Messages in this thread | | | From | Ard Biesheuvel <> | Date | Sat, 14 Dec 2019 20:40:57 +0000 | Subject | Re: [PATCH 03/10] efi/libstub: use a helper to iterate over a EFI handle array |
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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)
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