1 // SPDX-License-Identifier: GPL-2.0
3 * jump label x86 support
5 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
8 #include <linux/jump_label.h>
9 #include <linux/memory.h>
10 #include <linux/uaccess.h>
11 #include <linux/module.h>
12 #include <linux/list.h>
13 #include <linux/jhash.h>
14 #include <linux/cpu.h>
15 #include <asm/kprobes.h>
16 #include <asm/alternative.h>
17 #include <asm/text-patching.h>
19 union jump_code_union
{
20 char code
[JUMP_LABEL_NOP_SIZE
];
24 } __attribute__((packed
));
27 static void bug_at(unsigned char *ip
, int line
)
30 * The location is not an op that we were expecting.
31 * Something went wrong. Crash the box, as something could be
32 * corrupting the kernel.
34 pr_crit("jump_label: Fatal kernel bug, unexpected op at %pS [%p] (%5ph) %d\n", ip
, ip
, ip
, line
);
38 static void __jump_label_set_jump_code(struct jump_entry
*entry
,
39 enum jump_label_type type
,
40 union jump_code_union
*code
,
43 const unsigned char default_nop
[] = { STATIC_KEY_INIT_NOP
};
44 const unsigned char *ideal_nop
= ideal_nops
[NOP_ATOMIC5
];
49 code
->offset
= jump_entry_target(entry
) -
50 (jump_entry_code(entry
) + JUMP_LABEL_NOP_SIZE
);
53 expect
= default_nop
; line
= __LINE__
;
54 } else if (type
== JUMP_LABEL_JMP
) {
55 expect
= ideal_nop
; line
= __LINE__
;
57 expect
= code
->code
; line
= __LINE__
;
60 if (memcmp((void *)jump_entry_code(entry
), expect
, JUMP_LABEL_NOP_SIZE
))
61 bug_at((void *)jump_entry_code(entry
), line
);
63 if (type
== JUMP_LABEL_NOP
)
64 memcpy(code
, ideal_nop
, JUMP_LABEL_NOP_SIZE
);
67 static void __ref
__jump_label_transform(struct jump_entry
*entry
,
68 enum jump_label_type type
,
71 union jump_code_union code
;
73 __jump_label_set_jump_code(entry
, type
, &code
, init
);
76 * As long as only a single processor is running and the code is still
77 * not marked as RO, text_poke_early() can be used; Checking that
78 * system_state is SYSTEM_BOOTING guarantees it. It will be set to
79 * SYSTEM_SCHEDULING before other cores are awaken and before the
80 * code is write-protected.
82 * At the time the change is being done, just ignore whether we
83 * are doing nop -> jump or jump -> nop transition, and assume
84 * always nop being the 'currently valid' instruction
86 if (init
|| system_state
== SYSTEM_BOOTING
) {
87 text_poke_early((void *)jump_entry_code(entry
), &code
,
92 text_poke_bp((void *)jump_entry_code(entry
), &code
, JUMP_LABEL_NOP_SIZE
, NULL
);
95 void arch_jump_label_transform(struct jump_entry
*entry
,
96 enum jump_label_type type
)
98 mutex_lock(&text_mutex
);
99 __jump_label_transform(entry
, type
, 0);
100 mutex_unlock(&text_mutex
);
103 #define TP_VEC_MAX (PAGE_SIZE / sizeof(struct text_poke_loc))
104 static struct text_poke_loc tp_vec
[TP_VEC_MAX
];
105 static int tp_vec_nr
;
107 bool arch_jump_label_transform_queue(struct jump_entry
*entry
,
108 enum jump_label_type type
)
110 struct text_poke_loc
*tp
;
113 if (system_state
== SYSTEM_BOOTING
) {
115 * Fallback to the non-batching mode.
117 arch_jump_label_transform(entry
, type
);
122 * No more space in the vector, tell upper layer to apply
123 * the queue before continuing.
125 if (tp_vec_nr
== TP_VEC_MAX
)
128 tp
= &tp_vec
[tp_vec_nr
];
130 entry_code
= (void *)jump_entry_code(entry
);
133 * The INT3 handler will do a bsearch in the queue, so we need entries
134 * to be sorted. We can survive an unsorted list by rejecting the entry,
135 * forcing the generic jump_label code to apply the queue. Warning once,
136 * to raise the attention to the case of an unsorted entry that is
137 * better not happen, because, in the worst case we will perform in the
138 * same way as we do without batching - with some more overhead.
141 int prev
= tp_vec_nr
- 1;
142 struct text_poke_loc
*prev_tp
= &tp_vec
[prev
];
144 if (WARN_ON_ONCE(prev_tp
->addr
> entry_code
))
148 __jump_label_set_jump_code(entry
, type
,
149 (union jump_code_union
*)&tp
->text
, 0);
151 text_poke_loc_init(tp
, entry_code
, NULL
, JUMP_LABEL_NOP_SIZE
, NULL
);
158 void arch_jump_label_transform_apply(void)
163 mutex_lock(&text_mutex
);
164 text_poke_bp_batch(tp_vec
, tp_vec_nr
);
165 mutex_unlock(&text_mutex
);
174 } jlstate __initdata_or_module
= JL_STATE_START
;
176 __init_or_module
void arch_jump_label_transform_static(struct jump_entry
*entry
,
177 enum jump_label_type type
)
180 * This function is called at boot up and when modules are
181 * first loaded. Check if the default nop, the one that is
182 * inserted at compile time, is the ideal nop. If it is, then
183 * we do not need to update the nop, and we can leave it as is.
184 * If it is not, then we need to update the nop to the ideal nop.
186 if (jlstate
== JL_STATE_START
) {
187 const unsigned char default_nop
[] = { STATIC_KEY_INIT_NOP
};
188 const unsigned char *ideal_nop
= ideal_nops
[NOP_ATOMIC5
];
190 if (memcmp(ideal_nop
, default_nop
, 5) != 0)
191 jlstate
= JL_STATE_UPDATE
;
193 jlstate
= JL_STATE_NO_UPDATE
;
195 if (jlstate
== JL_STATE_UPDATE
)
196 __jump_label_transform(entry
, type
, 1);