1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __ASMARM_TLS_H
3 #define __ASMARM_TLS_H
4
5 #include <linux/compiler.h>
6 #include <asm/thread_info.h>
7
8 #ifdef __ASSEMBLY__
9 #include <asm/asm-offsets.h>
10 .macro switch_tls_none, base, tp, tpuser, tmp1, tmp2
11 .endm
12
13 .macro switch_tls_v6k, base, tp, tpuser, tmp1, tmp2
14 mrc p15, 0, \tmp2, c13, c0, 2 @ get the user r/w register
15 @ TLS register update is deferred until return to user space
16 mcr p15, 0, \tpuser, c13, c0, 2 @ set the user r/w register
17 str \tmp2, [\base, #TI_TP_VALUE + 4] @ save it
18 .endm
19
20 .macro switch_tls_v6, base, tp, tpuser, tmp1, tmp2
21 #ifdef CONFIG_SMP
22 ALT_SMP(nop)
23 ALT_UP_B(.L0_\@)
24 .subsection 1
25 #endif
26 .L0_\@:
27 ldr_va \tmp1, elf_hwcap
28 mov \tmp2, #0xffff0fff
29 tst \tmp1, #HWCAP_TLS @ hardware TLS available?
30 streq \tp, [\tmp2, #-15] @ set TLS value at 0xffff0ff0
31 beq .L2_\@
32 mcr p15, 0, \tp, c13, c0, 3 @ yes, set TLS register
33 #ifdef CONFIG_SMP
34 b .L1_\@
35 .previous
36 #endif
37 .L1_\@: switch_tls_v6k \base, \tp, \tpuser, \tmp1, \tmp2
38 .L2_\@:
39 .endm
40
41 .macro switch_tls_software, base, tp, tpuser, tmp1, tmp2
42 mov \tmp1, #0xffff0fff
43 str \tp, [\tmp1, #-15] @ set TLS value at 0xffff0ff0
44 .endm
45 #else
46 #include <asm/smp_plat.h>
47 #endif
48
49 #ifdef CONFIG_TLS_REG_EMUL
50 #define tls_emu 1
51 #define has_tls_reg 1
52 #define defer_tls_reg_update 0
53 #define switch_tls switch_tls_none
54 #elif defined(CONFIG_CPU_V6)
55 #define tls_emu 0
56 #define has_tls_reg (elf_hwcap & HWCAP_TLS)
57 #define defer_tls_reg_update is_smp()
58 #define switch_tls switch_tls_v6
59 #elif defined(CONFIG_CPU_32v6K)
60 #define tls_emu 0
61 #define has_tls_reg 1
62 #define defer_tls_reg_update 1
63 #define switch_tls switch_tls_v6k
64 #else
65 #define tls_emu 0
66 #define has_tls_reg 0
67 #define defer_tls_reg_update 0
68 #define switch_tls switch_tls_software
69 #endif
70
71 #ifndef __ASSEMBLY__
72
set_tls(unsigned long val)73 static inline void set_tls(unsigned long val)
74 {
75 struct thread_info *thread;
76
77 thread = current_thread_info();
78
79 thread->tp_value[0] = val;
80
81 /*
82 * This code runs with preemption enabled and therefore must
83 * be reentrant with respect to switch_tls.
84 *
85 * We need to ensure ordering between the shadow state and the
86 * hardware state, so that we don't corrupt the hardware state
87 * with a stale shadow state during context switch.
88 *
89 * If we're preempted here, switch_tls will load TPIDRURO from
90 * thread_info upon resuming execution and the following mcr
91 * is merely redundant.
92 */
93 barrier();
94
95 if (!tls_emu) {
96 if (has_tls_reg && !defer_tls_reg_update) {
97 asm("mcr p15, 0, %0, c13, c0, 3"
98 : : "r" (val));
99 } else if (!has_tls_reg) {
100 #ifdef CONFIG_KUSER_HELPERS
101 /*
102 * User space must never try to access this
103 * directly. Expect your app to break
104 * eventually if you do so. The user helper
105 * at 0xffff0fe0 must be used instead. (see
106 * entry-armv.S for details)
107 */
108 *((unsigned int *)0xffff0ff0) = val;
109 #endif
110 }
111
112 }
113 }
114
get_tpuser(void)115 static inline unsigned long get_tpuser(void)
116 {
117 unsigned long reg = 0;
118
119 if (has_tls_reg && !tls_emu)
120 __asm__("mrc p15, 0, %0, c13, c0, 2" : "=r" (reg));
121
122 return reg;
123 }
124
set_tpuser(unsigned long val)125 static inline void set_tpuser(unsigned long val)
126 {
127 /* Since TPIDRURW is fully context-switched (unlike TPIDRURO),
128 * we need not update thread_info.
129 */
130 if (has_tls_reg && !tls_emu) {
131 asm("mcr p15, 0, %0, c13, c0, 2"
132 : : "r" (val));
133 }
134 }
135
flush_tls(void)136 static inline void flush_tls(void)
137 {
138 set_tls(0);
139 set_tpuser(0);
140 }
141
142 #endif
143 #endif /* __ASMARM_TLS_H */
144