From: Michal Hocko <mhocko@kernel.org>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] elf: print userspace address with %lx
Date: Sat, 16 Mar 2019 09:28:20 +0100 [thread overview]
Message-ID: <20190316082820.GG15672@dhcp22.suse.cz> (raw)
In-Reply-To: <20190315160656.GB2135@avx2>
On Fri 15-03-19 19:06:56, Alexey Dobriyan wrote:
> On Fri, Mar 15, 2019 at 07:53:27AM +0100, Michal Hocko wrote:
> > On Thu 14-03-19 23:45:48, Alexey Dobriyan wrote:
> > > Use %lx, save a cast.
> > >
> > > "addr" is userspace address so using (and mangling) pointer was never
> > > necessary.
> >
> > There shouldn't be any mangling AFAIU. Documentation for pointer()
> > says
> >
> > * - 'x' For printing the address. Equivalent to "%lx".
>
> The implication of using %p/%px is that the address is kernel pointer
> which should or should not be mangled.
And px is not mangled AFAICS.
> But "map_addr" is not a kernel pointer.
Which should be irrelevant. It is a pointer and my understanding is that
%p$FOO should be used preferably for any pointers.
> And it saves a cast.
Is this really such an improvement? Why?
> > > --- a/fs/binfmt_elf.c
> > > +++ b/fs/binfmt_elf.c
> > > @@ -376,8 +376,8 @@ static unsigned long elf_map(struct file *filep, unsigned long addr,
> > > map_addr = vm_mmap(filep, addr, size, prot, type, off);
> > >
> > > if ((type & MAP_FIXED_NOREPLACE) && map_addr == -EEXIST)
> > > - pr_info("%d (%s): Uhuuh, elf segment at %px requested but the memory is mapped already\n",
> > > - task_pid_nr(current), current->comm, (void *)addr);
> > > + pr_info("%d (%s): Uhuuh, elf segment at %lx requested but the memory is mapped already\n",
> > > + task_pid_nr(current), current->comm, addr);
--
Michal Hocko
SUSE Labs
prev parent reply other threads:[~2019-03-16 8:28 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-14 20:45 [PATCH 2/2] elf: print userspace address with %lx Alexey Dobriyan
2019-03-15 6:53 ` Michal Hocko
2019-03-15 16:06 ` Alexey Dobriyan
2019-03-16 8:28 ` Michal Hocko [this message]
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