Re: [dpdk-dev] [RFC] mem_debug add more log

[Stephen Hemminger <stephen@networkplumber.org>]

On Fri, 18 Dec 2020 14:21:09 -0500
Peng Zhihong <zhihongx.peng@intel.com> wrote:

> 1. The debugging log in current DPDK RTE_MALLOC_DEBUG mode is insufficient,
>    which makes it difficult to locate the issues, such as:
>    a) When a memeory overlflow occur in rte_free, there is a little log
>       information. Even if abort here, we can find which API is core
>       dumped but we still need to read the source code to find out where
>       the requested memory is overflowed.
>    b) Current DPDK can NOT find that the overflow if the memory has been
>       used and not released.
>    c) If there are two pieces of continuous memory, when the first block
>       is not released and an overflow is occured and also the second block
>       of memory is covered, a memory overflow will be detected once the second
>       block of memory is released. However, current DPDK can not find the
>       correct point of memory overflow. It only detect the memory overflow
>       of the second block but should dedect the one of first block.
>       ----------------------------------------------------------------------------------
>       | header cookie | data1 | trailer cookie | header cookie | data2 |trailer cookie |
>       ----------------------------------------------------------------------------------
> 2. To fix above issues, we can store the requested information When DPDK
>    request memory. Including the requested address and requested momory's
>    file, function and numbers of rows and then put it into a list.
>    --------------------     ----------------------     ----------------------
>    | struct list_head |---->| struct malloc_info |---->| struct malloc_info |
>    --------------------     ----------------------     ----------------------
>    The above 3 problems can be solved through this implementation:
>    a) If there is a memory overflow in rte_free, you can traverse the
>       list to find the information of overflow memory and print the
>       overflow memory information. like this:
>       code:
>       37         char *p = rte_zmalloc(NULL, 64, 0);
>       38         memset(p, 0, 65);
>       39         rte_free(p);
>       40         //rte_malloc_validate_all_memory();
>       memory error:
>       EAL: Error: Invalid memory
>       malloc memory address 0x17ff2c340 overflow in \
>       file:../examples/helloworld/main.c function:main line:37
>    b)c) Provide a interface to check all memory overflow in function
>       rte_malloc_validate_all_memory, this function will check all
>       memory on the list. Call this funcation manually at the exit
>       point of business logic, we can find all overflow points in time.
> 
> Signed-off-by: Peng Zhihong <zhihongx.peng@intel.com>

Good concept, but doesn't this add significant overhead?

Maybe we could make rte_malloc work with existing address sanitizer infrastructure
in gcc/clang?  That would provide faster and more immediate better diagnostic
info.