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160 lines
3.8 KiB
160 lines
3.8 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 <unistd.h>
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#include <ucontext.h>
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/*
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* Register strict ordering>
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* rax = (regs + 0) = 0(%%reg)
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* rbx = (regs + 1) = 8(%%reg)
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* rcx = (regs + 2) = 16(%%reg)
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* rdx = (regs + 3) = 24(%%reg)
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* rbp = (regs + 4) = 32(%%reg)
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* rsp = (regs + 5) = 40(%%reg)
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* rsi = (regs + 6) = 48(%%reg)
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* rdi = (regs + 7) = 56(%%reg)
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* r8 = (regs + 8) = 64(%%reg)
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* r9 = (regs + 9) = 72(%%reg)
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* r10 = (regs + 10) = 80(%%reg)
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* r11 = (regs + 11) = 88(%%reg)
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* r12 = (regs + 12) = 96(%%reg)
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* r13 = (regs + 13) = 104(%%reg)
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* r14 = (regs + 14) = 112(%%reg)
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* r15 = (regs + 15) = 120(%%reg)
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* rip = (regs + 16) = 128(%%reg)
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*/
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typedef uint64_t reg_t;
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#define ARCH_NREGS (16 /* GP registers */ + 1 /* for IP */)
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#define ARCH_SIG_JMP_OFF 8
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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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extern void __attribute__((noreturn)) sandbox_switch_preempt(void);
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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 __thread arch_context_t base_context;
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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 != &base_context);
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ctx->regs[5] = 0;
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memcpy(&ctx->mctx, mc, sizeof(mcontext_t));
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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 != &base_context);
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// if ctx->regs[5] 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[5]) {
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mc->gregs[REG_RSP] = ctx->regs[5];
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mc->gregs[REG_RIP] = ctx->regs[16] + ARCH_SIG_JMP_OFF;
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ctx->regs[5] = 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 __attribute__((noinline))
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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 (
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"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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}
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*(actx->regs + 5) = sp;
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*(actx->regs + 16) = ip;
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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 = &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 = &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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/* TODO: slowpath: signal the current pthread if resuming a preempted sandbox! */
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asm volatile ( \
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"pushq %%rbp\n\t" \
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"movq %%rsp, %%rbp\n\t" \
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"movq $2f, 128(%%rax)\n\t" \
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"movq %%rsp, 40(%%rax)\n\t" \
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"cmpq $0, 40(%%rbx)\n\t" \
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"je 1f\n\t" \
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"movq 40(%%rbx), %%rsp\n\t" \
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"jmpq *128(%%rbx)\n\t" \
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"1:\n\t" \
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"call 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, 40(%%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",
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"r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15",
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"xmm0", "xmm1", "xmm2", "xmm3", "xmm4", "xmm5", "xmm6", "xmm7",
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"xmm8", "xmm9", "xmm10","xmm11","xmm12","xmm13","xmm14","xmm15"
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);
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return 0;
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}
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#endif /* ARCH_X86_64_CONTEXT_H */
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