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133 lines
3.4 KiB
133 lines
3.4 KiB
#ifndef ARCH_X86_64_CONTEXT_H
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#define ARCH_X86_64_CONTEXT_H
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#include <assert.h>
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#include <ucontext.h>
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#include <unistd.h>
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#define ARCH_NREGS 2 // for SP & IP only
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#define ARCH_SIG_JMP_OFF 8
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typedef uint64_t reg_t;
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/*
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* This is the slowpath switch to a preempted sandbox!
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* SIGUSR1 on the current thread and restore mcontext there!
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*/
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struct arch_context {
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reg_t regs[ARCH_NREGS];
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mcontext_t mctx;
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};
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typedef struct arch_context arch_context_t;
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extern void __attribute__((noreturn)) worker_thread_sandbox_switch_preempt(void);
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extern __thread arch_context_t worker_thread_base_context;
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static void __attribute__((noinline)) arch_context_init(arch_context_t *actx, reg_t ip, reg_t sp)
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{
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memset(&actx->mctx, 0, sizeof(mcontext_t));
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memset((void *)actx->regs, 0, sizeof(reg_t) * ARCH_NREGS);
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if (sp) {
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/*
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* context_switch conventions: bp is expected to be on top of the stack
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* when co-op context switching..
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*
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* so push sp on this new stack and use
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* that new sp as sp for switching to sandbox!
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*/
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asm volatile("movq %%rsp, %%rbx\n\t"
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"movq %%rax, %%rsp\n\t"
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"pushq %%rax\n\t"
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"movq %%rsp, %%rax\n\t"
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"movq %%rbx, %%rsp\n\t"
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: "=a"(sp)
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: "a"(sp)
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: "memory", "cc", "rbx");
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}
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*(actx->regs) = sp;
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*(actx->regs + 1) = ip;
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}
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static int
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arch_mcontext_restore(mcontext_t *mc, arch_context_t *ctx)
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{
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assert(ctx != &worker_thread_base_context);
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// if ctx->regs[0] is set, this was last in a user-level context switch state!
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// else restore mcontext..
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if (ctx->regs[0]) {
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mc->gregs[REG_RSP] = ctx->regs[0];
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mc->gregs[REG_RIP] = ctx->regs[1] + ARCH_SIG_JMP_OFF;
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ctx->regs[0] = 0;
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return 1;
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} else {
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memcpy(mc, &ctx->mctx, sizeof(mcontext_t));
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memset(&ctx->mctx, 0, sizeof(mcontext_t));
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}
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return 0;
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}
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static void
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arch_mcontext_save(arch_context_t *ctx, mcontext_t *mc)
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{
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assert(ctx != &worker_thread_base_context);
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ctx->regs[0] = 0;
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memcpy(&ctx->mctx, mc, sizeof(mcontext_t));
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}
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static inline int
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arch_context_switch(arch_context_t *ca, arch_context_t *na)
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{
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if (!ca) {
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assert(na);
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// switching from "no sandbox to execute" state to "executing a sandbox"
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ca = &worker_thread_base_context;
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} else if (!na) {
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assert(ca);
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// switching from "executing a sandbox" to "no execution" state.
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na = &worker_thread_base_context;
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} else {
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assert(na && ca);
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// switching between sandboxes.
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}
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reg_t *cr = ca->regs, *nr = na->regs;
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assert(cr && nr);
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asm volatile("pushq %%rbp\n\t"
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"movq %%rsp, %%rbp\n\t"
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"movq $2f, 8(%%rax)\n\t"
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"movq %%rsp, (%%rax)\n\t"
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"cmpq $0, (%%rbx)\n\t"
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"je 1f\n\t"
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"movq (%%rbx), %%rsp\n\t"
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"jmpq *8(%%rbx)\n\t"
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"1:\n\t"
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"call worker_thread_sandbox_switch_preempt\n\t"
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".align 8\n\t"
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"2:\n\t"
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"movq $0, (%%rbx)\n\t"
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".align 8\n\t"
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"3:\n\t"
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"popq %%rbp\n\t"
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:
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: "a"(cr), "b"(nr)
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: "memory", "cc", "rcx", "rdx", "rsi", "rdi", "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15",
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"xmm0", "xmm1", "xmm2", "xmm3", "xmm4", "xmm5", "xmm6", "xmm7", "xmm8", "xmm9", "xmm10", "xmm11",
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"xmm12", "xmm13", "xmm14", "xmm15");
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return 0;
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}
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#endif /* ARCH_X86_64_CONTEXT_H */
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