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Re: [uml-user] PC change, and errors in have_xstate_support
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From: Dan M. <i...@da...> - 2017-02-13 14:19:11
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Yes, CPU matters apparently. I got hit by this badly.
I traced the chain of calls into the kernel, and apparently this has to
do with fpu related features.
you have to set eagerfpu=off in your kernel boot options. Also note that
there is a 6 options limit. Any option after the 6th will be ignored.
On 02/13/2017 04:40 PM, Natale Patriciello wrote:
> Hello,
>
> I have a UML configuration that worked fine with the 4.10.0-rc8 version
> in my previous laptop (i7-2740 cpu, blabla.. does it really matters?).
> With "worked fine" I mean that I was able to boot in my custom Archlinux
> image (on an Archlinux host perfectly updated).
>
> I then copied the image and the config in a new laptop (new i7-7700),
> run the make for the kernel, got the kernel binary.
> When trying to start, I get the following message: (Sorry for the long message!)
>
> $ ./linux mem=512M ubd0=/home/nat/Work/Linux_UML/fs/fs.ext4
> Core dump limits :
> soft - NONE
> hard - NONE
> Checking that ptrace can change system call numbers...OK
> Checking syscall emulation patch for ptrace...OK
> Checking advanced syscall emulation patch for ptrace...OK
> Checking environment variables for a tempdir.../tmp/nat
> Checking if /tmp/nat is on tmpfs...OK
> Checking PROT_EXEC mmap in /tmp/nat...OK
> Adding 11587584 bytes to physical memory to account for exec-shield gap
> Linux version 4.10.0-rc8-uml-00205-g7089db84e356-dirty (nat@judith) (gcc version 6.3.1 20170109 (GCC) ) #16 Mon Feb 13 15:35:51 CET 2017
> Built 1 zonelists in Zone order, mobility grouping on. Total pages: 131808
> Kernel command line: mem=512M ubd0=/home/nat/Work/Linux_UML/fs/fs.ext4 root=98:0
> PID hash table entries: 4096 (order: 3, 32768 bytes)
> Dentry cache hash table entries: 131072 (order: 8, 1048576 bytes)
> Inode-cache hash table entries: 65536 (order: 7, 524288 bytes)
> Memory: 509848K/535604K available (2647K kernel code, 697K rwdata, 772K rodata, 111K init, 171K bss, 25756K reserved, 0K cma-reserved)
> NR_IRQS:15
> clocksource: timer: mask: 0xffffffffffffffff max_cycles: 0x1cd42e205, max_idle_ns: 881590404426 ns
> Calibrating delay loop... 6889.47 BogoMIPS (lpj=34447360)
> pid_max: default: 32768 minimum: 301
> Mount-cache hash table entries: 2048 (order: 2, 16384 bytes)
> Mountpoint-cache hash table entries: 2048 (order: 2, 16384 bytes)
> Checking that host ptys support output SIGIO...Yes
> Checking that host ptys support SIGIO on close...No, enabling workaround
> devtmpfs: initialized
> Using 2.6 host AIO
> clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
> NET: Registered protocol family 16
> clocksource: Switched to clocksource timer
> VFS: Disk quotas dquot_6.6.0
> VFS: Dquot-cache hash table entries: 512 (order 0, 4096 bytes)
> NET: Registered protocol family 2
> TCP established hash table entries: 8192 (order: 4, 65536 bytes)
> TCP bind hash table entries: 8192 (order: 4, 65536 bytes)
> TCP: Hash tables configured (established 8192 bind 8192)
> UDP hash table entries: 512 (order: 2, 16384 bytes)
> UDP-Lite hash table entries: 512 (order: 2, 16384 bytes)
> NET: Registered protocol family 1
> console [stderr0] disabled
> mconsole (version 2) initialized on /home/nat/.uml/FdImtj/mconsole
> Checking host MADV_REMOVE support...OK
> futex hash table entries: 256 (order: 0, 6144 bytes)
> workingset: timestamp_bits=46 max_order=17 bucket_order=0
> Block layer SCSI generic (bsg) driver version 0.4 loaded (major 254)
> io scheduler noop registered
> io scheduler deadline registered (default)
> NET: Registered protocol family 17
> Initialized stdio console driver
> Console initialized on /dev/tty0
> console [tty0] enabled
> Initializing software serial port version 1
> console [mc-1] enabled
> EXT4-fs (ubda): couldn't mount as ext3 due to feature incompatibilities
> EXT4-fs (ubda): couldn't mount as ext2 due to feature incompatibilities
> EXT4-fs (ubda): mounted filesystem with ordered data mode. Opts: (null)
> VFS: Mounted root (ext4 filesystem) readonly on device 98:0.
> devtmpfs: mounted
> This architecture does not have kernel memory protection.
> Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
>
> CPU: 0 PID: 1 Comm: init Not tainted 4.10.0-rc8-uml-00205-g7089db84e356-dirty #16
> Stack:
> 80433ba0 60064332 80430b00 6031bae8
> 600905cc 601d4673 80433bb0 601c9a41
> 80433cd0 60090332 80433be0 6002d3b1
> Call Trace:
> [<600905cc>] ?
> printk+0x0/0x94
> [<6001af21>]
> show_stack+0x108/0x15e
> [<60064332>] ?
> dump_stack_print_info+0xe4/0xed
> [<600905cc>] ?
> printk+0x0/0x94
> [<601d4673>] ?
> bust_spinlocks+0x0/0x3b
> [<601c9a41>]
> dump_stack+0x2a/0x2c
> [<60090332>]
> panic+0x170/0x311
> [<6002d3b1>] ?
> set_signals+0x28/0x40
> [<600f2c29>] ?
> mntput+0x2f/0x31
> [<600d723f>] ?
> __fput+0x1d3/0x1e2
> [<602aa6ec>] ?
> _cond_resched+0x0/0x42
> [<600d7292>] ?
> ____fput+0x10/0x12
> [<60089c12>] ?
> cgroup_exit+0x8c/0xcb
> [<600901c2>] ?
> panic+0x0/0x311
> [<60038a29>]
> do_exit+0x3c3/0x89d
> [<60038fd7>]
> do_group_exit+0x8f/0x106
> [<6002d1ac>] ?
> block_signals+0x0/0x16
> [<6002d1ac>] ?
> block_signals+0x0/0x16
> [<600423ae>]
> get_signal+0x4af/0x4e3
> [<6001ac75>]
> do_signal+0x27/0x121
> [<6002d3b1>] ?
> set_signals+0x28/0x40
> [<6002d389>] ?
> set_signals+0x0/0x40
> [<6004131d>] ?
> force_sig+0x18/0x1a
> [<60041932>] ?
> force_sigsegv+0x5f/0x69
> [<6001c2d8>]
> fatal_sigsegv+0x46/0x52
> [<60032a5f>] ?
> put_fp_registers+0x10/0x12
> [<6002fed5>]
> userspace+0x12b/0x447
> [<60019d6f>] ?
> interrupt_end+0x0/0xa0
> [<600dca10>] ?
> do_execveat_common+0x519/0x649
> [<600c9ce1>] ?
> kmem_cache_alloc+0x0/0x103
> [<600dcb61>] ?
> do_execve+0x21/0x23
> [<600183e4>] ?
> run_init_process+0x3e/0x42
> [<600183e8>] ?
> try_to_run_init_process+0x0/0x44
> [<600183fe>] ?
> try_to_run_init_process+0x16/0x44
> [<600183e8>] ?
> try_to_run_init_process+0x0/0x44
> [<60019b98>]
> new_thread_handler+0xa1/0xa3
>
> I have investigated it, and the problem is in arch/x86/um/os-Linux/registers.c :
>
> 49 int restore_fp_registers(int pid, unsigned long *fp_regs)
> 50 {
> 51 struct iovec iov;
> 52
> 53 if (have_xstate_support) {
> 54 iov.iov_base = fp_regs;
> 55 iov.iov_len = sizeof(struct _xstate);
> 56 if (ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
> 57 return -errno;
> 58 return 0;
> 59 } else {
> 60 return restore_i387_registers(pid, fp_regs);
> 61 }
> 62 }
>
> At line 56, there is a ptrace call. This call exits with -14. The 14
> number means EFAULT. Well, after some tries, I patched the function to
> always enter the else branch, and then calling restore_i387_registers .
> With my big surprise, using this function allows me to boot correctly
> the system.
>
> Why I can't successfully boot with the stock kernel, with
> have_xstate_support ?
>
> Thank you
> N.
>
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