[dpdk-dev] Questions about mmap in Asan APP

[Min Hu (Connor)]

Hi, Jonas Pfefferle and all,
	I met one questions:
	When I ran APP on Kasan OS, secondary process occasionally init
failed.

BTW:
testpmd is built with Asan, that is to add "CFLAGS="-fsanitize=address 
-fno-omit-frame-pointer -pthread"".
Kasan OS is what opens this:
CONFIG_SLUB_DEBUG=y
CONFIG_KASAN=y

The PRIMARY process APP(testpmd) log:
estuary:/home$ ./testpmd_kasan_debug    -w 0000:00:01.0 
--file-prefix=test --proc-type=auto -l 0-1 -n 2 -- -i --rxq=4 --txq=4
EAL: Detected 16 lcore(s)
EAL: Detected 1 NUMA nodes
Option -w, --pci-whitelist is deprecated, use -a, --allow option instead
EAL: Auto-detected process type: PRIMARY
EAL: Detected static linkage of DPDK
EAL: Multi-process socket /var/run/dpdk/test/mp_socket
EAL: Selected IOVA mode 'PA'
EAL: No available 32768 kB hugepages reported
EAL: No available 64 kB hugepages reported
EAL: No available 1048576 kB hugepages reported
EAL: VFIO support initialized

EAL: WARNING! Base virtual address hint (0xd01061000 != 0xfffb89e00000) 
not respected!
EAL:    This may cause issues with mapping memory into secondary processes

EAL:   Invalid NUMA socket, default to 0
EAL: Using IOMMU type 8 (No-IOMMU)
EAL: Probe PCI driver: net_hns3_vf (19e5:a22e) device: 0000:00:01.0 
(socket 0)
TELEMETRY: No legacy callbacks, legacy socket not created
Interactive-mode selected
testpmd: create a new mbuf pool <mb_pool_0>: n=155456, size=2176, socket=0
testpmd: preferred mempool ops selected: ring_mp_mc

Warning! port-topology=paired and odd forward ports number, the last 
port will pair with itself.

Configuring Port 0 (socket 0)
0000:00:01.0 hns3_parse_rss_key(): Default RSS hash key to be set

Port 0: link state change event
Port 0: 72:DE:F7:1B:F6:52
Checking link statuses...

"EAL: WARNING! Base virtual address hint (0xd01061000 != 0xfffb89e00000) 
not respected!  EAL:    This may cause issues with mapping memory into
secondary processes" should be noticed.



The SECONDARY APP(proc-info) log is:
estuary:/home$ ./proc-info -w 0000:00:01.0 --file-prefix=test 
--proc-type=auto -- --xstats-name rx_q0_packets
Option -w, --pci-whitelist is deprecated, use -a, --allow option instead
EAL: Cannot get a virtual area at requested address: 0xfffba6000000 (got 
0xfffb8ae3b000)

EAL: Cannot reserve 17179869184 bytes at [0xfffba6000000] - please use 
'--base-virtaddr' option

EAL: Cannot preallocate VA space for hugepage memory
EAL: FATAL: Cannot init memory
EAL: Cannot init memory
PANIC in main():
Cannot init EAL
4: [/lib/aarch64-linux-gnu/libc.so.6(__libc_start_main+0xe0) 
[0xffff8be5a8a0]]
3: [./proc-info(main+0x1098) [0x52a3a8]]
2: [./proc-info(__rte_panic+0x9c) [0x48cfac]]
1: [./proc-info(rte_dump_stack+0x20) [0x80d4b0]]
Aborted

"EAL: Cannot get a virtual area at requested address: 0xfffba6000000 
(got 0xfffb8ae3b000)" should be noticed.

According to my analysis, the reason is that the system call "mmap"
return the address which is different with the hint address(first
parameter). That is to say：
return_addr = mmap(void* start,size_t length,int prot,int flags,int
fd,off_t offset);
return_addr and start is different.

Why this happened? I guess Asan works based on shadow memory, shadow
memory will occupy the memory zone and it cannot be one for mmap.
So, it the shadow memory happens to be in the range of mmap region,
mmap will return a new address which is free(not occupied by shadow).

BTW，I think DPDK multiple process is not supported in that situation,
such as "Asan APP on Kasan OS".

What is your opinion? any will weclome, thanks.

	Best regards.