1 // SPDX-License-Identifier: GPL-2.0
2
3 #include <linux/compiler.h>
4 #include <linux/context_tracking.h>
5 #include <linux/errno.h>
6 #include <linux/nospec.h>
7 #include <linux/ptrace.h>
8 #include <linux/syscalls.h>
9
10 #include <asm/daifflags.h>
11 #include <asm/debug-monitors.h>
12 #include <asm/fpsimd.h>
13 #include <asm/syscall.h>
14 #include <asm/thread_info.h>
15 #include <asm/unistd.h>
16
17 long compat_arm_syscall(struct pt_regs *regs, int scno);
18 long sys_ni_syscall(void);
19
do_ni_syscall(struct pt_regs * regs,int scno)20 static long do_ni_syscall(struct pt_regs *regs, int scno)
21 {
22 #ifdef CONFIG_COMPAT
23 long ret;
24 if (is_compat_task()) {
25 ret = compat_arm_syscall(regs, scno);
26 if (ret != -ENOSYS)
27 return ret;
28 }
29 #endif
30
31 return sys_ni_syscall();
32 }
33
__invoke_syscall(struct pt_regs * regs,syscall_fn_t syscall_fn)34 static long __invoke_syscall(struct pt_regs *regs, syscall_fn_t syscall_fn)
35 {
36 return syscall_fn(regs);
37 }
38
invoke_syscall(struct pt_regs * regs,unsigned int scno,unsigned int sc_nr,const syscall_fn_t syscall_table[])39 static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
40 unsigned int sc_nr,
41 const syscall_fn_t syscall_table[])
42 {
43 long ret;
44
45 if (scno < sc_nr) {
46 syscall_fn_t syscall_fn;
47 syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)];
48 ret = __invoke_syscall(regs, syscall_fn);
49 } else {
50 ret = do_ni_syscall(regs, scno);
51 }
52
53 regs->regs[0] = ret;
54 }
55
has_syscall_work(unsigned long flags)56 static inline bool has_syscall_work(unsigned long flags)
57 {
58 return unlikely(flags & _TIF_SYSCALL_WORK);
59 }
60
61 int syscall_trace_enter(struct pt_regs *regs);
62 void syscall_trace_exit(struct pt_regs *regs);
63
64 #ifdef CONFIG_ARM64_ERRATUM_1463225
65 DECLARE_PER_CPU(int, __in_cortex_a76_erratum_1463225_wa);
66
cortex_a76_erratum_1463225_svc_handler(void)67 static void cortex_a76_erratum_1463225_svc_handler(void)
68 {
69 u32 reg, val;
70
71 if (!unlikely(test_thread_flag(TIF_SINGLESTEP)))
72 return;
73
74 if (!unlikely(this_cpu_has_cap(ARM64_WORKAROUND_1463225)))
75 return;
76
77 __this_cpu_write(__in_cortex_a76_erratum_1463225_wa, 1);
78 reg = read_sysreg(mdscr_el1);
79 val = reg | DBG_MDSCR_SS | DBG_MDSCR_KDE;
80 write_sysreg(val, mdscr_el1);
81 asm volatile("msr daifclr, #8");
82 isb();
83
84 /* We will have taken a single-step exception by this point */
85
86 write_sysreg(reg, mdscr_el1);
87 __this_cpu_write(__in_cortex_a76_erratum_1463225_wa, 0);
88 }
89 #else
cortex_a76_erratum_1463225_svc_handler(void)90 static void cortex_a76_erratum_1463225_svc_handler(void) { }
91 #endif /* CONFIG_ARM64_ERRATUM_1463225 */
92
el0_svc_common(struct pt_regs * regs,int scno,int sc_nr,const syscall_fn_t syscall_table[])93 static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
94 const syscall_fn_t syscall_table[])
95 {
96 unsigned long flags = current_thread_info()->flags;
97
98 regs->orig_x0 = regs->regs[0];
99 regs->syscallno = scno;
100
101 cortex_a76_erratum_1463225_svc_handler();
102 local_daif_restore(DAIF_PROCCTX);
103 user_exit();
104
105 if (has_syscall_work(flags)) {
106 /* set default errno for user-issued syscall(-1) */
107 if (scno == NO_SYSCALL)
108 regs->regs[0] = -ENOSYS;
109 scno = syscall_trace_enter(regs);
110 if (scno == NO_SYSCALL)
111 goto trace_exit;
112 }
113
114 invoke_syscall(regs, scno, sc_nr, syscall_table);
115
116 /*
117 * The tracing status may have changed under our feet, so we have to
118 * check again. However, if we were tracing entry, then we always trace
119 * exit regardless, as the old entry assembly did.
120 */
121 if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) {
122 local_daif_mask();
123 flags = current_thread_info()->flags;
124 if (!has_syscall_work(flags)) {
125 /*
126 * We're off to userspace, where interrupts are
127 * always enabled after we restore the flags from
128 * the SPSR.
129 */
130 trace_hardirqs_on();
131 return;
132 }
133 local_daif_restore(DAIF_PROCCTX);
134 }
135
136 trace_exit:
137 syscall_trace_exit(regs);
138 }
139
sve_user_discard(void)140 static inline void sve_user_discard(void)
141 {
142 if (!system_supports_sve())
143 return;
144
145 clear_thread_flag(TIF_SVE);
146
147 /*
148 * task_fpsimd_load() won't be called to update CPACR_EL1 in
149 * ret_to_user unless TIF_FOREIGN_FPSTATE is still set, which only
150 * happens if a context switch or kernel_neon_begin() or context
151 * modification (sigreturn, ptrace) intervenes.
152 * So, ensure that CPACR_EL1 is already correct for the fast-path case.
153 */
154 sve_user_disable();
155 }
156
el0_svc_handler(struct pt_regs * regs)157 asmlinkage void el0_svc_handler(struct pt_regs *regs)
158 {
159 sve_user_discard();
160 el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table);
161 }
162
163 #ifdef CONFIG_COMPAT
el0_svc_compat_handler(struct pt_regs * regs)164 asmlinkage void el0_svc_compat_handler(struct pt_regs *regs)
165 {
166 el0_svc_common(regs, regs->regs[7], __NR_compat_syscalls,
167 compat_sys_call_table);
168 }
169 #endif
170