xnu-7195.101.1.tar.gz

[apple/xnu.git] / libkern / os / log_mem.h

diff --git a/libkern/os/log_mem.h b/libkern/os/log_mem.h
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+/*
+ * Copyright (c) 2020 Apple Inc. All rights reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+#ifndef log_mem_h
+#define log_mem_h
+
+#include <stddef.h>
+#include <stdint.h>
+
+/*
+ * A simple allocator on a top of a plain byte array. Primarily intended to
+ * support OS kernel logging in order to avoid dependency to VM.
+ */
+typedef struct logmem_s {
+       lck_spin_t *lm_lock;
+       uint8_t     *lm_mem;
+       uint8_t     *lm_mem_map;
+       size_t      lm_cap_order;
+       size_t      lm_min_order;
+       size_t      lm_max_order;
+       uint32_t    lm_cnt_allocations;
+       uint32_t    lm_cnt_failed_size;
+       uint32_t    lm_cnt_failed_full;
+       uint32_t    lm_cnt_free;
+} logmem_t;
+
+/*
+ * Static initializer for global instances of logmem. Size order defines the
+ * total amount of logmem memory, the min and max order set the minimum and the
+ * maximum size respectively of the memory allocatable by the given logmem.
+ * Local or dynamically allocated instances of logmem should not be initialized
+ * by this macro.
+ */
+#define LOGMEM_STATIC_INIT(name, size_order, min_order, max_order) \
+    SIMPLE_LOCK_DECLARE(name##_lck, 0); \
+    logmem_t name = { \
+       .lm_lock = (lck_spin_t *)&name##_lck, \
+       .lm_mem = (uint8_t[(1 << (size_order))]){ 0 }, \
+       .lm_mem_map = (uint8_t[MAX(1, (1 << ((size_order) - (min_order) + 1)) / 8)]){ 0 }, \
+       .lm_cap_order = (size_order), \
+       .lm_max_order = (max_order), \
+       .lm_min_order = (min_order), \
+       .lm_cnt_free = (1 << (size_order)) \
+    };
+
+/*
+ * Allocates memory from a respective logmem. Returns a pointer to the beginning
+ * of the allocated block. The resulting size of the allocated block is equal or
+ * bigger than the size passed in during the call.
+ */
+void *logmem_alloc(logmem_t *, size_t *);
+
+/*
+ * Frees memory previously allocated by logmem_alloc(). The caller must call
+ * logmem_free() with exact pointer and size value returned by logmem_alloc().
+ */
+void logmem_free(logmem_t *, void *, size_t);
+
+/*
+ * Returns the maximum memory size allocatable by the logmem.
+ */
+size_t logmem_max_size(const logmem_t *);
+
+#endif /* log_mem_h */