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Re: [Qemu-devel] [RFC v3] monitor: add memory search commands s, sp


From: Claudio Fontana
Subject: Re: [Qemu-devel] [RFC v3] monitor: add memory search commands s, sp
Date: Tue, 21 Apr 2015 16:25:12 +0200
User-agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Thunderbird/24.0.1

Hello Luiz,

On 21.04.2015 00:01, Luiz Capitulino wrote:
> On Fri, 27 Mar 2015 17:19:30 +0100
> Claudio Fontana <address@hidden> wrote:
> 
>> Just a respectful ping on this one..
>> Luiz do you think you can integrate this into the monitor?
> 
> Would be nice to get a Reviewed-by from someone and,

gladly, I am definitely looking for Review, first I wanted to check if the idea 
itself was acceptable.

> I'm getting a build error:
> 
> /home/lcapitulino/work/src/upstream/qmp-unstable/monitor.c: In function 
> ‘memory_search’:
> /home/lcapitulino/work/src/upstream/qmp-unstable/monitor.c:1307:19: error: 
> ‘needle’ may be used uninitialized in this function 
> [-Werror=maybe-uninitialized]
>              match = memmem(mark, todo, needle, wsize);
>                    ^
> cc1: all warnings being treated as errors

right, this has been pointed out to me before also, I tried to move things 
around but that did not help apparently.

I seem not to get this warning with the compiler version I am currently using,
and after checking the code I could not find out why with some compilers would 
emit such a warning.

It is difficult for me to debug this issue since I do not get this..
I am using a slightly older compiler from Linaro for AArch64 (4.8.3 based)

Thanks,

Claudio

> 
>>
>> I have given it quite some testing for the LE host case,
>> I don't have a BE host to test with at the moment, maybe someone can advise 
>> about how to test that scenario?
>> I was trying to do some qemu under qemu self-emulation but didn't quite get 
>> there..
>>
>> Thanks,
>>
>> Claudio
>>
>> On 18.03.2015 14:30, Claudio Fontana wrote:
>>> Tested with kvm on aarch64 LE host with aarch64 LE guest,
>>> tested with tcg on aarch64 LE host with aarch64 LE/sparc BE/x86 LE guests.
>>> Would be interesting to test this also on a big endian host with different 
>>> guest combinations..
>>>
>>> Claudio
>>>
>>> On 16.03.2015 11:31, address@hidden wrote:
>>>> From: Claudio Fontana <address@hidden>
>>>>
>>>> usage is similar to the commands x, xp.
>>>>
>>>> Example with string: looking for "ELF" header in memory:
>>>>
>>>> (qemu) s/1000000cb 0x40001000 "ELF"
>>>> searching memory area [0000000040001000-00000000400f5240]
>>>> 0000000040090001
>>>> (qemu) x/20b 0x40090000
>>>> 0000000040090000: '\x7f' 'E' 'L' 'F' '\x02' '\x01' '\x01' '\x03'
>>>> 0000000040090008: '\x00' '\x00' '\x00' '\x00' '\x00' '\x00' '\x00' '\x00'
>>>> 0000000040090010: '\x02' '\x00' '\xb7' '\x00'
>>>>
>>>> Example with value: looking for 64bit variable value 0x990088
>>>>
>>>> (qemu) s/1000000xg 0xffff900042000000 0x990088
>>>> searching memory area [ffff900042000000-ffff9000427a1200]
>>>> ffff9000424b3000
>>>> ffff9000424c1000
>>>>
>>>> Signed-off-by: Claudio Fontana <address@hidden>
>>>> ---
>>>>  hmp-commands.hx |  28 ++++++++++++
>>>>  monitor.c       | 140 
>>>> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>>>  2 files changed, 168 insertions(+)
>>>>
>>>> Hello, looking for some comments on whether the addition of this
>>>> command is welcome, and whether the syntax chosen is acceptable,
>>>> or how it can made better.
>>>>
>>>> Thanks!
>>>>
>>>> Claudio
>>>>
>>>> changes from v2:
>>>> move value_raw array outside of the inner block.
>>>> Hopefully this will also make patchew tool happy.
>>>> Weird that I didn't get that warning/error.
>>>>
>>>> changes from v1:
>>>> make checkpatch happy by adding braces here and there.
>>>>
>>>> diff --git a/hmp-commands.hx b/hmp-commands.hx
>>>> index d5022d8..2bf5737 100644
>>>> --- a/hmp-commands.hx
>>>> +++ b/hmp-commands.hx
>>>> @@ -432,6 +432,34 @@ Start gdbserver session (default @var{port}=1234)
>>>>  ETEXI
>>>>  
>>>>      {
>>>> +        .name       = "s",
>>>> +        .args_type  = "fmt:/,addr:l,data:s",
>>>> +        .params     = "/fmt addr data",
>>>> +        .help       = "search virtual memory starting at 'addr' for 
>>>> 'data'",
>>>> +        .mhandler.cmd = hmp_memory_search,
>>>> +    },
>>>> +
>>>> +STEXI
>>>> address@hidden s/fmt @var{addr} @var{data}
>>>> address@hidden s
>>>> +Virtual memory search starting at @var{addr} for data described by 
>>>> @var{data}.
>>>> +ETEXI
>>>> +
>>>> +    {
>>>> +        .name       = "sp",
>>>> +        .args_type  = "fmt:/,addr:l,data:s",
>>>> +        .params     = "/fmt addr data",
>>>> +        .help       = "search physical memory starting at 'addr' for 
>>>> 'data'",
>>>> +        .mhandler.cmd = hmp_physical_memory_search,
>>>> +    },
>>>> +
>>>> +STEXI
>>>> address@hidden sp/fmt @var{addr} @var{data}
>>>> address@hidden sp
>>>> +Physical memory search starting at @var{addr} for data described by 
>>>> @var{data}.
>>>> +ETEXI
>>>> +
>>>> +    {
>>>>          .name       = "x",
>>>>          .args_type  = "fmt:/,addr:l",
>>>>          .params     = "/fmt addr",
>>>> diff --git a/monitor.c b/monitor.c
>>>> index c86a89e..7495d7e 100644
>>>> --- a/monitor.c
>>>> +++ b/monitor.c
>>>> @@ -1208,6 +1208,124 @@ static void monitor_printc(Monitor *mon, int c)
>>>>      monitor_printf(mon, "'");
>>>>  }
>>>>  
>>>> +static void monitor_print_addr(Monitor *mon, hwaddr addr, bool 
>>>> is_physical)
>>>> +{
>>>> +    if (is_physical) {
>>>> +        monitor_printf(mon, TARGET_FMT_plx "\n", addr);
>>>> +    } else {
>>>> +        monitor_printf(mon, TARGET_FMT_lx "\n", (target_ulong)addr);
>>>> +    }
>>>> +}
>>>> +
>>>> +/* simple memory search for a byte sequence. The sequence is generated 
>>>> from
>>>> + * a numeric value to look for in guest memory, or from a string.
>>>> + */
>>>> +static void memory_search(Monitor *mon, int count, int format, int wsize,
>>>> +                          hwaddr addr, const char *data_str, bool 
>>>> is_physical)
>>>> +{
>>>> +    int pos, len;           /* pos in the search area, len of area */
>>>> +    char *hay;              /* buffer for haystack */
>>>> +    int hay_size;           /* haystack size. Needle size is wsize. */
>>>> +    const char *needle;     /* needle to search in the haystack */
>>>> +    const char *format_str; /* numeric input format string */
>>>> +    char value_raw[8];      /* numeric input converted to raw data */
>>>> +#define MONITOR_S_CHUNK_SIZE 16000
>>>> +
>>>> +    len = wsize * count;
>>>> +    if (len < 1) {
>>>> +        monitor_printf(mon, "invalid search area length.\n");
>>>> +        return;
>>>> +    }
>>>> +    switch (format) {
>>>> +    case 'i':
>>>> +        monitor_printf(mon, "format '%c' not supported.\n", format);
>>>> +        return;
>>>> +    case 'c':
>>>> +        needle = data_str;
>>>> +        wsize = strlen(data_str);
>>>> +        if (wsize > MONITOR_S_CHUNK_SIZE) {
>>>> +            monitor_printf(mon, "search string too long [max %d].\n",
>>>> +                           MONITOR_S_CHUNK_SIZE);
>>>> +            return;
>>>> +        }
>>>> +        break;
>>>> +    case 'o':
>>>> +        format_str = "%" SCNo64;
>>>> +        break;
>>>> +    default:
>>>> +    case 'x':
>>>> +        format_str = "%" SCNx64;
>>>> +        break;
>>>> +    case 'u':
>>>> +        format_str = "%" SCNu64;
>>>> +        break;
>>>> +    case 'd':
>>>> +        format_str = "%" SCNd64;
>>>> +        break;
>>>> +    }
>>>> +    if (format != 'c') {
>>>> +        uint64_t value;      /* numeric input value */
>>>> +        void *from = &value;
>>>> +        if (sscanf(data_str, format_str, &value) != 1) {
>>>> +            monitor_printf(mon, "could not parse search string "
>>>> +                           "\"%s\" as format '%c'.\n", data_str, format);
>>>> +            return;
>>>> +        }
>>>> +#if defined(HOST_WORDS_BIGENDIAN) != defined(TARGET_WORDS_BIGENDIAN)
>>>> +        value = bswap64(value);
>>>> +#endif
>>>> +#if defined(TARGET_WORDS_BIGENDIAN)
>>>> +        from += 8 - wsize;
>>>> +#endif
>>>> +        memcpy(value_raw, from, wsize);
>>>> +        needle = value_raw;
>>>> +    }
>>>> +    monitor_printf(mon, "searching memory area ");
>>>> +    if (is_physical) {
>>>> +        monitor_printf(mon, "[" TARGET_FMT_plx "-" TARGET_FMT_plx "]\n",
>>>> +                       addr, addr + len);
>>>> +    } else {
>>>> +        monitor_printf(mon, "[" TARGET_FMT_lx "-" TARGET_FMT_lx "]\n",
>>>> +                       (target_ulong)addr, (target_ulong)addr + len);
>>>> +    }
>>>> +    hay_size = len < MONITOR_S_CHUNK_SIZE ? len : MONITOR_S_CHUNK_SIZE;
>>>> +    hay = g_malloc0(hay_size);
>>>> +
>>>> +    for (pos = 0; pos < len;) {
>>>> +        char *mark, *match; /* mark new starting position, eventual match 
>>>> */
>>>> +        int l, todo;        /* total length to be processed in current 
>>>> chunk */
>>>> +        l = len - pos;
>>>> +        if (l > hay_size) {
>>>> +            l = hay_size;
>>>> +        }
>>>> +        if (is_physical) {
>>>> +            cpu_physical_memory_read(addr, hay, l);
>>>> +        } else if (cpu_memory_rw_debug(ENV_GET_CPU(mon_get_cpu()), addr,
>>>> +                                       (uint8_t *)hay, l, 0) < 0) {
>>>> +            monitor_printf(mon, " Cannot access memory\n");
>>>> +            break;
>>>> +        }
>>>> +        for (mark = hay, todo = l; todo >= wsize;) {
>>>> +            match = memmem(mark, todo, needle, wsize);
>>>> +            if (!match) {
>>>> +                break;
>>>> +            }
>>>> +            monitor_print_addr(mon, addr + (match - hay), is_physical);
>>>> +            mark = match + 1;
>>>> +            todo = mark - hay;
>>>> +        }
>>>> +        if (pos + l < len) {
>>>> +            /* catch potential matches across chunks. */
>>>> +            pos += l - (wsize - 1);
>>>> +            addr += l - (wsize - 1);
>>>> +        } else {
>>>> +            pos += l;
>>>> +            addr += l;
>>>> +        }
>>>> +    }
>>>> +    g_free(hay);
>>>> +}
>>>> +
>>>>  static void memory_dump(Monitor *mon, int count, int format, int wsize,
>>>>                          hwaddr addr, int is_physical)
>>>>  {
>>>> @@ -1332,6 +1450,28 @@ static void memory_dump(Monitor *mon, int count, 
>>>> int format, int wsize,
>>>>      }
>>>>  }
>>>>  
>>>> +static void hmp_memory_search(Monitor *mon, const QDict *qdict)
>>>> +{
>>>> +    int count = qdict_get_int(qdict, "count");
>>>> +    int format = qdict_get_int(qdict, "format");
>>>> +    int size = qdict_get_int(qdict, "size");
>>>> +    target_long addr = qdict_get_int(qdict, "addr");
>>>> +    const char *data_str = qdict_get_str(qdict, "data");
>>>> +
>>>> +    memory_search(mon, count, format, size, addr, data_str, false);
>>>> +}
>>>> +
>>>> +static void hmp_physical_memory_search(Monitor *mon, const QDict *qdict)
>>>> +{
>>>> +    int count = qdict_get_int(qdict, "count");
>>>> +    int format = qdict_get_int(qdict, "format");
>>>> +    int size = qdict_get_int(qdict, "size");
>>>> +    hwaddr addr = qdict_get_int(qdict, "addr");
>>>> +    const char *data_str = qdict_get_str(qdict, "data");
>>>> +
>>>> +    memory_search(mon, count, format, size, addr, data_str, true);
>>>> +}
>>>> +
>>>>  static void hmp_memory_dump(Monitor *mon, const QDict *qdict)
>>>>  {
>>>>      int count = qdict_get_int(qdict, "count");
>>>>
>>>
>>>
>>
>>
> 


-- 
Claudio Fontana
Server Virtualization Architect
Huawei Technologies Duesseldorf GmbH
Riesstraße 25 - 80992 München

office: +49 89 158834 4135
mobile: +49 15253060158



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