Re: [PATCH] semihosting/uaccess.c: Replaced a malloc call with g_malloc

["Daniel P. Berrangé" <berrange@redhat.com>]

On Mon, Feb 26, 2024 at 10:48:14AM +0100, Philippe Mathieu-Daudé wrote:
> Hi,
> 
> On 26/2/24 10:06, dinglimin wrote:
> > Signed-off-by: dinglimin <dinglimin@cmss.chinamobile.com>
> > ---
> >   semihosting/uaccess.c | 6 +++---
> >   1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/semihosting/uaccess.c b/semihosting/uaccess.c
> > index dc587d73bc..7788ead9b2 100644
> > --- a/semihosting/uaccess.c
> > +++ b/semihosting/uaccess.c
> > @@ -14,10 +14,10 @@
> >   void *uaccess_lock_user(CPUArchState *env, target_ulong addr,
> >                           target_ulong len, bool copy)
> >   {
> > -    void *p = malloc(len);
> > +    void *p = g_try_malloc(len);
> >       if (p && copy) {
> >           if (cpu_memory_rw_debug(env_cpu(env), addr, p, len, 0)) {
> > -            free(p);
> > +            g_free(p);
> >               p = NULL;
> >           }
> >       }
> 
> This seems dangerous, now all users of uaccess_lock_user() must
> use g_free(), in particular lock_user_string() which is used more
> than a hundred of times:

This is not true for many years now.

GLib is hardcoded to always use the system allocator, so g_malloc
can be freely mixed with free, and vica-verca.

Using 'g_free' is stylistically preferred, but not functionally
required.

> 
> $ git grep -w lock_user_string | wc -l
>      116
> 
> > @@ -87,5 +87,5 @@ void uaccess_unlock_user(CPUArchState *env, void *p,
> >       if (len) {
> >           cpu_memory_rw_debug(env_cpu(env), addr, p, len, 1);
> >       }
> > -    free(p);
> > +    g_free(p);
> >   }
> 
> 

With regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|