Hey Arun,
On Tue, Apr 21, 2015 at 2:32 AM, Arun Prakash Jana <[email protected]>
wrote:
> Hi,
>
> I am calling unw_create_addr_space() in the following lines:
> --------------------------
> /* Create address space for little endian */
> addrspace = unw_create_addr_space(&accessors, 0);
> if (!addrspace) {
> fprintf(stderr, "unw_create_addr_space failed\n");
> return -1;
> }
> --------------------------
>
You haven't initialised accessors with anything at this point. I think you
are supposed to just pass in _UPT_accessors as per man page, but I haven't
really ever used the ptrace support.
>
>
> And I can verify from GDB that it is initialized:
> --------------------------
> (gdb) bt full
> #0 0x0000000000000000 in ?? ()
> No symbol table info available.
> #1 0x00007ffff7bbeee4 in _Ux86_64_init_remote () from
> /usr/lib/x86_64-linux-gnu/libunwind-x86_64.so.8
> No symbol table info available.
> #2 0x0000000000400d8c in main (argc=2, argv=0x7fffffffe0e8) at unwind.c:87
> addrspace = 0x603010
> uptinfo = 0x60dab0
> accessors = {find_proc_info = 0x7ffff7602c58, put_unwind_info =
> 0x1f25bc2, get_dyn_info_list_addr = 0x7fffffffdce0,
> access_mem = 0x7ffff7de4991 <_dl_lookup_symbol_x+305>,
> access_reg = 0x0, access_fpreg = 0x7ffff7fe0a58, resume = 0x7ffff7fe1000,
> get_proc_name = 0x7ffff7dda77c}
>
All of these addresses look to be junk and don't point to any procedures.
So when the tracing code calls them as functions, you'll just jump to
random memory addresses.
> cursor = {opaque = {6347440, 6303760, 4294967296, 4294969506,
> 140737354127864, 140737488346688, 140737488346496, 140737354009176, 1, 0,
> 2,
> 1, 2, 2, 2, 3, 2, 4, 2, 5, 2, 6, 2, 7, 2, 8, 2, 9, 2, 10, 2,
> 11, 2, 12, 2, 13, 2, 14, 2, 15, 2, 16, 2, 140737354127864,
> 140737351887448, 7, 140737351885856, 140737351884800,
> 140737488346816, 140737351936639, 140733193388033, 0, 0, 140737351925404,
> 140737488346672, 1700966438, 0, 1, 0, 140737351927416, 0,
> 140737488346656, 140737354113376, 140737488346928, 140737354113496,
> 140737488346912, 0, 140737351925404, 0, 4131212846, 3, 8,
> 140737354007936, 140737351927830, 0, 140737488346768, 140737343610152,
> 140737488347040, 140737343660456, 64550200, 140737488347024,
> 140737354132200, 0, 140737354008048, 140737354010624, 4196003,
> 140737343663480, 4195176, 4294967296, 4294969392, 0,
> 140737488347224, 140737488347184, 140737354008048, 1, 140737354130720,
> 140737354129864, 140737351928209, 0, 140737354008048, 1, 0,
> 140733193388033, 140737354129864, 0, 0, 0, 0, 0, 140737354130720,
> 140737488347040, 140737488347024, 4131212846, 4196003,
> 4294967295, 140737488347392, 140737343660456, 140737354010624,
> 140737354129864,
> 0, 1, 4198109, 140737488347136, 0, 4198032, 4196864,
> 140737488347360}}
> RIP = 140737354013160
> RBP = 140737488346080
> PID = 26450
> ret = 26450
> wait_loops = 18
> wait_time = 1000
> waitstatus = 4991
> stopped = 1
> (gdb)
> --------------------------
>
>
> Regards,
>
> Arun
>
Cheers,
Lassi
>
>
> On Tue, Apr 21, 2015 at 12:09 AM, Lassi Tuura <[email protected]> wrote:
>
>> It doesn't look like you are initialising your unw_accessors_t accessors.
>> From libunwind-ptrace man page:
>>
>> An application that wants to use the _UPT-facility first needs to create
>> a new libunwind address-space that represents the target process. This is
>> done by calling unw_create_addr_space(). In many cases, the application
>> will simply want to pass the address of _UPT_accessors as the first
>> argument to this routine
>>
>> On Mon, Apr 20, 2015 at 1:42 PM, Arun Prakash Jana <
>> [email protected]> wrote:
>>
>>> Hi,
>>>
>>> I am writing a small test program to check how libunwind can be used to
>>> trace a remote program.
>>>
>>> A call to unw_init_remote() throws SIGSEGV.
>>>
>>> *Relevant code snippet:*
>>> ------------------
>>> unw_addr_space_t addrspace;
>>> struct UPT_info *uptinfo;
>>> unw_accessors_t accessors;
>>> unw_cursor_t cursor;
>>> unw_word_t RIP, RBP;
>>>
>>> pid_t PID = 1;
>>> int ret = 0;
>>>
>>> if (argc !=2) {
>>> fprintf(stderr, "Usage: unwind PID\n");
>>> return -1;
>>> }
>>>
>>> if ((PID = atoi(argv[1])) <= 0) {
>>> fprintf(stderr, "Valid PID please!\n");
>>> return -1;
>>> }
>>>
>>> fprintf(stdout, "Tracing PID: %d\n", PID);
>>>
>>> /* Create address space for little endian */
>>> addrspace = unw_create_addr_space(&accessors, 0);
>>> if (!addrspace) {
>>> fprintf(stderr, "unw_create_addr_space failed\n");
>>> return -1;
>>> }
>>>
>>> uptinfo = (struct UPT_info *)_UPT_create(PID);
>>> if (!uptinfo) {
>>> fprintf(stderr, "_UPT_create failed\n");
>>> goto bail;
>>> }
>>>
>>> ret = unw_init_remote(&cursor, addrspace, uptinfo);
>>> if (ret < 0) {
>>> fprintf(stderr, "unw_init_remote failed\n");
>>> goto bail;
>>> }
>>> ------------------
>>>
>>> *strace output:*
>>> ------------------
>>> > strace ./unwind 8423
>>> execve("./unwind", ["./unwind", "8423"], [/* 85 vars */]) = 0
>>> brk(0) = 0x1cdd000
>>> access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or
>>> directory)
>>> mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
>>> = 0x7fc136cc9000
>>> access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or
>>> directory)
>>> open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
>>> fstat(3, {st_mode=S_IFREG|0644, st_size=81750, ...}) = 0
>>> mmap(NULL, 81750, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fc136cb5000
>>> close(3) = 0
>>> access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or
>>> directory)
>>> open("/usr/lib/x86_64-linux-gnu/libunwind-x86_64.so.8",
>>> O_RDONLY|O_CLOEXEC) = 3
>>> read(3,
>>> "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0p\27\0\0\0\0\0\0"..., 832) =
>>> 832
>>> fstat(3, {st_mode=S_IFREG|0644, st_size=67608, ...}) = 0
>>> mmap(NULL, 2223816, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3,
>>> 0) = 0x7fc13688a000
>>> mprotect(0x7fc13689a000, 2093056, PROT_NONE) = 0
>>> mmap(0x7fc136a99000, 8192, PROT_READ|PROT_WRITE,
>>> MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xf000) = 0x7fc136a99000
>>> mmap(0x7fc136a9b000, 57032, PROT_READ|PROT_WRITE,
>>> MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fc136a9b000
>>> close(3) = 0
>>> access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or
>>> directory)
>>> open("/usr/lib/x86_64-linux-gnu/libunwind-ptrace.so.0",
>>> O_RDONLY|O_CLOEXEC) = 3
>>> read(3,
>>> "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\0\17\0\0\0\0\0\0"..., 832)
>>> = 832
>>> fstat(3, {st_mode=S_IFREG|0644, st_size=14528, ...}) = 0
>>> mmap(NULL, 2109736, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3,
>>> 0) = 0x7fc136686000
>>> mprotect(0x7fc136689000, 2093056, PROT_NONE) = 0
>>> mmap(0x7fc136888000, 8192, PROT_READ|PROT_WRITE,
>>> MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2000) = 0x7fc136888000
>>> close(3) = 0
>>> access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or
>>> directory)
>>> open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
>>> read(3,
>>> "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\320\37\2\0\0\0\0\0"...,
>>> 832) = 832
>>> fstat(3, {st_mode=S_IFREG|0755, st_size=1840928, ...}) = 0
>>> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
>>> = 0x7fc136cb4000
>>> mmap(NULL, 3949248, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3,
>>> 0) = 0x7fc1362c1000
>>> mprotect(0x7fc13647c000, 2093056, PROT_NONE) = 0
>>> mmap(0x7fc13667b000, 24576, PROT_READ|PROT_WRITE,
>>> MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1ba000) = 0x7fc13667b000
>>> mmap(0x7fc136681000, 17088, PROT_READ|PROT_WRITE,
>>> MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fc136681000
>>> close(3) = 0
>>> access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or
>>> directory)
>>> open("/usr/lib/x86_64-linux-gnu/libunwind.so.8", O_RDONLY|O_CLOEXEC) = 3
>>> read(3,
>>> "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0000\37\0\0\0\0\0\0"..., 832)
>>> = 832
>>> fstat(3, {st_mode=S_IFREG|0644, st_size=51192, ...}) = 0
>>> mmap(NULL, 2207464, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3,
>>> 0) = 0x7fc1360a6000
>>> mprotect(0x7fc1360b2000, 2093056, PROT_NONE) = 0
>>> mmap(0x7fc1362b1000, 8192, PROT_READ|PROT_WRITE,
>>> MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xb000) = 0x7fc1362b1000
>>> mmap(0x7fc1362b3000, 57064, PROT_READ|PROT_WRITE,
>>> MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fc1362b3000
>>> close(3) = 0
>>> access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or
>>> directory)
>>> open("/lib/x86_64-linux-gnu/liblzma.so.5", O_RDONLY|O_CLOEXEC) = 3
>>> read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\320
>>> \0\0\0\0\0\0"..., 832) = 832
>>> fstat(3, {st_mode=S_IFREG|0644, st_size=137400, ...}) = 0
>>> mmap(NULL, 2232456, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3,
>>> 0) = 0x7fc135e84000
>>> mprotect(0x7fc135ea5000, 2093056, PROT_NONE) = 0
>>> mmap(0x7fc1360a4000, 8192, PROT_READ|PROT_WRITE,
>>> MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x20000) = 0x7fc1360a4000
>>> close(3) = 0
>>> access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or
>>> directory)
>>> open("/lib/x86_64-linux-gnu/libdl.so.2", O_RDONLY|O_CLOEXEC) = 3
>>> read(3,
>>> "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\320\16\0\0\0\0\0\0"...,
>>> 832) = 832
>>> fstat(3, {st_mode=S_IFREG|0644, st_size=14664, ...}) = 0
>>> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
>>> = 0x7fc136cb3000
>>> mmap(NULL, 2109744, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3,
>>> 0) = 0x7fc135c80000
>>> mprotect(0x7fc135c83000, 2093056, PROT_NONE) = 0
>>> mmap(0x7fc135e82000, 8192, PROT_READ|PROT_WRITE,
>>> MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2000) = 0x7fc135e82000
>>> close(3) = 0
>>> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
>>> = 0x7fc136cb2000
>>> mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
>>> = 0x7fc136cb0000
>>> arch_prctl(ARCH_SET_FS, 0x7fc136cb0780) = 0
>>> mprotect(0x7fc13667b000, 16384, PROT_READ) = 0
>>> mprotect(0x7fc135e82000, 4096, PROT_READ) = 0
>>> mprotect(0x7fc1360a4000, 4096, PROT_READ) = 0
>>> mprotect(0x7fc1362b1000, 4096, PROT_READ) = 0
>>> mprotect(0x7fc136888000, 4096, PROT_READ) = 0
>>> mprotect(0x7fc136a99000, 4096, PROT_READ) = 0
>>> mprotect(0x601000, 4096, PROT_READ) = 0
>>> mprotect(0x7fc136ccb000, 4096, PROT_READ) = 0
>>> munmap(0x7fc136cb5000, 81750) = 0
>>> fstat(1, {st_mode=S_IFREG|0664, st_size=5320, ...}) = 0
>>> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
>>> = 0x7fc136cc8000
>>> brk(0) = 0x1cdd000
>>> brk(0x1d08000) = 0x1d08000
>>> rt_sigprocmask(SIG_SETMASK, ~[RTMIN RT_1], [], 8) = 0
>>> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
>>> = 0x7fc136cc7000
>>> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
>>> = 0x7fc136cc6000
>>> mincore(0x7ffd4ae65b3f, 1, 0x7ffd4ae65b3f) = -1 EINVAL (Invalid argument)
>>> rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
>>> --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0} ---
>>> +++ killed by SIGSEGV +++
>>> fish: Job 1, “strace ./unwind 8423 > strace.log 2>&1” terminated by
>>> signal SIGSEGV (Address boundary error)
>>> ------------------
>>>
>>> I am on Ubuntu 14.04 (arch: x86_64). Can someone please explain what I'm
>>> doing wrong?
>>>
>>> Regards,
>>>
>>> Arun
>>>
>>> _______________________________________________
>>> Libunwind-devel mailing list
>>> [email protected]
>>> https://lists.nongnu.org/mailman/listinfo/libunwind-devel
>>>
>>>
>>
>
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