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Date: Thu, 27 Feb 2020 09:12:29 +0100 From: Ingo Molnar <mingo@...nel.org> To: Arvind Sankar <nivedita@...m.mit.edu> Cc: Ard Biesheuvel <ardb@...nel.org>, linux-efi@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org, linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de> Subject: Re: [PATCH v2 1/1] x86/boot/compressed: Fix reloading of GDTR post-relocation * Arvind Sankar <nivedita@...m.mit.edu> wrote: > Commit ef5a7b5eb13e ("efi/x86: Remove GDT setup from efi_main") > introduced GDT setup into the 32-bit kernel's startup_32, and reloads > the GDTR after relocating the kernel for paranoia's sake. > > Commit 32d009137a56 ("x86/boot: Reload GDTR after copying to the end of > the buffer") introduced a similar GDTR reload in the 64-bit kernel. > > The GDTR is adjusted by init_size - _end, however this may not be the > correct offset to apply if the kernel was loaded at a misaligned address > or below LOAD_PHYSICAL_ADDR, as in that case the decompression buffer > has an additional offset from the original load address. > > This should never happen for a conformant bootloader, but we're being > paranoid anyway, so just store the new GDT address in there instead of > adding any offsets, which is simpler as well. > > Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu> > Fixes: ef5a7b5eb13e ("efi/x86: Remove GDT setup from efi_main") > Fixes: 32d009137a56 ("x86/boot: Reload GDTR after copying to the end of the buffer") Have you or anyone else observed this condition practice, or have a suspicion that this could happen - or is this a mostly theoretical concern? Thanks, Ingo
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