Re: git: 70c067062217 - main - dtrace/arm64: Simplify dtrace_getarg() slightly

On Wed, Jan 29, 2025 at 03:06:20AM +0000, Jessica Clarke wrote:
> On 29 Jan 2025, at 02:21, Mark Johnston <markj@FreeBSD.org> wrote:
> > 
> > The branch main has been updated by markj:
> > 
> > URL: https://cgit.FreeBSD.org/src/commit/?id=70c067062217a5295ed321427b91cfd857c18b77
> > 
> > commit 70c067062217a5295ed321427b91cfd857c18b77
> > Author:     Mark Johnston <markj@FreeBSD.org>
> > AuthorDate: 2025-01-29 01:05:03 +0000
> > Commit:     Mark Johnston <markj@FreeBSD.org>
> > CommitDate: 2025-01-29 01:05:03 +0000
> > 
> >    dtrace/arm64: Simplify dtrace_getarg() slightly
> > 
> >    The use of memcpy here is redundant, and also incorrect since memcpy()
> >    might be instrumented by fbt or kinst.  dtrace_bcopy() exists, but we
> >    don't need it.
> > 
> >    MFC after:      2 weeks
> >    Sponsored by:   Innovate UK
> > ---
> > sys/cddl/dev/dtrace/aarch64/dtrace_isa.c | 4 +---
> > 1 file changed, 1 insertion(+), 3 deletions(-)
> > 
> > diff --git a/sys/cddl/dev/dtrace/aarch64/dtrace_isa.c b/sys/cddl/dev/dtrace/aarch64/dtrace_isa.c
> > index ff0e068006bd..3e36004c6f0d 100644
> > --- a/sys/cddl/dev/dtrace/aarch64/dtrace_isa.c
> > +++ b/sys/cddl/dev/dtrace/aarch64/dtrace_isa.c
> > @@ -256,7 +256,6 @@ dtrace_getarg(int arg, int aframes __unused)
> > return (tf->tf_x[arg]);
> > } else {
> > uintptr_t p;
> > - uint64_t val;
> > 
> > p = (tf->tf_sp + (arg - 8) * sizeof(uint64_t));
> > if ((p & 7) != 0) {
> > @@ -269,8 +268,7 @@ dtrace_getarg(int arg, int aframes __unused)
> > cpu_core[curcpu].cpuc_dtrace_illval = p;
> > return (0);
> > }
> > - memcpy(&val, (void *)p, sizeof(uint64_t));
> > - return (val);
> > + return (p);
> 
> Doesn’t this change from dereferencing p to returning it? Surely p
> should be a uint64_t * that is dereferenced?

Yes, thank you, that was a stupid mistake on my part.  I reverted it for
now and will fix the problem properly tomorrow.