Hi Alexandre,
On Fri, Mar 10, 2023 at 10:45:37AM +0100, Alexandre Ghiti wrote:
> This function allows to split a region in memblock.memory and will be
> useful when setting up the linear mapping with STRICT_KERNEL_RWX: it
> allows to isolate the kernel text/rodata and then avoid to map those
> regions with a PUD/P4D/PGD.
>
> Signed-off-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
> ---
> include/linux/memblock.h | 1 +
> mm/memblock.c | 22 +++++++++++++++++++++-
> 2 files changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index 50ad19662a32..2f7ef97c0da7 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -125,6 +125,7 @@ int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size);
> int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
> int memblock_mark_nomap(phys_addr_t base, phys_addr_t size);
> int memblock_clear_nomap(phys_addr_t base, phys_addr_t size);
> +int memblock_isolate_memory(phys_addr_t base, phys_addr_t size);
>
> void memblock_free_all(void);
> void memblock_free(void *ptr, size_t size);
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 25fd0626a9e7..d8cf1c9eccf0 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -753,7 +753,8 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
> int idx;
> struct memblock_region *rgn;
>
> - *start_rgn = *end_rgn = 0;
> + if (start_rgn && end_rgn)
> + *start_rgn = *end_rgn = 0;
Generally, it's possible that either start_rgn or end_rgn will be a valid
pointer and this should be handled here and below.
My preference, though would be to leave memblock_isolate_range() as is and
have unused start_rgn and end_rgn in memblock_isolate_memory().
>
> if (!size)
> return 0;
> @@ -795,6 +796,9 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
> memblock_get_region_node(rgn),
> rgn->flags);
> } else {
> + if (!end_rgn || !start_rgn)
> + continue;
> +
> /* @rgn is fully contained, record it */
> if (!*end_rgn)
> *start_rgn = idx;
> @@ -805,6 +809,22 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
> return 0;
> }
>
> +/**
> + * memblock_isolate_memory - isolate given range from memblock.memory
I think it'd better to use "... range in memblock.memory"
> + * @base: base of range to isolate
> + * @size: size of range to isolate
> + *
> + * Call memblock_isolate_range on memblock.memory to isolate the given range.
Please elaborate that isolate means that the range does not share regions
with other ranges.
> + *
> + * Return:
> + * 0 on success, -errno on failure.
> + */
> +
> +int __init_memblock memblock_isolate_memory(phys_addr_t base, phys_addr_t size)
> +{
> + return memblock_isolate_range(&memblock.memory, base, size, NULL, NULL);
> +}
> +
> static int __init_memblock memblock_remove_range(struct memblock_type *type,
> phys_addr_t base, phys_addr_t size)
> {
> --
> 2.37.2
>
--
Sincerely yours,
Mike.
