linux/arch/um/kernel
Renzo Davoli 86d6f2bf61 UML on UML fixed: it did not start
It is currently impossible to run a user-mode linux machine inside another
user-mode linux (UML on UML).  It breaks after a few instructions.  When
it tries to check whether SYSEMU is installed (the inner) UML receives an
inconsistent result (from the outer UML).

This is the output of a broken attempt:
$ ./linux mem=256m ubd0=cow
Locating the bottom of the address space ... 0x0
Locating the top of the address space ... 0xc0000000
Core dump limits :
        soft - 0
        hard - NONE
Checking that ptrace can change system call numbers...OK
Checking ptrace new tags for syscall emulation...unsupported
Checking syscall emulation patch for ptrace...check_sysemu : expected SIGTRAP, got status = 256
$

The problem is the following:

PTRACE_SYSCALL/SINGLESTEP is currently managed inside arch_ptrace for ARCH=um.

PTRACE_SYSEMU/SUSEMU_SINGLESTEP is not captured in arch_ptrace's switch,
therefore it is erroneously passed back to ptrace_request (in
kernel/ptrace).

This simple patch simply forces ptrace to return an error on
PTRACE_SYSEMU/SUSEMU_SINGLESTEP as it is unsupported on ARCH=um, and fixes
the problem.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Renzo Davoli <renzo@cs.unibo.it>
Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-03-12 16:20:23 -07:00
..
skas uml: fix mm_context memory leak 2008-02-08 09:22:43 -08:00
asm-offsets.c [PATCH] uml: fix missing KBUILD_BASENAME 2006-01-11 18:42:09 -08:00
config.c.in
dyn.lds.S uml: use PAGE_SIZE in linker scripts 2008-05-13 08:02:22 -07:00
exec.c x86, um: get rid of uml unistd.h 2008-10-22 22:55:21 -07:00
exitcode.c proc: remove proc_root from drivers 2008-04-29 08:06:18 -07:00
gmon_syms.c uml: style fixes in arch/um/kernel 2008-02-05 09:44:30 -08:00
gprof_syms.c uml: style fixes in arch/um/kernel 2008-02-05 09:44:30 -08:00
init_task.c take init_fs to saner place 2008-12-31 18:07:42 -05:00
initrd.c uml: fix initrd printk 2008-02-23 17:12:13 -08:00
internal.h x86, um: get rid of uml unistd.h 2008-10-22 22:55:21 -07:00
irq.c arch/um/kernel/irq.c: clean up some functions 2008-07-24 10:47:24 -07:00
ksyms.c arch/um/kernel/mem.c: remove arch_validate() 2008-07-24 10:47:24 -07:00
Makefile uml: style fixes pass 1 2007-10-16 09:43:05 -07:00
mem.c um: use generic show_mem() 2008-07-26 12:00:10 -07:00
physmem.c UML: make several more things static 2008-07-24 10:47:24 -07:00
process.c nohz: prevent tick stop outside of the idle loop 2008-07-18 18:10:28 +02:00
ptrace.c UML on UML fixed: it did not start 2009-03-12 16:20:23 -07:00
reboot.c uml: style fixes in arch/um/kernel 2008-02-05 09:44:30 -08:00
sigio.c uml: style fixes in arch/um/kernel 2008-02-05 09:44:30 -08:00
signal.c x86, um: sanitize uml sigcontext.h uses 2008-10-22 22:55:20 -07:00
smp.c cpumask: centralize cpu_online_map and cpu_possible_map 2008-12-13 21:19:41 +10:30
syscall.c x86, um: get rid of uml unistd.h 2008-10-22 22:55:21 -07:00
sysrq.c uml: style fixes in arch/um/kernel 2008-02-05 09:44:30 -08:00
time.c cpumask: convert struct clock_event_device to cpumask pointers. 2008-12-13 21:20:26 +10:30
tlb.c uml: style fixes in arch/um/kernel 2008-02-05 09:44:30 -08:00
trap.c mm: invoke oom-killer from page fault 2009-01-06 15:58:58 -08:00
uaccess.c UML: make several more things static 2008-07-24 10:47:24 -07:00
um_arch.c uml: deal with inaccessible address space start 2008-06-06 11:29:10 -07:00
umid.c uml: style fixes in arch/um/kernel 2008-02-05 09:44:30 -08:00
uml.lds.S uml: use PAGE_SIZE in linker scripts 2008-05-13 08:02:22 -07:00
vmlinux.lds.S [PATCH] uml: tidy biarch gcc support 2006-07-14 21:53:52 -07:00