// SPDX-License-Identifier: GPL-2.0-only
/*
* 32-bit syscall ABI conformance test.
*
* Copyright (c) 2015 Denys Vlasenko
*/
/*
* Can be built statically:
* gcc -Os -Wall -static -m32 test_syscall_vdso.c thunks_32.S
*/
#undef _GNU_SOURCE
#define _GNU_SOURCE 1
#undef __USE_GNU
#define __USE_GNU 1
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/select.h>
#include <sys/time.h>
#include <elf.h>
#include <sys/ptrace.h>
#include <sys/wait.h>
#if !defined(__i386__)
int main(int argc, char **argv, char **envp)
{
printf("[SKIP]\tNot a 32-bit x86 userspace\n");
return 0;
}
#else
long syscall_addr;
long get_syscall(char **envp)
{
Elf32_auxv_t *auxv;
while (*envp++ != NULL)
continue;
for (auxv = (void *)envp; auxv->a_type != AT_NULL; auxv++)
if (auxv->a_type == AT_SYSINFO)
return auxv->a_un.a_val;
printf("[WARN]\tAT_SYSINFO not supplied\n");
return 0;
}
asm (
" .pushsection .text\n"
" .global int80\n"
"int80:\n"
" int $0x80\n"
" ret\n"
" .popsection\n"
);
extern char int80;
struct regs64 {
uint64_t rax, rbx, rcx, rdx;
uint64_t rsi, rdi, rbp, rsp;
uint64_t r8, r9, r10, r11;
uint64_t r12, r13, r14, r15;
};
struct regs64 regs64;
int kernel_is_64bit;
asm (
" .pushsection .text\n"
" .code64\n"
"get_regs64:\n"
" push %rax\n"
" mov $regs64, %eax\n"
" pop 0*8(%rax)\n"
" movq %rbx, 1*8(%rax)\n"
" movq %rcx, 2*8(%rax)\n"
" movq %rdx, 3*8(%rax)\n"
" movq %rsi, 4*8(%rax)\n"
" movq %rdi, 5*8(%rax)\n"
" movq %rbp, 6*8(%rax)\n"
" movq %rsp, 7*8(%rax)\n"
" movq %r8, 8*8(%rax)\n"
" movq %r9, 9*8(%rax)\n"
" movq %r10, 10*8(%rax)\n"
" movq %r11, 11*8(%rax)\n"
" movq %r12, 12*8(%rax)\n"
" movq %r13, 13*8(%rax)\n"
" movq %r14, 14*8(%rax)\n"
" movq %r15, 15*8(%rax)\n"
" ret\n"
"poison_regs64:\n"
" movq $0x7f7f7f7f, %r8\n"
" shl $32, %r8\n"
" orq $0x7f7f7f7f, %r8\n"
" movq %r8, %r9\n"
" incq %r9\n"
" movq %r9, %r10\n"
" incq %r10\n"
" movq %r10, %r11\n"
" incq %r11\n"
" movq %r11, %r12\n"
" incq %r12\n"
" movq %r12, %r13\n"
" incq %r13\n"
" movq %r13, %r14\n"
" incq %r14\n"
" movq %r14, %r15\n"
" incq %r15\n"
" ret\n"
" .code32\n"
" .popsection\n"
);
extern void get_regs64(void);
extern void poison_regs64(void);
extern unsigned long call64_from_32(void (*function)(void));
void print_regs64(void)
{
if (!kernel_is_64bit)
return;
printf("ax:%016llx bx:%016llx cx:%016llx dx:%016llx\n", regs64.rax, regs64.rbx, regs64.rcx, regs64.rdx);
printf("si:%016llx di:%016llx bp:%016llx sp:%016llx\n", regs64.rsi, regs64.rdi, regs64.rbp, regs64.rsp);
printf(" 8:%016llx 9:%016llx 10:%016llx 11:%016llx\n", regs64.r8 , regs64.r9 , regs64.r10, regs64.r11);
printf("12:%016llx 13:%016llx 14:%016llx 15:%016llx\n", regs64.r12, regs64.r13, regs64.r14, regs64.r15);
}
int check_regs64(void)
{
int err = 0;
int num = 8;
uint64_t *r64 = ®s64.r8;
uint64_t expected = 0x7f7f7f7f7f7f7f7fULL;
if (!kernel_is_64bit)
return 0;
do {
if (*r64 == expected++)
continue; /* register did not change */
if (syscall_addr != (long)&int80) {
/*
* Non-INT80 syscall entrypoints are allowed to clobber R8+ regs:
* either clear them to 0, or for R11, load EFLAGS.
*/
if (*r64 == 0)
continue;
if (num == 11) {
printf("[NOTE]\tR11 has changed:%016llx - assuming clobbered by SYSRET insn\n", *r64);
continue;
}
} else {
/*
* INT80 syscall entrypoint can be used by
* 64-bit programs too, unlike SYSCALL/SYSENTER.
* Therefore it must preserve R12+
* (they are callee-saved registers in 64-bit C ABI).
*
* Starting in Linux 4.17 (and any kernel that
* backports the change), R8..11 are preserved.
* Historically (and probably unintentionally), they
* were clobbered or zeroed.
*/
}
printf("[FAIL]\tR%d has changed:%016llx\n", num, *r64);
err++;
} while (r64++, ++num < 16);
if (!err)
printf("[OK]\tR8..R15 did not leak kernel data\n");
return err;
}
int nfds;
fd_set rfds;
fd_set wfds;
fd_set efds;
struct timespec timeout;
sigset_t sigmask;
struct {
sigset_t *sp;
int sz;
} sigmask_desc;
void prep_args()
{
nfds = 42;
FD_ZERO(&rfds);
FD_ZERO(&wfds);
FD_ZERO(&efds);
FD_SET(0, &rfds);
FD_SET(1, &wfds);
FD_SET(2, &efds);
timeout.tv_sec = 0;
timeout.tv_nsec = 123;
sigemptyset(&sigmask);
sigaddset(&sigmask, SIGINT);
sigaddset(&sigmask, SIGUSR2);
sigaddset(&sigmask, SIGRTMAX);
sigmask_desc.sp = &sigmask;
sigmask_desc.sz = 8; /* bytes */
}
static void print_flags(const char *name, unsigned long r)
{
static const char *bitarray[] = {
"\n" ,"c\n" ,/* Carry Flag */
"0 " ,"1 " ,/* Bit 1 - always on */
"" ,"p " ,/* Parity Flag */
"0 " ,"3? " ,
"" ,"a " ,/* Auxiliary carry Flag */
"0 " ,"5? " ,
"" ,"z " ,/* Zero Flag */
"" ,"s " ,/* Sign Flag */
"" ,"t " ,/* Trap Flag */
"" ,"i " ,/* Interrupt Flag */
"" ,"d " ,/* Direction Flag */
"" ,"o " ,/* Overflow Flag */
"0 " ,"1 " ,/* I/O Privilege Level (2 bits) */
"0" ,"1" ,/* I/O Privilege Level (2 bits) */
"" ,"n " ,/* Nested Task */
"0 " ,"15? ",
"" ,"r " ,/* Resume Flag */
"" ,"v " ,/* Virtual Mode */
"" ,"ac " ,/* Alignment Check/Access Control */
"" ,"vif ",/* Virtual Interrupt Flag */
"" ,"vip ",/* Virtual Interrupt Pending */
"" ,"id " ,/* CPUID detection */
NULL
};
const char **bitstr;
int bit;
printf("%s=%016lx ", name, r);
bitstr = bitarray + 42;
bit = 21;
if ((r >> 22) != 0)
printf("(extra bits are set) ");
do {
if (bitstr[(r >> bit) & 1][0])
fputs(bitstr[(r >> bit) & 1], stdout);
bitstr -= 2;
bit--;
} while (bit >= 0);
}
int run_syscall(void)
{
long flags, bad_arg;
prep_args();
if (kernel_is_64bit)
call64_from_32(poison_regs64);
/*print_regs64();*/
asm("\n"
/* Try 6-arg syscall: pselect. It should return quickly */
" push %%ebp\n"
" mov $308, %%eax\n" /* PSELECT */
" mov nfds, %%ebx\n" /* ebx arg1 */
" mov $rfds, %%ecx\n" /* ecx arg2 */
" mov $wfds, %%edx\n" /* edx arg3 */
" mov $efds, %%esi\n" /* esi arg4 */
" mov $timeout, %%edi\n" /* edi arg5 */
" mov $sigmask_desc, %%ebp\n" /* %ebp arg6 */
" push $0x200ed7\n" /* set almost all flags */
" popf\n" /* except TF, IOPL, NT, RF, VM, AC, VIF, VIP */
" call *syscall_addr\n"
/* Check that registers are not clobbered */
" pushf\n"
" pop %%eax\n"
" cld\n"
" cmp nfds, %%ebx\n" /* ebx arg1 */
" mov $1, %%ebx\n"
" jne 1f\n"
" cmp $rfds, %%ecx\n" /* ecx arg2 */
" mov $2, %%ebx\n"
" jne 1f\n"
" cmp $wfds, %%edx\n" /* edx arg3 */
" mov $3, %%ebx\n"
" jne 1f\n"
" cmp $efds, %%esi\n" /* esi arg4 */
" mov $4, %%ebx\n"
" jne 1f\n"
" cmp $timeout, %%edi\n" /* edi arg5 */
" mov $5, %%ebx\n"
" jne 1f\n"
" cmpl $sigmask_desc, %%ebp\n" /* %ebp arg6 */
" mov $6, %%ebx\n"
" jne 1f\n"
" mov $0, %%ebx\n"
"1:\n"
" pop %%ebp\n"
: "=a" (flags), "=b" (bad_arg)
:
: "cx", "dx", "si", "di"
);
if (kernel_is_64bit) {
memset(®s64, 0x77, sizeof(regs64));
call64_from_32(get_regs64);
/*print_regs64();*/
}
/*
* On paravirt kernels, flags are not preserved across syscalls.
* Thus, we do not consider it a bug if some are changed.
* We just show ones which do.
*/
if ((0x200ed7 ^ flags) != 0) {
print_flags("[WARN]\tFlags before", 0x200ed7);
print_flags("[WARN]\tFlags after", flags);
print_flags("[WARN]\tFlags change", (0x200ed7 ^ flags));
}
if (bad_arg) {
printf("[FAIL]\targ#%ld clobbered\n", bad_arg);
return 1;
}
printf("[OK]\tArguments are preserved across syscall\n");
return check_regs64();
}
int run_syscall_twice()
{
int exitcode = 0;
long sv;
if (syscall_addr) {
printf("[RUN]\tExecuting 6-argument 32-bit syscall via VDSO\n");
exitcode = run_syscall();
}
sv = syscall_addr;
syscall_addr = (long)&int80;
printf("[RUN]\tExecuting 6-argument 32-bit syscall via INT 80\n");
exitcode += run_syscall();
syscall_addr = sv;
return exitcode;
}
void ptrace_me()
{
pid_t pid;
fflush(NULL);
pid = fork();
if (pid < 0)
exit(1);
if (pid == 0) {
/* child */
if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) != 0)
exit(0);
raise(SIGSTOP);
return;
}
/* parent */
printf("[RUN]\tRunning tests under ptrace\n");
while (1) {
int status;
pid = waitpid(-1, &status, __WALL);
if (WIFEXITED(status))
exit(WEXITSTATUS(status));
if (WIFSIGNALED(status))
exit(WTERMSIG(status));
if (pid <= 0 || !WIFSTOPPED(status)) /* paranoia */
exit(255);
/*
* Note: we do not inject sig = WSTOPSIG(status).
* We probably should, but careful: do not inject SIGTRAP
* generated by syscall entry/exit stops.
* That kills the child.
*/
ptrace(PTRACE_SYSCALL, pid, 0L, 0L /*sig*/);
}
}
int main(int argc, char **argv, char **envp)
{
int exitcode = 0;
int cs;
asm("\n"
" movl %%cs, %%eax\n"
: "=a" (cs)
);
kernel_is_64bit = (cs == 0x23);
if (!kernel_is_64bit)
printf("[NOTE]\tNot a 64-bit kernel, won't test R8..R15 leaks\n");
/* This only works for non-static builds:
* syscall_addr = dlsym(dlopen("linux-gate.so.1", RTLD_NOW), "__kernel_vsyscall");
*/
syscall_addr = get_syscall(envp);
exitcode += run_syscall_twice();
ptrace_me();
exitcode += run_syscall_twice();
return exitcode;
}
#endif