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https://github.com/JakeHillion/drgn.git
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eea5422546
drgn has a couple of issues unwinding stack traces for kernel core dumps: 1. It can't unwind the stack for the idle task (PID 0), which commonly appears in core dumps. 2. It uses the PID in PRSTATUS, which is racy and can't actually be trusted. The solution for both of these is to look up the PRSTATUS note by CPU instead of PID. For the live kernel, drgn refuses to unwind the stack of tasks in the "R" state. However, the "R" state is running *or runnable*, so in the latter case, we can still unwind the stack. The solution for this is to look at on_cpu for the task instead of the state.
236 lines
6.3 KiB
C
236 lines
6.3 KiB
C
// Copyright (c) Facebook, Inc. and its affiliates.
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// SPDX-License-Identifier: GPL-3.0+
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/**
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* @file
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*
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* Program internals.
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*
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* See @ref ProgramInternals.
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*/
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#ifndef DRGN_PROGRAM_H
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#define DRGN_PROGRAM_H
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#include <elfutils/libdwfl.h>
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#ifdef WITH_LIBKDUMPFILE
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#include <libkdumpfile/kdumpfile.h>
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#endif
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#include "hash_table.h"
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#include "memory_reader.h"
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#include "object_index.h"
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#include "platform.h"
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#include "type_index.h"
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#include "vector.h"
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/**
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* @ingroup Internals
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*
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* @defgroup ProgramInternals Programs
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*
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* Program internals.
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*
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* @{
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*/
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/** The important parts of the VMCOREINFO note of a Linux kernel core. */
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struct vmcoreinfo {
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/** <tt>uname -r</tt> */
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char osrelease[128];
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/** PAGE_SIZE of the kernel. */
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uint64_t page_size;
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/**
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* The offset from the compiled address of the kernel image to its
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* actual address in memory.
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*
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* This is non-zero if kernel address space layout randomization (KASLR)
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* is enabled.
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*/
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uint64_t kaslr_offset;
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/** Kernel page table. */
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uint64_t swapper_pg_dir;
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/** Whether 5-level paging was enabled. */
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bool pgtable_l5_enabled;
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};
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DEFINE_VECTOR_TYPE(drgn_prstatus_vector, struct string)
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DEFINE_HASH_MAP_TYPE(drgn_prstatus_map, uint32_t, struct string)
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struct drgn_dwarf_info_cache;
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struct drgn_dwarf_index;
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struct drgn_program {
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/** @privatesection */
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struct drgn_memory_reader reader;
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struct drgn_type_index tindex;
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struct drgn_object_index oindex;
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struct drgn_memory_file_segment *file_segments;
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/* Default language of the program. */
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const struct drgn_language *lang;
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/*
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* Valid iff <tt>flags & DRGN_PROGRAM_IS_LINUX_KERNEL</tt>.
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*/
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struct vmcoreinfo vmcoreinfo;
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/* Cached PAGE_OFFSET. */
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uint64_t page_offset;
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/* Cached vmemmap. */
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uint64_t vmemmap;
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/* Cached THREAD_SIZE. */
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uint64_t thread_size;
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#ifdef WITH_LIBKDUMPFILE
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kdump_ctx_t *kdump_ctx;
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#endif
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/*
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* Valid iff <tt>!(flags & DRGN_PROGRAM_IS_LIVE)</tt>, unless the file
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* was a kdump file.
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*/
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Elf *core;
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int core_fd;
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/*
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* Valid iff
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* <tt>(flags & (DRGN_PROGRAM_IS_LINUX_KERNEL | DRGN_PROGRAM_IS_LIVE)) ==
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* DRGN_PROGRAM_IS_LIVE</tt>.
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*/
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pid_t pid;
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struct drgn_dwarf_info_cache *_dicache;
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union {
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/*
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* For the Linux kernel, PRSTATUS notes indexed by CPU. See @ref
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* drgn_architecture_info::linux_kernel_set_initial_registers
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* for why we don't use the PID map.
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*/
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struct drgn_prstatus_vector prstatus_vector;
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/* For userspace programs, PRSTATUS notes indexed by PID. */
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struct drgn_prstatus_map prstatus_map;
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};
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/* See @ref drgn_object_stack_trace(). */
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struct drgn_error *stack_trace_err;
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/* See @ref drgn_object_stack_trace_next_thread(). */
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const struct drgn_object *stack_trace_obj;
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uint32_t stack_trace_tid;
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enum drgn_program_flags flags;
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struct drgn_platform platform;
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bool has_platform;
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bool attached_dwfl_state;
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bool prstatus_cached;
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/*
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* Whether @ref drgn_program::pgtable_it is currently being used. Used
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* to prevent address translation from recursing.
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*/
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bool pgtable_it_in_use;
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/* Page table iterator for linux_helper_read_vm(). */
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struct pgtable_iterator *pgtable_it;
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/* Cache for @ref linux_helper_task_state_to_char(). */
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char *task_state_chars;
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uint64_t task_report;
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};
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/** Initialize a @ref drgn_program. */
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void drgn_program_init(struct drgn_program *prog,
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const struct drgn_platform *platform);
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/** Deinitialize a @ref drgn_program. */
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void drgn_program_deinit(struct drgn_program *prog);
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/**
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* Set the @ref drgn_platform of a @ref drgn_program if it hasn't been set
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* yet.
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*/
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void drgn_program_set_platform(struct drgn_program *prog,
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const struct drgn_platform *platform);
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/**
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* Implement @ref drgn_program_from_core_dump() on an initialized @ref
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* drgn_program.
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*/
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struct drgn_error *drgn_program_init_core_dump(struct drgn_program *prog,
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const char *path);
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/**
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* Implement @ref drgn_program_from_kernel() on an initialized @ref
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* drgn_program.
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*/
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struct drgn_error *drgn_program_init_kernel(struct drgn_program *prog);
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/**
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* Implement @ref drgn_program_from_pid() on an initialized @ref drgn_program.
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*/
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struct drgn_error *drgn_program_init_pid(struct drgn_program *prog, pid_t pid);
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static inline bool drgn_program_is_little_endian(struct drgn_program *prog)
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{
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assert(prog->has_platform);
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return prog->platform.flags & DRGN_PLATFORM_IS_LITTLE_ENDIAN;
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}
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/**
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* Return whether a @ref drgn_program has a different endianness than the host
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* system.
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*/
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static inline bool drgn_program_bswap(struct drgn_program *prog)
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{
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return (drgn_program_is_little_endian(prog) !=
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(__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__));
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}
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static inline bool drgn_program_is_64_bit(struct drgn_program *prog)
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{
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assert(prog->has_platform);
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return prog->platform.flags & DRGN_PLATFORM_IS_64_BIT;
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}
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struct drgn_error *drgn_program_get_dwfl(struct drgn_program *prog, Dwfl **ret);
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/**
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* Find the @c NT_PRSTATUS note for the given CPU.
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*
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* This is only valid for the Linux kernel.
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*
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* @param[out] ret Returned note data. If not found, <tt>ret->str</tt> is set to
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* @c NULL and <tt>ret->len</tt> is set to zero.
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*/
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struct drgn_error *drgn_program_find_prstatus_by_cpu(struct drgn_program *prog,
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uint32_t cpu,
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struct string *ret);
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/**
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* Find the @c NT_PRSTATUS note for the given thread ID.
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*
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* This is only valid for userspace programs.
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*
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* @param[out] ret Returned note data. If not found, <tt>ret->str</tt> is set to
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* @c NULL and <tt>ret->len</tt> is set to zero.
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*/
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struct drgn_error *drgn_program_find_prstatus_by_tid(struct drgn_program *prog,
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uint32_t tid,
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struct string *ret);
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/**
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* Cache the @c NT_PRSTATUS note provided by @p data in @p prog.
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*
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* @param[in] data The pointer to the note data.
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* @param[in] size Size of data in note.
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*/
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struct drgn_error *drgn_program_cache_prstatus_entry(struct drgn_program *prog,
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char *data, size_t size);
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/*
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* Like @ref drgn_program_find_symbol_by_address(), but @p ret is already
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* allocated, we may already know the module, and doesn't return a @ref
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* drgn_error.
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*
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* @param[in] module Module containing the address. May be @c NULL, in which
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* case this will look it up.
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* @return Whether the symbol was found.
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*/
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bool drgn_program_find_symbol_by_address_internal(struct drgn_program *prog,
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uint64_t address,
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Dwfl_Module *module,
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struct drgn_symbol *ret);
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/** @} */
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#endif /* DRGN_PROGRAM_H */
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