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110 lines
3.8 KiB
110 lines
3.8 KiB
#pragma once
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/*
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* This header is the single entry point into the arch_context code.
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* It includes processor independent code and conditionally includes architecture
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* dependent code.
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*/
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/*
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* These preprocessor conditionals load architecture-dependent code.
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*
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* Each of these headers include common.h, a sibling header that contains common
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* structures, enums, and externs used by the processor independent code. Those
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* definitions are thus transitively loaded here with the appropriate architecture
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* specific code.
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*
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* While the code in common.h could be located in this file above the conditionals,
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* structuring the code as such prevents IDEs from knowing how to resolve the
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* symbols when aarch64/context.h or x86_64/context is the active file.
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*/
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#if defined(AARCH64) || defined(aarch64)
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#include "aarch64/context.h"
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#elif defined(X86_64) || defined(x86_64)
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#include "x86_64/context.h"
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#else
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#warning "Architecture not set. Using x86_64"
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#define X86_64
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#include "x86_64/context.h"
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#endif
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/**
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* Restore a full mcontext
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* Writes sandbox_context to active_context and then zeroes sandbox_context out
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* @param active_context - the context of the current worker thread
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* @param sandbox_context - the context that we want to restore
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*/
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static inline void
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arch_mcontext_restore(mcontext_t *active_context, struct arch_context *sandbox_context)
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{
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assert(!software_interrupt_is_enabled());
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assert(active_context != NULL);
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assert(sandbox_context != NULL);
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/* Validate that the sandbox_context is well formed */
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assert(sandbox_context->variant == arch_context_slow);
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assert(sandbox_context->mctx.gregs[REG_RSP] != 0);
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assert(sandbox_context->mctx.gregs[REG_RIP] != 0);
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assert(sandbox_context != &worker_thread_base_context);
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/* Restore mcontext */
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memcpy(active_context, &sandbox_context->mctx, sizeof(mcontext_t));
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memset(&sandbox_context->mctx, 0, sizeof(mcontext_t));
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}
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/**
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* Restore a sandbox that was previously executing and preempted for higher-priority work.
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* This method restores only the instruction pointer and stack pointer registers rather than
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* a full mcontext, so it is less expensive than arch_mcontext_restore.
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* @param active_context - the context of the current worker thread
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* @param sandbox_context - the context that we want to restore
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*/
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static void
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arch_context_restore(mcontext_t *active_context, struct arch_context *sandbox_context)
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{
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assert(active_context != NULL);
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assert(sandbox_context != NULL);
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assert(sandbox_context->variant == arch_context_fast);
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assert(sandbox_context != &worker_thread_base_context);
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/* TODO: Phani explained that we need to be able to restore a sandbox with an IP of 0. Why is this? */
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assert(sandbox_context->regs[ureg_rsp]);
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active_context->gregs[REG_RSP] = sandbox_context->regs[ureg_rsp];
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active_context->gregs[REG_RIP] = sandbox_context->regs[ureg_rip] + ARCH_SIG_JMP_OFF;
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sandbox_context->regs[ureg_rsp] = 0;
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sandbox_context->regs[ureg_rip] = 0;
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}
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/**
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* Save the full mcontext of the currently executing process
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* @param sandbox_context - destination
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* @param active_context - source
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*/
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static inline void
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arch_mcontext_save(struct arch_context *sandbox_context, const mcontext_t *active_context)
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{
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assert(sandbox_context != NULL);
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assert(active_context != NULL);
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/* Assumption: Only called indirectly via signal handler, so interrupts should be disabled */
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assert(!software_interrupt_is_enabled());
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/* Assumption: The base context should never be modified */
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assert(sandbox_context != &worker_thread_base_context);
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/* Assumption: The executing process has sane IP and SP values */
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assert(active_context->gregs[REG_RIP] != 0);
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assert(active_context->gregs[REG_RSP] != 0);
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sandbox_context->variant = arch_context_slow;
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sandbox_context->regs[ureg_rsp] = 0;
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sandbox_context->regs[ureg_rip] = 0;
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/* Copy mcontext */
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memcpy(&sandbox_context->mctx, active_context, sizeof(mcontext_t));
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}
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