Problem compiling 5.7.2

[Matthias Urlichs]

… or rather, I can compile 5.7.2 (i.e. Neil's branch) just fine but it crashes when booting.

[    0.549585] futex hash table entries: 1024 (order: 3, 32768 bytes, linear)
[    0.563190] CPU 0 Unable to handle kernel paging request at virtual address 00000000, epc == 80092b80, ra == 80092b70
[    0.584268] Oops[#1]:
[    0.588734] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.7.2-00057-g5cfdc518329a #61
[    0.603935] $ 0   : 00000000 00000001 00000000 9bc48000
[    0.614299] $ 4   : fffffff2 00000000 00000000 00000000
[    0.624668] $ 8   : 9bc51e28 9bd60000 00000400 00000000
[    0.635035] $12   : 80d20000 00000000 00000043 00000000
[    0.645403] $16   : 80830000 00000001 8082c370 80830000
[    0.655772] $20   : 80cf0000 80883404 8085909c 00000008
[    0.666139] $24   : 00000001 00000000                  
[    0.676507] $28   : 9bc50000 9bc51de0 80883424 80092b70
[    0.686876] Hi    : 00000000
[    0.692578] Lo    : 00000000
[    0.698308] epc   : 80092b80 cmpxchg_futex_value_locked+0x28/0x64
[    0.710382] ra    : 80092b70 cmpxchg_futex_value_locked+0x18/0x64
[    0.722472] Status: 11008403    KERNEL EXL IE
[    0.730768] Cause : 40800008 (ExcCode 02)
[    0.738716] BadVA : 00000000
[    0.744420] PrId  : 0001992f (MIPS 1004Kc)
[    0.752539] Modules linked in:
[    0.758593] Process swapper/0 (pid: 1, threadinfo=(ptrval), task=(ptrval), tls=00000000)
[    0.774658] Stack : 80cf0000 80883404 8085909c 00000008 80883424 80863d8c ffbc1930 0043e6cf
[    0.791246]         806b0000 80834470 00000000 9bc51e24 00000000 00000400 00000400 8085909c
[    0.807835]         00000008 0000000a 80883404 86790d73 80879d80 80830000 80863cd8 ffffffff
[    0.824423]         00000000 80001714 00000000 9bc51e4c 9bc51e4c 86790d73 8081f8a0 80830000
[    0.841012]         00000000 80859000 8081b320 00000001 00000001 00000000 80830000 80770000
[    0.857601]         ...
[    0.862442] Call Trace:
[    0.867286] [<80092b80>] cmpxchg_futex_value_locked+0x28/0x64
[    0.878706] [<80863d8c>] futex_init+0xb4/0x128
[    0.887503] [<80001714>] do_one_initcall+0x84/0x1bc
[    0.897190] [<80859f3c>] kernel_init_freeable+0x220/0x258
[    0.907903] [<806a010c>] kernel_init+0x14/0x10c
[    0.916883] [<80006a98>] ret_from_kernel_thread+0x14/0x1c
[    0.927592] Code: 2404fff2  00001025  0000000f <c0a30000> 14660005  00000000  00e00825  e0a10000  1020fff9
[    0.946939]
[    0.949912] ---[ end trace 59c355a297aca262 ]---
[    0.959043] Kernel panic - not syncing: Fatal exception
[    0.969441] Rebooting in 1 seconds..
[    3.367209] Reboot failed -- System halted

I tried mipsel-GCC 6,8,10 from Debian. No change. Original gbpc1-5.7 config file.

Any ideas what could possibly be going wrong here? Neil's 5.7.2 images work perfectly but I need a few modules he doesn't have.

(gdb) disass cmpxchg_futex_value_locked
Dump of assembler code for function cmpxchg_futex_value_locked:
   0x80093a50 <+0>:    addiu    sp,sp,-24
   0x80093a54 <+4>:    sw    ra,20(sp)
   0x80093a58 <+8>:    jal    0x800936fc <pagefault_disable>
   0x80093a5c <+12>:    move    t0,a0
   0x80093a60 <+16>:    jal    0x80093a38 <__access_ok>
   0x80093a64 <+20>:    move    a0,a1
   0x80093a68 <+24>:    beqz    v0,0x80093a9c <cmpxchg_futex_value_locked+76>
   0x80093a6c <+28>:    li    a0,-14
   0x80093a70 <+32>:    move    v0,zero
   0x80093a74 <+36>:    sync
   0x80093a78 <+40>:    ll    v1,0(a1)
   0x80093a7c <+44>:    bne    v1,a2,0x80093a94 <cmpxchg_futex_value_locked+68>
   0x80093a80 <+48>:    nop
   0x80093a84 <+52>:    move    at,a3
   0x80093a88 <+56>:    sc    at,0(a1)
   0x80093a8c <+60>:    beqz    at,0x80093a74 <cmpxchg_futex_value_locked+36>
   0x80093a90 <+64>:    nop
   0x80093a94 <+68>:    move    a0,v0
   0x80093a98 <+72>:    sw    v1,0(t0)
   0x80093a9c <+76>:    jal    0x80093714 <pagefault_enable>
   0x80093aa0 <+80>:    nop
   0x80093aa4 <+84>:    lw    ra,20(sp)
   0x80093aa8 <+88>:    move    v0,a0
   0x80093aac <+92>:    jr    ra
   0x80093ab0 <+96>:    addiu    sp,sp,24
End of assembler dump.

(gdb) disass futex_init
Dump of assembler code for function futex_init:

   0x807e7df8 <+0>:    addiu    sp,sp,-80
…

   0x807e7e7c <+132>:    jal    0x807ed5a4 <alloc_large_system_hash>
   0x807e7e80 <+136>:    sw    v0,16(sp)
   0x807e7e84 <+140>:    move    a3,zero
   0x807e7e88 <+144>:    lw    t2,44(sp)
   0x807e7e8c <+148>:    move    a2,zero
   0x807e7e90 <+152>:    move    a1,zero
   0x807e7e94 <+156>:    sw    v0,880(s3)
   0x807e7e98 <+160>:    addiu    a0,sp,48
   0x807e7e9c <+164>:    sllv    t2,s1,t2
   0x807e7ea0 <+168>:    move    t1,v0
   0x807e7ea4 <+172>:    jal    0x80093a50 <cmpxchg_futex_value_locked>
   0x807e7ea8 <+176>:    sw    t2,4(s2)
   0x807e7eac <+180>:    li    v1,-14
   0x807e7eb0 <+184>:    bne    v0,v1,0x807e7ec4 <futex_init+204>
   0x807e7eb4 <+188>:    addiu    v0,t1,8
   0x807e7eb8 <+192>:    lui    v0,0x807b
   0x807e7ebc <+196>:    sw    s1,888(v0)
   0x807e7ec0 <+200>:    addiu    v0,t1,8
…

[Neil Brown]

> 5.7.2-00057-g5cfdc518329a

This says that the code you were compiling was git commit 5cfdc518329a.  That commit doesn't exist in my tree.  So you presumably added something.

Probably it was minor, but if you could report exactly the differences from b78761c3e78aa, that might help.

I hope to find time in the next couple of week to build and test a 5.10 kernel.... no promised though.

[Matthias Urlichs]

On 17.12.20 06:08, Neil Brown wrote:
> This says that the code you were compiling was git commit
> 5cfdc518329a.  That commit doesn't exist in my tree.  So you
> presumably added something.

That's just a stopgap fix to the Debian package build instructions. They
don't forward the "CC" or "CROSS" variables. Otherwise I couldn't have
cross-compiled / built things with gcc 6 or 8 in the first place.

I'll try to build the kernel on the production machine I've got lying
around, maybe it's a bug in the cross-compiling toolset.

The problem after that is that with your precompiled kernel and Debian
Buster, perl 4.28 throws a SIGBUS. :-(
I didn't yet try to investigate that further.

--
-- Matthias Urlichs

[Matthias Urlichs]

OK, I identified the kernel problem, the bug appears to be with the cross compiler or linker. I can build a working kernel by installing a chroot environment and running the kernel compilation under qemu-mipsel-static.

No idea yet what to do about Perl.

[Matthias Urlichs]

Perl is only broken in Debian Stable/buster. Testing/bullseye works. Good enough for me.

[Neil Brown]

Sounds like a good result :-)

What version of compile and bin-utils were you using?  It might be useful to document that there is a problem.

I'm using gcc-7.2.0 and bin-utils 2.29.1.20170915 without problems.