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linux-user/i386: Emulate x86_64 vsyscalls
Notice the magic page during translate, much like we already do for the arm32 commpage. At runtime, raise an exception to return cpu_loop for emulation. Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Richard Henderson <richard.henderson@linaro.org> Message-Id: <20200213032223.14643-4-richard.henderson@linaro.org> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
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3 changed files with 128 additions and 1 deletions
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@ -92,6 +92,109 @@ static void gen_signal(CPUX86State *env, int sig, int code, abi_ptr addr)
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queue_signal(env, info.si_signo, QEMU_SI_FAULT, &info);
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}
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#ifdef TARGET_X86_64
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static bool write_ok_or_segv(CPUX86State *env, abi_ptr addr, size_t len)
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{
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/*
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* For all the vsyscalls, NULL means "don't write anything" not
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* "write it at address 0".
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*/
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if (addr == 0 || access_ok(VERIFY_WRITE, addr, len)) {
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return true;
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}
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env->error_code = PG_ERROR_W_MASK | PG_ERROR_U_MASK;
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gen_signal(env, TARGET_SIGSEGV, TARGET_SEGV_MAPERR, addr);
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return false;
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}
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/*
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* Since v3.1, the kernel traps and emulates the vsyscall page.
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* Entry points other than the official generate SIGSEGV.
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*/
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static void emulate_vsyscall(CPUX86State *env)
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{
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int syscall;
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abi_ulong ret;
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uint64_t caller;
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/*
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* Validate the entry point. We have already validated the page
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* during translation to get here; now verify the offset.
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*/
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switch (env->eip & ~TARGET_PAGE_MASK) {
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case 0x000:
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syscall = TARGET_NR_gettimeofday;
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break;
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case 0x400:
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syscall = TARGET_NR_time;
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break;
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case 0x800:
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syscall = TARGET_NR_getcpu;
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break;
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default:
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goto sigsegv;
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}
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/*
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* Validate the return address.
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* Note that the kernel treats this the same as an invalid entry point.
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*/
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if (get_user_u64(caller, env->regs[R_ESP])) {
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goto sigsegv;
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}
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/*
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* Validate the the pointer arguments.
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*/
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switch (syscall) {
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case TARGET_NR_gettimeofday:
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if (!write_ok_or_segv(env, env->regs[R_EDI],
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sizeof(struct target_timeval)) ||
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!write_ok_or_segv(env, env->regs[R_ESI],
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sizeof(struct target_timezone))) {
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return;
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}
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break;
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case TARGET_NR_time:
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if (!write_ok_or_segv(env, env->regs[R_EDI], sizeof(abi_long))) {
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return;
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}
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break;
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case TARGET_NR_getcpu:
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if (!write_ok_or_segv(env, env->regs[R_EDI], sizeof(uint32_t)) ||
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!write_ok_or_segv(env, env->regs[R_ESI], sizeof(uint32_t))) {
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return;
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}
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break;
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default:
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g_assert_not_reached();
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}
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/*
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* Perform the syscall. None of the vsyscalls should need restarting.
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*/
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ret = do_syscall(env, syscall, env->regs[R_EDI], env->regs[R_ESI],
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env->regs[R_EDX], env->regs[10], env->regs[8],
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env->regs[9], 0, 0);
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g_assert(ret != -TARGET_ERESTARTSYS);
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g_assert(ret != -TARGET_QEMU_ESIGRETURN);
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if (ret == -TARGET_EFAULT) {
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goto sigsegv;
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}
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env->regs[R_EAX] = ret;
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/* Emulate a ret instruction to leave the vsyscall page. */
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env->eip = caller;
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env->regs[R_ESP] += 8;
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return;
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sigsegv:
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/* Like force_sig(SIGSEGV). */
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gen_signal(env, TARGET_SIGSEGV, TARGET_SI_KERNEL, 0);
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}
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#endif
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void cpu_loop(CPUX86State *env)
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{
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CPUState *cs = env_cpu(env);
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@ -141,6 +244,11 @@ void cpu_loop(CPUX86State *env)
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env->regs[R_EAX] = ret;
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}
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break;
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#endif
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#ifdef TARGET_X86_64
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case EXCP_VSYSCALL:
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emulate_vsyscall(env);
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break;
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#endif
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case EXCP0B_NOSEG:
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case EXCP0C_STACK:
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