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 /* 102 * BTI note: 103 * The architecture does not guarantee that SPSR.BTYPE is zero 104 * on taking an SVC, so we could return to userspace with a 105 * non-zero BTYPE after the syscall. 106 * 107 * This shouldn't matter except when userspace is explicitly 108 * doing something stupid, such as setting PROT_BTI on a page 109 * that lacks conforming BTI/PACIxSP instructions, falling 110 * through from one executable page to another with differing 111 * PROT_BTI, or messing with BTYPE via ptrace: in such cases, 112 * userspace should not be surprised if a SIGILL occurs on 113 * syscall return. 114 * 115 * So, don't touch regs->pstate & PSR_BTYPE_MASK here. 116 * (Similarly for HVC and SMC elsewhere.) 117 */ 118 119 cortex_a76_erratum_1463225_svc_handler(); 120 local_daif_restore(DAIF_PROCCTX); 121 user_exit(); 122 123 if (has_syscall_work(flags)) { 124 /* set default errno for user-issued syscall(-1) */ 125 if (scno == NO_SYSCALL) 126 regs->regs[0] = -ENOSYS; 127 scno = syscall_trace_enter(regs); 128 if (scno == NO_SYSCALL) 129 goto trace_exit; 130 } 131 132 invoke_syscall(regs, scno, sc_nr, syscall_table); 133 134 /* 135 * The tracing status may have changed under our feet, so we have to 136 * check again. However, if we were tracing entry, then we always trace 137 * exit regardless, as the old entry assembly did. 138 */ 139 if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) { 140 local_daif_mask(); 141 flags = current_thread_info()->flags; 142 if (!has_syscall_work(flags)) { 143 /* 144 * We're off to userspace, where interrupts are 145 * always enabled after we restore the flags from 146 * the SPSR. 147 */ 148 trace_hardirqs_on(); 149 return; 150 } 151 local_daif_restore(DAIF_PROCCTX); 152 } 153 154 trace_exit: 155 syscall_trace_exit(regs); 156 } 157 158 static inline void sve_user_discard(void) 159 { 160 if (!system_supports_sve()) 161 return; 162 163 clear_thread_flag(TIF_SVE); 164 165 /* 166 * task_fpsimd_load() won't be called to update CPACR_EL1 in 167 * ret_to_user unless TIF_FOREIGN_FPSTATE is still set, which only 168 * happens if a context switch or kernel_neon_begin() or context 169 * modification (sigreturn, ptrace) intervenes. 170 * So, ensure that CPACR_EL1 is already correct for the fast-path case. 171 */ 172 sve_user_disable(); 173 } 174 175 void do_el0_svc(struct pt_regs *regs) 176 { 177 sve_user_discard(); 178 el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table); 179 } 180 181 #ifdef CONFIG_COMPAT 182 void do_el0_svc_compat(struct pt_regs *regs) 183 { 184 el0_svc_common(regs, regs->regs[7], __NR_compat_syscalls, 185 compat_sys_call_table); 186 } 187 #endif 188