mcheck: introduce essentials of mcheck

The core part of mcheck, but without memalign.
memalign - to be added in ensuing commits.

Signed-off-by: Eugene Uriev <eugeneuriev@gmail.com>

1 files changed, 220 insertions, 0 deletions

diff --git a/common/mcheck_core.inc.h b/common/mcheck_core.inc.h
new file mode 100644
index 0000000000..6f26ef00d9
--- /dev/null
+++ b/common/mcheck_core.inc.h
@@ -0,0 +1,220 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (C) 2024 Free Software Foundation, Inc.
+ * Written by Eugene Uriev, based on glibc 2.0 prototype of Mike Haertel.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 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
+ * Library General Public License for more details.
+ * <https://www.gnu.org/licenses/>
+ */
+
+/*
+ * TL;DR: this is a porting of glibc mcheck into U-Boot
+ *
+ * This file contains no entities for external linkage.
+ * So mcheck protection may be used in parallel, e.g. for "malloc_simple(..)" and "malloc(..)".
+ * To do so, the file should be shared/include twice, - without linkage conflicts.
+ * I.e. "core"-part is shared as a source, but not as a binary.
+ * Maybe some optimization here make sense, to engage more binary sharing too.
+ * But, currently I strive to keep it as simple, as possible.
+ * And this, programmers'-only, mode don't pretend to be main.
+ *
+ * This library is aware of U-Boot specific. It's also aware of ARM alignment concerns.
+ * Unlike glibc-clients, U-Boot has limited malloc-usage, and only one thread.
+ * So it's better to make the protection heavier.
+ * Thus overflow canary here is greater, than glibc's one. Underflow canary is bigger too.
+ * Heavy canary allows to catch not only memset(..)-errors,
+ * but overflow/underflow of struct-array access:
+ *	{
+ *		struct mystruct* p = malloc(sizeof(struct mystruct) * N);
+ *		p[-1].field1 = 0;
+ *		p[N].field2 = 13;
+ *	}
+ * TODO: In order to guarantee full coverage of that kind of errors, a user can add variable-size
+ *       canaries here. So pre- and post-canary with size >= reqested_size, could be provided
+ *       (with the price of 3x heap-usage). Therefore, it would catch 100% of changes beyond
+ *       an array, for index(+1/-1) errors.
+ *
+ * U-Boot is a BL, not an OS with a lib. Activity of the library is set not in runtime,
+ * rather in compile-time, by MCHECK_HEAP_PROTECTION macro. That guarantees that
+ * we haven't missed first malloc.
+ */
+#ifndef _MCHECKCORE_INC_H
+#define _MCHECKCORE_INC_H      1
+#include "mcheck.h"
+
+#if defined(MCHECK_HEAP_PROTECTION)
+#define mcheck_flood memset
+
+// these are from /dev/random:
+#define MAGICWORD	0x99ccf430fa562a05ULL
+#define MAGICFREE	0x4875e63c0c6fc08eULL
+#define MAGICTAIL	0x918dbcd7df78dcd6ULL
+#define MALLOCFLOOD	((char)0xb6)
+#define FREEFLOOD	((char)0xf5)
+#define PADDINGFLOOD	((char)0x58)
+
+#define CANARY_DEPTH	2
+
+typedef unsigned long long mcheck_elem;
+typedef struct {
+	mcheck_elem elems[CANARY_DEPTH];
+} mcheck_canary;
+struct mcheck_hdr {
+	size_t size; /* Exact size requested by user.  */
+	mcheck_canary canary; /* Magic number to check header integrity.  */
+};
+
+static void mcheck_default_abort(enum mcheck_status status)
+{
+	const char *msg;
+
+	switch (status) {
+	case MCHECK_OK:
+		msg = "memory is consistent, library is buggy\n";
+		break;
+	case MCHECK_HEAD:
+		msg = "memory clobbered before allocated block\n";
+		break;
+	case MCHECK_TAIL:
+		msg = "memory clobbered past end of allocated block\n";
+		break;
+	case MCHECK_FREE:
+		msg = "block freed twice\n";
+		break;
+	default:
+		msg = "bogus mcheck_status, library is buggy\n";
+		break;
+	}
+	printf("\n\nmcheck: %s!!!\n\n", msg);
+}
+
+static mcheck_abortfunc_t mcheck_abortfunc = &mcheck_default_abort;
+
+static inline size_t allign_size_up(size_t sz, size_t grain)
+{
+	return (sz + grain - 1) & ~(grain - 1);
+}
+
+#define mcheck_allign_customer_size(SZ) allign_size_up(SZ, sizeof(mcheck_elem))
+
+static enum mcheck_status mcheck_OnNok(enum mcheck_status status)
+{
+	(*mcheck_abortfunc)(status);
+	return status;
+}
+
+static enum mcheck_status mcheck_checkhdr(const struct mcheck_hdr *hdr)
+{
+	int i;
+
+	for (i = 0; i < CANARY_DEPTH; ++i)
+		if (hdr->canary.elems[i] == MAGICFREE)
+			return mcheck_OnNok(MCHECK_FREE);
+
+	for (i = 0; i < CANARY_DEPTH; ++i)
+		if (hdr->canary.elems[i] != MAGICWORD)
+			return mcheck_OnNok(MCHECK_HEAD);
+
+	const size_t payload_size = hdr->size;
+	const size_t payload_size_aligned = mcheck_allign_customer_size(payload_size);
+	const size_t padd_size = payload_size_aligned - hdr->size;
+
+	const char *payload = (const char *)&hdr[1];
+
+	for (i = 0; i < padd_size; ++i)
+		if (payload[payload_size + i] != PADDINGFLOOD)
+			return mcheck_OnNok(MCHECK_TAIL);
+
+	const mcheck_canary *tail = (const mcheck_canary *)&payload[payload_size_aligned];
+
+	for (i = 0; i < CANARY_DEPTH; ++i)
+		if (tail->elems[i] != MAGICTAIL)
+			return mcheck_OnNok(MCHECK_TAIL);
+	return MCHECK_OK;
+}
+
+enum { KEEP_CONTENT = 0, CLEAN_CONTENT, ANY_ALIGNMENT = 1 };
+static void *mcheck_free_helper(void *ptr, int clean_content)
+{
+	if (!ptr)
+		return ptr;
+
+	struct mcheck_hdr *hdr = &((struct mcheck_hdr *)ptr)[-1];
+	int i;
+
+	mcheck_checkhdr(hdr);
+	for (i = 0; i < CANARY_DEPTH; ++i)
+		hdr->canary.elems[i] = MAGICFREE;
+
+	if (clean_content)
+		mcheck_flood(ptr, FREEFLOOD, mcheck_allign_customer_size(hdr->size));
+	return hdr;
+}
+
+static void *mcheck_free_prehook(void *ptr) { return mcheck_free_helper(ptr, CLEAN_CONTENT); }
+static void *mcheck_reallocfree_prehook(void *ptr) { return mcheck_free_helper(ptr, KEEP_CONTENT); }
+
+static size_t mcheck_alloc_prehook(size_t sz)
+{
+	sz = mcheck_allign_customer_size(sz);
+	return sizeof(struct mcheck_hdr) + sz + sizeof(mcheck_canary);
+}
+
+static void *mcheck_allocated_helper(void *altoghether_ptr, size_t customer_sz,
+				     size_t alignment, int clean_content)
+{
+	struct mcheck_hdr *hdr = (struct mcheck_hdr *)altoghether_ptr;
+	int i;
+
+	hdr->size = customer_sz;
+	for (i = 0; i < CANARY_DEPTH; ++i)
+		hdr->canary.elems[i] = MAGICWORD;
+
+	char *payload = (char *)&hdr[1];
+
+	if (clean_content)
+		mcheck_flood(payload, MALLOCFLOOD, customer_sz);
+
+	const size_t customer_size_aligned = mcheck_allign_customer_size(customer_sz);
+
+	mcheck_flood(payload + customer_sz, PADDINGFLOOD, customer_size_aligned - customer_sz);
+
+	mcheck_canary *tail = (mcheck_canary *)&payload[customer_size_aligned];
+
+	for (i = 0; i < CANARY_DEPTH; ++i)
+		tail->elems[i] = MAGICTAIL;
+	return payload;
+}
+
+static void *mcheck_alloc_posthook(void *altoghether_ptr, size_t customer_sz)
+{
+	return mcheck_allocated_helper(altoghether_ptr, customer_sz, ANY_ALIGNMENT, CLEAN_CONTENT);
+}
+
+static void *mcheck_alloc_noclean_posthook(void *altoghether_ptr, size_t customer_sz)
+{
+	return mcheck_allocated_helper(altoghether_ptr, customer_sz, ANY_ALIGNMENT, KEEP_CONTENT);
+}
+
+static enum mcheck_status mcheck_mprobe(void *ptr)
+{
+	struct mcheck_hdr *hdr = &((struct mcheck_hdr *)ptr)[-1];
+
+	return mcheck_checkhdr(hdr);
+}
+
+static void mcheck_initialize(mcheck_abortfunc_t new_func, char pedantic_flag)
+{
+	mcheck_abortfunc = (new_func) ? new_func : &mcheck_default_abort;
+}
+
+#endif
+#endif