[Qemu-devel] [RFC PATCH 0/1] linux-user: Issue running applications through ld.so

[Meador Inge]

Hi All,

I am running into an issue where QEMU fails to map a target executable
due to hitting the lower limit on /proc/sys/vm/mmap_min_addr.  This normally
just works because of all the nice guest base probing we have in place:

$ cat /proc/sys/vm/mmap_min_addr 
4096
$ qemu-arm ./hello.out
Hello, World!

In cases where the executable is run through the glibc loader we are not so
lucky:

$ qemu-arm /path/to/lib/ld-2.15.so --library-path /path/to/lib/ ./hello.out 
./hello.out: error while loading shared libraries: ./hello.out: failed to map
segment from shared object: Permission denied

The reason is that we successfully load the loader (since it can be put
anywhere), but later ld.so goes to map in hello.out at a fixed address
and fails because that fixed address is bellow mmap_min_addr and it is
too late to fixup the guest base.

I am able to fix the issue by probing for the guest base when needed for
shared objects.  This worked for all the test cases I threw at it
(including running the gcc and glibc test suites through QEMU).  However,
I am not all that familiar with the Linux usermode pieces and would like
some feedback.

Thoughts?
 
Meador Inge (1):
  linux-user: Probe the guest base for shared objects when needed

 linux-user/elfload.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

-- 
1.7.7.6