Re: port-xen/52662: Almost everything crashes on -current kernel

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

Here's what I found so far:

makemandb, gzip and gdb all dies at the same point in libpthread:
Core was generated by `gdb'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x0000793be0208fad in ?? () from /usr/lib/libpthread.so.1
(gdb) x/i 0x0000793be0208fad
=> 0x793be0208fad:      nopl   %cs:0x0(%rax,%rax,1)
(gdb) info registers
rax            0x0      0
rbx            0x793be2907800   133298111150080
rcx            0x53     83
rdx            0x793be020ac83   133298070269059
rsi            0x0      0
rdi            0x793be096d4e0   133298078012640
rbp            0x793be0411840   0x793be0411840 <pthread.allqueue>
rsp            0x7f7fff8c8d58   0x7f7fff8c8d58
r8             0x101010101010101        72340172838076673
r9             0x8080808080808080       -9187201950435737472
r10            0x793be063eb0a   133298074675978
r11            0x202    514
r12            0x0      0
r13            0x0      0
r14            0x793be020ac83   133298070269059
r15            0x793be0638820   133298074650656
rip            0x793be0208fad   0x793be0208fad
eflags         0x10246  [ PF ZF IF RF ]
cs             0xe033   57395
ss             0xe02b   57387
ds             0x23     35
es             0x23     35
fs             0x0      0
gs             0x0      0

atf-run and atf-report are different:
Core was generated by `atf-run'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007f7f92e0a4f0 in _rtld_process_hints () from /usr/libexec/ld.elf_so
(gdb) x/i 0x00007f7f92e0a4f0
=> 0x7f7f92e0a4f0 <_rtld_process_hints+1717>:   callq  0x7f7f92e07012 <xmalloc>
(gdb) info registers
rax            0x1      1
rbx            0x7a5b14b19240   134531607794240
rcx            0x4      4
rdx            0x4e22b364       1310896996
rsi            0x4e445d30       1313103152
rdi            0x7a5b14f13160   134531611963744
rbp            0x4e22b364       0x4e22b364 <tools::system_error::~system_error()>
rsp            0x7f7fffcfdba8   0x7f7fffcfdba8
r8             0x7a5b14b2c11c   134531607871772
r9             0x7a5b14b2c14c   134531607871820
r10            0x7263742f30486e4e       8242559489040477774
r11            0xfffffffffffffffc       -4
r12            0x4e445d30       1313103152
r13            0x7a5b14b19240   134531607794240
r14            0x7f7fffcfdc00   140187729386496
r15            0x7f7fffcfdef0   140187729387248
rip            0x7f7f92e0a4f0   0x7f7f92e0a4f0 <_rtld_process_hints+1717>
eflags         0x10202  [ IF RF ]
cs             0xe033   57395
ss             0xe02b   57387
ds             0x23     35
es             0x92e00023       -1830813661
fs             0x0      0
gs             0x0      0

On a working netbsd-8 domU I get:
cs             0xe033   57395
ss             0xe02b   57387
ds             0x3f     63
es             0xffff003f       -65473
fs             0x0      0
gs             0x0      0
while on bare-metal:
cs             0x47     71
ss             0x3f     63
ds             0x3f     63
es             0x3f     63
fs             0x0      0
gs             0x0      0

So I suspect Xen is remapping GDT enstries, and we can't blindly reset them
to our defaults.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--