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02912ca7d0
I implemented the case of a segment in a core file with p_filesz < p_memsz by treating the difference as zero bytes. This is correct for ET_EXEC and ET_DYN, but for ET_CORE, it actually means that the memory existed in the program but was not saved. For userspace core dumps, this typically happens for read-only file mappings. For kernel core dumps, makedumpfile does this to indicate memory that was excluded. Instead, let's return a DRGN_FAULT_ERROR if an attempt is made to read from these bytes. In the future, we need to read from the executable/library files when we can. Signed-off-by: Omar Sandoval <osandov@osandov.com>
148 lines
4.2 KiB
C
148 lines
4.2 KiB
C
// Copyright (c) Meta Platforms, Inc. and affiliates.
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// SPDX-License-Identifier: GPL-3.0-or-later
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/**
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* @file
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*
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* Memory reading interface.
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*
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* See @ref MemoryReader.
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*/
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#ifndef DRGN_MEMORY_READER_H
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#define DRGN_MEMORY_READER_H
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#include "binary_search_tree.h"
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#include "drgn.h"
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/**
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* @ingroup Internals
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*
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* @defgroup MemoryReader Memory reader
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*
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* Memory reading interface.
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*
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* @ref drgn_memory_reader provides a common interface for registering regions
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* of memory in a program and reading from memory.
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*
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* @ref drgn_memory_reader does not have a notion of the maximum address or
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* address overflow/wrap-around. Those must be handled at a higher layer.
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*
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* @{
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*/
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/** Memory segment in a @ref drgn_memory_reader. */
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struct drgn_memory_segment {
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struct binary_tree_node node;
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/** Address range of the segment in memory (inclusive). */
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uint64_t min_address, max_address;
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/**
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* The address of the segment when it was added, before any truncations.
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*
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* This is always less than or equal to @ref
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* drgn_memory_segment::min_address.
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*/
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uint64_t orig_min_address;
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/** Read callback. */
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drgn_memory_read_fn read_fn;
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/** Argument to pass to @ref drgn_memory_segment::read_fn. */
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void *arg;
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};
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static inline uint64_t
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drgn_memory_segment_to_key(const struct drgn_memory_segment *entry)
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{
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return entry->min_address;
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}
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DEFINE_BINARY_SEARCH_TREE_TYPE(drgn_memory_segment_tree,
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struct drgn_memory_segment,
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node, drgn_memory_segment_to_key)
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/**
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* Memory reader.
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*
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* A memory reader maps the segments of memory in an address space to callbacks
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* which can be used to read memory from those segments.
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*/
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struct drgn_memory_reader {
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/** Virtual memory segments. */
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struct drgn_memory_segment_tree virtual_segments;
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/** Physical memory segments. */
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struct drgn_memory_segment_tree physical_segments;
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};
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/**
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* Initialize a @ref drgn_memory_reader.
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*
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* The reader is initialized with no segments.
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*/
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void drgn_memory_reader_init(struct drgn_memory_reader *reader);
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/** Deinitialize a @ref drgn_memory_reader. */
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void drgn_memory_reader_deinit(struct drgn_memory_reader *reader);
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/** Return whether a @ref drgn_memory_reader has no segments. */
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bool drgn_memory_reader_empty(struct drgn_memory_reader *reader);
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/**
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* Add a segment to a @ref drgn_memory_reader.
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*
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* @param[in] reader Memory reader.
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* @param[in] min_address Start address (inclusive).
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* @param[in] max_address End address (inclusive). Must be `>= min_address`.
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* @param[in] read_fn Callback to read from segment.
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* @param[in] arg Argument to pass to @p read_fn.
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* @param[in] physical Whether to add a physical memory segment.
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* @return @c NULL on success, non-@c NULL on error.
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*/
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struct drgn_error *
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drgn_memory_reader_add_segment(struct drgn_memory_reader *reader,
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uint64_t min_address, uint64_t max_address,
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drgn_memory_read_fn read_fn, void *arg,
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bool physical);
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/**
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* Read from a @ref drgn_memory_reader.
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*
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* @param[in] reader Memory reader.
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* @param[out] buf Buffer to read into.
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* @param[in] address Starting address in memory to read.
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* @param[in] count Number of bytes to read. `address + count - 1` must be
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* `<= UINT64_MAX`
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* @param[in] physical Whether @c address is physical.
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* @return @c NULL on success, non-@c NULL on error.
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*/
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struct drgn_error *drgn_memory_reader_read(struct drgn_memory_reader *reader,
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void *buf, uint64_t address,
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size_t count, bool physical);
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/** Argument for @ref drgn_read_memory_file(). */
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struct drgn_memory_file_segment {
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/** Offset in the file where the segment starts. */
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uint64_t file_offset;
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/**
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* Size of the segment in the file. This may be less than the size of
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* the segment in memory, which means that the remaining bytes were in
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* the program's memory but were not saved in the core dump. Attempting
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* to read these bytes is treated as a fault.
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*/
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uint64_t file_size;
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/** File descriptor. */
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int fd;
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/**
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* If @c true, EIO is treated as a fault. Otherwise, it is treated as an
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* OS error.
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*/
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bool eio_is_fault;
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};
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/** @ref drgn_memory_read_fn which reads from a file. */
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struct drgn_error *drgn_read_memory_file(void *buf, uint64_t address,
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size_t count, uint64_t offset,
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void *arg, bool physical);
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/** @} */
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#endif /* DRGN_MEMORY_READER_H */
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