Re: A native armv7 panic during kyua runs: sys/netinet6/exthdr:exthdr -> Fatal kernel mode data abort: 'Alignment Fault' on read

On Aug 5, 2023, at 14:04, Mark Millard <[email protected]> wrote:

> On Aug 5, 2023, at 11:27, Michal Meloun <[email protected]> wrote:
> 
>> Hi Mark,
>> can you please try a this patch?
>> https://github.com/strejda/tegra/commit/bd4390c5f6a8b66b2fc83966d4fadb945a19dc23
> 
> I'll take a stab at testing it.
> 
> But I'll note that description of the patch is somewhat odd:
> 
> QUOTE
> Pack IP structures directly used for access packet data.
> All structures used to access data in byte buffers shall be marked
> as packed. Otherwise, this is undefined behavior - formally on
> every platform.
> END QUOTE
> 
> __packed (and whatever it might be a macro for) is not part of
> any vintage of the C standard, not even as explicitly
> implementation defined nor as explicitly undefined. (C23's
> "attribute specifier sequence" notation use would give an
> implementation defined status as an understand, but not via
> explicit identification of the concept of packed in the standard.)
> As far as the language is concerned, there is no guarantee that
> a code generator will ensure to break things up into aligned
> accesses with assembly of the overall value if the members are
> not aligned in the first place, __packed or not. Nor does the
> language guarantee pack of padding in the layout for __packed.
> 
> Past that, it is toolchain specific if __packed would avoid
> unaligned accesses for simple member access notation bytes
> yet also avoid having pad bytes. We will see for this context.
> (My history suggests a lack of overall uniformity in the
> interpretations given to declaring struct's as packed --or
> analogous wording for other languages that are not explicit
> about it.)
> 
>> I'm sorry, but I don't have the time or energy to fully test it... I only hope the actual patch is much easier than the one listed in PR271759.
> 

[Older history deleted.]

No notable change in behavior, I'm afraid . . .

sys/netinet6/exthdr:exthdr  ->  
Fatal kernel mode data abort: 'Alignment Fault' on read
trapframe: 0xc51fbaa0
FSR=00000001, FAR=daed4476, spsr=60000013
r0 =daf787c0, r1 =c51fbb34, r2 =00000000, r3 =00000000
r4 =00000000, r5 =00000000, r6 =daed4476, r7 =daed4466
r8 =c0965c3c, r9 =00000000, r10=db0e4400, r11=c51fbb60
r12=00000000, ssp=c51fbb30, slr=c0b524c0, pc =c04e8e78

panic: Fatal abort
cpuid = 1
time = 1691270886
KDB: stack backtrace:
db_trace_self() at db_trace_self
         pc = 0xc0661824  lr = 0xc007db80 (db_trace_self_wrapper+0x30)
         sp = 0xc51fb858  fp = 0xc51fb970
db_trace_self_wrapper() at db_trace_self_wrapper+0x30
         pc = 0xc007db80  lr = 0xc031a834 (vpanic+0x140)
         sp = 0xc51fb978  fp = 0xc51fb998
         r4 = 0x00000100  r5 = 0x00000000
         r6 = 0xc07c5a9a  r7 = 0xc0b36e58
vpanic() at vpanic+0x140
         pc = 0xc031a834  lr = 0xc031a6f4 (vpanic)
         sp = 0xc51fb9a0  fp = 0xc51fb9a4
         r4 = 0xc51fbaa0  r5 = 0x00000013
         r6 = 0xdaed4476  r7 = 0x00000001
         r8 = 0x00000001  r9 = 0xdaf787c0
        r10 = 0xdaed4476
vpanic() at vpanic
         pc = 0xc031a6f4  lr = 0xc0686ddc (abort_align)
         sp = 0xc51fb9ac  fp = 0xc51fb9d8
         r4 = 0x00000001  r5 = 0x00000001
         r6 = 0xdaf787c0  r7 = 0xdaed4476
         r8 = 0xc51fb9a4  r9 = 0xc031a6f4
        r10 = 0xc51fb9ac
abort_align() at abort_align
         pc = 0xc0686ddc  lr = 0xc0686e50 (abort_align+0x74)
         sp = 0xc51fb9e0  fp = 0xc51fb9f8
         r4 = 0x00000013 r10 = 0xdaed4476
abort_align() at abort_align+0x74
         pc = 0xc0686e50  lr = 0xc0686aa8 (abort_handler+0x45c)
         sp = 0xc51fba00  fp = 0xc51fba98
         r4 = 0x00000000 r10 = 0xdaed4476
abort_handler() at abort_handler+0x45c
         pc = 0xc0686aa8  lr = 0xc06640d8 (exception_exit)
         sp = 0xc51fbaa0  fp = 0xc51fbb60
         r4 = 0x00000000  r5 = 0x00000000
         r6 = 0xdaed4476  r7 = 0xdaed4466
         r8 = 0xc0965c3c  r9 = 0x00000000
        r10 = 0xdb0e4400
exception_exit() at exception_exit
         pc = 0xc06640d8  lr = 0xc0b524c0 (__pcpu+0x200)
         sp = 0xc51fbb30  fp = 0xc51fbb60
         r0 = 0xdaf787c0  r1 = 0xc51fbb34
         r2 = 0x00000000  r3 = 0x00000000
         r4 = 0x00000000  r5 = 0x00000000
         r6 = 0xdaed4476  r7 = 0xdaed4466
         r8 = 0xc0965c3c  r9 = 0x00000000
        r10 = 0xdb0e4400 r12 = 0x00000000
in6ifa_ifwithaddr() at in6ifa_ifwithaddr+0x30
         pc = 0xc04e8e78  lr = 0xc04fb338 (ip6_input+0xd38)
         sp = 0xc51fbb68  fp = 0xc51fbc28
         r4 = 0xdaed4476  r5 = 0xdaed445e
         r6 = 0x00000000  r7 = 0xdaed4466
ip6_input() at ip6_input+0xd38
         pc = 0xc04fb338  lr = 0xc046d66c (netisr_dispatch_src+0xf8)
         sp = 0xc51fbc30  fp = 0xc51fbc58
         r4 = 0xdaed4400  r5 = 0x00000006
         r6 = 0x00000001  r7 = 0xc0b4dd50
         r8 = 0xdaf9d900  r9 = 0xdaed4400
        r10 = 0x00000086
netisr_dispatch_src() at netisr_dispatch_src+0xf8
         pc = 0xc046d66c  lr = 0xc04641b0 (ether_demux+0x18c)
         sp = 0xc51fbc60  fp = 0xc51fbc78
         r4 = 0x00000006  r5 = 0x00001201
         r6 = 0xdb0e4400  r7 = 0x000000ff
         r8 = 0xdaf9d900  r9 = 0xdaed4400
        r10 = 0x00000086
ether_demux() at ether_demux+0x18c
         pc = 0xc04641b0  lr = 0xc0465880 (ether_nh_input+0x490)
         sp = 0xc51fbc80  fp = 0xc51fbce0
         r4 = 0xdb0e4400  r5 = 0xdaed4400
         r6 = 0xdaed4450 r10 = 0x00000086
ether_nh_input() at ether_nh_input+0x490
         pc = 0xc0465880  lr = 0xc046d66c (netisr_dispatch_src+0xf8)
         sp = 0xc51fbce8  fp = 0xc51fbd10
         r4 = 0xdaed4400  r5 = 0x00000005
         r6 = 0x00000003  r7 = 0xc0b4dd30
         r8 = 0xdaf9d900  r9 = 0xdaed4400
        r10 = 0xc098f58f
netisr_dispatch_src() at netisr_dispatch_src+0xf8
         pc = 0xc046d66c  lr = 0xc04645c4 (ether_input+0x50)
         sp = 0xc51fbd18  fp = 0xc51fbd48
         r4 = 0xdaed4400  r5 = 0x00000000
         r6 = 0x00008803  r7 = 0x00000000
         r8 = 0xdaf9d900  r9 = 0xdaed4400
        r10 = 0xc098f58f
ether_input() at ether_input+0x50
         pc = 0xc04645c4  lr = 0xdffb3f08 ($a.10+0x108)
         sp = 0xc51fbd50  fp = 0xc51fbd78
         r4 = 0xdb0e4400  r5 = 0xdaff4000
         r6 = 0xdaff4010  r7 = 0x00000000
         r8 = 0x00000000 r10 = 0xc098f58f
$a.10() at $a.10+0x108
         pc = 0xdffb3f08  lr = 0xc038cb2c (taskqueue_run_locked+0x1c4)
         sp = 0xc51fbd80  fp = 0xc51fbdd8
         r4 = 0xdaff2100  r5 = 0xdaff402c
         r6 = 0xdaff2150  r7 = 0x00000001
         r8 = 0x00000000  r9 = 0xc51fbd90
        r10 = 0x00000001
taskqueue_run_locked() at taskqueue_run_locked+0x1c4
         pc = 0xc038cb2c  lr = 0xc038e4e4 (taskqueue_thread_loop+0x1b0)
         sp = 0xc51fbde0  fp = 0xc51fbe10
         r4 = 0xdaff2100  r5 = 0xdaff2140
         r6 = 0xc07b18c4  r7 = 0x00000000
         r8 = 0xc098f58f  r9 = 0x00000100
        r10 = 0xc0b268a0
taskqueue_thread_loop() at taskqueue_thread_loop+0x1b0
         pc = 0xc038e4e4  lr = 0xc02cdf0c (fork_exit+0xc0)
         sp = 0xc51fbe18  fp = 0xc51fbe38
         r4 = 0xdaf787c0  r5 = 0xc0b264e0
         r6 = 0xc038e334  r7 = 0xdffc4f54
         r8 = 0xc51fbe40  r9 = 0xc098f591
fork_exit() at fork_exit+0xc0
         pc = 0xc02cdf0c  lr = 0xc066406c (swi_exit)
         sp = 0xc51fbe40  fp = 0x00000000
         r4 = 0xc038e334  r5 = 0xdffc4f54
         r6 = 0xc0b48d84  r7 = 0xd73bd3e0
         r8 = 0x00000001 r10 = 0xc0b268a0
swi_exit() at swi_exit
         pc = 0xc066406c  lr = 0xc066406c (swi_exit)
         sp = 0xc51fbe40  fp = 0x00000000
KDB: enter: panic
[ thread pid 0 tid 100226 ]


I've just restored the sources involved but still have
the .diff I that got via github.




===
Mark Millard
marklmi at yahoo.com