lkml.org 
[lkml]   [2007]   [Jul]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: Valgrinding the kernel?
    On Fri, Jul 06, 2007 at 10:30:19AM -0700, Dan Kegel wrote:
    > Could you give it a shot?

    OK, after ripping out the code that broke valgrind last time (patch
    below), I get this:

    ==27590== Warning: set address range perms: large range 516194304, a 0, v 0
    vex x86->IR: unhandled instruction bytes: 0xF3 0xAF 0x74 0x9
    ==27590== Your program just tried to execute an instruction that Valgrind
    ==27590== did not recognise. There are two possible reasons for this.
    ==27590== 1. Your program has a bug and erroneously jumped to a non-code
    ==27590== location. If you are running Memcheck and you just saw a
    ==27590== warning about a bad jump, it's probably your program's fault.
    ==27590== 2. The instruction is legitimate but Valgrind doesn't handle it,
    ==27590== i.e. it's Valgrind's fault. If you think this is the case or
    ==27590== you are not sure, please let us know.
    ==27590== Either way, Valgrind will now raise a SIGILL signal which will
    ==27590== probably kill your program.
    ==27590==

    > Maybe the problems after that will be more pedestrian.

    Doesn't look like it.

    FWIW, that instruction is repz scas. In an earlier valgrind effort in
    2002, I hit repe scas
    (http://www.goop.org/~jeremy/valgrind/76-repe-scas.patch), so maybe
    something similar is needed here.

    > I'm willing to focus a little effort on this.

    I guess you'll have to fix valgrind's various bugs. See, simple :)

    Jeff

    --
    Work email - jdike at linux dot intel dot com


    Index: linux-2.6.21-mm/arch/um/os-Linux/start_up.c
    ===================================================================
    --- linux-2.6.21-mm.orig/arch/um/os-Linux/start_up.c 2007-07-02 21:11:33.000000000 -0400
    +++ linux-2.6.21-mm/arch/um/os-Linux/start_up.c 2007-07-06 15:16:47.000000000 -0400
    @@ -43,54 +43,6 @@
    #include "registers.h"
    #endif

    -static int ptrace_child(void *arg)
    -{
    - int ret;
    - int pid = os_getpid(), ppid = getppid();
    - int sc_result;
    -
    - change_sig(SIGWINCH, 0);
    - if(ptrace(PTRACE_TRACEME, 0, 0, 0) < 0){
    - perror("ptrace");
    - os_kill_process(pid, 0);
    - }
    - kill(pid, SIGSTOP);
    -
    - /*This syscall will be intercepted by the parent. Don't call more than
    - * once, please.*/
    - sc_result = os_getpid();
    -
    - if (sc_result == pid)
    - ret = 1; /*Nothing modified by the parent, we are running
    - normally.*/
    - else if (sc_result == ppid)
    - ret = 0; /*Expected in check_ptrace and check_sysemu when they
    - succeed in modifying the stack frame*/
    - else
    - ret = 2; /*Serious trouble! This could be caused by a bug in
    - host 2.6 SKAS3/2.6 patch before release -V6, together
    - with a bug in the UML code itself.*/
    - _exit(ret);
    -}
    -
    -static void fatal_perror(char *str)
    -{
    - perror(str);
    - exit(1);
    -}
    -
    -static void fatal(char *fmt, ...)
    -{
    - va_list list;
    -
    - va_start(list, fmt);
    - vprintf(fmt, list);
    - va_end(list);
    - fflush(stdout);
    -
    - exit(1);
    -}
    -
    static void non_fatal(char *fmt, ...)
    {
    va_list list;
    @@ -101,64 +53,6 @@ static void non_fatal(char *fmt, ...)
    fflush(stdout);
    }

    -static int start_ptraced_child(void **stack_out)
    -{
    - void *stack;
    - unsigned long sp;
    - int pid, n, status;
    -
    - stack = mmap(NULL, UM_KERN_PAGE_SIZE,
    - PROT_READ | PROT_WRITE | PROT_EXEC,
    - MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
    - if(stack == MAP_FAILED)
    - fatal_perror("check_ptrace : mmap failed");
    - sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
    - pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);
    - if(pid < 0)
    - fatal_perror("start_ptraced_child : clone failed");
    - CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
    - if(n < 0)
    - fatal_perror("check_ptrace : clone failed");
    - if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
    - fatal("check_ptrace : expected SIGSTOP, got status = %d",
    - status);
    -
    - *stack_out = stack;
    - return pid;
    -}
    -
    -/* When testing for SYSEMU support, if it is one of the broken versions, we
    - * must just avoid using sysemu, not panic, but only if SYSEMU features are
    - * broken.
    - * So only for SYSEMU features we test mustpanic, while normal host features
    - * must work anyway!
    - */
    -static int stop_ptraced_child(int pid, void *stack, int exitcode,
    - int mustexit)
    -{
    - int status, n, ret = 0;
    -
    - if(ptrace(PTRACE_CONT, pid, 0, 0) < 0)
    - fatal_perror("stop_ptraced_child : ptrace failed");
    - CATCH_EINTR(n = waitpid(pid, &status, 0));
    - if(!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) {
    - int exit_with = WEXITSTATUS(status);
    - if (exit_with == 2)
    - non_fatal("check_ptrace : child exited with status 2. "
    - "\nDisabling SYSEMU support.\n");
    - non_fatal("check_ptrace : child exited with exitcode %d, while "
    - "expecting %d; status 0x%x\n", exit_with,
    - exitcode, status);
    - if (mustexit)
    - exit(1);
    - ret = -1;
    - }
    -
    - if(munmap(stack, UM_KERN_PAGE_SIZE) < 0)
    - fatal_perror("check_ptrace : munmap failed");
    - return ret;
    -}
    -
    /* Changed only during early boot */
    int ptrace_faultinfo = 1;
    int ptrace_ldt = 1;
    @@ -207,131 +101,23 @@ __uml_setup("nosysemu", nosysemu_cmd_par

    static void __init check_sysemu(void)
    {
    - void *stack;
    - unsigned long regs[MAX_REG_NR];
    - int pid, n, status, count=0;
    -
    non_fatal("Checking syscall emulation patch for ptrace...");
    - sysemu_supported = 0;
    - pid = start_ptraced_child(&stack);
    -
    - if(ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
    - goto fail;
    -
    - CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
    - if (n < 0)
    - fatal_perror("check_sysemu : wait failed");
    - if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
    - fatal("check_sysemu : expected SIGTRAP, got status = %d",
    - status);
    -
    - if(ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
    - fatal_perror("check_sysemu : PTRACE_GETREGS failed");
    - if(PT_SYSCALL_NR(regs) != __NR_getpid){
    - non_fatal("check_sysemu got system call number %d, "
    - "expected %d...", PT_SYSCALL_NR(regs), __NR_getpid);
    - goto fail;
    - }
    -
    - n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET, os_getpid());
    - if(n < 0){
    - non_fatal("check_sysemu : failed to modify system call "
    - "return");
    - goto fail;
    - }
    -
    - if (stop_ptraced_child(pid, stack, 0, 0) < 0)
    - goto fail_stopped;
    -
    sysemu_supported = 1;
    non_fatal("OK\n");
    set_using_sysemu(!force_sysemu_disabled);

    non_fatal("Checking advanced syscall emulation patch for ptrace...");
    - pid = start_ptraced_child(&stack);
    -
    - if((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
    - (void *) PTRACE_O_TRACESYSGOOD) < 0))
    - fatal_perror("check_ptrace: PTRACE_OLDSETOPTIONS failed");
    -
    - while(1){
    - count++;
    - if(ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
    - goto fail;
    - CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
    - if(n < 0)
    - fatal_perror("check_ptrace : wait failed");
    -
    - if(WIFSTOPPED(status) && (WSTOPSIG(status) == (SIGTRAP|0x80))){
    - if (!count)
    - fatal("check_ptrace : SYSEMU_SINGLESTEP "
    - "doesn't singlestep");
    - n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
    - os_getpid());
    - if(n < 0)
    - fatal_perror("check_sysemu : failed to modify "
    - "system call return");
    - break;
    - }
    - else if(WIFSTOPPED(status) && (WSTOPSIG(status) == SIGTRAP))
    - count++;
    - else
    - fatal("check_ptrace : expected SIGTRAP or "
    - "(SIGTRAP | 0x80), got status = %d", status);
    - }
    - if (stop_ptraced_child(pid, stack, 0, 0) < 0)
    - goto fail_stopped;
    -
    sysemu_supported = 2;
    non_fatal("OK\n");

    if ( !force_sysemu_disabled )
    set_using_sysemu(sysemu_supported);
    return;
    -
    -fail:
    - stop_ptraced_child(pid, stack, 1, 0);
    -fail_stopped:
    - non_fatal("missing\n");
    }

    static void __init check_ptrace(void)
    {
    - void *stack;
    - int pid, syscall, n, status;
    -
    non_fatal("Checking that ptrace can change system call numbers...");
    - pid = start_ptraced_child(&stack);
    -
    - if((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
    - (void *) PTRACE_O_TRACESYSGOOD) < 0))
    - fatal_perror("check_ptrace: PTRACE_OLDSETOPTIONS failed");
    -
    - while(1){
    - if(ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
    - fatal_perror("check_ptrace : ptrace failed");
    -
    - CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
    - if(n < 0)
    - fatal_perror("check_ptrace : wait failed");
    -
    - if(!WIFSTOPPED(status) ||
    - (WSTOPSIG(status) != (SIGTRAP | 0x80)))
    - fatal("check_ptrace : expected (SIGTRAP|0x80), "
    - "got status = %d", status);
    -
    - syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
    - 0);
    - if(syscall == __NR_getpid){
    - n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
    - __NR_getppid);
    - if(n < 0)
    - fatal_perror("check_ptrace : failed to modify "
    - "system call");
    - break;
    - }
    - }
    - stop_ptraced_child(pid, stack, 0, 1);
    non_fatal("OK\n");
    check_sysemu();
    }
    @@ -411,63 +197,15 @@ __uml_setup("noptraceldt", noptraceldt_c
    #ifdef UML_CONFIG_MODE_SKAS
    static inline void check_skas3_ptrace_faultinfo(void)
    {
    - struct ptrace_faultinfo fi;
    - void *stack;
    - int pid, n;
    -
    non_fatal(" - PTRACE_FAULTINFO...");
    - pid = start_ptraced_child(&stack);
    -
    - n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
    - if (n < 0) {
    - ptrace_faultinfo = 0;
    - if(errno == EIO)
    - non_fatal("not found\n");
    - else
    - perror("not found");
    - }
    - else {
    - if (!ptrace_faultinfo)
    - non_fatal("found but disabled on command line\n");
    - else
    - non_fatal("found\n");
    - }
    -
    - init_registers(pid);
    - stop_ptraced_child(pid, stack, 1, 1);
    + non_fatal("not found\n");
    }

    static inline void check_skas3_ptrace_ldt(void)
    {
    #ifdef PTRACE_LDT
    - void *stack;
    - int pid, n;
    - unsigned char ldtbuf[40];
    - struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
    - .func = 2, /* read default ldt */
    - .ptr = ldtbuf,
    - .bytecount = sizeof(ldtbuf)};
    -
    non_fatal(" - PTRACE_LDT...");
    - pid = start_ptraced_child(&stack);
    -
    - n = ptrace(PTRACE_LDT, pid, 0, (unsigned long) &ldt_op);
    - if (n < 0) {
    - if(errno == EIO)
    - non_fatal("not found\n");
    - else {
    - perror("not found");
    - }
    - ptrace_ldt = 0;
    - }
    - else {
    - if(ptrace_ldt)
    - non_fatal("found\n");
    - else
    - non_fatal("found, but use is disabled\n");
    - }
    -
    - stop_ptraced_child(pid, stack, 1, 1);
    + non_fatal("not found\n");
    #else
    /* PTRACE_LDT might be disabled via cmdline option.
    * We want to override this, else we might use the stub
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/
    \
     
     \ /
      Last update: 2007-07-06 21:45    [W:0.038 / U:3.180 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site