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Date: Fri, 02 Jun 2017 10:04:09 +0200
From: Thomas Meyer <thomas@...3r.de>
To: Florian Fainelli <f.fainelli@...il.com>,
Richard Weinberger <richard@....at>,
linux-kernel@...r.kernel.org
Cc: Jeff Dike <jdike@...toit.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
"open list:USER-MODE LINUX (UML)"
<user-mode-linux-devel@...ts.sourceforge.net>,
"open list:USER-MODE LINUX (UML)"
<user-mode-linux-user@...ts.sourceforge.net>
Subject: Re: [PATCH v2] um: Avoid longjmp/setjmp symbol clashes with
libpthread.a
Am Donnerstag, den 01.06.2017, 22:49 -0700 schrieb Florian Fainelli:
>
> On 06/01/2017 02:25 PM, Thomas Meyer wrote:
> > Am Donnerstag, den 01.06.2017, 22:58 +0200 schrieb Richard
> > Weinberger:
> > >
> > > Sorry, I thought you are CC'ed.
> > > Thomas please speak up. AFAIR UML fails to boot on one of your
> > > new
> > > Laptops.
> >
> > Hi,
> >
> > yes, the first userspace process failes here:
> >
> > void userspace(struct uml_pt_regs *regs)
> > {
> > int err, status, op, pid = userspace_pid[0];
> > /* To prevent races if using_sysemu changes under us.*/
> > int local_using_sysemu;
> > siginfo_t si;
> >
> > /* Handle any immediate reschedules or signals */
> > interrupt_end();
> >
> > while (1) {
> >
> > /*
> > * This can legitimately fail if the process loads
> > a
> > * bogus value into a segment register. It will
> > * segfault and PTRACE_GETREGS will read that value
> > * out of the process. However, PTRACE_SETREGS
> > will
> > * fail. In this case, there is nothing to do but
> > * just kill the process.
> > */
> > if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp))
> > fatal_sigsegv();
> >
> > if (put_fp_registers(pid, regs->fp))
> > -> fatal_sigsegv();
> >
> > the put_fp_registers fails with errno 4 if I recall correctly.
> >
> > I didn't investigate yet further, why the the xstate ptrace call
> > fails.
>
> Which of the branches is put_fp_registers() taking?
#0 restore_fp_registers (pid=2226, fp_regs=0xafcbf738) at arch/x86/um/os-Linux/registers.c:57
#1 0x0000000060084c80 in put_fp_registers (pid=<optimized out>, regs=<optimized out>) at arch/x86/um/os-Linux/registers.c:124
#2 0x00000000600814e1 in userspace (regs=0xafcbf660) at arch/um/os-Linux/skas/process.c:329
#3 0x0000000060070fc1 in new_thread_handler () at arch/um/kernel/process.c:134
#4 0x0000000000000000 in ?? ()
> The restore_fpx_registers() or restore_fp_registers()?
> 4 would be EINTR...
Yes, strange, indeed.
> What kernel version is used on your host running the UML binary?
It's a VirtualBox with Fedora 25 and "Linux localhost.localdomain 4.10.15-200.fc25.x86_64 #1 SMP Mon May 8 18:46:06 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux"
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 142
model name : Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz
stepping : 9
cpu MHz : 2904.002
cache size : 4096 KB
physical id : 0
siblings : 2
core id : 0
cpu cores : 2
apicid : 0
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 22
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr
pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx rdtscp
lm constant_tsc rep_good nopl xtopology nonstop_tsc pni pclmulqdq ssse3
cx16 sse4_1 sse4_2 x2apic movbe popcnt aes xsave avx rdrand hypervisor
lahf_lm abm 3dnowprefetch rdseed clflushopt
bugs :
bogomips : 5808.00
clflush size : 64
cache_alignment : 64
address sizes : 39 bits physical, 48 bits virtual
power management:
I see this in the kernel log:
[ 0.000000] ------------[ cut here ]------------
[ 0.000000] WARNING: CPU: 0 PID: 0 at arch/x86/kernel/fpu/xstate.c:595 fpu__init_system_xstate+0x4d0/0x877
[ 0.000000] XSAVE consistency problem, dumping leaves
[ 0.000000] Modules linked in:
[ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.10.15-200.fc25.x86_64 #1
[ 0.000000] Call Trace:
[ 0.000000] dump_stack+0x63/0x86
[ 0.000000] __warn+0xcb/0xf0
[ 0.000000] warn_slowpath_fmt+0x5f/0x80
[ 0.000000] ? xfeature_size+0x5a/0x78
[ 0.000000] fpu__init_system_xstate+0x4d0/0x877
[ 0.000000] ? msr_clear_bit+0x3a/0xa0
[ 0.000000] ? 0xffffffffa3000000
[ 0.000000] fpu__init_system+0x194/0x1be
[ 0.000000] early_cpu_init+0xf7/0xf9
[ 0.000000] setup_arch+0xba/0xcf0
[ 0.000000] ? printk+0x57/0x73
[ 0.000000] ? early_idt_handler_array+0x120/0x120
[ 0.000000] start_kernel+0xb2/0x48a
[ 0.000000] ? early_idt_handler_array+0x120/0x120
[ 0.000000] x86_64_start_reservations+0x24/0x26
[ 0.000000] x86_64_start_kernel+0x14d/0x170
[ 0.000000] start_cpu+0x14/0x14
[ 0.000000] ---[ end trace d5213d72358dda94 ]---
[ 0.000000] CPUID[0d, 00]: eax=00000007 ebx=00000440 ecx=00000440 edx=00000000
[...]
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
[ 0.000000] x86/fpu: xstate_offset[2]: 576, xstate_sizes[2]: 256
[ 0.000000] x86/fpu: Enabled xstate features 0x7, context size is 1088 bytes, using 'standard' format.
UML kernel is:
v4.12-rc3-69-g9ea15a5
CONFIG_UML_X86=y
CONFIG_64BIT=y
# CONFIG_X86_32 is not set
CONFIG_X86_64=y
> Thanks
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