/* * Compatibility mode system call entry point for x86-64. * * Copyright 2000-2002 Andi Kleen, SuSE Labs. */ #include "calling.h" #include #include #include #include #include #include #include #include #include #include #include .section .entry.text, "ax" #ifdef CONFIG_PARAVIRT ENTRY(native_usergs_sysret32) swapgs sysretl ENDPROC(native_usergs_sysret32) #endif /* * 32-bit SYSENTER instruction entry. * * SYSENTER loads ss, rsp, cs, and rip from previously programmed MSRs. * IF and VM in rflags are cleared (IOW: interrupts are off). * SYSENTER does not save anything on the stack, * and does not save old rip (!!!) and rflags. * * Arguments: * eax system call number * ebx arg1 * ecx arg2 * edx arg3 * esi arg4 * edi arg5 * ebp user stack * 0(%ebp) arg6 * * This is purely a fast path. For anything complicated we use the int 0x80 * path below. We set up a complete hardware stack frame to share code * with the int 0x80 path. */ ENTRY(entry_SYSENTER_compat) /* Interrupts are off on entry. */ SWAPGS_UNSAFE_STACK movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp /* * User tracing code (ptrace or signal handlers) might assume that * the saved RAX contains a 32-bit number when we're invoking a 32-bit * syscall. Just in case the high bits are nonzero, zero-extend * the syscall number. (This could almost certainly be deleted * with no ill effects.) */ movl %eax, %eax /* Construct struct pt_regs on stack */ pushq $__USER32_DS /* pt_regs->ss */ pushq %rcx /* pt_regs->sp */ /* * Push flags. This is nasty. First, interrupts are currently * off, but we need pt_regs->flags to have IF set. Second, even * if TF was set when SYSENTER started, it's clear by now. We fix * that later using TIF_SINGLESTEP. */ pushfq /* pt_regs->flags (except IF = 0) */ orl $X86_EFLAGS_IF, (%rsp) /* Fix saved flags */ ASM_CLAC /* Clear AC after saving FLAGS */ pushq $__USER32_CS /* pt_regs->cs */ xorq %r8,%r8 pushq %r8 /* pt_regs->ip = 0 (placeholder) */ pushq %rax /* pt_regs->orig_ax */ pushq %rdi /* pt_regs->di */ pushq %rsi /* pt_regs->si */ pushq %rdx /* pt_regs->dx */ pushq %rcx /* pt_regs->cx (will be overwritten) */ pushq $-ENOSYS /* pt_regs->ax */ pushq %r8 /* pt_regs->r8 = 0 */ pushq %r8 /* pt_regs->r9 = 0 */ pushq %r8 /* pt_regs->r10 = 0 */ pushq %r8 /* pt_regs->r11 = 0 */ pushq %rbx /* pt_regs->rbx */ pushq %rbp /* pt_regs->rbp */ pushq %r8 /* pt_regs->r12 = 0 */ pushq %r8 /* pt_regs->r13 = 0 */ pushq %r8 /* pt_regs->r14 = 0 */ pushq %r8 /* pt_regs->r15 = 0 */ cld /* * Sysenter doesn't filter flags, so we need to clear NT * ourselves. To save a few cycles, we can check whether * NT was set instead of doing an unconditional popfq. * This needs to happen before enabling interrupts so that * we don't get preempted with NT set. * * NB.: sysenter_fix_flags is a label with the code under it moved * out-of-line as an optimization: NT is unlikely to be set in the * majority of the cases and instead of polluting the I$ unnecessarily, * we're keeping that code behind a branch which will predict as * not-taken and therefore its instructions won't be fetched. */ testl $X86_EFLAGS_NT, EFLAGS(%rsp) jnz sysenter_fix_flags sysenter_flags_fixed: /* * User mode is traced as though IRQs are on, and SYSENTER * turned them off. */ TRACE_IRQS_OFF movq %rsp, %rdi call do_fast_syscall_32 testl %eax, %eax jz .Lsyscall_32_done jmp sysret32_from_system_call sysenter_fix_flags: pushq $X86_EFLAGS_FIXED popfq jmp sysenter_flags_fixed ENDPROC(entry_SYSENTER_compat) /* * 32-bit SYSCALL instruction entry. * * 32-bit SYSCALL saves rip to rcx, clears rflags.RF, then saves rflags to r11, * then loads new ss, cs, and rip from previously programmed MSRs. * rflags gets masked by a value from another MSR (so CLD and CLAC * are not needed). SYSCALL does not save anything on the stack * and does not change rsp. * * Note: rflags saving+masking-with-MSR happens only in Long mode * (in legacy 32-bit mode, IF, RF and VM bits are cleared and that's it). * Don't get confused: rflags saving+masking depends on Long Mode Active bit * (EFER.LMA=1), NOT on bitness of userspace where SYSCALL executes * or target CS descriptor's L bit (SYSCALL does not read segment descriptors). * * Arguments: * eax system call number * ecx return address * ebx arg1 * ebp arg2 (note: not saved in the stack frame, should not be touched) * edx arg3 * esi arg4 * edi arg5 * esp user stack * 0(%esp) arg6 */ ENTRY(entry_SYSCALL_compat) /* Interrupts are off on entry. */ SWAPGS_UNSAFE_STACK /* Stash user ESP and switch to the kernel stack. */ movl %esp, %r8d movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp /* Zero-extending 32-bit regs, do not remove */ movl %eax, %eax /* Construct struct pt_regs on stack */ pushq $__USER32_DS /* pt_regs->ss */ pushq %r8 /* pt_regs->sp */ pushq %r11 /* pt_regs->flags */ pushq $__USER32_CS /* pt_regs->cs */ pushq %rcx /* pt_regs->ip */ pushq %rax /* pt_regs->orig_ax */ pushq %rdi /* pt_regs->di */ pushq %rsi /* pt_regs->si */ pushq %rdx /* pt_regs->dx */ pushq %rcx /* pt_regs->cx (will be overwritten) */ pushq $-ENOSYS /* pt_regs->ax */ xorq %r8,%r8 pushq %r8 /* pt_regs->r8 = 0 */ pushq %r8 /* pt_regs->r9 = 0 */ pushq %r8 /* pt_regs->r10 = 0 */ pushq %r8 /* pt_regs->r11 = 0 */ pushq %rbx /* pt_regs->rbx */ pushq %rbp /* pt_regs->rbp */ pushq %r8 /* pt_regs->r12 = 0 */ pushq %r8 /* pt_regs->r13 = 0 */ pushq %r8 /* pt_regs->r14 = 0 */ pushq %r8 /* pt_regs->r15 = 0 */ /* * User mode is traced as though IRQs are on, and SYSENTER * turned them off. */ TRACE_IRQS_OFF movq %rsp, %rdi call do_fast_syscall_32 testl %eax, %eax jz .Lsyscall_32_done /* Opportunistic SYSRET */ sysret32_from_system_call: TRACE_IRQS_ON /* User mode traces as IRQs on. */ movq RBX(%rsp), %rbx /* pt_regs->rbx */ movq RBP(%rsp), %rbp /* pt_regs->rbp */ movq EFLAGS(%rsp), %r11 /* pt_regs->flags (in r11) */ movq RIP(%rsp), %rcx /* pt_regs->ip (in rcx) */ addq $RAX, %rsp /* Skip r8-r15 */ popq %rax /* pt_regs->rax */ popq %rdx /* Skip pt_regs->cx */ popq %rdx /* pt_regs->dx */ popq %rsi /* pt_regs->si */ popq %rdi /* pt_regs->di */ /* * USERGS_SYSRET32 does: * GSBASE = user's GS base * EIP = ECX * RFLAGS = R11 * CS = __USER32_CS * SS = __USER_DS * * ECX will not match pt_regs->cx, but we're returning to a vDSO * trampoline that will fix up RCX, so this is okay. * * R12-R15 are callee-saved, so they contain whatever was in them * when the system call started, which is already known to user * code. We zero R8-R10 to avoid info leaks. */ xorq %r8, %r8 xorq %r9, %r9 xorq %r10, %r10 movq RSP-ORIG_RAX(%rsp), %rsp USERGS_SYSRET32 END(entry_SYSCALL_compat) /* * Emulated IA32 system calls via int 0x80. * * Arguments: * eax system call number * ebx arg1 * ecx arg2 * edx arg3 * esi arg4 * edi arg5 * ebp arg6 (note: not saved in the stack frame, should not be touched) * * Notes: * Uses the same stack frame as the x86-64 version. * All registers except eax must be saved (but ptrace may violate that). * Arguments are zero extended. For system calls that want sign extension and * take long arguments a wrapper is needed. Most calls can just be called * directly. * Assumes it is only called from user space and entered with interrupts off. */ ENTRY(entry_INT80_compat) /* * Interrupts are off on entry. */ PARAVIRT_ADJUST_EXCEPTION_FRAME SWAPGS /* * User tracing code (ptrace or signal handlers) might assume that * the saved RAX contains a 32-bit number when we're invoking a 32-bit * syscall. Just in case the high bits are nonzero, zero-extend * the syscall number. (This could almost certainly be deleted * with no ill effects.) */ movl %eax, %eax /* Construct struct pt_regs on stack (iret frame is already on stack) */ pushq %rax /* pt_regs->orig_ax */ pushq %rdi /* pt_regs->di */ pushq %rsi /* pt_regs->si */ pushq %rdx /* pt_regs->dx */ pushq %rcx /* pt_regs->cx */ pushq $-ENOSYS /* pt_regs->ax */ xorq %r8,%r8 pushq %r8 /* pt_regs->r8 = 0 */ pushq %r8 /* pt_regs->r9 = 0 */ pushq %r8 /* pt_regs->r10 = 0 */ pushq %r8 /* pt_regs->r11 = 0 */ pushq %rbx /* pt_regs->rbx */ pushq %rbp /* pt_regs->rbp */ pushq %r12 /* pt_regs->r12 */ pushq %r13 /* pt_regs->r13 */ pushq %r14 /* pt_regs->r14 */ pushq %r15 /* pt_regs->r15 */ cld /* * User mode is traced as though IRQs are on, and the interrupt * gate turned them off. */ TRACE_IRQS_OFF movq %rsp, %rdi call do_syscall_32_irqs_off .Lsyscall_32_done: /* Go back to user mode. */ TRACE_IRQS_ON SWAPGS jmp restore_regs_and_iret END(entry_INT80_compat) ALIGN GLOBAL(stub32_clone) /* * The 32-bit clone ABI is: clone(..., int tls_val, int *child_tidptr). * The 64-bit clone ABI is: clone(..., int *child_tidptr, int tls_val). * * The native 64-bit kernel's sys_clone() implements the latter, * so we need to swap arguments here before calling it: */ xchg %r8, %rcx jmp sys_clone