Hi Nikos,
On 11/10/20 2:42 PM, Nikos Nikoleris wrote:
> From: Luc Maranget <Luc.Maranget@xxxxxxxx>
>
> Add the mmu_get_pte() function that allows a test to get a pointer to
> the PTE for a valid virtual address. Return NULL if the MMU is off.
>
> Signed-off-by: Nikos Nikoleris <nikos.nikoleris@xxxxxxx>
> Signed-off-by: Luc Maranget <Luc.Maranget@xxxxxxxx>
> Co-Developed-by: Nikos Nikoleris <nikos.nikoleris@xxxxxxx>
> Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
> Reviewed-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
> ---
> lib/arm/asm/mmu-api.h | 1 +
> lib/arm/mmu.c | 32 +++++++++++++++++++++-----------
> 2 files changed, 22 insertions(+), 11 deletions(-)
>
> diff --git a/lib/arm/asm/mmu-api.h b/lib/arm/asm/mmu-api.h
> index 2bbe1fa..3d04d03 100644
> --- a/lib/arm/asm/mmu-api.h
> +++ b/lib/arm/asm/mmu-api.h
> @@ -22,5 +22,6 @@ extern void mmu_set_range_sect(pgd_t *pgtable, uintptr_t virt_offset,
> extern void mmu_set_range_ptes(pgd_t *pgtable, uintptr_t virt_offset,
> phys_addr_t phys_start, phys_addr_t phys_end,
> pgprot_t prot);
> +extern pteval_t *mmu_get_pte(pgd_t *pgtable, uintptr_t vaddr);
> extern void mmu_clear_user(pgd_t *pgtable, unsigned long vaddr);
> #endif
> diff --git a/lib/arm/mmu.c b/lib/arm/mmu.c
> index d937f20..e58da10 100644
> --- a/lib/arm/mmu.c
> +++ b/lib/arm/mmu.c
> @@ -212,15 +212,21 @@ unsigned long __phys_to_virt(phys_addr_t addr)
> return addr;
> }
>
> -void mmu_clear_user(pgd_t *pgtable, unsigned long vaddr)
> +pteval_t *mmu_get_pte(pgd_t *pgtable, uintptr_t vaddr)
> {
> + /*
> + * NOTE: The Arm architecture requires the use of a
> + * break-before-make sequence before making any changes to
> + * PTEs (Arm ARM D5-2669 for AArch64, B3-1378 for AArch32).
> + */
That should go above the function definition. Also, break-before-make is not
required for every PTE change, only when certain conditions are met.
Thanks,
Alex
