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Diffstat (limited to '')
| -rw-r--r-- | arch/arm64/kernel/syscall.c | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c new file mode 100644 index 000000000..befde0eaa --- /dev/null +++ b/arch/arm64/kernel/syscall.c @@ -0,0 +1,203 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <linux/compiler.h> +#include <linux/context_tracking.h> +#include <linux/errno.h> +#include <linux/nospec.h> +#include <linux/ptrace.h> +#include <linux/syscalls.h> + +#include <asm/daifflags.h> +#include <asm/debug-monitors.h> +#include <asm/fpsimd.h> +#include <asm/syscall.h> +#include <asm/thread_info.h> +#include <asm/unistd.h> + +long compat_arm_syscall(struct pt_regs *regs, int scno); +long sys_ni_syscall(void); + +static long do_ni_syscall(struct pt_regs *regs, int scno) +{ +#ifdef CONFIG_COMPAT + long ret; + if (is_compat_task()) { + ret = compat_arm_syscall(regs, scno); + if (ret != -ENOSYS) + return ret; + } +#endif + + return sys_ni_syscall(); +} + +static long __invoke_syscall(struct pt_regs *regs, syscall_fn_t syscall_fn) +{ + return syscall_fn(regs); +} + +static void invoke_syscall(struct pt_regs *regs, unsigned int scno, + unsigned int sc_nr, + const syscall_fn_t syscall_table[]) +{ + long ret; + + if (scno < sc_nr) { + syscall_fn_t syscall_fn; + syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)]; + ret = __invoke_syscall(regs, syscall_fn); + } else { + ret = do_ni_syscall(regs, scno); + } + + syscall_set_return_value(current, regs, 0, ret); +} + +static inline bool has_syscall_work(unsigned long flags) +{ + return unlikely(flags & _TIF_SYSCALL_WORK); +} + +int syscall_trace_enter(struct pt_regs *regs); +void syscall_trace_exit(struct pt_regs *regs); + +#ifdef CONFIG_ARM64_ERRATUM_1463225 +DECLARE_PER_CPU(int, __in_cortex_a76_erratum_1463225_wa); + +static void cortex_a76_erratum_1463225_svc_handler(void) +{ + u32 reg, val; + + if (!unlikely(test_thread_flag(TIF_SINGLESTEP))) + return; + + if (!unlikely(this_cpu_has_cap(ARM64_WORKAROUND_1463225))) + return; + + __this_cpu_write(__in_cortex_a76_erratum_1463225_wa, 1); + reg = read_sysreg(mdscr_el1); + val = reg | DBG_MDSCR_SS | DBG_MDSCR_KDE; + write_sysreg(val, mdscr_el1); + asm volatile("msr daifclr, #8"); + isb(); + + /* We will have taken a single-step exception by this point */ + + write_sysreg(reg, mdscr_el1); + __this_cpu_write(__in_cortex_a76_erratum_1463225_wa, 0); +} +#else +static void cortex_a76_erratum_1463225_svc_handler(void) { } +#endif /* CONFIG_ARM64_ERRATUM_1463225 */ + +static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr, + const syscall_fn_t syscall_table[]) +{ + unsigned long flags = current_thread_info()->flags; + + regs->orig_x0 = regs->regs[0]; + regs->syscallno = scno; + + /* + * BTI note: + * The architecture does not guarantee that SPSR.BTYPE is zero + * on taking an SVC, so we could return to userspace with a + * non-zero BTYPE after the syscall. + * + * This shouldn't matter except when userspace is explicitly + * doing something stupid, such as setting PROT_BTI on a page + * that lacks conforming BTI/PACIxSP instructions, falling + * through from one executable page to another with differing + * PROT_BTI, or messing with BTYPE via ptrace: in such cases, + * userspace should not be surprised if a SIGILL occurs on + * syscall return. + * + * So, don't touch regs->pstate & PSR_BTYPE_MASK here. + * (Similarly for HVC and SMC elsewhere.) + */ + + cortex_a76_erratum_1463225_svc_handler(); + local_daif_restore(DAIF_PROCCTX); + + if (system_supports_mte() && (flags & _TIF_MTE_ASYNC_FAULT)) { + /* + * Process the asynchronous tag check fault before the actual + * syscall. do_notify_resume() will send a signal to userspace + * before the syscall is restarted. + */ + syscall_set_return_value(current, regs, -ERESTARTNOINTR, 0); + return; + } + + if (has_syscall_work(flags)) { + /* + * The de-facto standard way to skip a system call using ptrace + * is to set the system call to -1 (NO_SYSCALL) and set x0 to a + * suitable error code for consumption by userspace. However, + * this cannot be distinguished from a user-issued syscall(-1) + * and so we must set x0 to -ENOSYS here in case the tracer doesn't + * issue the skip and we fall into trace_exit with x0 preserved. + * + * This is slightly odd because it also means that if a tracer + * sets the system call number to -1 but does not initialise x0, + * then x0 will be preserved for all system calls apart from a + * user-issued syscall(-1). However, requesting a skip and not + * setting the return value is unlikely to do anything sensible + * anyway. + */ + if (scno == NO_SYSCALL) + syscall_set_return_value(current, regs, -ENOSYS, 0); + scno = syscall_trace_enter(regs); + if (scno == NO_SYSCALL) + goto trace_exit; + } + + invoke_syscall(regs, scno, sc_nr, syscall_table); + + /* + * The tracing status may have changed under our feet, so we have to + * check again. However, if we were tracing entry, then we always trace + * exit regardless, as the old entry assembly did. + */ + if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) { + local_daif_mask(); + flags = current_thread_info()->flags; + if (!has_syscall_work(flags) && !(flags & _TIF_SINGLESTEP)) + return; + local_daif_restore(DAIF_PROCCTX); + } + +trace_exit: + syscall_trace_exit(regs); +} + +static inline void sve_user_discard(void) +{ + if (!system_supports_sve()) + return; + + clear_thread_flag(TIF_SVE); + + /* + * task_fpsimd_load() won't be called to update CPACR_EL1 in + * ret_to_user unless TIF_FOREIGN_FPSTATE is still set, which only + * happens if a context switch or kernel_neon_begin() or context + * modification (sigreturn, ptrace) intervenes. + * So, ensure that CPACR_EL1 is already correct for the fast-path case. + */ + sve_user_disable(); +} + +void do_el0_svc(struct pt_regs *regs) +{ + sve_user_discard(); + el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table); +} + +#ifdef CONFIG_COMPAT +void do_el0_svc_compat(struct pt_regs *regs) +{ + el0_svc_common(regs, regs->regs[7], __NR_compat_syscalls, + compat_sys_call_table); +} +#endif |