Re: [Libunwind-devel] unw_step() fails at aarch64

[Bingzheng Wu]

Thanks for your reply.

It works with -funwind-tables indeed!

I also try this in pi64[https://github.com/bamarni/pi64] which is
based on Debian with GCC 6.3.0.
I think this is a new version GCC, but it still need the -funwind-tables flag.

Which OS and GCC version do you use?

Thanks,
Wu

2017-10-04 0:09 GMT+08:00 Dave Watson <address@hidden>:
> On 09/29/17 09:48 PM, Bingzheng Wu wrote:
>> Hi all
>>
>> I use libunwind at aarch64, but unw_step() fails.
>>
>> Machine: Raspberry Pi 3B
>> OS: SUSE Linux Enterprise Server
>> [https://urldefense.proofpoint.com/v2/url?u=https-3A__www.suse.com_products_arm_raspberry-2Dpi_&d=DwICAg&c=5VD0RTtNlTh3ycd41b3MUw&r=vou6lT5jmE_fWQWZZgNrsMWu4RT87QAB9V07tPHlP5U&m=r0pyTsM85cT0L4vwRpatiU8zRUpyLyIBTJFvuTXPAwI&s=dS3FN1I_eYJcl-YDu1Zx1ID4ftvVuCDiH_o2yD6cIN8&e=
>>  ]
>> Version of libunwind: 1.12.1
>>
>> I just use the sample code in the man page
>> [https://urldefense.proofpoint.com/v2/url?u=http-3A__www.nongnu.org_libunwind_man_libunwind-283-29.html&d=DwICAg&c=5VD0RTtNlTh3ycd41b3MUw&r=vou6lT5jmE_fWQWZZgNrsMWu4RT87QAB9V07tPHlP5U&m=r0pyTsM85cT0L4vwRpatiU8zRUpyLyIBTJFvuTXPAwI&s=Su-y7JDyDrX9j4K8mIRdQ-nPxJKjML7dsTZIeGnyCQA&e=
>>  ] , but it fails
>> with the debug output:
>>
>> ====
>>  >_ULaarch64_init_local: (cursor=0xffffdd72d120)
>>  >_ULaarch64_step: (cursor=0xffffdd72d120, ip=0x0000000000400b8c,
>> cfa=0x0000ffffdd72bf30))
>>                 >access_mem: mem[400b8c] -> 531f7800b9401fa0
>>                 >get_rs_cache: acquiring lock
>>               >_ULaarch64_dwarf_find_proc_info: looking for IP=0x400b8b
>>                >_ULaarch64_dwarf_callback: checking , base=0x0)
>>                >_ULaarch64_dwarf_callback: found table `':
>> segbase=0x400ce4, len=2, gp=0x41ffe8, table_data=0x400cf0
>>                >lookup: e->start_ip_offset = ffffffffffffff7c
>>                >lookup: e->start_ip_offset = ffffffffffffff04
>>  >_ULaarch64_dwarf_search_unwind_table: IP 400b8b inside range
>> 400000-400d6c, but no explicit unwind info found
>>                 >put_rs_cache: unmasking signals/interrupts and releasing 
>> lock
>>                >_ULaarch64_dwarf_step: returning -10
>>  >_ULaarch64_step: dwarf_step()=-10
>> ====
>>
>> It seem that dwarf_search_unwind_table() returns -UNW_ENOINFO(-10).
>>
>> Dose anyone have the same problem?
>> Anyone has idea?
>
> Without more info, it sounds like missing unwind info? Maybe check
> using readelf if you have unwind info for IP 400b8b.
>
> In older gcc versions it was sometimes necessary to pass extra flags,
> like -funwind-tables, -fasynchronous-unwind-tables, or -fexceptions,
> -fnon-call-exceptions, etc to get full unwind info for all IPs