From 6ce10c3c2ff516aabdef8b4d198690e7e7a87ca4 Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Tue, 24 Mar 2020 12:40:52 +0000 Subject: amd64: introduce kernelEntry kernelEntry is split from CPU that contains minimal CPU-specific arch state that can be mapped at the upper of the address space. It is prepared for KPTI for gvisor. Signed-off-by: Lai Jiangshan Signed-off-by: Lai Jiangshan --- pkg/sentry/platform/ring0/defs_amd64.go | 31 ++++++-- pkg/sentry/platform/ring0/entry_amd64.s | 110 +++++++++++++++-------------- pkg/sentry/platform/ring0/kernel_amd64.go | 5 +- pkg/sentry/platform/ring0/offsets_amd64.go | 12 +++- 4 files changed, 94 insertions(+), 64 deletions(-) (limited to 'pkg/sentry/platform/ring0') diff --git a/pkg/sentry/platform/ring0/defs_amd64.go b/pkg/sentry/platform/ring0/defs_amd64.go index 9c709f271..2c48bf49d 100644 --- a/pkg/sentry/platform/ring0/defs_amd64.go +++ b/pkg/sentry/platform/ring0/defs_amd64.go @@ -80,14 +80,35 @@ type KernelArchState struct { globalIDT idt64 } -// CPUArchState contains CPU-specific arch state. -type CPUArchState struct { +// kernelEntry contains minimal CPU-specific arch state +// that can be mapped at the upper of the address space. +// Malicious APP might steal info from it via CPU bugs. +type kernelEntry struct { // stack is the stack used for interrupts on this CPU. stack [256]byte + // scratch space for temporary usage. + scratch0 uint64 + scratch1 uint64 + + // stackTop is the top of the stack. + stackTop uint64 + + // cpuSelf is back reference to CPU. + cpuSelf *CPU + // kernelCR3 is the cr3 used for sentry kernel. kernelCR3 uintptr + // gdt is the CPU's descriptor table. + gdt descriptorTable + + // tss is the CPU's task state. + tss TaskState64 +} + +// CPUArchState contains CPU-specific arch state. +type CPUArchState struct { // errorCode is the error code from the last exception. errorCode uintptr @@ -100,11 +121,7 @@ type CPUArchState struct { // exception. errorType uintptr - // gdt is the CPU's descriptor table. - gdt descriptorTable - - // tss is the CPU's task state. - tss TaskState64 + *kernelEntry } // ErrorCode returns the last error code. diff --git a/pkg/sentry/platform/ring0/entry_amd64.s b/pkg/sentry/platform/ring0/entry_amd64.s index e54582ede..82689a194 100644 --- a/pkg/sentry/platform/ring0/entry_amd64.s +++ b/pkg/sentry/platform/ring0/entry_amd64.s @@ -84,15 +84,9 @@ #define SYSRET64() \ BYTE $0x48; BYTE $0x0f; BYTE $0x07; -// LOAD_KERNEL_ADDRESS loads a kernel address. -#define LOAD_KERNEL_ADDRESS(from, to) \ - MOVQ from, to; \ - ORQ ·KernelStartAddress(SB), to; - // LOAD_KERNEL_STACK loads the kernel stack. -#define LOAD_KERNEL_STACK(from) \ - LOAD_KERNEL_ADDRESS(CPU_SELF(from), SP); \ - LEAQ CPU_STACK_TOP(SP), SP; +#define LOAD_KERNEL_STACK(entry) \ + MOVQ ENTRY_STACK_TOP(entry), SP; // See kernel.go. TEXT ·Halt(SB),NOSPLIT,$0 @@ -128,6 +122,7 @@ TEXT ·sysret(SB),NOSPLIT,$0-24 MOVQ AX, CPU_REGISTERS+PTRACE_RAX(BX) // save SP AX userCR3 on the kernel stack. + MOVQ CPU_ENTRY(BX), BX LOAD_KERNEL_STACK(BX) PUSHQ PTRACE_RSP(AX) PUSHQ PTRACE_RAX(AX) @@ -160,6 +155,7 @@ TEXT ·iret(SB),NOSPLIT,$0-24 MOVQ AX, CPU_REGISTERS+PTRACE_RAX(BX) // Build an IRET frame & restore state. + MOVQ CPU_ENTRY(BX), BX LOAD_KERNEL_STACK(BX) PUSHQ PTRACE_SS(AX) PUSHQ PTRACE_RSP(AX) @@ -177,18 +173,18 @@ TEXT ·iret(SB),NOSPLIT,$0-24 // See entry_amd64.go. TEXT ·resume(SB),NOSPLIT,$0 // See iret, above. - MOVQ CPU_REGISTERS+PTRACE_SS(GS), BX; PUSHQ BX - MOVQ CPU_REGISTERS+PTRACE_RSP(GS), CX; PUSHQ CX - MOVQ CPU_REGISTERS+PTRACE_FLAGS(GS), DX; PUSHQ DX - MOVQ CPU_REGISTERS+PTRACE_CS(GS), DI; PUSHQ DI - MOVQ CPU_REGISTERS+PTRACE_RIP(GS), SI; PUSHQ SI - REGISTERS_LOAD(GS, CPU_REGISTERS) - MOVQ CPU_REGISTERS+PTRACE_RAX(GS), AX + MOVQ ENTRY_CPU_SELF(GS), AX // Load vCPU. + PUSHQ CPU_REGISTERS+PTRACE_SS(AX) + PUSHQ CPU_REGISTERS+PTRACE_RSP(AX) + PUSHQ CPU_REGISTERS+PTRACE_FLAGS(AX) + PUSHQ CPU_REGISTERS+PTRACE_CS(AX) + PUSHQ CPU_REGISTERS+PTRACE_RIP(AX) + REGISTERS_LOAD(AX, CPU_REGISTERS) + MOVQ CPU_REGISTERS+PTRACE_RAX(AX), AX IRET() // See entry_amd64.go. TEXT ·Start(SB),NOSPLIT,$0 - LOAD_KERNEL_STACK(AX) // Set the stack. PUSHQ $0x0 // Previous frame pointer. MOVQ SP, BP // Set frame pointer. PUSHQ AX // First argument (CPU). @@ -206,21 +202,24 @@ TEXT ·sysenter(SB),NOSPLIT,$0 user: SWAP_GS() - MOVQ AX, CPU_REGISTERS+PTRACE_RCX(GS) // Save user AX on scratch. - MOVQ CPU_KERNEL_CR3(GS), AX // Get kernel cr3 on AX. + MOVQ AX, ENTRY_SCRATCH0(GS) // Save user AX on scratch. + MOVQ ENTRY_KERNEL_CR3(GS), AX // Get kernel cr3 on AX. WRITE_CR3() // Switch to kernel cr3. - XCHGQ CPU_REGISTERS+PTRACE_RSP(GS), SP // Swap stacks. - MOVQ CPU_REGISTERS+PTRACE_RAX(GS), AX // Get user regs. + MOVQ ENTRY_CPU_SELF(GS), AX // Load vCPU. + MOVQ CPU_REGISTERS+PTRACE_RAX(AX), AX // Get user regs. REGISTERS_SAVE(AX, 0) // Save all except IP, FLAGS, SP, AX. - MOVQ CPU_REGISTERS+PTRACE_RCX(GS), BX // Load saved user AX value. - MOVQ BX, PTRACE_RAX(AX) // Save everything else. - MOVQ BX, PTRACE_ORIGRAX(AX) MOVQ CX, PTRACE_RIP(AX) MOVQ R11, PTRACE_FLAGS(AX) - MOVQ CPU_REGISTERS+PTRACE_RSP(GS), BX; MOVQ BX, PTRACE_RSP(AX) - MOVQ $0, CPU_ERROR_CODE(GS) // Clear error code. - MOVQ $1, CPU_ERROR_TYPE(GS) // Set error type to user. + MOVQ SP, PTRACE_RSP(AX) + MOVQ ENTRY_SCRATCH0(GS), CX // Load saved user AX value. + MOVQ CX, PTRACE_RAX(AX) // Save everything else. + MOVQ CX, PTRACE_ORIGRAX(AX) + + MOVQ ENTRY_CPU_SELF(GS), AX // Load vCPU. + MOVQ CPU_REGISTERS+PTRACE_RSP(AX), SP // Get stacks. + MOVQ $0, CPU_ERROR_CODE(AX) // Clear error code. + MOVQ $1, CPU_ERROR_TYPE(AX) // Set error type to user. // Return to the kernel, where the frame is: // @@ -230,25 +229,27 @@ user: // cpu (sp+8) // vcpu.Switch (sp+0) // - MOVQ CPU_REGISTERS+PTRACE_RBP(GS), BP // Original base pointer. + MOVQ CPU_REGISTERS+PTRACE_RBP(AX), BP // Original base pointer. MOVQ $Syscall, 32(SP) // Output vector. RET kernel: // We can't restore the original stack, but we can access the registers // in the CPU state directly. No need for temporary juggling. - MOVQ AX, CPU_REGISTERS+PTRACE_ORIGRAX(GS) - MOVQ AX, CPU_REGISTERS+PTRACE_RAX(GS) - REGISTERS_SAVE(GS, CPU_REGISTERS) - MOVQ CX, CPU_REGISTERS+PTRACE_RIP(GS) - MOVQ R11, CPU_REGISTERS+PTRACE_FLAGS(GS) - MOVQ SP, CPU_REGISTERS+PTRACE_RSP(GS) - MOVQ $0, CPU_ERROR_CODE(GS) // Clear error code. - MOVQ $0, CPU_ERROR_TYPE(GS) // Set error type to kernel. + MOVQ AX, ENTRY_SCRATCH0(GS) + MOVQ ENTRY_CPU_SELF(GS), AX // Load vCPU. + REGISTERS_SAVE(AX, CPU_REGISTERS) + MOVQ CX, CPU_REGISTERS+PTRACE_RIP(AX) + MOVQ R11, CPU_REGISTERS+PTRACE_FLAGS(AX) + MOVQ SP, CPU_REGISTERS+PTRACE_RSP(AX) + MOVQ ENTRY_SCRATCH0(GS), BX + MOVQ BX, CPU_REGISTERS+PTRACE_ORIGRAX(AX) + MOVQ BX, CPU_REGISTERS+PTRACE_RAX(AX) + MOVQ $0, CPU_ERROR_CODE(AX) // Clear error code. + MOVQ $0, CPU_ERROR_TYPE(AX) // Set error type to kernel. // Call the syscall trampoline. LOAD_KERNEL_STACK(GS) - MOVQ CPU_SELF(GS), AX // Load vCPU. PUSHQ AX // First argument (vCPU). CALL ·kernelSyscall(SB) // Call the trampoline. POPQ AX // Pop vCPU. @@ -285,10 +286,11 @@ user: ADDQ $-8, SP // Adjust for flags. MOVQ $_KERNEL_FLAGS, 0(SP); BYTE $0x9d; // Reset flags (POPFQ). PUSHQ AX // Save user AX on stack. - MOVQ CPU_KERNEL_CR3(GS), AX // Get kernel cr3 on AX. + MOVQ ENTRY_KERNEL_CR3(GS), AX // Get kernel cr3 on AX. WRITE_CR3() // Switch to kernel cr3. - MOVQ CPU_REGISTERS+PTRACE_RAX(GS), AX // Get user regs. + MOVQ ENTRY_CPU_SELF(GS), AX // Load vCPU. + MOVQ CPU_REGISTERS+PTRACE_RAX(AX), AX // Get user regs. REGISTERS_SAVE(AX, 0) // Save all except IP, FLAGS, SP, AX. POPQ BX // Restore original AX. MOVQ BX, PTRACE_RAX(AX) // Save it. @@ -300,34 +302,36 @@ user: MOVQ 48(SP), SI; MOVQ SI, PTRACE_SS(AX) // Copy out and return. + MOVQ ENTRY_CPU_SELF(GS), AX // Load vCPU. MOVQ 0(SP), BX // Load vector. MOVQ 8(SP), CX // Load error code. - MOVQ CPU_REGISTERS+PTRACE_RSP(GS), SP // Original stack (kernel version). - MOVQ CPU_REGISTERS+PTRACE_RBP(GS), BP // Original base pointer. - MOVQ CX, CPU_ERROR_CODE(GS) // Set error code. - MOVQ $1, CPU_ERROR_TYPE(GS) // Set error type to user. + MOVQ CPU_REGISTERS+PTRACE_RSP(AX), SP // Original stack (kernel version). + MOVQ CPU_REGISTERS+PTRACE_RBP(AX), BP // Original base pointer. + MOVQ CX, CPU_ERROR_CODE(AX) // Set error code. + MOVQ $1, CPU_ERROR_TYPE(AX) // Set error type to user. MOVQ BX, 32(SP) // Output vector. RET kernel: // As per above, we can save directly. - MOVQ AX, CPU_REGISTERS+PTRACE_RAX(GS) - MOVQ AX, CPU_REGISTERS+PTRACE_ORIGRAX(GS) - REGISTERS_SAVE(GS, CPU_REGISTERS) - MOVQ 16(SP), AX; MOVQ AX, CPU_REGISTERS+PTRACE_RIP(GS) - MOVQ 32(SP), BX; MOVQ BX, CPU_REGISTERS+PTRACE_FLAGS(GS) - MOVQ 40(SP), CX; MOVQ CX, CPU_REGISTERS+PTRACE_RSP(GS) + PUSHQ AX + MOVQ ENTRY_CPU_SELF(GS), AX // Load vCPU. + REGISTERS_SAVE(AX, CPU_REGISTERS) + POPQ BX + MOVQ BX, CPU_REGISTERS+PTRACE_RAX(AX) + MOVQ BX, CPU_REGISTERS+PTRACE_ORIGRAX(AX) + MOVQ 16(SP), BX; MOVQ BX, CPU_REGISTERS+PTRACE_RIP(AX) + MOVQ 32(SP), BX; MOVQ BX, CPU_REGISTERS+PTRACE_FLAGS(AX) + MOVQ 40(SP), BX; MOVQ BX, CPU_REGISTERS+PTRACE_RSP(AX) // Set the error code and adjust the stack. - MOVQ 8(SP), AX // Load the error code. - MOVQ AX, CPU_ERROR_CODE(GS) // Copy out to the CPU. - MOVQ $0, CPU_ERROR_TYPE(GS) // Set error type to kernel. + MOVQ 8(SP), BX // Load the error code. + MOVQ BX, CPU_ERROR_CODE(AX) // Copy out to the CPU. + MOVQ $0, CPU_ERROR_TYPE(AX) // Set error type to kernel. MOVQ 0(SP), BX // BX contains the vector. - ADDQ $48, SP // Drop the exception frame. // Call the exception trampoline. LOAD_KERNEL_STACK(GS) - MOVQ CPU_SELF(GS), AX // Load vCPU. PUSHQ BX // Second argument (vector). PUSHQ AX // First argument (vCPU). CALL ·kernelException(SB) // Call the trampoline. diff --git a/pkg/sentry/platform/ring0/kernel_amd64.go b/pkg/sentry/platform/ring0/kernel_amd64.go index 196afd6bb..7c420ecf4 100644 --- a/pkg/sentry/platform/ring0/kernel_amd64.go +++ b/pkg/sentry/platform/ring0/kernel_amd64.go @@ -41,6 +41,8 @@ func (k *Kernel) init(opts KernelOpts) { // init initializes architecture-specific state. func (c *CPU) init() { + c.kernelEntry = &kernelEntry{} + c.cpuSelf = c // Null segment. c.gdt[0].setNull() @@ -65,6 +67,7 @@ func (c *CPU) init() { // Set the kernel stack pointer in the TSS (virtual address). stackAddr := c.StackTop() + c.stackTop = stackAddr c.tss.rsp0Lo = uint32(stackAddr) c.tss.rsp0Hi = uint32(stackAddr >> 32) c.tss.ist1Lo = uint32(stackAddr) @@ -215,7 +218,7 @@ func (c *CPU) SwitchToUser(switchOpts SwitchOpts) (vector Vector) { //go:nosplit func start(c *CPU) { // Save per-cpu & FS segment. - WriteGS(kernelAddr(c)) + WriteGS(kernelAddr(c.kernelEntry)) WriteFS(uintptr(c.registers.Fs_base)) // Initialize floating point. diff --git a/pkg/sentry/platform/ring0/offsets_amd64.go b/pkg/sentry/platform/ring0/offsets_amd64.go index d6df12c2f..bcb73cb31 100644 --- a/pkg/sentry/platform/ring0/offsets_amd64.go +++ b/pkg/sentry/platform/ring0/offsets_amd64.go @@ -30,12 +30,18 @@ func Emit(w io.Writer) { c := &CPU{} fmt.Fprintf(w, "\n// CPU offsets.\n") - fmt.Fprintf(w, "#define CPU_SELF 0x%02x\n", reflect.ValueOf(&c.self).Pointer()-reflect.ValueOf(c).Pointer()) fmt.Fprintf(w, "#define CPU_REGISTERS 0x%02x\n", reflect.ValueOf(&c.registers).Pointer()-reflect.ValueOf(c).Pointer()) - fmt.Fprintf(w, "#define CPU_STACK_TOP 0x%02x\n", reflect.ValueOf(&c.stack[0]).Pointer()-reflect.ValueOf(c).Pointer()+uintptr(len(c.stack))) - fmt.Fprintf(w, "#define CPU_KERNEL_CR3 0x%02x\n", reflect.ValueOf(&c.kernelCR3).Pointer()-reflect.ValueOf(c).Pointer()) fmt.Fprintf(w, "#define CPU_ERROR_CODE 0x%02x\n", reflect.ValueOf(&c.errorCode).Pointer()-reflect.ValueOf(c).Pointer()) fmt.Fprintf(w, "#define CPU_ERROR_TYPE 0x%02x\n", reflect.ValueOf(&c.errorType).Pointer()-reflect.ValueOf(c).Pointer()) + fmt.Fprintf(w, "#define CPU_ENTRY 0x%02x\n", reflect.ValueOf(&c.kernelEntry).Pointer()-reflect.ValueOf(c).Pointer()) + + e := &kernelEntry{} + fmt.Fprintf(w, "\n// CPU entry offsets.\n") + fmt.Fprintf(w, "#define ENTRY_SCRATCH0 0x%02x\n", reflect.ValueOf(&e.scratch0).Pointer()-reflect.ValueOf(e).Pointer()) + fmt.Fprintf(w, "#define ENTRY_SCRATCH1 0x%02x\n", reflect.ValueOf(&e.scratch1).Pointer()-reflect.ValueOf(e).Pointer()) + fmt.Fprintf(w, "#define ENTRY_STACK_TOP 0x%02x\n", reflect.ValueOf(&e.stackTop).Pointer()-reflect.ValueOf(e).Pointer()) + fmt.Fprintf(w, "#define ENTRY_CPU_SELF 0x%02x\n", reflect.ValueOf(&e.cpuSelf).Pointer()-reflect.ValueOf(e).Pointer()) + fmt.Fprintf(w, "#define ENTRY_KERNEL_CR3 0x%02x\n", reflect.ValueOf(&e.kernelCR3).Pointer()-reflect.ValueOf(e).Pointer()) fmt.Fprintf(w, "\n// Bits.\n") fmt.Fprintf(w, "#define _RFLAGS_IF 0x%02x\n", _RFLAGS_IF) -- cgit v1.2.3