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Message-Id: <200903060042.19084.rob@landley.net> Date: Fri, 6 Mar 2009 00:42:14 -0600 From: Rob Landley <rob@...dley.net> To: user-mode-linux-devel@...ts.sourceforge.net Cc: linux-kernel@...r.kernel.org Subject: [PATCH] Fix ARCH=um segfault on x86-64. Apparently, nobody other than me has ever attempted to use User Mode Linux built from 2.6.28 on x86-64, because it doesn't work. It still doesn't work in current git. I complained about it not working back in January: http://sourceforge.net/mailarchive/forum.php?thread_name=200901130159.04389.rob%40landley.net&forum_name=user- mode-linux-devel http://lkml.indiana.edu/hypermail/linux/kernel/0901.2/00669.html And today, I bothered to track down why. This is the commit that broke it, when Peter Anvin merged x86 and x86-64 for ARCH=um: http://kernel.org/hg/linux-2.6/rev/117978 Here's a patch that fixes it for me: Signed-off-by: Rob Landley <rob@...dley.net> diff -r 178a096e9e38 arch/um/Kconfig.x86 --- a/arch/um/Kconfig.x86 Fri Feb 27 16:49:46 2009 -0800 +++ b/arch/um/Kconfig.x86 Thu Mar 05 23:35:55 2009 -0600 @@ -26,9 +26,8 @@ def_bool !X86_XADD config 3_LEVEL_PGTABLES - bool "Three-level pagetables (EXPERIMENTAL)" if !64BIT + bool default 64BIT - depends on EXPERIMENTAL help Three-level pagetables will let UML have more than 4G of physical memory. All the memory that can't be mapped directly will be treated . What changed is that the resulting .config no longer contains the line "CONFIG_3_LEVEL_PGTABLES=y" (it's not visible, and thus not written out into the config file file). Without that symbol defined, x86-64 dies trying to boot. If you tweak the Kconfig so the symbol gets written out, it starts working again. I have no idea how ANYBODY has EVER managed to use 2.6.28 User Mode Linux on an x86-64 host. My theory is that nobody ever did. I suspect that very few people use UML anymore now that KVM and the rustyvisor and such are available, and those legacy users still fiddling with it are apparently all either using old versions or 32-bit hosts. (I still like being able to stick printfs into the kernel.) Here's the panic, in case you're wondering: $ ./linux rw init=/bin/bash rootfstype=hostfs Core dump limits : soft - 0 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 for tmpfs mount on /dev/shm...OK Checking PROT_EXEC mmap in /dev/shm/...OK Checking for the skas3 patch in the host: - /proc/mm...not found: No such file or directory - PTRACE_FAULTINFO...not found - PTRACE_LDT...not found UML running in SKAS0 mode Adding 4390912 bytes to physical memory to account for exec-shield gap Linux version 2.6.29-rc7 (landley@...ftwood) (gcc version 4.3.2 (Ubuntu 4.3.2-1ubuntu11) ) #1 Thu Mar 5 21:20:14 CST 2009 Built 1 zonelists in Zone order, mobility grouping on. Total pages: 9137 Kernel command line: rw init=/bin/bash rootfstype=hostfs root=98:0 PID hash table entries: 256 (order: 8, 2048 bytes) Dentry cache hash table entries: 8192 (order: 4, 65536 bytes) Inode-cache hash table entries: 4096 (order: 3, 32768 bytes) Memory: 29244k available SLUB: Genslabs=12, HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1 Calibrating delay loop... 209.30 BogoMIPS (lpj=1046528) Mount-cache hash table entries: 256 Checking that host ptys support output SIGIO...Yes Checking that host ptys support SIGIO on close...No, enabling workaround Using 2.6 host AIO bio: create slab <bio-0> at 0 Switched to NOHz mode on CPU #0 io scheduler noop registered (default) loop: module loaded Initialized stdio console driver Using a channel type which is configured out of UML parse_chan_pair failed for device 1 : Configuration failed Using a channel type which is configured out of UML parse_chan_pair failed for device 2 : Configuration failed Using a channel type which is configured out of UML parse_chan_pair failed for device 3 : Configuration failed Using a channel type which is configured out of UML parse_chan_pair failed for device 4 : Configuration failed Using a channel type which is configured out of UML parse_chan_pair failed for device 5 : Configuration failed Using a channel type which is configured out of UML parse_chan_pair failed for device 6 : Configuration failed Using a channel type which is configured out of UML parse_chan_pair failed for device 7 : Configuration failed Using a channel type which is configured out of UML parse_chan_pair failed for device 8 : Configuration failed Using a channel type which is configured out of UML parse_chan_pair failed for device 9 : Configuration failed Using a channel type which is configured out of UML parse_chan_pair failed for device 10 : Configuration failed Using a channel type which is configured out of UML parse_chan_pair failed for device 11 : Configuration failed Using a channel type which is configured out of UML parse_chan_pair failed for device 12 : Configuration failed Using a channel type which is configured out of UML parse_chan_pair failed for device 13 : Configuration failed Using a channel type which is configured out of UML parse_chan_pair failed for device 14 : Configuration failed Using a channel type which is configured out of UML parse_chan_pair failed for device 15 : Configuration failed Console initialized on /dev/tty0 console [tty0] enabled VFS: Mounted root (hostfs filesystem) on device 0:8. IRQ 3/console-write: IRQF_DISABLED is not guaranteed on shared IRQs IRQ 2/console: IRQF_DISABLED is not guaranteed on shared IRQs IRQ 10/winch: IRQF_DISABLED is not guaranteed on shared IRQs Pid: 1, comm: swapper Not tainted 2.6.29-rc7 RIP: 0033:[<000000006001b342>] RSP: 0000000062029dd0 EFLAGS: 00010216 RAX: 00000000622af800 RBX: 00000000621b0000 RCX: 0000000003ffc09f RDX: fffffffffff02800 RSI: 0000000060313900 RDI: 00000000622af800 RBP: 0000000060d10048 R08: 0000000000000000 R09: 0000000000100000 R10: 0000000000000000 R11: 0000000060197a00 R12: 000000006211f300 R13: 000000006211f300 R14: 0000000060206440 R15: 0000000062020300 Call Trace: 602058f8: [<600160c5>] timer_one_shot+0x55/0x80 60205908: [<6000e4b9>] segv+0x2a9/0x2d0 60205918: [<6001b342>] __memcpy+0xe/0xac 60205928: [<6003f376>] tick_dev_program_event+0x36/0xb0 60205958: [<6003f5c4>] tick_check_oneshot_change+0xf4/0x100 60205968: [<6002bc6d>] run_timer_softirq+0x1cd/0x210 602059e8: [<6000e530>] segv_handler+0x50/0xe0 60205a08: [<6003f250>] tick_handle_periodic+0x10/0x60 60205a48: [<60026a7d>] do_softirq+0x4d/0x70 60205a68: [<60026bf2>] irq_exit+0x42/0xa0 60205a88: [<6000aecf>] do_IRQ+0x2f/0x50 60205aa8: [<600154e4>] sig_handler_common+0x64/0xe0 60205b30: [<6001b342>] __memcpy+0xe/0xac 60205b50: [<600ae3de>] sysfs_new_dirent+0xfe/0x120 60205bd8: [<600156aa>] sig_handler+0x1a/0x40 60205be8: [<60015983>] handle_signal+0x73/0xb0 60205c28: [<60100140>] __restore_rt+0x0/0x10 60205cd8: [<6001b342>] __memcpy+0xe/0xac Kernel panic - not syncing: Segfault with no mm Pid: 1, comm: swapper Not tainted 2.6.29-rc7 RIP: 0033:[<00000000601003a7>] RSP: 00007fff8026e2a8 EFLAGS: 00000246 RAX: 0000000000000000 RBX: 0000000000001cc4 RCX: ffffffffffffffff RDX: 0000000000000000 RSI: 0000000000000013 RDI: 0000000000001cc4 RBP: 0000000000001cc0 R08: 00007fff8026e1f0 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff8026e3b8 R13: 0000000000000004 R14: 00007fff8026e580 R15: 00007fff8026e414 Call Trace: 602057b8: [<6003aacd>] up+0x1d/0x50 602057c8: [<6000e77d>] panic_exit+0x2d/0x50 602057d8: [<600214ac>] release_console_sem+0x19c/0x1e0 602057e8: [<6003ac87>] notifier_call_chain+0x37/0x70 60205818: [<60167cd7>] panic+0xd0/0x164 60205858: [<60100370>] __sigprocmask+0x10/0x40 60205878: [<60167df6>] printk+0x8b/0x95 60205898: [<6001604e>] os_nsecs+0xe/0x30 602058b8: [<6001b342>] __memcpy+0xe/0xac 602058c8: [<6000d080>] show_trace+0x60/0xc0 602058e8: [<6001b148>] show_regs+0x28/0x30 60205908: [<6000e4c5>] segv+0x2b5/0x2d0 60205918: [<6001b342>] __memcpy+0xe/0xac 60205928: [<6003f376>] tick_dev_program_event+0x36/0xb0 60205958: [<6003f5c4>] tick_check_oneshot_change+0xf4/0x100 60205968: [<6002bc6d>] run_timer_softirq+0x1cd/0x210 602059e8: [<6000e530>] segv_handler+0x50/0xe0 60205a08: [<6003f250>] tick_handle_periodic+0x10/0x60 60205a48: [<60026a7d>] do_softirq+0x4d/0x70 60205a68: [<60026bf2>] irq_exit+0x42/0xa0 60205a88: [<6000aecf>] do_IRQ+0x2f/0x50 60205aa8: [<600154e4>] sig_handler_common+0x64/0xe0 60205b30: [<6001b342>] __memcpy+0xe/0xac 60205b50: [<600ae3de>] sysfs_new_dirent+0xfe/0x120 60205bd8: [<600156aa>] sig_handler+0x1a/0x40 60205be8: [<60015983>] handle_signal+0x73/0xb0 60205c28: [<60100140>] __restore_rt+0x0/0x10 60205cd8: [<6001b342>] __memcpy+0xe/0xac Segmentation fault Rob
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