[Qemu-devel] Alpha linux-user support

[Qemu-devel] Alpha linux-user support

[Vince Weaver]

Hello

I forget who is working on the Alpha architecture support.

I've managed to scrounge together a working Alpha machine from that parts 
of 3 broken machines, and it is running debian and has been stable so far.

I tried compiling some simple binaries (on the Alpha) and running them 
with qemu alpha-linux-user (on an x86_64 machine) with no luck.  The gdb 
interface seems to be broken as well, making it hard to track down what 
the issues are.

Is there anything I can do to help out the architecture, or should I wait 
until some more TCG work has been done?

Vince

Re: [Qemu-devel] Alpha linux-user support

[Laurent Desnogues]

On Wed, Nov 5, 2008 at 7:01 PM, Vince Weaver <vince@csl.cornell.edu> wrote:
>
> I tried compiling some simple binaries (on the Alpha) and running them with
> qemu alpha-linux-user (on an x86_64 machine) with no luck.

How is it failing?  All I was able to run was some simple hand written
assembly programs.  For C programs I got:

   - Illegal instruction, no matter what CPU setting I am giving to gcc;
     to get around this try to add ctx->amask |= AMASK_BWX to
     cpu_alpha_init

   - once the amask is set I get "kernel too old".

Basically my Alpha cross toolchain does not look right or there's a
bug in the translator.


Laurent

Re: [Qemu-devel] Alpha linux-user support

[Vince Weaver]

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Hello

First, I found a bug in the alpha emulation of the "ret" instruction, see 
a separate e-mail to the list.

> How is it failing?  All I was able to run was some simple hand written
> assembly programs.  For C programs I got:

For C programs I get infinite "Unsupported Syscall 394" errors.
This is the futex() syscall.  Maybe my toolchain (gcc 4.2.4) is trying to 
make NPTL binaries.   Hmmm.

I've attached my simple assembly program I am working with.  It should 
print hello world, but doesn't because the address passed to the write 
syscall is wrong.  I can't easily track down where things are going wrong 
though because the gdbstub doesn't work for alpha.  Does anyone know the 
status of that?

Vince

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#  as -o hello.o hello.s ; ld -o hello hello.o

.equ SYSCALL_EXIT,1	
.equ SYSCALL_WRITE,4
		
.equ STDIN,0
.equ STDOUT,1
.equ STDERR,2	
	
	.globl _start
_start:
	
	br      $27,0           # fake branch, to grab the location
	                        # of our entry point
	ldgp    $gp,0($27)      # load the GP proper for our entry point
				# this does automagic stuff...
				# gp is used for 64-bit jumps and constants
				# so if you use "la" and the like it will
				# load from gp for you.  
				

	lda	$17,hello_string	
	br	$26,write_stdout

	#================================
	# Exit
	#================================
exit:		
        clr	$16			# 0 exit value
        mov	SYSCALL_EXIT,$0		# put the exit syscall number in v0
        callsys				# and exit

	
	#================================
	# WRITE_STDOUT
	#================================
	# $17 has string
	# $1 is trashed
	
write_stdout:	
	ldil	$0,SYSCALL_WRITE	# Write syscall in $0
	ldil	$16,STDOUT		# 1 in $16 (stdout)
	clr	$18			# 0 (count) in $18
	
str_loop1:
	addq	$17,$18,$1		# offset in $1
	ldbu    $1,0($1)		# load byte
	addq	$18,1,$18		# increment pointer
	bne	$1,str_loop1		# if not nul, repeat
	
	subq	$18,1,$18		# correct count
	callsys				# Make syscall
	
	ret	$26			# return
			
	
#===========================================================================
.data
#===========================================================================

hello_string:		.ascii  "Hello World\n\0"

[-- Attachment #3: Type: APPLICATION/octet-stream, Size: 1304 bytes --]

Re: [Qemu-devel] Alpha linux-user support

[Laurent Desnogues]

On Wed, Nov 5, 2008 at 11:03 PM, Vince Weaver <vince@csl.cornell.edu> wrote:
>
> First, I found a bug in the alpha emulation of the "ret" instruction, see a
> separate e-mail to the list.
[...]
> I've attached my simple assembly program I am working with.  It should print
> hello world, but doesn't because the address passed to the write syscall is
> wrong.  I can't easily track down where things are going wrong though
> because the gdbstub doesn't work for alpha.  Does anyone know the status of
> that?

After applying your ret patch, it works for me on an x86_64 platform.
However the first callsys instruction fails on ia32 and returns EFAULT
(bad address).

In fact what happens looks like a problem of 64 -> 32 bit mapping:
page_check_range fails (called by access_ok which is called by
lock_user in do_syscall).  It doesn't like the 0x120010100 address.


Laurent

Re: [Qemu-devel] Alpha linux-user support

[Tristan Gingold]

Vince,

I did some work on the alpha side.
There is at least a compilable example in test/ dir.
Using a slightly older version of glibc and -static, I was also able  
to run some native programs
(ie an hello-world using printf is ok).

Use a 64 bits host.

Tristan.

Re: [Qemu-devel] Alpha linux-user support

[Aurelien Jarno]

On Wed, Nov 05, 2008 at 01:01:22PM -0500, Vince Weaver wrote:
> Hello
>
> I forget who is working on the Alpha architecture support.

There is no maintainer, only a few people sending patches

> I've managed to scrounge together a working Alpha machine from that parts 
> of 3 broken machines, and it is running debian and has been stable so 
> far.
>
> I tried compiling some simple binaries (on the Alpha) and running them  
> with qemu alpha-linux-user (on an x86_64 machine) with no luck.  The gdb  
> interface seems to be broken as well, making it hard to track down what  
> the issues are.

I am personally able to run statically compiled C program if they are
built with a non-NPTL toolchain.

> Is there anything I can do to help out the architecture, or should I wait 
> until some more TCG work has been done?
>

Patches are welcome.

Aurelien

-- 
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