On Wed, 16 May 2018, Kirill A. Shutemov wrote: > cleanup_trampoline() relocates the top-level page table out of > trampoline memory. We use 'top_pgtable' as our new top-level page table. > > But if the 'top_pgtable' would be referenced from C in a usual way, > the address of the table will be calculated relative to RIP. > After kernel gets relocated, the address will be in the middle of > decompression buffer and the page table may get overwritten. > This leads to a crash. > > We calculate the address of other page tables relative to the relocation > address. It makes them safe. We should do the same for 'top_pgtable'. > > Calculate the address of 'top_pgtable' in assembly and pass down to > cleanup_trampoline(). > > Move the page table to .pgtable section where the rest of page tables > are. The section is @nobits so we save 4k in kernel image. > > Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com> > Fixes: e9d0e6330eb8 ("x86/boot/compressed/64: Prepare new top-level page > table for trampoline")
Reviewed-by: Thomas Gleixner <t...@linutronix.de>