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Diffstat (limited to 'arch/x86/entry/common.c')
| -rw-r--r-- | arch/x86/entry/common.c | 523 |
1 files changed, 0 insertions, 523 deletions
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c deleted file mode 100644 index 94941c5a10ac..000000000000 --- a/arch/x86/entry/common.c +++ /dev/null @@ -1,523 +0,0 @@ -// SPDX-License-Identifier: GPL-2.0-only -/* - * common.c - C code for kernel entry and exit - * Copyright (c) 2015 Andrew Lutomirski - * - * Based on asm and ptrace code by many authors. The code here originated - * in ptrace.c and signal.c. - */ - -#include <linux/kernel.h> -#include <linux/sched.h> -#include <linux/sched/task_stack.h> -#include <linux/entry-common.h> -#include <linux/mm.h> -#include <linux/smp.h> -#include <linux/errno.h> -#include <linux/ptrace.h> -#include <linux/export.h> -#include <linux/nospec.h> -#include <linux/syscalls.h> -#include <linux/uaccess.h> -#include <linux/init.h> - -#ifdef CONFIG_XEN_PV -#include <xen/xen-ops.h> -#include <xen/events.h> -#endif - -#include <asm/apic.h> -#include <asm/desc.h> -#include <asm/traps.h> -#include <asm/vdso.h> -#include <asm/cpufeature.h> -#include <asm/fpu/api.h> -#include <asm/nospec-branch.h> -#include <asm/io_bitmap.h> -#include <asm/syscall.h> -#include <asm/irq_stack.h> - -#ifdef CONFIG_X86_64 - -static __always_inline bool do_syscall_x64(struct pt_regs *regs, int nr) -{ - /* - * Convert negative numbers to very high and thus out of range - * numbers for comparisons. - */ - unsigned int unr = nr; - - if (likely(unr < NR_syscalls)) { - unr = array_index_nospec(unr, NR_syscalls); - regs->ax = x64_sys_call(regs, unr); - return true; - } - return false; -} - -static __always_inline bool do_syscall_x32(struct pt_regs *regs, int nr) -{ - /* - * Adjust the starting offset of the table, and convert numbers - * < __X32_SYSCALL_BIT to very high and thus out of range - * numbers for comparisons. - */ - unsigned int xnr = nr - __X32_SYSCALL_BIT; - - if (IS_ENABLED(CONFIG_X86_X32_ABI) && likely(xnr < X32_NR_syscalls)) { - xnr = array_index_nospec(xnr, X32_NR_syscalls); - regs->ax = x32_sys_call(regs, xnr); - return true; - } - return false; -} - -/* Returns true to return using SYSRET, or false to use IRET */ -__visible noinstr bool do_syscall_64(struct pt_regs *regs, int nr) -{ - add_random_kstack_offset(); - nr = syscall_enter_from_user_mode(regs, nr); - - instrumentation_begin(); - - if (!do_syscall_x64(regs, nr) && !do_syscall_x32(regs, nr) && nr != -1) { - /* Invalid system call, but still a system call. */ - regs->ax = __x64_sys_ni_syscall(regs); - } - - instrumentation_end(); - syscall_exit_to_user_mode(regs); - - /* - * Check that the register state is valid for using SYSRET to exit - * to userspace. Otherwise use the slower but fully capable IRET - * exit path. - */ - - /* XEN PV guests always use the IRET path */ - if (cpu_feature_enabled(X86_FEATURE_XENPV)) - return false; - - /* SYSRET requires RCX == RIP and R11 == EFLAGS */ - if (unlikely(regs->cx != regs->ip || regs->r11 != regs->flags)) - return false; - - /* CS and SS must match the values set in MSR_STAR */ - if (unlikely(regs->cs != __USER_CS || regs->ss != __USER_DS)) - return false; - - /* - * On Intel CPUs, SYSRET with non-canonical RCX/RIP will #GP - * in kernel space. This essentially lets the user take over - * the kernel, since userspace controls RSP. - * - * TASK_SIZE_MAX covers all user-accessible addresses other than - * the deprecated vsyscall page. - */ - if (unlikely(regs->ip >= TASK_SIZE_MAX)) - return false; - - /* - * SYSRET cannot restore RF. It can restore TF, but unlike IRET, - * restoring TF results in a trap from userspace immediately after - * SYSRET. - */ - if (unlikely(regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF))) - return false; - - /* Use SYSRET to exit to userspace */ - return true; -} -#endif - -#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) -static __always_inline int syscall_32_enter(struct pt_regs *regs) -{ - if (IS_ENABLED(CONFIG_IA32_EMULATION)) - current_thread_info()->status |= TS_COMPAT; - - return (int)regs->orig_ax; -} - -#ifdef CONFIG_IA32_EMULATION -bool __ia32_enabled __ro_after_init = !IS_ENABLED(CONFIG_IA32_EMULATION_DEFAULT_DISABLED); - -static int ia32_emulation_override_cmdline(char *arg) -{ - return kstrtobool(arg, &__ia32_enabled); -} -early_param("ia32_emulation", ia32_emulation_override_cmdline); -#endif - -/* - * Invoke a 32-bit syscall. Called with IRQs on in CT_STATE_KERNEL. - */ -static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs, int nr) -{ - /* - * Convert negative numbers to very high and thus out of range - * numbers for comparisons. - */ - unsigned int unr = nr; - - if (likely(unr < IA32_NR_syscalls)) { - unr = array_index_nospec(unr, IA32_NR_syscalls); - regs->ax = ia32_sys_call(regs, unr); - } else if (nr != -1) { - regs->ax = __ia32_sys_ni_syscall(regs); - } -} - -#ifdef CONFIG_IA32_EMULATION -static __always_inline bool int80_is_external(void) -{ - const unsigned int offs = (0x80 / 32) * 0x10; - const u32 bit = BIT(0x80 % 32); - - /* The local APIC on XENPV guests is fake */ - if (cpu_feature_enabled(X86_FEATURE_XENPV)) - return false; - - /* - * If vector 0x80 is set in the APIC ISR then this is an external - * interrupt. Either from broken hardware or injected by a VMM. - * - * Note: In guest mode this is only valid for secure guests where - * the secure module fully controls the vAPIC exposed to the guest. - */ - return apic_read(APIC_ISR + offs) & bit; -} - -/** - * do_int80_emulation - 32-bit legacy syscall C entry from asm - * - * This entry point can be used by 32-bit and 64-bit programs to perform - * 32-bit system calls. Instances of INT $0x80 can be found inline in - * various programs and libraries. It is also used by the vDSO's - * __kernel_vsyscall fallback for hardware that doesn't support a faster - * entry method. Restarted 32-bit system calls also fall back to INT - * $0x80 regardless of what instruction was originally used to do the - * system call. - * - * This is considered a slow path. It is not used by most libc - * implementations on modern hardware except during process startup. - * - * The arguments for the INT $0x80 based syscall are on stack in the - * pt_regs structure: - * eax: system call number - * ebx, ecx, edx, esi, edi, ebp: arg1 - arg 6 - */ -__visible noinstr void do_int80_emulation(struct pt_regs *regs) -{ - int nr; - - /* Kernel does not use INT $0x80! */ - if (unlikely(!user_mode(regs))) { - irqentry_enter(regs); - instrumentation_begin(); - panic("Unexpected external interrupt 0x80\n"); - } - - /* - * Establish kernel context for instrumentation, including for - * int80_is_external() below which calls into the APIC driver. - * Identical for soft and external interrupts. - */ - enter_from_user_mode(regs); - - instrumentation_begin(); - add_random_kstack_offset(); - - /* Validate that this is a soft interrupt to the extent possible */ - if (unlikely(int80_is_external())) - panic("Unexpected external interrupt 0x80\n"); - - /* - * The low level idtentry code pushed -1 into regs::orig_ax - * and regs::ax contains the syscall number. - * - * User tracing code (ptrace or signal handlers) might assume - * that the regs::orig_ax contains a 32-bit number on invoking - * a 32-bit syscall. - * - * Establish the syscall convention by saving the 32bit truncated - * syscall number in regs::orig_ax and by invalidating regs::ax. - */ - regs->orig_ax = regs->ax & GENMASK(31, 0); - regs->ax = -ENOSYS; - - nr = syscall_32_enter(regs); - - local_irq_enable(); - nr = syscall_enter_from_user_mode_work(regs, nr); - do_syscall_32_irqs_on(regs, nr); - - instrumentation_end(); - syscall_exit_to_user_mode(regs); -} - -#ifdef CONFIG_X86_FRED -/* - * A FRED-specific INT80 handler is warranted for the follwing reasons: - * - * 1) As INT instructions and hardware interrupts are separate event - * types, FRED does not preclude the use of vector 0x80 for external - * interrupts. As a result, the FRED setup code does not reserve - * vector 0x80 and calling int80_is_external() is not merely - * suboptimal but actively incorrect: it could cause a system call - * to be incorrectly ignored. - * - * 2) It is called only for handling vector 0x80 of event type - * EVENT_TYPE_SWINT and will never be called to handle any external - * interrupt (event type EVENT_TYPE_EXTINT). - * - * 3) FRED has separate entry flows depending on if the event came from - * user space or kernel space, and because the kernel does not use - * INT insns, the FRED kernel entry handler fred_entry_from_kernel() - * falls through to fred_bad_type() if the event type is - * EVENT_TYPE_SWINT, i.e., INT insns. So if the kernel is handling - * an INT insn, it can only be from a user level. - * - * 4) int80_emulation() does a CLEAR_BRANCH_HISTORY. While FRED will - * likely take a different approach if it is ever needed: it - * probably belongs in either fred_intx()/ fred_other() or - * asm_fred_entrypoint_user(), depending on if this ought to be done - * for all entries from userspace or only system - * calls. - * - * 5) INT $0x80 is the fast path for 32-bit system calls under FRED. - */ -DEFINE_FREDENTRY_RAW(int80_emulation) -{ - int nr; - - enter_from_user_mode(regs); - - instrumentation_begin(); - add_random_kstack_offset(); - - /* - * FRED pushed 0 into regs::orig_ax and regs::ax contains the - * syscall number. - * - * User tracing code (ptrace or signal handlers) might assume - * that the regs::orig_ax contains a 32-bit number on invoking - * a 32-bit syscall. - * - * Establish the syscall convention by saving the 32bit truncated - * syscall number in regs::orig_ax and by invalidating regs::ax. - */ - regs->orig_ax = regs->ax & GENMASK(31, 0); - regs->ax = -ENOSYS; - - nr = syscall_32_enter(regs); - - local_irq_enable(); - nr = syscall_enter_from_user_mode_work(regs, nr); - do_syscall_32_irqs_on(regs, nr); - - instrumentation_end(); - syscall_exit_to_user_mode(regs); -} -#endif -#else /* CONFIG_IA32_EMULATION */ - -/* Handles int $0x80 on a 32bit kernel */ -__visible noinstr void do_int80_syscall_32(struct pt_regs *regs) -{ - int nr = syscall_32_enter(regs); - - add_random_kstack_offset(); - /* - * Subtlety here: if ptrace pokes something larger than 2^31-1 into - * orig_ax, the int return value truncates it. This matches - * the semantics of syscall_get_nr(). - */ - nr = syscall_enter_from_user_mode(regs, nr); - instrumentation_begin(); - - do_syscall_32_irqs_on(regs, nr); - - instrumentation_end(); - syscall_exit_to_user_mode(regs); -} -#endif /* !CONFIG_IA32_EMULATION */ - -static noinstr bool __do_fast_syscall_32(struct pt_regs *regs) -{ - int nr = syscall_32_enter(regs); - int res; - - add_random_kstack_offset(); - /* - * This cannot use syscall_enter_from_user_mode() as it has to - * fetch EBP before invoking any of the syscall entry work - * functions. - */ - syscall_enter_from_user_mode_prepare(regs); - - instrumentation_begin(); - /* Fetch EBP from where the vDSO stashed it. */ - if (IS_ENABLED(CONFIG_X86_64)) { - /* - * Micro-optimization: the pointer we're following is - * explicitly 32 bits, so it can't be out of range. - */ - res = __get_user(*(u32 *)®s->bp, - (u32 __user __force *)(unsigned long)(u32)regs->sp); - } else { - res = get_user(*(u32 *)®s->bp, - (u32 __user __force *)(unsigned long)(u32)regs->sp); - } - - if (res) { - /* User code screwed up. */ - regs->ax = -EFAULT; - - local_irq_disable(); - instrumentation_end(); - irqentry_exit_to_user_mode(regs); - return false; - } - - nr = syscall_enter_from_user_mode_work(regs, nr); - - /* Now this is just like a normal syscall. */ - do_syscall_32_irqs_on(regs, nr); - - instrumentation_end(); - syscall_exit_to_user_mode(regs); - return true; -} - -/* Returns true to return using SYSEXIT/SYSRETL, or false to use IRET */ -__visible noinstr bool do_fast_syscall_32(struct pt_regs *regs) -{ - /* - * Called using the internal vDSO SYSENTER/SYSCALL32 calling - * convention. Adjust regs so it looks like we entered using int80. - */ - unsigned long landing_pad = (unsigned long)current->mm->context.vdso + - vdso_image_32.sym_int80_landing_pad; - - /* - * SYSENTER loses EIP, and even SYSCALL32 needs us to skip forward - * so that 'regs->ip -= 2' lands back on an int $0x80 instruction. - * Fix it up. - */ - regs->ip = landing_pad; - - /* Invoke the syscall. If it failed, keep it simple: use IRET. */ - if (!__do_fast_syscall_32(regs)) - return false; - - /* - * Check that the register state is valid for using SYSRETL/SYSEXIT - * to exit to userspace. Otherwise use the slower but fully capable - * IRET exit path. - */ - - /* XEN PV guests always use the IRET path */ - if (cpu_feature_enabled(X86_FEATURE_XENPV)) - return false; - - /* EIP must point to the VDSO landing pad */ - if (unlikely(regs->ip != landing_pad)) - return false; - - /* CS and SS must match the values set in MSR_STAR */ - if (unlikely(regs->cs != __USER32_CS || regs->ss != __USER_DS)) - return false; - - /* If the TF, RF, or VM flags are set, use IRET */ - if (unlikely(regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF | X86_EFLAGS_VM))) - return false; - - /* Use SYSRETL/SYSEXIT to exit to userspace */ - return true; -} - -/* Returns true to return using SYSEXIT/SYSRETL, or false to use IRET */ -__visible noinstr bool do_SYSENTER_32(struct pt_regs *regs) -{ - /* SYSENTER loses RSP, but the vDSO saved it in RBP. */ - regs->sp = regs->bp; - - /* SYSENTER clobbers EFLAGS.IF. Assume it was set in usermode. */ - regs->flags |= X86_EFLAGS_IF; - - return do_fast_syscall_32(regs); -} -#endif - -SYSCALL_DEFINE0(ni_syscall) -{ - return -ENOSYS; -} - -#ifdef CONFIG_XEN_PV -#ifndef CONFIG_PREEMPTION -/* - * Some hypercalls issued by the toolstack can take many 10s of - * seconds. Allow tasks running hypercalls via the privcmd driver to - * be voluntarily preempted even if full kernel preemption is - * disabled. - * - * Such preemptible hypercalls are bracketed by - * xen_preemptible_hcall_begin() and xen_preemptible_hcall_end() - * calls. - */ -DEFINE_PER_CPU(bool, xen_in_preemptible_hcall); -EXPORT_SYMBOL_GPL(xen_in_preemptible_hcall); - -/* - * In case of scheduling the flag must be cleared and restored after - * returning from schedule as the task might move to a different CPU. - */ -static __always_inline bool get_and_clear_inhcall(void) -{ - bool inhcall = __this_cpu_read(xen_in_preemptible_hcall); - - __this_cpu_write(xen_in_preemptible_hcall, false); - return inhcall; -} - -static __always_inline void restore_inhcall(bool inhcall) -{ - __this_cpu_write(xen_in_preemptible_hcall, inhcall); -} -#else -static __always_inline bool get_and_clear_inhcall(void) { return false; } -static __always_inline void restore_inhcall(bool inhcall) { } -#endif - -static void __xen_pv_evtchn_do_upcall(struct pt_regs *regs) -{ - struct pt_regs *old_regs = set_irq_regs(regs); - - inc_irq_stat(irq_hv_callback_count); - - xen_evtchn_do_upcall(); - - set_irq_regs(old_regs); -} - -__visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs) -{ - irqentry_state_t state = irqentry_enter(regs); - bool inhcall; - - instrumentation_begin(); - run_sysvec_on_irqstack_cond(__xen_pv_evtchn_do_upcall, regs); - - inhcall = get_and_clear_inhcall(); - if (inhcall && !WARN_ON_ONCE(state.exit_rcu)) { - irqentry_exit_cond_resched(); - instrumentation_end(); - restore_inhcall(inhcall); - } else { - instrumentation_end(); - irqentry_exit(regs, state); - } -} -#endif /* CONFIG_XEN_PV */ |