libipt/internal/include/pt_section.h

/*
 * Copyright (c) 2013-2018, Intel Corporation
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  * Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *  * Neither the name of Intel Corporation nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef PT_SECTION_H
#define PT_SECTION_H

#include <stdint.h>
#include <stddef.h>

#if defined(FEATURE_THREADS)
#  include <threads.h>
#endif /* defined(FEATURE_THREADS) */

#include "intel-pt.h"

struct pt_block_cache;


/* A section of contiguous memory loaded from a file. */
struct pt_section {
	/* The name of the file. */
	char *filename;

	/* The offset into the file. */
	uint64_t offset;

	/* The (adjusted) size in bytes.  The size is truncated to match the
	 * actual file size.
	 */
	uint64_t size;

	/* A pointer to OS-specific file status for detecting changes.
	 *
	 * The status is initialized on first pt_section_map() and will be
	 * left in the section until the section is destroyed.  This field
	 * is owned by the OS-specific mmap-based section implementation.
	 */
	void *status;

	/* A pointer to implementation-specific mapping information - NULL if
	 * the section is currently not mapped.
	 *
	 * This field is set in pt_section_map() and owned by the mapping
	 * implementation.
	 */
	void *mapping;

	/* A pointer to an optional block cache.
	 *
	 * The cache is created on request and destroyed implicitly when the
	 * section is unmapped.
	 *
	 * We read this field without locking and only lock the section in order
	 * to install the block cache.
	 *
	 * We rely on guaranteed atomic operations as specified in section 8.1.1
	 * in Volume 3A of the Intel(R) Software Developer's Manual at
	 * http://www.intel.com/sdm.
	 */
	struct pt_block_cache *bcache;

	/* A pointer to the iscache attached to this section.
	 *
	 * The pointer is initialized when the iscache attaches and cleared when
	 * it detaches again.  There can be at most one iscache attached to this
	 * section at any time.
	 *
	 * When attaching, the iscache will also obtain a reference to the
	 * section, which it will drop again when detaching.
	 */
	struct pt_image_section_cache *iscache;

	/* A pointer to the unmap function - NULL if the section is currently
	 * not mapped.
	 *
	 * This field is set in pt_section_map() and owned by the mapping
	 * implementation.
	 */
	int (*unmap)(struct pt_section *sec);

	/* A pointer to the read function - NULL if the section is currently
	 * not mapped.
	 *
	 * This field is set in pt_section_map() and owned by the mapping
	 * implementation.
	 */
	int (*read)(const struct pt_section *sec, uint8_t *buffer,
		    uint16_t size, uint64_t offset);

	/* A pointer to the memsize function - NULL if the section is currently
	 * not mapped.
	 *
	 * This field is set in pt_section_map() and owned by the mapping
	 * implementation.
	 */
	int (*memsize)(const struct pt_section *section, uint64_t *size);

#if defined(FEATURE_THREADS)
	/* A lock protecting this section.
	 *
	 * Most operations do not require the section to be locked.  All
	 * actual locking should be handled by pt_section_* functions.
	 */
	mtx_t lock;

	/* A lock protecting the @iscache and @acount fields.
	 *
	 * We need separate locks to protect against a deadlock scenario when
	 * the iscache is mapping or unmapping this section.
	 *
	 * The attach lock must not be taken while holding the section lock; the
	 * other way round is OK.
	 */
	mtx_t alock;
#endif /* defined(FEATURE_THREADS) */

	/* The number of current users.  The last user destroys the section. */
	uint16_t ucount;

	/* The number of attaches.  This must be <= @ucount. */
	uint16_t acount;

	/* The number of current mappers.  The last unmaps the section. */
	uint16_t mcount;
};

/* Create a section.
 *
 * The returned section describes the contents of @file starting at @offset
 * for @size bytes.
 *
 * If @file is shorter than the requested @size, the section is silently
 * truncated to the size of @file.
 *
 * If @offset lies beyond the end of @file, no section is created.
 *
 * The returned section is not mapped and starts with a user count of one and
 * instruction caching enabled.
 *
 * Returns a new section on success, NULL otherwise.
 */
extern struct pt_section *pt_mk_section(const char *file, uint64_t offset,
					uint64_t size);

/* Lock a section.
 *
 * Locks @section.  The section must not be locked.
 *
 * Returns a new section on success, NULL otherwise.
 * Returns -pte_bad_lock on any locking error.
 */
extern int pt_section_lock(struct pt_section *section);

/* Unlock a section.
 *
 * Unlocks @section.  The section must be locked.
 *
 * Returns a new section on success, NULL otherwise.
 * Returns -pte_bad_lock on any locking error.
 */
extern int pt_section_unlock(struct pt_section *section);

/* Add another user.
 *
 * Increments the user count of @section.
 *
 * Returns zero on success, a negative error code otherwise.
 * Returns -pte_internal if @section is NULL.
 * Returns -pte_overflow if the user count would overflow.
 * Returns -pte_bad_lock on any locking error.
 */
extern int pt_section_get(struct pt_section *section);

/* Remove a user.
 *
 * Decrements the user count of @section.  Destroys the section if the
 * count reaches zero.
 *
 * Returns zero on success, a negative error code otherwise.
 * Returns -pte_internal if @section is NULL.
 * Returns -pte_internal if the user count is already zero.
 * Returns -pte_bad_lock on any locking error.
 */
extern int pt_section_put(struct pt_section *section);

/* Attaches the image section cache user.
 *
 * Similar to pt_section_get() but sets @section->iscache to @iscache.
 *
 * Returns zero on success, a negative error code otherwise.
 * Returns -pte_internal if @section or @iscache is NULL.
 * Returns -pte_internal if a different cache is already attached.
 * Returns -pte_overflow if the attach count would overflow.
 * Returns -pte_bad_lock on any locking error.
 */
extern int pt_section_attach(struct pt_section *section,
			     struct pt_image_section_cache *iscache);

/* Detaches the image section cache user.
 *
 * Similar to pt_section_put() but clears @section->iscache.
 *
 * Returns zero on success, a negative error code otherwise.
 * Returns -pte_internal if @section or @iscache is NULL.
 * Returns -pte_internal if the attach count is already zero.
 * Returns -pte_internal if @section->iscache is not equal to @iscache.
 * Returns -pte_bad_lock on any locking error.
 */
extern int pt_section_detach(struct pt_section *section,
			     struct pt_image_section_cache *iscache);

/* Return the filename of @section. */
extern const char *pt_section_filename(const struct pt_section *section);

/* Return the offset of the section in bytes. */
extern uint64_t pt_section_offset(const struct pt_section *section);

/* Return the size of the section in bytes. */
extern uint64_t pt_section_size(const struct pt_section *section);

/* Return the amount of memory currently used by the section in bytes.
 *
 * We only consider the amount of memory required for mapping @section; we
 * ignore the size of the section object itself and the size of the status
 * object.
 *
 * If @section is currently not mapped, the size is zero.
 *
 * Returns zero on success, a negative pt_error_code otherwise.
 * Returns -pte_internal if @size of @section is NULL.
 */
extern int pt_section_memsize(struct pt_section *section, uint64_t *size);

/* Allocate a block cache.
 *
 * Returns zero on success, a negative error code otherwise.
 * Returns -pte_internal if @section is NULL.
 * Returns -pte_nomem if the block cache can't be allocated.
 * Returns -pte_bad_lock on any locking error.
 */
extern int pt_section_alloc_bcache(struct pt_section *section);

/* Request block caching.
 *
 * The caller must ensure that @section is mapped.
 */
static inline int pt_section_request_bcache(struct pt_section *section)
{
	if (!section)
		return -pte_internal;

	if (section->bcache)
		return 0;

	return pt_section_alloc_bcache(section);
}

/* Return @section's block cache, if available.
 *
 * The caller must ensure that @section is mapped.
 *
 * The cache is not use-counted.  It is only valid as long as the caller keeps
 * @section mapped.
 */
static inline struct pt_block_cache *
pt_section_bcache(const struct pt_section *section)
{
	if (!section)
		return NULL;

	return section->bcache;
}

/* Create the OS-specific file status.
 *
 * On success, allocates a status object, provides a pointer to it in @pstatus
 * and provides the file size in @psize.
 *
 * The status object will be free()'ed when its section is.
 *
 * This function is implemented in the OS-specific section implementation.
 *
 * Returns zero on success, a negative error code otherwise.
 * Returns -pte_internal if @pstatus, @psize, or @filename is NULL.
 * Returns -pte_bad_image if @filename can't be opened.
 * Returns -pte_nomem if the status object can't be allocated.
 */
extern int pt_section_mk_status(void **pstatus, uint64_t *psize,
				const char *filename);

/* Perform on-map maintenance work.
 *
 * Notifies an attached image section cache about the mapping of @section.
 *
 * This function is called by the OS-specific pt_section_map() implementation
 * after @section has been successfully mapped and @section has been unlocked.
 *
 * Returns zero on success, a negative error code otherwise.
 * Returns -pte_internal if @section is NULL.
 * Returns -pte_bad_lock on any locking error.
 */
extern int pt_section_on_map_lock(struct pt_section *section);

static inline int pt_section_on_map(struct pt_section *section)
{
	if (section && !section->iscache)
		return 0;

	return pt_section_on_map_lock(section);
}

/* Map a section.
 *
 * Maps @section into memory.  Mappings are use-counted.  The number of
 * pt_section_map() calls must match the number of pt_section_unmap()
 * calls.
 *
 * This function is implemented in the OS-specific section implementation.
 *
 * Returns zero on success, a negative error code otherwise.
 * Returns -pte_internal if @section is NULL.
 * Returns -pte_bad_image if @section changed or can't be opened.
 * Returns -pte_bad_lock on any locking error.
 * Returns -pte_nomem if @section can't be mapped into memory.
 * Returns -pte_overflow if the map count would overflow.
 */
extern int pt_section_map(struct pt_section *section);

/* Share a section mapping.
 *
 * Increases the map count for @section without notifying an attached image
 * section cache.
 *
 * This function should only be used by the attached image section cache to
 * resolve a deadlock scenario when mapping a section it intends to cache.
 *
 * Returns zero on success, a negative error code otherwise.
 * Returns -pte_internal if @section is NULL.
 * Returns -pte_internal if @section->mcount is zero.
 * Returns -pte_bad_lock on any locking error.
 */
extern int pt_section_map_share(struct pt_section *section);

/* Unmap a section.
 *
 * Unmaps @section from memory.
 *
 * Returns zero on success, a negative error code otherwise.
 * Returns -pte_internal if @section is NULL.
 * Returns -pte_bad_lock on any locking error.
 * Returns -pte_internal if @section has not been mapped.
 */
extern int pt_section_unmap(struct pt_section *section);

/* Read memory from a section.
 *
 * Reads at most @size bytes from @section at @offset into @buffer.  @section
 * must be mapped.
 *
 * Returns the number of bytes read on success, a negative error code otherwise.
 * Returns -pte_internal if @section or @buffer are NULL.
 * Returns -pte_nomap if @offset is beyond the end of the section.
 */
extern int pt_section_read(const struct pt_section *section, uint8_t *buffer,
			   uint16_t size, uint64_t offset);

#endif /* PT_SECTION_H */