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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/fpsimd.h>
12 #include <asm/syscall.h>
13 #include <asm/thread_info.h>
14 #include <asm/unistd.h>
15
16 long compat_arm_syscall(struct pt_regs *regs);
17
18 long sys_ni_syscall(void);
19
20 asmlinkage long do_ni_syscall(struct pt_regs *regs)
21 {
22 #ifdef CONFIG_COMPAT
23         long ret;
24         if (is_compat_task()) {
25                 ret = compat_arm_syscall(regs);
26                 if (ret != -ENOSYS)
27                         return ret;
28         }
29 #endif
30
31         return sys_ni_syscall();
32 }
33
34 static long __invoke_syscall(struct pt_regs *regs, syscall_fn_t syscall_fn)
35 {
36         return syscall_fn(regs);
37 }
38
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);
51         }
52
53         regs->regs[0] = ret;
54 }
55
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 static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
65                            const syscall_fn_t syscall_table[])
66 {
67         unsigned long flags = current_thread_info()->flags;
68
69         regs->orig_x0 = regs->regs[0];
70         regs->syscallno = scno;
71
72         local_daif_restore(DAIF_PROCCTX);
73         user_exit();
74
75         if (has_syscall_work(flags)) {
76                 /* set default errno for user-issued syscall(-1) */
77                 if (scno == NO_SYSCALL)
78                         regs->regs[0] = -ENOSYS;
79                 scno = syscall_trace_enter(regs);
80                 if (scno == NO_SYSCALL)
81                         goto trace_exit;
82         }
83
84         invoke_syscall(regs, scno, sc_nr, syscall_table);
85
86         /*
87          * The tracing status may have changed under our feet, so we have to
88          * check again. However, if we were tracing entry, then we always trace
89          * exit regardless, as the old entry assembly did.
90          */
91         if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) {
92                 local_daif_mask();
93                 flags = current_thread_info()->flags;
94                 if (!has_syscall_work(flags)) {
95                         /*
96                          * We're off to userspace, where interrupts are
97                          * always enabled after we restore the flags from
98                          * the SPSR.
99                          */
100                         trace_hardirqs_on();
101                         return;
102                 }
103                 local_daif_restore(DAIF_PROCCTX);
104         }
105
106 trace_exit:
107         syscall_trace_exit(regs);
108 }
109
110 static inline void sve_user_discard(void)
111 {
112         if (!system_supports_sve())
113                 return;
114
115         clear_thread_flag(TIF_SVE);
116
117         /*
118          * task_fpsimd_load() won't be called to update CPACR_EL1 in
119          * ret_to_user unless TIF_FOREIGN_FPSTATE is still set, which only
120          * happens if a context switch or kernel_neon_begin() or context
121          * modification (sigreturn, ptrace) intervenes.
122          * So, ensure that CPACR_EL1 is already correct for the fast-path case.
123          */
124         sve_user_disable();
125 }
126
127 asmlinkage void el0_svc_handler(struct pt_regs *regs)
128 {
129         sve_user_discard();
130         el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table);
131 }
132
133 #ifdef CONFIG_COMPAT
134 asmlinkage void el0_svc_compat_handler(struct pt_regs *regs)
135 {
136         el0_svc_common(regs, regs->regs[7], __NR_compat_syscalls,
137                        compat_sys_call_table);
138 }
139 #endif
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