Commit 1de1502c ("x86, um: now we can get rid of trivial uml headers")
removed accidentally bug.h which broke UML's call tracer and bug
handler.

Without asm-generic/bug.h UML uses BUG() from arch/x86/ which makes use
of ud2.  UML cannot use ud2, it raises SIGILL in user mode.  As UML has
a different stack for handling signals the call trace will be cut off.
Signed-off-by: NRichard Weinberger <richard@nod.at>
Reported-by: NSergei Trofimovich <slyich@gmail.com>
Tested-by: NSergei Trofimovich <slyich@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

Get UML to use the generic bug support rather than arch specific one.

If I insert an artificial bug right before loading init, I get this:

 Kernel panic - not syncing: Kernel mode signal 4

 EIP: 0023:[<0819d501>] CPU: 0 Not tainted ESP: 002b:f7fd4fbc EFLAGS: 00000246
    Not tainted
    EAX: 00000000 EBX: 00007870 ECX: 00000013 EDX: 00007870
    ESI: 0000786d EDI: 00000011 EBP: f7fd4fd8 DS: 002b ES: 002b
    08273bec:  [<0806e814>] show_regs+0x104/0x106
    08273c08:  [<08058927>] panic_exit+0x2c/0x4b
    08273c18:  [<08080ee7>] notifier_call_chain+0x32/0x5b
    08273c38:  [<08080fbd>] __atomic_notifier_call_chain+0x30/0x32
    08273c54:  [<08080fee>] atomic_notifier_call_chain+0x2f/0x31
    08273c70:  [<08073b88>] panic+0x75/0x131
    08273c94:  [<080586c7>] relay_signal+0x87/0x95
    08273cb0:  [<0806b9ee>] sig_handler_common_skas+0x9e/0x120
    08273cd8:  [<08067738>] sig_handler+0x28/0x4f
    08273cec:  [<0806792e>] handle_signal+0x53/0x89
    08273d0c:  [<08069f60>] hard_handler+0x18/0x28
    08273d1c:  [<ffffe500>] transitions+0xf7d598b8/0xfffffff0

With this patch in place, this is how it looks:

 BUG: failure at init/main.c:779/init_post()!
 Kernel panic - not syncing: BUG!

 EIP: 0023:[<081a65d1>] CPU: 0 Not tainted ESP: 002b:f7f0dfbc EFLAGS: 00000246
    Not tainted
    EAX: 00000000 EBX: 000069db ECX: 00000013 EDX: 000069db
    ESI: 000069d8 EDI: 00000011 EBP: f7f0dfd8 DS: 002b ES: 002b
    098efedc:  [<0806e9a4>] show_regs+0x104/0x106
    098efef8:  [<080589c7>] panic_exit+0x2c/0x4b
    098eff08:  [<080818d7>] notifier_call_chain+0x32/0x5b
    098eff28:  [<080819ad>] __atomic_notifier_call_chain+0x30/0x32
    098eff44:  [<080819de>] atomic_notifier_call_chain+0x2f/0x31
    098eff60:  [<08073f28>] panic+0x75/0x131
    098eff84:  [<080541d5>] init_post+0xcd/0xe8
    098eff9c:  [<08048ad4>] kernel_init+0x8e/0x9a
    098effb4:  [<08066dee>] run_kernel_thread+0x41/0x53
    098effe0:  [<08058e75>] new_thread_handler+0x62/0x8b
    098efffc:  [<a55a5a5a>] 0xa55a5a5a

[ jdike - added BUG_TABLE to linker script ]
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NJeff Dike <jdike@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The BUG changes in -mm3 need some arch support.  This patch adds the UML
support needed.  For the most part, it was stolen from the underlying
architecture.  The exception is the kernel eip < PAGE_OFFSET test, which is
wrong for skas mode UMLs.
Signed-off-by: NJeff Dike <jdike@addtoit.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!