Re: [Qemu-devel] [PATCH 1/2] target/nios2: Fix bug in semihosted exit handling

[Sandra Loosemore <sandra@codesourcery.com>]

On 8/21/19 8:41 AM, Laurent Vivier wrote:
> Le 21/08/2019 à 16:21, Sandra Loosemore a écrit :
>> This patch fixes a bug that caused semihosted exit to always return
>> status 0; it was incorrectly using the value of register R_ARG0 (which
>> contains the HOSTED_EXIT request number) instead of register R_ARG1.
>>
>> Signed-off-by: Sandra Loosemore <sandra@codesourcery.com>
>> ---
>>   target/nios2/nios2-semi.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/target/nios2/nios2-semi.c b/target/nios2/nios2-semi.c
>> index d7a80dd..06c0861 100644
>> --- a/target/nios2/nios2-semi.c
>> +++ b/target/nios2/nios2-semi.c
>> @@ -215,8 +215,8 @@ void do_nios2_semihosting(CPUNios2State *env)
>>       args = env->regs[R_ARG1];
>>       switch (nr) {
>>       case HOSTED_EXIT:
>> -        gdb_exit(env, env->regs[R_ARG0]);
>> -        exit(env->regs[R_ARG0]);
>> +        gdb_exit(env, env->regs[R_ARG1]);
>> +        exit(env->regs[R_ARG1]);
> 
> It's weird: in line 215,  env->regs[R_ARG1] is args.
> 
> Are you sure it's not something like:
> 
>          GET_ARG(0)
>          gdb_exit(env, arg0);
>          exit(arg0);
> 
> same for m68k.
> 
> Did you check the kernel code?

It's not the kernel that's involved here, it's libgloss.  And yes, the 
HOSTED_EXIT case takes an immediate argument in the register rather than 
a pointer to an argument block.

Here's the documentation for nios2 semihosting.

https://www.sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;a=blob;f=libgloss/nios2/nios2-semi.txt;h=ded3a093c03dbae84cb95b4cd45bc3e0d751eda2;hb=HEAD

And m68k:

https://www.sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;a=blob;f=libgloss/m68k/m68k-semi.txt;h=50520c15292aa7edf7eef28e09fd9202ce75b153;hb=HEAD

Again, a lot of cutting and pasting involved here.  ;-)

-Sandra