1#ifndef JEMALLOC_INTERNAL_HOOK_H
2#define JEMALLOC_INTERNAL_HOOK_H
3
4#include "jemalloc/internal/tsd.h"
5
6/*
7 * This API is *extremely* experimental, and may get ripped out, changed in API-
8 * and ABI-incompatible ways, be insufficiently or incorrectly documented, etc.
9 *
10 * It allows hooking the stateful parts of the API to see changes as they
11 * happen.
12 *
13 * Allocation hooks are called after the allocation is done, free hooks are
14 * called before the free is done, and expand hooks are called after the
15 * allocation is expanded.
16 *
17 * For realloc and rallocx, if the expansion happens in place, the expansion
18 * hook is called.  If it is moved, then the alloc hook is called on the new
19 * location, and then the free hook is called on the old location (i.e. both
20 * hooks are invoked in between the alloc and the dalloc).
21 *
22 * If we return NULL from OOM, then usize might not be trustworthy.  Calling
23 * realloc(NULL, size) only calls the alloc hook, and calling realloc(ptr, 0)
24 * only calls the free hook.  (Calling realloc(NULL, 0) is treated as malloc(0),
25 * and only calls the alloc hook).
26 *
27 * Reentrancy:
28 *   Reentrancy is guarded against from within the hook implementation.  If you
29 *   call allocator functions from within a hook, the hooks will not be invoked
30 *   again.
31 * Threading:
32 *   The installation of a hook synchronizes with all its uses.  If you can
33 *   prove the installation of a hook happens-before a jemalloc entry point,
34 *   then the hook will get invoked (unless there's a racing removal).
35 *
36 *   Hook insertion appears to be atomic at a per-thread level (i.e. if a thread
37 *   allocates and has the alloc hook invoked, then a subsequent free on the
38 *   same thread will also have the free hook invoked).
39 *
40 *   The *removal* of a hook does *not* block until all threads are done with
41 *   the hook.  Hook authors have to be resilient to this, and need some
42 *   out-of-band mechanism for cleaning up any dynamically allocated memory
43 *   associated with their hook.
44 * Ordering:
45 *   Order of hook execution is unspecified, and may be different than insertion
46 *   order.
47 */
48
49#define HOOK_MAX 4
50
51enum hook_alloc_e {
52	hook_alloc_malloc,
53	hook_alloc_posix_memalign,
54	hook_alloc_aligned_alloc,
55	hook_alloc_calloc,
56	hook_alloc_memalign,
57	hook_alloc_valloc,
58	hook_alloc_mallocx,
59
60	/* The reallocating functions have both alloc and dalloc variants */
61	hook_alloc_realloc,
62	hook_alloc_rallocx,
63};
64/*
65 * We put the enum typedef after the enum, since this file may get included by
66 * jemalloc_cpp.cpp, and C++ disallows enum forward declarations.
67 */
68typedef enum hook_alloc_e hook_alloc_t;
69
70enum hook_dalloc_e {
71	hook_dalloc_free,
72	hook_dalloc_dallocx,
73	hook_dalloc_sdallocx,
74
75	/*
76	 * The dalloc halves of reallocation (not called if in-place expansion
77	 * happens).
78	 */
79	hook_dalloc_realloc,
80	hook_dalloc_rallocx,
81};
82typedef enum hook_dalloc_e hook_dalloc_t;
83
84
85enum hook_expand_e {
86	hook_expand_realloc,
87	hook_expand_rallocx,
88	hook_expand_xallocx,
89};
90typedef enum hook_expand_e hook_expand_t;
91
92typedef void (*hook_alloc)(
93    void *extra, hook_alloc_t type, void *result, uintptr_t result_raw,
94    uintptr_t args_raw[3]);
95
96typedef void (*hook_dalloc)(
97    void *extra, hook_dalloc_t type, void *address, uintptr_t args_raw[3]);
98
99typedef void (*hook_expand)(
100    void *extra, hook_expand_t type, void *address, size_t old_usize,
101    size_t new_usize, uintptr_t result_raw, uintptr_t args_raw[4]);
102
103typedef struct hooks_s hooks_t;
104struct hooks_s {
105	hook_alloc alloc_hook;
106	hook_dalloc dalloc_hook;
107	hook_expand expand_hook;
108	void *extra;
109};
110
111/*
112 * Begin implementation details; everything above this point might one day live
113 * in a public API.  Everything below this point never will.
114 */
115
116/*
117 * The realloc pathways haven't gotten any refactoring love in a while, and it's
118 * fairly difficult to pass information from the entry point to the hooks.  We
119 * put the informaiton the hooks will need into a struct to encapsulate
120 * everything.
121 *
122 * Much of these pathways are force-inlined, so that the compiler can avoid
123 * materializing this struct until we hit an extern arena function.  For fairly
124 * goofy reasons, *many* of the realloc paths hit an extern arena function.
125 * These paths are cold enough that it doesn't matter; eventually, we should
126 * rewrite the realloc code to make the expand-in-place and the
127 * free-then-realloc paths more orthogonal, at which point we don't need to
128 * spread the hook logic all over the place.
129 */
130typedef struct hook_ralloc_args_s hook_ralloc_args_t;
131struct hook_ralloc_args_s {
132	/* I.e. as opposed to rallocx. */
133	bool is_realloc;
134	/*
135	 * The expand hook takes 4 arguments, even if only 3 are actually used;
136	 * we add an extra one in case the user decides to memcpy without
137	 * looking too closely at the hooked function.
138	 */
139	uintptr_t args[4];
140};
141
142/*
143 * Returns an opaque handle to be used when removing the hook.  NULL means that
144 * we couldn't install the hook.
145 */
146bool hook_boot();
147
148void *hook_install(tsdn_t *tsdn, hooks_t *hooks);
149/* Uninstalls the hook with the handle previously returned from hook_install. */
150void hook_remove(tsdn_t *tsdn, void *opaque);
151
152/* Hooks */
153
154void hook_invoke_alloc(hook_alloc_t type, void *result, uintptr_t result_raw,
155    uintptr_t args_raw[3]);
156
157void hook_invoke_dalloc(hook_dalloc_t type, void *address,
158    uintptr_t args_raw[3]);
159
160void hook_invoke_expand(hook_expand_t type, void *address, size_t old_usize,
161    size_t new_usize, uintptr_t result_raw, uintptr_t args_raw[4]);
162
163#endif /* JEMALLOC_INTERNAL_HOOK_H */
164