diff options
Diffstat (limited to 'kernel/arch/x86/entry/entry_64_compat.S')
| -rw-r--r-- | kernel/arch/x86/entry/entry_64_compat.S | 328 |
1 files changed, 328 insertions, 0 deletions
diff --git a/kernel/arch/x86/entry/entry_64_compat.S b/kernel/arch/x86/entry/entry_64_compat.S new file mode 100644 index 000000000..15cfebaa7 --- /dev/null +++ b/kernel/arch/x86/entry/entry_64_compat.S @@ -0,0 +1,328 @@ +/* + * Compatibility mode system call entry point for x86-64. + * + * Copyright 2000-2002 Andi Kleen, SuSE Labs. + */ +#include "calling.h" +#include <asm/asm-offsets.h> +#include <asm/current.h> +#include <asm/errno.h> +#include <asm/ia32_unistd.h> +#include <asm/thread_info.h> +#include <asm/segment.h> +#include <asm/irqflags.h> +#include <asm/asm.h> +#include <asm/smap.h> +#include <linux/linkage.h> +#include <linux/err.h> + + .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 %rbp /* pt_regs->sp (stashed in bp) */ + + /* + * 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 */ + pushq $-ENOSYS /* pt_regs->ax */ + pushq %r8 /* pt_regs->r8 = 0 */ + pushq %r8 /* pt_regs->r9 = 0 */ + pushq %r8 /* pt_regs->r10 = 0 */ + pushq %r8 /* pt_regs->r11 = 0 */ + pushq %rbx /* pt_regs->rbx */ + pushq %rbp /* pt_regs->rbp (will be overwritten) */ + pushq %r8 /* pt_regs->r12 = 0 */ + pushq %r8 /* pt_regs->r13 = 0 */ + pushq %r8 /* pt_regs->r14 = 0 */ + pushq %r8 /* pt_regs->r15 = 0 */ + cld + + /* + * Sysenter doesn't filter flags, so we need to clear NT + * ourselves. To save a few cycles, we can check whether + * NT was set instead of doing an unconditional popfq. + * This needs to happen before enabling interrupts so that + * we don't get preempted with NT set. + * + * NB.: sysenter_fix_flags is a label with the code under it moved + * out-of-line as an optimization: NT is unlikely to be set in the + * majority of the cases and instead of polluting the I$ 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 + /* XEN PV guests always use IRET path */ + ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \ + "jmp .Lsyscall_32_done", X86_FEATURE_XENPV + 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 %rbp /* pt_regs->cx (stashed in bp) */ + 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 (will be overwritten) */ + 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 + /* XEN PV guests always use IRET path */ + ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \ + "jmp .Lsyscall_32_done", X86_FEATURE_XENPV + + /* 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 + ASM_CLAC /* Do this early to minimize exposure */ + 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 |