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| author | Renzo Davoli <renzo@cs.unibo.it> | 2009-03-13 00:31:23 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-03-13 02:20:23 +0300 |
| commit | 86d6f2bf61eb2a28fa63c0a19330d36226426477 (patch) | |
| tree | 5eced3cf400712bd3b08038ee29feade9efb0466 /arch/um | |
| parent | f1c7404e37a8970bd58cc10a6d96534d42b9aac6 (diff) | |
| download | linux-86d6f2bf61eb2a28fa63c0a19330d36226426477.tar.xz | |
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>
Diffstat (limited to 'arch/um')
| -rw-r--r-- | arch/um/kernel/ptrace.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/um/kernel/ptrace.c b/arch/um/kernel/ptrace.c index 15e8b7c4de13..8e3d69e4fcb5 100644 --- a/arch/um/kernel/ptrace.c +++ b/arch/um/kernel/ptrace.c @@ -64,6 +64,11 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data) ret = poke_user(child, addr, data); break; + case PTRACE_SYSEMU: + case PTRACE_SYSEMU_SINGLESTEP: + ret = -EIO; + break; + /* continue and stop at next (return from) syscall */ case PTRACE_SYSCALL: /* restart after signal. */ |