Messages in this thread | | | Date | Tue, 18 Apr 2023 10:31:33 +0100 | Subject | Re: [PATCH v3 34/60] arm64: head: Move early kernel mapping routines into C code | From | Ryan Roberts <> |
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On 07/03/2023 14:04, Ard Biesheuvel wrote: > The asm version of the kernel mapping code works fine for creating a > coarse grained identity map, but for mapping the kernel down to its > exact boundaries with the right attributes, it is not suitable. This is > why we create a preliminary RWX kernel mapping first, and then rebuild > it from scratch later on. > > So let's reimplement this in C, in a way that will make it unnecessary > to create the kernel page tables yet another time in paging_init(). > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > ---
> [...]
> diff --git a/arch/arm64/kernel/pi/map_kernel.c b/arch/arm64/kernel/pi/map_kernel.c > new file mode 100644 > index 0000000000000000..b573c964c7d88d1b > --- /dev/null > +++ b/arch/arm64/kernel/pi/map_kernel.c > @@ -0,0 +1,171 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +// Copyright 2023 Google LLC > +// Author: Ard Biesheuvel <ardb@google.com> > + > +#include <linux/init.h> > +#include <linux/libfdt.h> > +#include <linux/linkage.h> > +#include <linux/types.h> > +#include <linux/sizes.h> > +#include <linux/string.h> > + > +#include <asm/memory.h> > +#include <asm/pgalloc.h> > +#include <asm/pgtable.h> > +#include <asm/tlbflush.h> > + > +#include "pi.h" > + > +extern const u8 __eh_frame_start[], __eh_frame_end[]; > + > +extern void idmap_cpu_replace_ttbr1(void *pgdir); > + > +static void map_segment(pgd_t *pg_dir, u64 *pgd, u64 va_offset, > + void *start, void *end, pgprot_t prot, > + bool may_use_cont, int root_level) > +{ > + map_range(pgd, ((u64)start + va_offset) & ~PAGE_OFFSET, > + ((u64)end + va_offset) & ~PAGE_OFFSET, (u64)start, > + prot, root_level, (pte_t *)pg_dir, may_use_cont, 0);
I don't understand what you are doing with ~PAGE_OFFSET here. Is this intended to be page alignment with PAGE_MASK? I'm guessing not, because you would want to forward align the end address in that case.
> +} > + > +static void unmap_segment(pgd_t *pg_dir, u64 va_offset, void *start, > + void *end, int root_level) > +{ > + map_segment(pg_dir, NULL, va_offset, start, end, __pgprot(0), > + false, root_level); > +} > +
> [...]
> diff --git a/arch/arm64/kernel/pi/map_range.c b/arch/arm64/kernel/pi/map_range.c > new file mode 100644 > index 0000000000000000..61cbd6e82418c033 > --- /dev/null > +++ b/arch/arm64/kernel/pi/map_range.c > @@ -0,0 +1,87 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +// Copyright 2023 Google LLC > +// Author: Ard Biesheuvel <ardb@google.com> > + > +#include <linux/types.h> > +#include <linux/sizes.h> > + > +#include <asm/memory.h> > +#include <asm/pgalloc.h> > +#include <asm/pgtable.h> > + > +#include "pi.h" > + > +/** > + * map_range - Map a contiguous range of physical pages into virtual memory > + * > + * @pte: Address of physical pointer to array of pages to > + * allocate page tables from > + * @start: Virtual address of the start of the range > + * @end: Virtual address of the end of the range (exclusive) > + * @pa: Physical address of the start of the range > + * @level: Translation level for the mapping > + * @tbl: The level @level page table to create the mappings in > + * @may_use_cont: Whether the use of the contiguous attribute is allowed > + * @va_offset: Offset between a physical page and its current mapping > + * in the VA space > + */ > +void __init map_range(u64 *pte, u64 start, u64 end, u64 pa, pgprot_t prot, > + int level, pte_t *tbl, bool may_use_cont, u64 va_offset)
va_offset is always 0 (because the memory at *pte is id-mapped). Can it be dropped? Or perhaps you are using this function later, once the memory is no longer id-mapped?
> +{ > + u64 cmask = (level == 3) ? CONT_PTE_SIZE - 1 : U64_MAX; > + u64 protval = pgprot_val(prot) & ~PTE_TYPE_MASK; > + int lshift = (3 - level) * (PAGE_SHIFT - 3); > + u64 lmask = (PAGE_SIZE << lshift) - 1; > + > + start &= PAGE_MASK; > + pa &= PAGE_MASK; > +
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