409 lines
9.5 KiB
C
409 lines
9.5 KiB
C
/*
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* 32-bit syscall ABI conformance test.
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*
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* Copyright (c) 2015 Denys Vlasenko
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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/*
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* Can be built statically:
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* gcc -Os -Wall -static -m32 test_syscall_vdso.c thunks_32.S
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*/
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#undef _GNU_SOURCE
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#define _GNU_SOURCE 1
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#undef __USE_GNU
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#define __USE_GNU 1
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#include <unistd.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdio.h>
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#include <signal.h>
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#include <sys/types.h>
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#include <sys/select.h>
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#include <sys/time.h>
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#include <elf.h>
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#include <sys/ptrace.h>
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#include <sys/wait.h>
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#if !defined(__i386__)
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int main(int argc, char **argv, char **envp)
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{
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printf("[SKIP]\tNot a 32-bit x86 userspace\n");
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return 0;
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}
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#else
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long syscall_addr;
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long get_syscall(char **envp)
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{
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Elf32_auxv_t *auxv;
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while (*envp++ != NULL)
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continue;
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for (auxv = (void *)envp; auxv->a_type != AT_NULL; auxv++)
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if (auxv->a_type == AT_SYSINFO)
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return auxv->a_un.a_val;
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printf("[WARN]\tAT_SYSINFO not supplied\n");
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return 0;
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}
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asm (
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" .pushsection .text\n"
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" .global int80\n"
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"int80:\n"
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" int $0x80\n"
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" ret\n"
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" .popsection\n"
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);
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extern char int80;
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struct regs64 {
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uint64_t rax, rbx, rcx, rdx;
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uint64_t rsi, rdi, rbp, rsp;
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uint64_t r8, r9, r10, r11;
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uint64_t r12, r13, r14, r15;
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};
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struct regs64 regs64;
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int kernel_is_64bit;
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asm (
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" .pushsection .text\n"
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" .code64\n"
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"get_regs64:\n"
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" push %rax\n"
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" mov $regs64, %eax\n"
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" pop 0*8(%rax)\n"
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" movq %rbx, 1*8(%rax)\n"
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" movq %rcx, 2*8(%rax)\n"
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" movq %rdx, 3*8(%rax)\n"
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" movq %rsi, 4*8(%rax)\n"
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" movq %rdi, 5*8(%rax)\n"
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" movq %rbp, 6*8(%rax)\n"
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" movq %rsp, 7*8(%rax)\n"
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" movq %r8, 8*8(%rax)\n"
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" movq %r9, 9*8(%rax)\n"
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" movq %r10, 10*8(%rax)\n"
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" movq %r11, 11*8(%rax)\n"
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" movq %r12, 12*8(%rax)\n"
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" movq %r13, 13*8(%rax)\n"
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" movq %r14, 14*8(%rax)\n"
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" movq %r15, 15*8(%rax)\n"
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" ret\n"
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"poison_regs64:\n"
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" movq $0x7f7f7f7f, %r8\n"
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" shl $32, %r8\n"
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" orq $0x7f7f7f7f, %r8\n"
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" movq %r8, %r9\n"
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" incq %r9\n"
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" movq %r9, %r10\n"
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" incq %r10\n"
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" movq %r10, %r11\n"
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" incq %r11\n"
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" movq %r11, %r12\n"
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" incq %r12\n"
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" movq %r12, %r13\n"
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" incq %r13\n"
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" movq %r13, %r14\n"
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" incq %r14\n"
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" movq %r14, %r15\n"
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" incq %r15\n"
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" ret\n"
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" .code32\n"
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" .popsection\n"
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);
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extern void get_regs64(void);
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extern void poison_regs64(void);
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extern unsigned long call64_from_32(void (*function)(void));
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void print_regs64(void)
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{
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if (!kernel_is_64bit)
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return;
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printf("ax:%016llx bx:%016llx cx:%016llx dx:%016llx\n", regs64.rax, regs64.rbx, regs64.rcx, regs64.rdx);
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printf("si:%016llx di:%016llx bp:%016llx sp:%016llx\n", regs64.rsi, regs64.rdi, regs64.rbp, regs64.rsp);
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printf(" 8:%016llx 9:%016llx 10:%016llx 11:%016llx\n", regs64.r8 , regs64.r9 , regs64.r10, regs64.r11);
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printf("12:%016llx 13:%016llx 14:%016llx 15:%016llx\n", regs64.r12, regs64.r13, regs64.r14, regs64.r15);
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}
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int check_regs64(void)
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{
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int err = 0;
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int num = 8;
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uint64_t *r64 = ®s64.r8;
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uint64_t expected = 0x7f7f7f7f7f7f7f7fULL;
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if (!kernel_is_64bit)
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return 0;
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do {
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if (*r64 == expected++)
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continue; /* register did not change */
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if (syscall_addr != (long)&int80) {
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/*
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* Non-INT80 syscall entrypoints are allowed to clobber R8+ regs:
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* either clear them to 0, or for R11, load EFLAGS.
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*/
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if (*r64 == 0)
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continue;
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if (num == 11) {
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printf("[NOTE]\tR11 has changed:%016llx - assuming clobbered by SYSRET insn\n", *r64);
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continue;
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}
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} else {
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/*
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* INT80 syscall entrypoint can be used by
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* 64-bit programs too, unlike SYSCALL/SYSENTER.
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* Therefore it must preserve R12+
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* (they are callee-saved registers in 64-bit C ABI).
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*
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* Starting in Linux 4.17 (and any kernel that
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* backports the change), R8..11 are preserved.
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* Historically (and probably unintentionally), they
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* were clobbered or zeroed.
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*/
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}
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printf("[FAIL]\tR%d has changed:%016llx\n", num, *r64);
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err++;
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} while (r64++, ++num < 16);
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if (!err)
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printf("[OK]\tR8..R15 did not leak kernel data\n");
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return err;
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}
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int nfds;
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fd_set rfds;
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fd_set wfds;
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fd_set efds;
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struct timespec timeout;
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sigset_t sigmask;
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struct {
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sigset_t *sp;
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int sz;
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} sigmask_desc;
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void prep_args()
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{
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nfds = 42;
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FD_ZERO(&rfds);
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FD_ZERO(&wfds);
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FD_ZERO(&efds);
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FD_SET(0, &rfds);
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FD_SET(1, &wfds);
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FD_SET(2, &efds);
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timeout.tv_sec = 0;
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timeout.tv_nsec = 123;
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sigemptyset(&sigmask);
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sigaddset(&sigmask, SIGINT);
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sigaddset(&sigmask, SIGUSR2);
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sigaddset(&sigmask, SIGRTMAX);
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sigmask_desc.sp = &sigmask;
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sigmask_desc.sz = 8; /* bytes */
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}
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static void print_flags(const char *name, unsigned long r)
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{
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static const char *bitarray[] = {
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"\n" ,"c\n" ,/* Carry Flag */
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"0 " ,"1 " ,/* Bit 1 - always on */
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"" ,"p " ,/* Parity Flag */
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"0 " ,"3? " ,
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"" ,"a " ,/* Auxiliary carry Flag */
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"0 " ,"5? " ,
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"" ,"z " ,/* Zero Flag */
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"" ,"s " ,/* Sign Flag */
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"" ,"t " ,/* Trap Flag */
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"" ,"i " ,/* Interrupt Flag */
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"" ,"d " ,/* Direction Flag */
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"" ,"o " ,/* Overflow Flag */
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"0 " ,"1 " ,/* I/O Privilege Level (2 bits) */
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"0" ,"1" ,/* I/O Privilege Level (2 bits) */
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"" ,"n " ,/* Nested Task */
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"0 " ,"15? ",
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"" ,"r " ,/* Resume Flag */
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"" ,"v " ,/* Virtual Mode */
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"" ,"ac " ,/* Alignment Check/Access Control */
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"" ,"vif ",/* Virtual Interrupt Flag */
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"" ,"vip ",/* Virtual Interrupt Pending */
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"" ,"id " ,/* CPUID detection */
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NULL
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};
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const char **bitstr;
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int bit;
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printf("%s=%016lx ", name, r);
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bitstr = bitarray + 42;
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bit = 21;
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if ((r >> 22) != 0)
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printf("(extra bits are set) ");
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do {
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if (bitstr[(r >> bit) & 1][0])
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fputs(bitstr[(r >> bit) & 1], stdout);
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bitstr -= 2;
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bit--;
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} while (bit >= 0);
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}
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int run_syscall(void)
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{
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long flags, bad_arg;
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prep_args();
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if (kernel_is_64bit)
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call64_from_32(poison_regs64);
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/*print_regs64();*/
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asm("\n"
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/* Try 6-arg syscall: pselect. It should return quickly */
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" push %%ebp\n"
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" mov $308, %%eax\n" /* PSELECT */
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" mov nfds, %%ebx\n" /* ebx arg1 */
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" mov $rfds, %%ecx\n" /* ecx arg2 */
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" mov $wfds, %%edx\n" /* edx arg3 */
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" mov $efds, %%esi\n" /* esi arg4 */
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" mov $timeout, %%edi\n" /* edi arg5 */
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" mov $sigmask_desc, %%ebp\n" /* %ebp arg6 */
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" push $0x200ed7\n" /* set almost all flags */
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" popf\n" /* except TF, IOPL, NT, RF, VM, AC, VIF, VIP */
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" call *syscall_addr\n"
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/* Check that registers are not clobbered */
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" pushf\n"
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" pop %%eax\n"
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" cld\n"
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" cmp nfds, %%ebx\n" /* ebx arg1 */
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" mov $1, %%ebx\n"
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" jne 1f\n"
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" cmp $rfds, %%ecx\n" /* ecx arg2 */
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" mov $2, %%ebx\n"
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" jne 1f\n"
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" cmp $wfds, %%edx\n" /* edx arg3 */
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" mov $3, %%ebx\n"
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" jne 1f\n"
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" cmp $efds, %%esi\n" /* esi arg4 */
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" mov $4, %%ebx\n"
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" jne 1f\n"
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" cmp $timeout, %%edi\n" /* edi arg5 */
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" mov $5, %%ebx\n"
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" jne 1f\n"
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" cmpl $sigmask_desc, %%ebp\n" /* %ebp arg6 */
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" mov $6, %%ebx\n"
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" jne 1f\n"
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" mov $0, %%ebx\n"
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"1:\n"
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" pop %%ebp\n"
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: "=a" (flags), "=b" (bad_arg)
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:
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: "cx", "dx", "si", "di"
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);
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if (kernel_is_64bit) {
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memset(®s64, 0x77, sizeof(regs64));
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call64_from_32(get_regs64);
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/*print_regs64();*/
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}
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/*
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* On paravirt kernels, flags are not preserved across syscalls.
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* Thus, we do not consider it a bug if some are changed.
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* We just show ones which do.
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*/
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if ((0x200ed7 ^ flags) != 0) {
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print_flags("[WARN]\tFlags before", 0x200ed7);
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print_flags("[WARN]\tFlags after", flags);
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print_flags("[WARN]\tFlags change", (0x200ed7 ^ flags));
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}
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if (bad_arg) {
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printf("[FAIL]\targ#%ld clobbered\n", bad_arg);
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return 1;
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}
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printf("[OK]\tArguments are preserved across syscall\n");
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return check_regs64();
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}
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int run_syscall_twice()
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{
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int exitcode = 0;
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long sv;
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if (syscall_addr) {
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printf("[RUN]\tExecuting 6-argument 32-bit syscall via VDSO\n");
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exitcode = run_syscall();
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}
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sv = syscall_addr;
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syscall_addr = (long)&int80;
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printf("[RUN]\tExecuting 6-argument 32-bit syscall via INT 80\n");
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exitcode += run_syscall();
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syscall_addr = sv;
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return exitcode;
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}
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void ptrace_me()
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{
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pid_t pid;
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fflush(NULL);
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pid = fork();
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if (pid < 0)
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exit(1);
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if (pid == 0) {
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/* child */
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if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) != 0)
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exit(0);
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raise(SIGSTOP);
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return;
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}
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/* parent */
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printf("[RUN]\tRunning tests under ptrace\n");
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while (1) {
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int status;
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pid = waitpid(-1, &status, __WALL);
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if (WIFEXITED(status))
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exit(WEXITSTATUS(status));
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if (WIFSIGNALED(status))
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exit(WTERMSIG(status));
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if (pid <= 0 || !WIFSTOPPED(status)) /* paranoia */
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exit(255);
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/*
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* Note: we do not inject sig = WSTOPSIG(status).
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* We probably should, but careful: do not inject SIGTRAP
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* generated by syscall entry/exit stops.
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* That kills the child.
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*/
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ptrace(PTRACE_SYSCALL, pid, 0L, 0L /*sig*/);
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}
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}
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int main(int argc, char **argv, char **envp)
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{
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int exitcode = 0;
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int cs;
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asm("\n"
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" movl %%cs, %%eax\n"
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: "=a" (cs)
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);
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kernel_is_64bit = (cs == 0x23);
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if (!kernel_is_64bit)
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printf("[NOTE]\tNot a 64-bit kernel, won't test R8..R15 leaks\n");
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/* This only works for non-static builds:
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* syscall_addr = dlsym(dlopen("linux-gate.so.1", RTLD_NOW), "__kernel_vsyscall");
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*/
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syscall_addr = get_syscall(envp);
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exitcode += run_syscall_twice();
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ptrace_me();
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exitcode += run_syscall_twice();
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return exitcode;
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}
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#endif
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