[PREC/RFA] Add not_replay to make precord support release memory better
Hui Zhu
teawater@gmail.com
Mon Aug 3 05:19:00 GMT 2009
The record_exec_entry don't have big contact with core dump patch.
I think the new version is more clear.
On the other hand, there is not multithread work, core dump need
record_exec_entry, it need "mem_entry_not_accessible" too.
Because some lib address when work with core, cannot really access.
Thanks,
Hui
On Mon, Aug 3, 2009 at 13:01, Michael Snyder<msnyder@vmware.com> wrote:
> Oops, now this patch has parts of your newer patch from
> the other thread mixed in.
>
> I'm sorry, we've got multiple patches going back and forth.
> Partly my fault, I've sent you a couple and I'm sure its
> confusing.
>
> Let's try to keep them separate, OK?
>
> If you like the last patch that I sent you on this thread,
> just say OK and I'll check it in. Then we can discuss
> 'record_exec_entry' etc. on the other thread.
>
> Michael
>
> Hui Zhu wrote:
>>
>> On Sun, Aug 2, 2009 at 12:10, Hui Zhu<teawater@gmail.com> wrote:
>>>
>>> I think this patch is very good.
>>>
>>> I a new changelog for it:
>>> 2009-08-02 Michael Snyder <msnyder@vmware.com>
>>> Hui Zhu <teawater@gmail.com>
>>>
>>> * record.c (record_mem_entry): New field
>>> 'mem_entry_not_accessible'.
>>> (record_arch_list_add_mem): Initialize
>>> 'mem_entry_not_accessible' to 0.
>>> (record_wait): Set 'mem_entry_not_accessible' flag if target
>>> memory not readable. Don't try to change target memory if
>>> 'mem_entry_not_accessible' is set.
>>>
>>> Do you think it's ok?
>>>
>>> Thanks,
>>> Hui
>>>
>>> On Sun, Aug 2, 2009 at 07:00, Michael Snyder<msnyder@vmware.com> wrote:
>>>>
>>>> Hui Zhu wrote:
>>>>>
>>>>> On Sun, Jul 26, 2009 at 04:41, Michael Snyder<msnyder@vmware.com>
>>>>> wrote:
>>>>>>
>>>>>> Hui Zhu wrote:
>>>>>>>
>>>>>>> On Fri, Jul 24, 2009 at 10:10, Michael Snyder<msnyder@vmware.com>
>>>>>>> wrote:
>>>>>>>>
>>>>>>>> 1) During the recording "pass", there's no change.
>>>>>>>> 2) During the reverse-replay pass, if the memory is
>>>>>>>> not readable or writable, we will set this flag to TRUE.
>>>>>>>> 3) Finally, during the forward-replay pass, if the flag
>>>>>>>> has previously been set to TRUE, we will skip this entry
>>>>>>>> (and set the flag to FALSE.)
>>>>>>>>
>>>>>>>> So my question is -- is there any reason to set it to FALSE here?
>>>>>>>> Is there any way that the memory can ever become readable again?
>>>>>>>>
>>>>>>>> Seems to me, once it is set TRUE, we might as well just leave it
>>>>>>>> TRUE.
>>>>>>>> Am I right?
>>>>>>>
>>>>>>> I thought about it too. I think if we don't need this entry. We can
>>>>>>> delete it directly.
>>>>>>> But there is a special status, after release memory, inferior alloc
>>>>>>> some memory and its address is same with the memory that released
>>>>>>> memory. Then the memory entry will can be use in this status. User
>>>>>>> can get the right value of memory before this entry. So I think
>>>>>>> maybe
>>>>>>> we can keep it.
>>>>>>>
>>>>>>> What do you think about it?
>>>>>>
>>>>>> Let's say a program does something like this:
>>>>>>
>>>>>> buf = mmap (...);
>>>>>> munmap (...);
>>>>>> buf = mmap (...);
>>>>>> munmap (...);
>>>>>> buf = mmap (...);
>>>>>>
>>>>>> and so on. And suppose that, for whatever reason, mmap always
>>>>>> returns the same address.
>>>>>>
>>>>>> Then it seems to me (and please correct me if I am wrong), that
>>>>>> it all depends on where we stop the recording.
>>>>>>
>>>>>> If we stop the recording after mmap, but before munmap, then
>>>>>> the memory will be readable throughout the ENTIRE recording.
>>>>>>
>>>>>> But if we stop the recording after munmap, but before mmap, then
>>>>>> the memory will NOT be readable (again for the entire recording).
>>>>>>
>>>>>> So as you replay backward and forward through the recording, the
>>>>>> readability state of the memory location will never change -- it
>>>>>> will remain either readable, or unreadable, depending only on
>>>>>> the mapped-state when the recording ended.
>>>>>>
>>>>>> The only way for it to change, I think, would be if we could
>>>>>> resume the process and add some more execution to the end of
>>>>>> the existing recording.
>>>>>>
>>>>> Agree with you. We can do more thing around release memory.
>>>>>
>>>>> But this patch make prec work OK even if inferior release some memory.
>>>>> Of course, the released memory we still can not access. But other
>>>>> memory is OK.
>>>>>
>>>>> This is a low cost idea for release memory. And we still can add
>>>>> other thing about release memory.
>>>>
>>>> Yes, I like the patch, and I want to see it go in, but
>>>> you haven't really answered my question:
>>>>
>>>> Once we have set this flag to TRUE in a recording entry,
>>>> why would we ever need to set it to FALSE?
>>>>
>>>> The patch is simpler and easier to understand if we simply
>>>> leave the flag TRUE. It worries me to see it toggling back
>>>> and forth between TRUE and FALSE every time we play through
>>>> the recording, if there is no benefit to doing that. Plus
>>>> it means that we keep trying to read the target memory even
>>>> though we know it will fail.
>>>>
>>>> I'm attaching a diff to show what I mean, in case it isn't clear.
>>>> This diff gives me the same behavior with your munmap test case
>>>> as your diff does.
>>>>
>>>>
>>>>
>>>>
>>>> Index: record.c
>>>> ===================================================================
>>>> RCS file: /cvs/src/src/gdb/record.c,v
>>>> retrieving revision 1.9
>>>> diff -u -p -r1.9 record.c
>>>> --- record.c 22 Jul 2009 05:31:26 -0000 1.9
>>>> +++ record.c 1 Aug 2009 22:59:55 -0000
>>>> @@ -51,6 +51,7 @@ struct record_mem_entry
>>>> {
>>>> CORE_ADDR addr;
>>>> int len;
>>>> + int mem_entry_not_accessible;
>>>> gdb_byte *val;
>>>> };
>>>>
>>>> @@ -275,6 +276,7 @@ record_arch_list_add_mem (CORE_ADDR addr
>>>> rec->type = record_mem;
>>>> rec->u.mem.addr = addr;
>>>> rec->u.mem.len = len;
>>>> + rec->u.mem.mem_entry_not_accessible = 0;
>>>>
>>>> if (target_read_memory (addr, rec->u.mem.val, len))
>>>> {
>>>> @@ -727,32 +729,52 @@ record_wait (struct target_ops *ops,
>>>> else if (record_list->type == record_mem)
>>>> {
>>>> /* mem */
>>>> - gdb_byte *mem = alloca (record_list->u.mem.len);
>>>> - if (record_debug > 1)
>>>> - fprintf_unfiltered (gdb_stdlog,
>>>> - "Process record: record_mem %s to "
>>>> - "inferior addr = %s len = %d.\n",
>>>> - host_address_to_string
>>>> (record_list),
>>>> - paddress (gdbarch,
>>>> record_list->u.mem.addr),
>>>> - record_list->u.mem.len);
>>>> -
>>>> - if (target_read_memory
>>>> - (record_list->u.mem.addr, mem,
>>>> record_list->u.mem.len))
>>>> - error (_("Process record: error reading memory at "
>>>> - "addr = %s len = %d."),
>>>> - paddress (gdbarch, record_list->u.mem.addr),
>>>> - record_list->u.mem.len);
>>>> -
>>>> - if (target_write_memory
>>>> - (record_list->u.mem.addr, record_list->u.mem.val,
>>>> - record_list->u.mem.len))
>>>> - error (_
>>>> - ("Process record: error writing memory at "
>>>> - "addr = %s len = %d."),
>>>> - paddress (gdbarch, record_list->u.mem.addr),
>>>> - record_list->u.mem.len);
>>>> -
>>>> - memcpy (record_list->u.mem.val, mem,
>>>> record_list->u.mem.len);
>>>> + if (record_list->u.mem.mem_entry_not_accessible == 0)
>>>> + {
>>>> + gdb_byte *mem = alloca (record_list->u.mem.len);
>>>> + if (record_debug > 1)
>>>> + fprintf_unfiltered (gdb_stdlog,
>>>> + "Process record: record_mem %s
>>>> to "
>>>> + "inferior addr = %s len =
>>>> %d.\n",
>>>> + host_address_to_string
>>>> (record_list),
>>>> + paddress (gdbarch,
>>>> +
>>>> record_list->u.mem.addr),
>>>> + record_list->u.mem.len);
>>>> +
>>>> + if (target_read_memory (record_list->u.mem.addr, mem,
>>>> + record_list->u.mem.len))
>>>> + {
>>>> + if (execution_direction != EXEC_REVERSE)
>>>> + error (_("Process record: error reading memory
>>>> at "
>>>> + "addr = %s len = %d."),
>>>> + paddress (gdbarch,
>>>> record_list->u.mem.addr),
>>>> + record_list->u.mem.len);
>>>> + else
>>>> + record_list->u.mem.mem_entry_not_accessible = 1;
>>>> + }
>>>> + else
>>>> + {
>>>> + if (target_write_memory (record_list->u.mem.addr,
>>>> + record_list->u.mem.val,
>>>> + record_list->u.mem.len))
>>>> + {
>>>> + if (execution_direction != EXEC_REVERSE)
>>>> + error (_("Process record: error writing
>>>> memory
>>>> at "
>>>> + "addr = %s len = %d."),
>>>> + paddress (gdbarch,
>>>> record_list->u.mem.addr),
>>>> + record_list->u.mem.len);
>>>> + else
>>>> + {
>>>> +
>>>> record_list->u.mem.mem_entry_not_accessible =
>>>> 1;
>>>> + }
>>>> + }
>>>> + else
>>>> + {
>>>> + memcpy (record_list->u.mem.val, mem,
>>>> + record_list->u.mem.len);
>>>> + }
>>>> + }
>>>> + }
>>>> }
>>>> else
>>>> {
>>>>
>>>>
>>
>> Hi Michael,
>>
>> I make a new patch for this function.
>> Please help me review it.
>>
>> Thanks,
>> Hui
>>
>>
>> 2009-08-03 Michael Snyder <msnyder@vmware.com>
>> Hui Zhu <teawater@gmail.com>
>>
>> * record.c (record_mem_entry): New field
>> 'mem_entry_not_accessible'.
>> (record_arch_list_add_mem): Initialize
>> 'mem_entry_not_accessible' to 0.
>> (record_exec_entry): New function.
>> (record_wait): Call 'record_exec_entry'.
>>
>> ---
>> record.c | 133
>> +++++++++++++++++++++++++++++++++++++++++----------------------
>> 1 file changed, 87 insertions(+), 46 deletions(-)
>>
>> --- a/record.c
>> +++ b/record.c
>> @@ -51,6 +51,7 @@ struct record_mem_entry
>> {
>> CORE_ADDR addr;
>> int len;
>> + int mem_entry_not_accessible;
>> gdb_byte *val;
>> };
>>
>> @@ -275,6 +276,7 @@ record_arch_list_add_mem (CORE_ADDR addr
>> rec->type = record_mem;
>> rec->u.mem.addr = addr;
>> rec->u.mem.len = len;
>> + rec->u.mem.mem_entry_not_accessible = 0;
>>
>> if (target_read_memory (addr, rec->u.mem.val, len))
>> {
>> @@ -412,6 +414,89 @@ record_gdb_operation_disable_set (void)
>> return old_cleanups;
>> }
>>
>> +static inline void
>> +record_exec_entry (struct regcache *regcache, struct gdbarch *gdbarch,
>> + struct record_entry *entry)
>> +{
>> + switch (entry->type)
>> + {
>> + case record_reg: /* reg */
>> + {
>> + gdb_byte reg[MAX_REGISTER_SIZE];
>> +
>> + if (record_debug > 1)
>> + fprintf_unfiltered (gdb_stdlog,
>> + "Process record: record_reg %s to "
>> + "inferior num = %d.\n",
>> + host_address_to_string (entry),
>> + entry->u.reg.num);
>> +
>> + regcache_cooked_read (regcache, entry->u.reg.num, reg);
>> + regcache_cooked_write (regcache, entry->u.reg.num,
>> entry->u.reg.val);
>> + memcpy (entry->u.reg.val, reg, MAX_REGISTER_SIZE);
>> + }
>> + break;
>> +
>> + case record_mem: /* mem */
>> + {
>> + if (!record_list->u.mem.mem_entry_not_accessible)
>> + {
>> + gdb_byte *mem = alloca (entry->u.mem.len);
>> +
>> + if (record_debug > 1)
>> + fprintf_unfiltered (gdb_stdlog,
>> + "Process record: record_mem %s to "
>> + "inferior addr = %s len = %d.\n",
>> + host_address_to_string (entry),
>> + paddress (gdbarch, entry->u.mem.addr),
>> + record_list->u.mem.len);
>> +
>> + if (target_read_memory (entry->u.mem.addr, mem,
>> entry->u.mem.len))
>> + {
>> + if (execution_direction == EXEC_REVERSE)
>> + {
>> + record_list->u.mem.mem_entry_not_accessible = 1;
>> + if (record_debug)
>> + warning (_("Process record: error reading memory at
>> "
>> + "addr = %s len = %d."),
>> + paddress (gdbarch, entry->u.mem.addr),
>> + entry->u.mem.len);
>> + }
>> + else
>> + error (_("Process record: error reading memory at "
>> + "addr = %s len = %d."),
>> + paddress (gdbarch, entry->u.mem.addr),
>> + entry->u.mem.len);
>> + }
>> + else
>> + {
>> + if (target_write_memory (entry->u.mem.addr,
>> entry->u.mem.val,
>> + entry->u.mem.len))
>> + {
>> + if (execution_direction == EXEC_REVERSE)
>> + {
>> + record_list->u.mem.mem_entry_not_accessible = 1;
>> + if (record_debug)
>> + warning (_("Process record: error writing
>> memory at "
>> + "addr = %s len = %d."),
>> + paddress (gdbarch, entry->u.mem.addr),
>> + entry->u.mem.len);
>> + }
>> + else
>> + error (_("Process record: error writing memory at "
>> + "addr = %s len = %d."),
>> + paddress (gdbarch, entry->u.mem.addr),
>> + entry->u.mem.len);
>> + }
>> + }
>> +
>> + memcpy (entry->u.mem.val, mem, entry->u.mem.len);
>> + }
>> + }
>> + break;
>> + }
>> +}
>> +
>> static void
>> record_open (char *name, int from_tty)
>> {
>> @@ -708,53 +793,9 @@ record_wait (struct target_ops *ops,
>> break;
>> }
>>
>> - /* Set ptid, register and memory according to record_list. */
>> - if (record_list->type == record_reg)
>> - {
>> - /* reg */
>> - gdb_byte reg[MAX_REGISTER_SIZE];
>> - if (record_debug > 1)
>> - fprintf_unfiltered (gdb_stdlog,
>> - "Process record: record_reg %s to "
>> - "inferior num = %d.\n",
>> - host_address_to_string (record_list),
>> - record_list->u.reg.num);
>> - regcache_cooked_read (regcache, record_list->u.reg.num,
>> reg);
>> - regcache_cooked_write (regcache, record_list->u.reg.num,
>> - record_list->u.reg.val);
>> - memcpy (record_list->u.reg.val, reg, MAX_REGISTER_SIZE);
>> - }
>> - else if (record_list->type == record_mem)
>> - {
>> - /* mem */
>> - gdb_byte *mem = alloca (record_list->u.mem.len);
>> - if (record_debug > 1)
>> - fprintf_unfiltered (gdb_stdlog,
>> - "Process record: record_mem %s to "
>> - "inferior addr = %s len = %d.\n",
>> - host_address_to_string (record_list),
>> - paddress (gdbarch,
>> record_list->u.mem.addr),
>> - record_list->u.mem.len);
>> -
>> - if (target_read_memory
>> - (record_list->u.mem.addr, mem, record_list->u.mem.len))
>> - error (_("Process record: error reading memory at "
>> - "addr = %s len = %d."),
>> - paddress (gdbarch, record_list->u.mem.addr),
>> - record_list->u.mem.len);
>> -
>> - if (target_write_memory
>> - (record_list->u.mem.addr, record_list->u.mem.val,
>> - record_list->u.mem.len))
>> - error (_
>> - ("Process record: error writing memory at "
>> - "addr = %s len = %d."),
>> - paddress (gdbarch, record_list->u.mem.addr),
>> - record_list->u.mem.len);
>> + record_exec_entry (regcache, gdbarch, record_list);
>>
>> - memcpy (record_list->u.mem.val, mem,
>> record_list->u.mem.len);
>> - }
>> - else
>> + if (record_list->type == record_end)
>> {
>> if (record_debug > 1)
>> fprintf_unfiltered (gdb_stdlog,
>>
>>
>> ------------------------------------------------------------------------
>>
>> ---
>> record.c | 133
>> +++++++++++++++++++++++++++++++++++++++++----------------------
>> 1 file changed, 87 insertions(+), 46 deletions(-)
>>
>> --- a/record.c
>> +++ b/record.c
>> @@ -51,6 +51,7 @@ struct record_mem_entry
>> {
>> CORE_ADDR addr;
>> int len;
>> + int mem_entry_not_accessible;
>> gdb_byte *val;
>> };
>> @@ -275,6 +276,7 @@ record_arch_list_add_mem (CORE_ADDR addr
>> rec->type = record_mem;
>> rec->u.mem.addr = addr;
>> rec->u.mem.len = len;
>> + rec->u.mem.mem_entry_not_accessible = 0;
>> if (target_read_memory (addr, rec->u.mem.val, len))
>> {
>> @@ -412,6 +414,89 @@ record_gdb_operation_disable_set (void)
>> return old_cleanups;
>> }
>> +static inline void
>> +record_exec_entry (struct regcache *regcache, struct gdbarch *gdbarch,
>> + struct record_entry *entry)
>> +{
>> + switch (entry->type)
>> + {
>> + case record_reg: /* reg */
>> + {
>> + gdb_byte reg[MAX_REGISTER_SIZE];
>> +
>> + if (record_debug > 1)
>> + fprintf_unfiltered (gdb_stdlog,
>> + "Process record: record_reg %s to "
>> + "inferior num = %d.\n",
>> + host_address_to_string (entry),
>> + entry->u.reg.num);
>> +
>> + regcache_cooked_read (regcache, entry->u.reg.num, reg);
>> + regcache_cooked_write (regcache, entry->u.reg.num,
>> entry->u.reg.val);
>> + memcpy (entry->u.reg.val, reg, MAX_REGISTER_SIZE);
>> + }
>> + break;
>> +
>> + case record_mem: /* mem */
>> + {
>> + if (!record_list->u.mem.mem_entry_not_accessible)
>> + {
>> + gdb_byte *mem = alloca (entry->u.mem.len);
>> +
>> + if (record_debug > 1)
>> + fprintf_unfiltered (gdb_stdlog,
>> + "Process record: record_mem %s to "
>> + "inferior addr = %s len = %d.\n",
>> + host_address_to_string (entry),
>> + paddress (gdbarch, entry->u.mem.addr),
>> + record_list->u.mem.len);
>> +
>> + if (target_read_memory (entry->u.mem.addr, mem,
>> entry->u.mem.len))
>> + {
>> + if (execution_direction == EXEC_REVERSE)
>> + {
>> + record_list->u.mem.mem_entry_not_accessible = 1;
>> + if (record_debug)
>> + warning (_("Process record: error reading memory at
>> "
>> + "addr = %s len = %d."),
>> + paddress (gdbarch, entry->u.mem.addr),
>> + entry->u.mem.len);
>> + }
>> + else
>> + error (_("Process record: error reading memory at "
>> + "addr = %s len = %d."),
>> + paddress (gdbarch, entry->u.mem.addr),
>> + entry->u.mem.len);
>> + }
>> + else
>> + {
>> + if (target_write_memory (entry->u.mem.addr,
>> entry->u.mem.val,
>> + entry->u.mem.len))
>> + {
>> + if (execution_direction == EXEC_REVERSE)
>> + {
>> + record_list->u.mem.mem_entry_not_accessible = 1;
>> + if (record_debug)
>> + warning (_("Process record: error writing
>> memory at "
>> + "addr = %s len = %d."),
>> + paddress (gdbarch, entry->u.mem.addr),
>> + entry->u.mem.len);
>> + }
>> + else
>> + error (_("Process record: error writing memory at "
>> + "addr = %s len = %d."),
>> + paddress (gdbarch, entry->u.mem.addr),
>> + entry->u.mem.len);
>> + }
>> + }
>> +
>> + memcpy (entry->u.mem.val, mem, entry->u.mem.len);
>> + }
>> + }
>> + break;
>> + }
>> +}
>> +
>> static void
>> record_open (char *name, int from_tty)
>> {
>> @@ -708,53 +793,9 @@ record_wait (struct target_ops *ops,
>> break;
>> }
>> - /* Set ptid, register and memory according to record_list. */
>> - if (record_list->type == record_reg)
>> - {
>> - /* reg */
>> - gdb_byte reg[MAX_REGISTER_SIZE];
>> - if (record_debug > 1)
>> - fprintf_unfiltered (gdb_stdlog,
>> - "Process record: record_reg %s to "
>> - "inferior num = %d.\n",
>> - host_address_to_string (record_list),
>> - record_list->u.reg.num);
>> - regcache_cooked_read (regcache, record_list->u.reg.num,
>> reg);
>> - regcache_cooked_write (regcache, record_list->u.reg.num,
>> - record_list->u.reg.val);
>> - memcpy (record_list->u.reg.val, reg, MAX_REGISTER_SIZE);
>> - }
>> - else if (record_list->type == record_mem)
>> - {
>> - /* mem */
>> - gdb_byte *mem = alloca (record_list->u.mem.len);
>> - if (record_debug > 1)
>> - fprintf_unfiltered (gdb_stdlog,
>> - "Process record: record_mem %s to "
>> - "inferior addr = %s len = %d.\n",
>> - host_address_to_string (record_list),
>> - paddress (gdbarch,
>> record_list->u.mem.addr),
>> - record_list->u.mem.len);
>> -
>> - if (target_read_memory
>> - (record_list->u.mem.addr, mem, record_list->u.mem.len))
>> - error (_("Process record: error reading memory at "
>> - "addr = %s len = %d."),
>> - paddress (gdbarch, record_list->u.mem.addr),
>> - record_list->u.mem.len);
>> -
>> - if (target_write_memory
>> - (record_list->u.mem.addr, record_list->u.mem.val,
>> - record_list->u.mem.len))
>> - error (_
>> - ("Process record: error writing memory at "
>> - "addr = %s len = %d."),
>> - paddress (gdbarch, record_list->u.mem.addr),
>> - record_list->u.mem.len);
>> + record_exec_entry (regcache, gdbarch, record_list);
>> - memcpy (record_list->u.mem.val, mem,
>> record_list->u.mem.len);
>> - }
>> - else
>> + if (record_list->type == record_end)
>> {
>> if (record_debug > 1)
>> fprintf_unfiltered (gdb_stdlog,
>
>
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