[Qemu-devel] [patch] Fix arm self-modifying code

[Qemu-devel] [patch] Fix arm self-modifying code

[Paul Brook]

The patch adds the signal handling necessary to make arm self-modifying code 
work. You'll notice it looks remarkably similar to the sparc routine :)

This should fix the "uncaught target signal 11" crash people have been seeing.

Paul

Index: cpu-exec.c
===================================================================
RCS file: /cvsroot/qemu/qemu/cpu-exec.c,v
retrieving revision 1.38
diff -u -p -r1.38 cpu-exec.c
--- cpu-exec.c	14 Jul 2004 17:20:55 -0000	1.38
+++ cpu-exec.c	2 Aug 2004 00:24:46 -0000
@@ -718,6 +719,10 @@ static inline int handle_cpu_signal(unsi
                                     int is_write, sigset_t *old_set,
                                     void *puc)
 {
+    /* XXX: locking issue */
+    if (is_write && page_unprotect(address, pc, puc)) {
+        return 1;
+    }
     /* XXX: do more */
     return 0;
 }

Re: [Qemu-devel] [patch] Fix arm self-modifying code

[Lennert Buytenhek]

On Mon, Aug 02, 2004 at 01:29:58AM +0100, Paul Brook wrote:

> The patch adds the signal handling necessary to make arm self-modifying
> code work. You'll notice it looks remarkably similar to the sparc routine :)
> 
> This should fix the "uncaught target signal 11" crash people have
> been seeing.

OK.. I made two 'hello world' binaries with these toolchains:
- armv5te-redhat-linux, gcc 3.3.3, glibc 2.3.2
- arm-unknown-linux-gnu, gcc 2.95.3, glibc 2.1.3

They both fail with 'uncaught target signal 11' when run under latest
qemu plus your patch.

The arm-unknown-linux-gnu binary shows something really strange:

% ./qemu-arm ./hi-gcc-2.95.3-glibc-2.1.3
qemu: uncaught target signal 11 (Segmentation fault) - exiting
% setarch i686 ./qemu-arm ./hi-gcc-2.95.3-glibc-2.1.3
hi!
% 

So, then I backed out your patch from qemu, running a vanilla qemu
from CVS.  Same result -- crash when run directly, and works when
run under setarch i686.

(I'm on Fedora Core 2.)

So then I grab strace, and see these differences (old vs. new) during
startup:

-old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xf7030000
+old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x55001000

and:

-old_mmap(NULL, 528384, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xf6faf000
-mprotect(0xf702f000, 4096, PROT_NONE)   = 0
-munmap(0xf7030000, 4096)                = 0
+old_mmap(NULL, 528384, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x55002000
+mprotect(0x55082000, 4096, PROT_NONE)   = 0
+munmap(0x55001000, 4096)                = 0

Perhaps qemu-arm can't deal with 4G-split kernels?

(The setarch i686 trick doesn't work for the armv5te-redhat-linux
binary, though.)


--L

Re: [Qemu-devel] [patch] Fix arm self-modifying code

[Lennert Buytenhek]

On Mon, Aug 02, 2004 at 02:21:23PM +0200, Lennert Buytenhek wrote:

> OK.. I made two 'hello world' binaries with these toolchains:
> - armv5te-redhat-linux, gcc 3.3.3, glibc 2.3.2
> - arm-unknown-linux-gnu, gcc 2.95.3, glibc 2.1.3

Some more data points.

I built seven different toolchains:
- arm-unknown-linux-gnu, gcc 2.95.3, glibc 2.1.3
- armv4e-redhat-linux, gcc 3.3.3, glibc 2.3.2
- armv4eb-redhat-linux, gcc 3.3.3, glibc 2.3.2
- armv5e-redhat-linux, gcc 3.3.3, glibc 2.3.2
- armv5eb-redhat-linux, gcc 3.3.3, glibc 2.3.2
- armv5te-redhat-linux, gcc 3.3.3, glibc 2.3.2
- armv5teb-redhat-linux, gcc 3.3.3, glibc 2.3.2

Results without setarch i686, latest qemu CVS without extra patches:

arm-unknown-linux-gnu           sig11
armv4e-redhat-linux             sig11
armv4eb-redhat-linux            Error loading ./hi-armv4eb-redhat-linux
armv5e-redhat-linux             sig11
armv5eb-redhat-linux            Error loading ./hi-armv5eb-redhat-linux
armv5te-redhat-linux            sig11
armv5teb-redhat-linux           Error loading ./hi-armv5teb-redhat-linux

Results with setarch i686, latest qemu CVS without extra patches:

arm-unknown-linux-gnu           hi!
armv4e-redhat-linux             hi!
armv4eb-redhat-linux            Error loading ./hi-armv4eb-redhat-linux
armv5e-redhat-linux             sig11
armv5eb-redhat-linux            Error loading ./hi-armv5eb-redhat-linux
armv5te-redhat-linux            sig11
armv5teb-redhat-linux           Error loading ./hi-armv5teb-redhat-linux

Results with setarch i686, latest qemu CVS plus your patch.qemu_5e:

arm-unknown-linux-gnu		hi!
armv4e-redhat-linux		hi!
armv4eb-redhat-linux		Error loading ./hi-armv4eb-redhat-linux
armv5e-redhat-linux		qemu: uncaught target signal 4 (Illegal instruction) - exiting
armv5eb-redhat-linux		Error loading ./hi-armv5eb-redhat-linux
armv5te-redhat-linux		qemu: uncaught target signal 4 (Illegal instruction) - exiting
armv5teb-redhat-linux		Error loading ./hi-armv5teb-redhat-linux
 
Results with setarch i686, latest qemu CVS plus your patch.qemu_5e
plus your patch_qemu.rrx:

arm-unknown-linux-gnu		hi!
armv4e-redhat-linux		hi!
armv4eb-redhat-linux		Error loading ./hi-armv4eb-redhat-linux
armv5e-redhat-linux		qemu: uncaught target signal 4 (Illegal instruction) - exiting
armv5eb-redhat-linux		Error loading ./hi-armv5eb-redhat-linux
armv5te-redhat-linux		qemu: uncaught target signal 4 (Illegal instruction) - exiting
armv5teb-redhat-linux		Error loading ./hi-armv5teb-redhat-linux

Results with setarch i686, latest qemu CVS plus your patch.qemu_5e
plus your patch_qemu.rrx plus your self-modify patch:

arm-unknown-linux-gnu		hi!
armv4e-redhat-linux		hi!
armv4eb-redhat-linux		Error loading ./hi-armv4eb-redhat-linux
armv5e-redhat-linux		qemu: uncaught target signal 4 (Illegal instruction) - exiting
armv5eb-redhat-linux		Error loading ./hi-armv5eb-redhat-linux
armv5te-redhat-linux		qemu: uncaught target signal 4 (Illegal instruction) - exiting
armv5teb-redhat-linux		Error loading ./hi-armv5teb-redhat-linux


--L

Re: [Qemu-devel] [patch] Fix arm self-modifying code

[Hetz Ben Hamo]

> % ./qemu-arm ./hi-gcc-2.95.3-glibc-2.1.3
> qemu: uncaught target signal 11 (Segmentation fault) - exiting
> % setarch i686 ./qemu-arm ./hi-gcc-2.95.3-glibc-2.1.3
> hi!
> %

QEMU with FC2 does create this segfault even with qemu-i386 and I use the 
LD_ASSUME_KERNEL=2.2.5 trick to override this problem..

Could you retry with the same trick please?

Thanks,
Hetz

Re: [Qemu-devel] [patch] Fix arm self-modifying code

[Lennert Buytenhek]

On Mon, Aug 02, 2004 at 03:39:07PM +0300, Hetz Ben Hamo wrote:

> > % ./qemu-arm ./hi-gcc-2.95.3-glibc-2.1.3
> > qemu: uncaught target signal 11 (Segmentation fault) - exiting
> > % setarch i686 ./qemu-arm ./hi-gcc-2.95.3-glibc-2.1.3
> > hi!
> > %
> 
> QEMU with FC2 does create this segfault even with qemu-i386 and I
> use the LD_ASSUME_KERNEL=2.2.5 trick to override this problem..
> 
> Could you retry with the same trick please?

That doesn't seem to make a difference:

% ./qemu-arm ./hi-gcc-2.95.3-glibc-2.1.3
qemu: uncaught target signal 11 (Segmentation fault) - exiting
% setarch i686 ./qemu-arm ./hi-gcc-2.95.3-glibc-2.1.3
hi!
% LD_ASSUME_KERNEL=2.2.5 ./qemu-arm ./hi-gcc-2.95.3-glibc-2.1.3
qemu: uncaught target signal 11 (Segmentation fault) - exiting
% export LD_ASSUME_KERNEL=2.2.5
% ./qemu-arm ./hi-gcc-2.95.3-glibc-2.1.3
qemu: uncaught target signal 11 (Segmentation fault) - exiting
%


--L

[Qemu-devel] Re: [patch] Fix arm self-modifying code

[Ronald]

Le Mon, 02 Aug 2004 14:21:23 +0200, Lennert Buytenhek a écrit :

> On Mon, Aug 02, 2004 at 01:29:58AM +0100, Paul Brook wrote:
> 
>> The patch adds the signal handling necessary to make arm self-modifying
>> code work. You'll notice it looks remarkably similar to the sparc
>> routine :)
>> 
>> This should fix the "uncaught target signal 11" crash people have been
>> seeing.
> 
> OK.. I made two 'hello world' binaries with these toolchains: -
> armv5te-redhat-linux, gcc 3.3.3, glibc 2.3.2 - arm-unknown-linux-gnu, gcc
> 2.95.3, glibc 2.1.3
> 
> They both fail with 'uncaught target signal 11' when run under latest qemu
> plus your patch.
> 

Don't know if this can help but when playing with qemu-ppc I've
experienced problem like this.
glibc-2.3.2 was build with --enable-kernel=2.4.0, setting this same
option to 2.2.0 corrected the whole thing.