On 05/01/2026 12:35, Harry Ramsey wrote:
> From: Penny Zheng <[email protected]>
>
> Implement the function `free_init_memory` for MPU systems. In order to
> support this, the function `modify_xen_mappings` is implemented.
>
> On MPU systems, we map the init text and init data sections using
> separate MPU memory regions. Therefore these are removed separately in
> `free_init_memory`.
>
> Additionally remove warning messages from `is_mm_attr_match` as some
> permissions can now be updated by `xen_mpumap_update_entry`.
>
> Signed-off-by: Penny Zheng <[email protected]>
> Signed-off-by: Wei Chen <[email protected]>
> Signed-off-by: Luca Fancellu <[email protected]>
> Signed-off-by: Hari Limaye <[email protected]>
> Signed-off-by: Harry Ramsey <[email protected]>
> ---
> v2:
> - Refactor `is_mm_attr_match` to return logical values regarding the
> permission mismatch.
> - Improve code documentation.
> ---
> xen/arch/arm/include/asm/mpu/mm.h | 6 +-
> xen/arch/arm/include/asm/setup.h | 2 +
> xen/arch/arm/mpu/mm.c | 113 +++++++++++++++++++++++-------
> 3 files changed, 95 insertions(+), 26 deletions(-)
>
> diff --git a/xen/arch/arm/include/asm/mpu/mm.h
> b/xen/arch/arm/include/asm/mpu/mm.h
> index 1b5ffa5b64..f0941de295 100644
> --- a/xen/arch/arm/include/asm/mpu/mm.h
> +++ b/xen/arch/arm/include/asm/mpu/mm.h
> @@ -15,7 +15,11 @@
> #define MPUMAP_REGION_FOUND 1
> #define MPUMAP_REGION_INCLUSIVE 2
>
> -#define INVALID_REGION_IDX 0xFFU
> +#define MPU_ATTR_RO_MISMATCH -1
> +#define MPU_ATTR_XN_MISMATCH -2
> +#define MPU_ATTR_AI_MISMATCH -3
You don't seem to use these outside of mm.c, so I would suggest to move them
there.
> +
> +#define INVALID_REGION_IDX 0xFFU
>
> extern struct page_info *frame_table;
>
> diff --git a/xen/arch/arm/include/asm/setup.h
> b/xen/arch/arm/include/asm/setup.h
> index 1eaf13bd66..005cf7be59 100644
> --- a/xen/arch/arm/include/asm/setup.h
> +++ b/xen/arch/arm/include/asm/setup.h
> @@ -65,6 +65,8 @@ int map_irq_to_domain(struct domain *d, unsigned int irq,
> int map_range_to_domain(const struct dt_device_node *dev,
> uint64_t addr, uint64_t len, void *data);
>
> +extern const char __init_data_begin[], __bss_start[], __bss_end[];
> +
> struct init_info
> {
> /* Pointer to the stack, used by head.S when entering in C */
> diff --git a/xen/arch/arm/mpu/mm.c b/xen/arch/arm/mpu/mm.c
> index 207e8d2d91..4194d4fefd 100644
> --- a/xen/arch/arm/mpu/mm.c
> +++ b/xen/arch/arm/mpu/mm.c
> @@ -171,33 +171,18 @@ int mpumap_contains_region(pr_t *table, uint8_t
> nr_regions, paddr_t base,
> return MPUMAP_REGION_NOTFOUND;
> }
>
> -static bool is_mm_attr_match(pr_t *region, unsigned int attributes)
> +static int is_mm_attr_match(pr_t *region, unsigned int attributes)
> {
> if ( region->prbar.reg.ro != PAGE_RO_MASK(attributes) )
> - {
> - printk(XENLOG_WARNING
> - "Mismatched Access Permission attributes (%#x instead of
> %#x)\n",
> - region->prbar.reg.ro, PAGE_RO_MASK(attributes));
> - return false;
> - }
> + return MPU_ATTR_RO_MISMATCH;
>
> if ( region->prbar.reg.xn != PAGE_XN_MASK(attributes) )
> - {
> - printk(XENLOG_WARNING
> - "Mismatched Execute Never attributes (%#x instead of %#x)\n",
> - region->prbar.reg.xn, PAGE_XN_MASK(attributes));
> - return false;
> - }
> + return MPU_ATTR_XN_MISMATCH;
Later below you don't seem to differentiate between MPU_ATTR_RO_MISMATCH and
MPU_ATTR_XN_MISMATCH. Therefore I would suggest to keep them as one to simplify
the code.
>
> if ( region->prlar.reg.ai != PAGE_AI_MASK(attributes) )
> - {
> - printk(XENLOG_WARNING
> - "Mismatched Memory Attribute Index (%#x instead of %#x)\n",
> - region->prlar.reg.ai, PAGE_AI_MASK(attributes));
> - return false;
> - }
> + return MPU_ATTR_AI_MISMATCH;
>
> - return true;
> + return 0;
> }
>
> /* Map a frame table to cover physical addresses ps through pe */
> @@ -357,12 +342,45 @@ static int xen_mpumap_update_entry(paddr_t base,
> paddr_t limit,
> */
> if ( flags_has_page_present && (rc >= MPUMAP_REGION_FOUND) )
> {
> - if ( !is_mm_attr_match(&xen_mpumap[idx], flags) )
> + int attr_match = is_mm_attr_match(&xen_mpumap[idx], flags);
> +
> + /* We do not support modifying AI attribute. */
> + if ( MPU_ATTR_AI_MISMATCH == attr_match )
> {
> - printk("Modifying an existing entry is not supported\n");
> + printk(XENLOG_ERR
> + "Modifying memory attribute is not supported\n");
> return -EINVAL;
> }
>
> + /*
> + * Permissions RO and XN can be changed only by the full region.
> + * Permissions that match can continue and just increment refcount.
> + */
> + if ( MPU_ATTR_RO_MISMATCH == attr_match ||
Enlcose in brackets () || ()
> + MPU_ATTR_XN_MISMATCH == attr_match )
> + {
> + if ( rc == MPUMAP_REGION_INCLUSIVE )
> + {
> + printk(XENLOG_ERR
> + "Cannot modify partial region permissions\n");
> + return -EINVAL;
> + }
> +
> + if ( xen_mpumap[idx].refcount != 0 )
> + {
> + printk(XENLOG_ERR
> + "Cannot modify memory permissions for a region mapped
> multiple times\n");
Memory permission? Here you are checking for XN/RO.
> + return -EINVAL;
> + }
> +
> + /* Set new permission */
> + xen_mpumap[idx].prbar.reg.ro = PAGE_RO_MASK(flags);
> + xen_mpumap[idx].prbar.reg.xn = PAGE_XN_MASK(flags);
Here you always change both, that's why there is no need to provide two separate
macros as I mentioned above.
~Michal
