/*
 * 32-bit syscall ABI conformance test.
 *
 * Copyright (c) 2015 Denys Vlasenko
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 */
/*
 * 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 = &regs64.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(&regs64, 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