On Wed, 29 Jul, at 12:04:18PM, Ard Biesheuvel wrote: > In some cases, e.g., when allocating memory for the arm64 kernel, > we need memory at a certain offset from an aligned boundary. So add > an offset parameter to efi_low_alloc(), and update the existing > callers to pass zero by default. > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > --- > arch/arm64/kernel/efi-stub.c | 2 +- > arch/x86/boot/compressed/eboot.c | 4 ++-- > drivers/firmware/efi/libstub/efi-stub-helper.c | 20 +++++++++++++++----- > include/linux/efi.h | 2 +- > 4 files changed, 19 insertions(+), 9 deletions(-) [...] > @@ -269,10 +269,19 @@ efi_status_t efi_low_alloc(efi_system_table_t *sys_table_arg, > * checks pointers against NULL. Skip the first 8 > * bytes so we start at a nice even number. > */ > - if (start == 0x0) > + if (start + offset == 0x0) > start += 8; > > - start = round_up(start, align); > + /* > + * Check if the offset exceeds the misalignment of this region. > + * In that case, we can round down instead of up, and the > + * resulting start value will be correctly aligned and still > + * point past the start of the region. > + */ > + if (offset >= (start & (align - 1))) > + start = round_down(start, align) + offset; > + else > + start = round_up(start, align) + offset; > if ((start + size) > end) > continue; Aha, now I see what you mean. Thanks for doing this Ard, these are much more polished than what I was expecting. I'm gonna have to NAK this because it's just too much of a special case to support directly in efi_low_alloc(), which I think was the exact point that you made originally, and which I was too tired/dumb to understand. Sorry. In particular, the fact that you can use the offset argument to violate the requested alignment seems like it would trip up most users. -- Matt Fleming, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
