Re: [dpdk-dev] [PATCH v2] eal: use madvise to exclude unmapped memory from being dumped

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 24-Apr-20 11:50 AM, Li Feng wrote:
> Currently, even though memory is mapped with PROT_NONE, this does not
> cause it to be excluded from core dumps. This is counter-productive,
> because in a lot of cases, this memory will go unused (e.g. when the
> memory subsystem preallocates VA space but hasn't yet mapped physical
> pages into it).
> 
> Use `madvise()` call with MADV_DONTDUMP parameter to exclude the
> unmapped memory from being dumped.
> 
> Signed-off-by: Li Feng <fengli@smartx.com>
> ---
> V2:
> - add support for freebsd.
> - when free_seg is called, mark the memory MADV_DONTDUMP.
> - when alloc_seg is called, mark the memory MADV_DODUMP.

Isn't this v3 now?

> 
>   lib/librte_eal/common/eal_common_memory.c | 26 ++++++++++++++++++++++++++
>   lib/librte_eal/linux/eal_memalloc.c       |  6 ++++++
>   2 files changed, 32 insertions(+)
> 
> diff --git a/lib/librte_eal/common/eal_common_memory.c b/lib/librte_eal/common/eal_common_memory.c
> index cc7d54e0c..83be94a20 100644
> --- a/lib/librte_eal/common/eal_common_memory.c
> +++ b/lib/librte_eal/common/eal_common_memory.c
> @@ -177,6 +177,32 @@ eal_get_virtual_area(void *requested_addr, size_t *size,
>   		after_len = RTE_PTR_DIFF(map_end, aligned_end);
>   		if (after_len > 0)
>   			munmap(aligned_end, after_len);
> +
> +		/*
> +		 * Exclude this pages from a core dump.
> +		 */
> +#ifdef RTE_EXEC_ENV_LINUX
> +		if (madvise(aligned_addr, *size, MADV_DONTDUMP) != 0)
> +			RTE_LOG(DEBUG, EAL, "madvise failed: %s\n",
> +				strerror(errno));
> +#elif RTE_EXEC_ENV_FREEBSD
> +		if (madvise(aligned_addr, *size, MADV_NOCORE) != 0)
> +			RTE_LOG(DEBUG, EAL, "madvise failed: %s\n",
> +				strerror(errno));
> +#endif
> +	} else {
> +		/*
> +		 * Exclude this pages from a core dump.
> +		 */
> +#ifdef RTE_EXEC_ENV_LINUX
> +		if (madvise(mapped_addr, map_sz, MADV_DONTDUMP) != 0)
> +			RTE_LOG(DEBUG, EAL, "madvise failed: %s\n",
> +				strerror(errno));
> +#elif RTE_EXEC_ENV_FREEBSD
> +		if (madvise(mapped_addr, map_sz, MADV_NOCORE) != 0)
> +			RTE_LOG(DEBUG, EAL, "madvise failed: %s\n",
> +				strerror(errno));
> +#endif
>   	}

DRY (Don't Repeat Yourself) :) Probably easier to do "if (!unmap) ..." 
than putting this into two places.

>   
>   	return aligned_addr;
> diff --git a/lib/librte_eal/linux/eal_memalloc.c b/lib/librte_eal/linux/eal_memalloc.c
> index af6d0d023..9d2a6fc6f 100644
> --- a/lib/librte_eal/linux/eal_memalloc.c
> +++ b/lib/librte_eal/linux/eal_memalloc.c
> @@ -571,6 +571,9 @@ alloc_seg(struct rte_memseg *ms, void *addr, int socket_id,
>   		goto resized;
>   	}
>   
> +	if (madvise(addr, alloc_sz, MADV_DODUMP) != 0)
> +		RTE_LOG(DEBUG, EAL, "madvise failed: %s\n", strerror(errno));
> +

See discussion for v2, i believe this is unnecessary.

>   	/* In linux, hugetlb limitations, like cgroup, are
>   	 * enforced at fault time instead of mmap(), even
>   	 * with the option of MAP_POPULATE. Kernel will send
> @@ -687,6 +690,9 @@ free_seg(struct rte_memseg *ms, struct hugepage_info *hi,
>   		return -1;
>   	}
>   
> +	if (madvise(ms->addr, ms->len, MADV_DONTDUMP) != 0)
> +		RTE_LOG(DEBUG, EAL, "madvise failed: %s\n", strerror(errno));
> +
>   	exit_early = false;
>   
>   	/* if we're using anonymous hugepages, nothing to be done */
> 


-- 
Thanks,
Anatoly