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- /* Copyright (C) 2014 Stony Brook University
- This file is part of Graphene Library OS.
- Graphene Library OS is free software: you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public License
- as published by the Free Software Foundation, either version 3 of the
- License, or (at your option) any later version.
- Graphene Library OS is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU Lesser General Public License for more details.
- You should have received a copy of the GNU Lesser General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>. */
- /*
- * db_signal.c
- *
- * This file contains APIs to set up handlers of exceptions issued by the
- * host, and the methods to pass the exceptions to the upcalls.
- */
- #include "pal_defs.h"
- #include "pal_linux_defs.h"
- #include "pal.h"
- #include "pal_internal.h"
- #include "pal_linux.h"
- #include "pal_error.h"
- #include "pal_security.h"
- #include "api.h"
- #include "ecall_types.h"
- #include <atomic.h>
- #include <sigset.h>
- #include <linux/signal.h>
- #include <ucontext.h>
- static bool
- _DkGenericSignalHandle(int event_num, PAL_NUM arg, PAL_CONTEXT* context) {
- PAL_EVENT_HANDLER upcall = _DkGetExceptionHandler(event_num);
- if (upcall) {
- (*upcall)(NULL, arg, context);
- return true;
- }
- return false;
- }
- #define ADDR_IN_PAL(addr) \
- ((void*)(addr) > TEXT_START && (void*)(addr) < TEXT_END)
- /*
- * Restore an sgx_cpu_context_t as generated by .Lhandle_exception. Execution will
- * continue as specified by the rip in the context.
- */
- noreturn static void restore_sgx_context(sgx_cpu_context_t* uc,
- PAL_XREGS_STATE* xregs_state) {
- if (xregs_state == NULL)
- xregs_state = (PAL_XREGS_STATE*)xsave_reset_state;
- _restore_sgx_context(uc, xregs_state);
- }
- noreturn static void restore_pal_context(sgx_cpu_context_t* uc, PAL_CONTEXT* ctx) {
- uc->rax = ctx->rax;
- uc->rbx = ctx->rbx;
- uc->rcx = ctx->rcx;
- uc->rdx = ctx->rdx;
- uc->rsp = ctx->rsp;
- uc->rbp = ctx->rbp;
- uc->rsi = ctx->rsi;
- uc->rdi = ctx->rdi;
- uc->r8 = ctx->r8;
- uc->r9 = ctx->r9;
- uc->r10 = ctx->r10;
- uc->r11 = ctx->r11;
- uc->r12 = ctx->r12;
- uc->r13 = ctx->r13;
- uc->r14 = ctx->r14;
- uc->r15 = ctx->r15;
- uc->rflags = ctx->efl;
- uc->rip = ctx->rip;
- restore_sgx_context(uc, ctx->fpregs);
- }
- static void save_pal_context(PAL_CONTEXT* ctx, sgx_cpu_context_t* uc,
- PAL_XREGS_STATE* xregs_state) {
- memset(ctx, 0, sizeof(*ctx));
- ctx->rax = uc->rax;
- ctx->rbx = uc->rbx;
- ctx->rcx = uc->rcx;
- ctx->rdx = uc->rdx;
- ctx->rsp = uc->rsp;
- ctx->rbp = uc->rbp;
- ctx->rsi = uc->rsi;
- ctx->rdi = uc->rdi;
- ctx->r8 = uc->r8;
- ctx->r9 = uc->r9;
- ctx->r10 = uc->r10;
- ctx->r11 = uc->r11;
- ctx->r12 = uc->r12;
- ctx->r13 = uc->r13;
- ctx->r14 = uc->r14;
- ctx->r15 = uc->r15;
- ctx->efl = uc->rflags;
- ctx->rip = uc->rip;
- union pal_csgsfs csgsfs = {
- .cs = 0x33, // __USER_CS(5) | 0(GDT) | 3(RPL)
- .fs = 0,
- .gs = 0,
- .ss = 0x2b, // __USER_DS(6) | 0(GDT) | 3(RPL)
- };
- ctx->csgsfs = csgsfs.csgsfs;
- assert(xregs_state);
- ctx->fpregs = xregs_state;
- /* Emulate format for fp registers Linux sets up as signal frame.
- * https://elixir.bootlin.com/linux/v5.4.13/source/arch/x86/kernel/fpu/signal.c#L86
- * https://elixir.bootlin.com/linux/v5.4.13/source/arch/x86/kernel/fpu/signal.c#L459
- */
- PAL_FPX_SW_BYTES* fpx_sw = &xregs_state->fpstate.sw_reserved;
- fpx_sw->magic1 = PAL_FP_XSTATE_MAGIC1;
- fpx_sw->extended_size = xsave_size;
- fpx_sw->xfeatures = xsave_features;
- memset(fpx_sw->padding, 0, sizeof(fpx_sw->padding));
- if (xsave_enabled) {
- fpx_sw->xstate_size = xsave_size + PAL_FP_XSTATE_MAGIC2_SIZE;
- *(__typeof__(PAL_FP_XSTATE_MAGIC2)*)((void*)xregs_state + xsave_size) =
- PAL_FP_XSTATE_MAGIC2;
- } else {
- fpx_sw->xstate_size = xsave_size;
- }
- }
- /*
- * return value:
- * true: #UD is handled.
- * the execution can be continued without propagating #UD.
- * false: #UD is not handled.
- * the exception needs to be raised up to LibOS or user application.
- */
- static bool handle_ud(sgx_cpu_context_t * uc)
- {
- uint8_t * instr = (uint8_t *) uc->rip;
- if (instr[0] == 0xcc) { /* skip int 3 */
- uc->rip++;
- return true;
- } else if (instr[0] == 0x0f && instr[1] == 0xa2) {
- /* cpuid */
- unsigned int values[4];
- if (!_DkCpuIdRetrieve(uc->rax & 0xffffffff,
- uc->rcx & 0xffffffff, values)) {
- uc->rip += 2;
- uc->rax = values[0];
- uc->rbx = values[1];
- uc->rcx = values[2];
- uc->rdx = values[3];
- return true;
- }
- } else if (instr[0] == 0x0f && instr[1] == 0x31) {
- /* rdtsc */
- uc->rip += 2;
- uc->rdx = 0;
- uc->rax = 0;
- return true;
- } else if (instr[0] == 0x0f && instr[1] == 0x05) {
- /* syscall: LibOS may know how to handle this */
- return false;
- }
- SGX_DBG(DBG_E, "Unknown or illegal instruction at RIP 0x%016lx\n", uc->rip);
- return false;
- }
- void _DkExceptionHandler(
- unsigned int exit_info, sgx_cpu_context_t* uc, PAL_XREGS_STATE* xregs_state) {
- assert(IS_ALIGNED_PTR(xregs_state, PAL_XSTATE_ALIGN));
- union {
- sgx_arch_exit_info_t info;
- unsigned int intval;
- } ei = { .intval = exit_info };
- int event_num;
- if (!ei.info.valid) {
- event_num = exit_info;
- } else {
- switch (ei.info.vector) {
- case SGX_EXCEPTION_VECTOR_BR:
- event_num = PAL_EVENT_NUM_BOUND;
- break;
- case SGX_EXCEPTION_VECTOR_UD:
- if (handle_ud(uc)) {
- restore_sgx_context(uc, xregs_state);
- /* NOTREACHED */
- }
- event_num = PAL_EVENT_ILLEGAL;
- break;
- case SGX_EXCEPTION_VECTOR_DE:
- case SGX_EXCEPTION_VECTOR_MF:
- case SGX_EXCEPTION_VECTOR_XM:
- event_num = PAL_EVENT_ARITHMETIC_ERROR;
- break;
- case SGX_EXCEPTION_VECTOR_AC:
- event_num = PAL_EVENT_MEMFAULT;
- break;
- case SGX_EXCEPTION_VECTOR_DB:
- case SGX_EXCEPTION_VECTOR_BP:
- default:
- restore_sgx_context(uc, xregs_state);
- /* NOTREACHED */
- }
- }
- if (ADDR_IN_PAL(uc->rip) &&
- /* event isn't asynchronous */
- (event_num != PAL_EVENT_QUIT &&
- event_num != PAL_EVENT_SUSPEND &&
- event_num != PAL_EVENT_RESUME)) {
- printf("*** An unexpected AEX vector occurred inside PAL. "
- "Exiting the thread. *** \n"
- "(vector = 0x%x, type = 0x%x valid = %d, RIP = +0x%08lx)\n"
- "rax: 0x%08lx rcx: 0x%08lx rdx: 0x%08lx rbx: 0x%08lx\n"
- "rsp: 0x%08lx rbp: 0x%08lx rsi: 0x%08lx rdi: 0x%08lx\n"
- "r8 : 0x%08lx r9 : 0x%08lx r10: 0x%08lx r11: 0x%08lx\n"
- "r12: 0x%08lx r13: 0x%08lx r14: 0x%08lx r15: 0x%08lx\n"
- "rflags: 0x%08lx rip: 0x%08lx\n",
- ei.info.vector, ei.info.exit_type, ei.info.valid,
- uc->rip - (uintptr_t) TEXT_START,
- uc->rax, uc->rcx, uc->rdx, uc->rbx,
- uc->rsp, uc->rbp, uc->rsi, uc->rdi,
- uc->r8, uc->r9, uc->r10, uc->r11,
- uc->r12, uc->r13, uc->r14, uc->r15,
- uc->rflags, uc->rip);
- #ifdef DEBUG
- printf("pausing for debug\n");
- while (true)
- __asm__ volatile("pause");
- #endif
- _DkThreadExit(/*clear_child_tid=*/NULL);
- }
- PAL_CONTEXT ctx;
- save_pal_context(&ctx, uc, xregs_state);
- /* TODO: save EXINFO from MISC region and populate below fields */
- ctx.err = 0;
- ctx.trapno = ei.info.valid ? ei.info.vector : event_num;
- ctx.oldmask = 0;
- ctx.cr2 = 0;
- PAL_NUM arg = 0;
- switch (event_num) {
- case PAL_EVENT_ILLEGAL:
- arg = uc->rip;
- break;
- case PAL_EVENT_MEMFAULT:
- /* TODO
- * SGX1 doesn't provide fault address.
- * SGX2 gives providing page. (lower address bits are masked)
- */
- break;
- default:
- /* nothing */
- break;
- }
- _DkGenericSignalHandle(event_num, arg, &ctx);
- restore_pal_context(uc, &ctx);
- }
- void _DkRaiseFailure(int error) {
- _DkGenericSignalHandle(PAL_EVENT_FAILURE, error, /*context=*/NULL);
- }
- void _DkExceptionReturn(void* event) {
- __UNUSED(event);
- }
- noreturn void _DkHandleExternalEvent(
- PAL_NUM event, sgx_cpu_context_t* uc, PAL_XREGS_STATE* xregs_state) {
- assert(event);
- assert(IS_ALIGNED_PTR(xregs_state, PAL_XSTATE_ALIGN));
- /* We only end up in _DkHandleExternalEvent() if interrupted during
- * host syscall; Inform LibOS layer that PAL was interrupted (by setting PAL_ERRNO). */
- _DkRaiseFailure(PAL_ERROR_INTERRUPTED);
- PAL_CONTEXT ctx;
- save_pal_context(&ctx, uc, xregs_state);
- ctx.err = 0;
- /* TODO: event is a PAL event; is that what LibOS/app wants to see? */
- ctx.trapno = event;
- ctx.oldmask = 0;
- ctx.cr2 = 0;
- if (!_DkGenericSignalHandle(event, 0, &ctx) && event != PAL_EVENT_RESUME) {
- _DkThreadExit(/*clear_child_tid=*/NULL);
- }
- /*
- * The modification to PAL_CONTEXT is discarded.
- * It is assumed that LibOS won't change context (GPRs, fp registers)
- * if RIP is in PAL.
- *
- * TODO: in long term, record the signal and trigger the signal handler
- * when returning from PAL by the use of
- * ENTER_PAL_CALL/LEAVE_PAL_CALL/LEAVE_PAL_CALL_RETURN.
- */
- restore_sgx_context(uc, xregs_state);
- }
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