dlmalloc simultaneously.

My tests were for ARM SoC, 64bit, so the patch is
aware of alignment.

Primary this patch is for using by developers: to verify,
if a change doesn't break the heap integrity.
By default the mcheck is disabled and wouldn't affect the boot.

I used pedantic mode, canary=16byte, registry-size=6608.
For my system the overhead was 230ms.

1 files changed, 51 insertions, 0 deletions

diff --git a/include/mcheck.h b/include/mcheck.h
new file mode 100644
index 0000000..bd506ae
--- /dev/null
+++ b/include/mcheck.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.1+ */
+/*
+ * Copyright (C) 1996-2024 Free Software Foundation, Inc.
+ * This file is part of the GNU C Library.
+ *
+ * This 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.
+ *
+ * This 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.
+ * <https://www.gnu.org/licenses/>.
+ */
+#ifndef _MCHECK_H
+#define _MCHECK_H       1
+
+/*
+ * Return values for `mprobe': these are the kinds of inconsistencies that
+ * `mcheck' enables detection of.
+ */
+enum mcheck_status {
+	MCHECK_DISABLED = -1,         /* Consistency checking is not turned on.  */
+	MCHECK_OK,                    /* Block is fine.  */
+	MCHECK_FREE,                  /* Block freed twice.  */
+	MCHECK_HEAD,                  /* Memory before the block was clobbered.  */
+	MCHECK_TAIL                   /* Memory after the block was clobbered.  */
+};
+
+typedef void (*mcheck_abortfunc_t)(enum mcheck_status, const void *p);
+
+int mcheck(mcheck_abortfunc_t func);
+
+/*
+ * Similar to `mcheck' but performs checks for all block whenever one of
+ * the memory handling functions is called.  This can be very slow.
+ */
+int mcheck_pedantic(mcheck_abortfunc_t f);
+
+/* Force check of all blocks now.  */
+void mcheck_check_all(void);
+
+/*
+ * Check for aberrations in a particular malloc'd block. These are the
+ * same checks that `mcheck' does, when you free or reallocate a block.
+ */
+enum mcheck_status mprobe(void *__ptr);
+
+#endif