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 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 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, scno); 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 #ifdef CONFIG_ARM64_ERRATUM_1463225 65 DECLARE_PER_CPU(int, __in_cortex_a76_erratum_1463225_wa); 66 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 90 static void cortex_a76_erratum_1463225_svc_handler(void) { } 91 #endif /* CONFIG_ARM64_ERRATUM_1463225 */ 92 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 } 139 140 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 } 156 157 void do_el0_svc(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 164 void do_el0_svc_compat(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