From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Ard Biesheuvel <ardb@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-efi <linux-efi@vger.kernel.org>,
Hans de Goede <hdegoede@redhat.com>,
Matthew Garrett <matthewgarrett@google.com>,
Ingo Molnar <mingo@kernel.org>, Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 03/10] efi/libstub: use a helper to iterate over a EFI handle array
Date: Sat, 14 Dec 2019 21:04:10 +0000 [thread overview]
Message-ID: <CAKv+Gu9kEySOrKM0Q01a-ZFbSTZz51TcfmnWbSq=LWqKw=8cNw@mail.gmail.com> (raw)
In-Reply-To: <CAKv+Gu-XAvYf8G+7Oi-XVM+DvR89_zkmETmou-2ftgC41tnvMw@mail.gmail.com>
On Sat, 14 Dec 2019 at 21:40, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
>
> On Sat, 14 Dec 2019 at 21:33, Arvind Sankar <nivedita@alum.mit.edu> wrote:
> >
> > On Sat, Dec 14, 2019 at 06:57:28PM +0100, Ard Biesheuvel wrote:
> > > Iterating over a EFI handle array is a bit finicky, since we have
> > > to take mixed mode into account, where handles are only 32-bit
> > > while the native efi_handle_t type is 64-bit.
> > >
> > > So introduce a helper, and replace the various occurrences of
> > > this pattern.
> > >
> > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > > ---
> > >
> > > +#define for_each_efi_handle(handle, array, size, i) \
> > > + for (i = 1, handle = efi_is_64bit() \
> > > + ? (efi_handle_t)(unsigned long)((u64 *)(array))[0] \
> > > + : (efi_handle_t)(unsigned long)((u32 *)(array))[0]; \
> > > + i++ <= (size) / (efi_is_64bit() ? sizeof(efi_handle_t) \
> > > + : sizeof(u32)); \
> > > + handle = efi_is_64bit() \
> > > + ? (efi_handle_t)(unsigned long)((u64 *)(array))[i] \
> > > + : (efi_handle_t)(unsigned long)((u32 *)(array))[i])
> > > +
> > > /*
> > > * The UEFI spec and EDK2 reference implementation both define EFI_GUID as
> > > * struct { u32 a; u16; b; u16 c; u8 d[8]; }; and so the implied alignment
> > > --
> > > 2.17.1
> > >
> >
> > This would access one past the array, no? Eg if the array has one
> > handle, i is incremented to 2 the first time the condition is checked,
> > then the loop increment will access array[2] before the condition is
> > checked again. There seem to be at least a couple of other for_each
> > macros that might have similar issues.
> >
>
> Indeed.
>
> > How about the below instead?
> >
> > #define for_each_efi_handle(handle, array, size, i) \
> > for (i = 0; \
> > (i < (size) / (efi_is_64bit() ? sizeof(efi_handle_t) \
> > : sizeof(u32))) && \
> > ((handle = efi_is_64bit() \
> > ? ((efi_handle_t *)(array))[i] \
> > : (efi_handle_t)(unsigned long)((u32 *)(array))[i]), 1);\
> > i++)
> >
>
> Yeah, that looks correct to me, but perhaps we can come up with
> something slightly more readable? :-)
> (Not saying my code was better in that respect)
How about
#define efi_get_handle_at(array, idx) \
(efi_is_64bit() ? (efi_handle_t)(unsigned long)((u64 *)(array))[idx] \
: (efi_handle_t)(unsigned long)((u32 *)(array))[i])
#define efi_get_handle_num(size) \
((size) / (efi_is_64bit() ? sizeof(u64) : sizeof(u32)))
#define for_each_efi_handle(handle, array, size, i) \
for (i = 0; \
i < efi_get_handle_num(size) && \
((handle = efi_get_handle_at((array), i)) || true); \
i++)
next prev parent reply other threads:[~2019-12-14 21:04 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-14 17:57 [PATCH 00/10] efi/x86: confine type unsafe casting to mixed mode Ard Biesheuvel
2019-12-14 17:57 ` [PATCH 01/10] efi/libstub: remove unused __efi_call_early() macro Ard Biesheuvel
2019-12-14 17:57 ` [PATCH 02/10] efi/x86: rename efi_is_native() to efi_is_mixed() Ard Biesheuvel
2019-12-14 17:57 ` [PATCH 03/10] efi/libstub: use a helper to iterate over a EFI handle array Ard Biesheuvel
2019-12-14 20:32 ` Arvind Sankar
2019-12-14 20:40 ` Ard Biesheuvel
2019-12-14 21:04 ` Ard Biesheuvel [this message]
2019-12-14 21:11 ` Arvind Sankar
2019-12-14 21:07 ` Arvind Sankar
2019-12-14 17:57 ` [PATCH 04/10] efi/libstub: add missing apple_properties_protocol_t definition Ard Biesheuvel
2019-12-14 17:57 ` [PATCH 05/10] efi/libstub: distinguish between native/mixed not 32/64 bit Ard Biesheuvel
2019-12-14 19:46 ` Arvind Sankar
2019-12-14 19:49 ` Arvind Sankar
2019-12-14 19:54 ` Ard Biesheuvel
2019-12-14 20:13 ` Arvind Sankar
2019-12-14 20:27 ` Ard Biesheuvel
2019-12-14 21:17 ` Arvind Sankar
2019-12-14 21:30 ` Ard Biesheuvel
2019-12-14 22:14 ` Arvind Sankar
2019-12-14 22:14 ` Ard Biesheuvel
2019-12-14 23:02 ` Arvind Sankar
2019-12-14 17:57 ` [PATCH 06/10] efi/libstub/x86: use mixed mode helpers to populate efi_config Ard Biesheuvel
2019-12-14 17:57 ` [PATCH 07/10] efi/libstub: drop explicit 64-bit protocol definitions Ard Biesheuvel
2019-12-14 17:57 ` [PATCH 08/10] efi/libstub: use stricter typing for firmware function pointers Ard Biesheuvel
2019-12-14 17:57 ` [PATCH 09/10] efi/libstub: annotate firmware routines as __efiapi Ard Biesheuvel
2019-12-17 15:01 ` Brian Gerst
2019-12-14 17:57 ` [PATCH 10/10] efi/libstub/x86: avoid thunking for native firmware calls Ard Biesheuvel
2019-12-15 19:30 ` Arvind Sankar
2019-12-17 8:32 ` Ard Biesheuvel
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