On 13/01/2026 17:23, 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
> attributes 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]>
> ---
> v3:
> - Refactor MPU_ATTR_* defines
> v2:
> - Refactor `is_mm_attr_match` to return logical values regarding the
> attribute mismatch.
> - Improve code documentation.
> ---
> xen/arch/arm/include/asm/setup.h | 2 +
> xen/arch/arm/mpu/mm.c | 119 +++++++++++++++++++++++--------
> 2 files changed, 93 insertions(+), 28 deletions(-)
>
> 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 14a988ea0c..5633c1c4c5 100644
> --- a/xen/arch/arm/mpu/mm.c
> +++ b/xen/arch/arm/mpu/mm.c
> @@ -15,6 +15,9 @@
> #include <asm/setup.h>
> #include <asm/sysregs.h>
>
> +#define MPU_ATTR_XN_RO_MISMATCH -1
> +#define MPU_ATTR_AI_MISMATCH -2
> +
> struct page_info *frame_table;
>
> /* Maximum number of supported MPU memory regions by the EL2 MPU. */
> @@ -171,33 +174,16 @@ 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;
> - }
> -
> - 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;
> - }
> + if ( (region->prbar.reg.xn != PAGE_XN_MASK(attributes)) ||
> + (region->prbar.reg.ro != PAGE_RO_MASK(attributes)) )
> + return MPU_ATTR_XN_RO_MISMATCH;
>
> 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 */
> @@ -358,12 +344,44 @@ 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");
Because this message is the same as the one a bit lower I would suggest to do
s/memory/AI/ here...
> return -EINVAL;
> }
>
> + /*
> + * Attributes RO and XN can be changed only by the full region.
> + * Attributes that match can continue and just increment refcount.
> + */
> + if ( MPU_ATTR_XN_RO_MISMATCH == attr_match )
> + {
> + if ( rc == MPUMAP_REGION_INCLUSIVE )
> + {
> + printk(XENLOG_ERR
> + "Cannot modify partial region attributes\n");
> + return -EINVAL;
> + }
> +
> + if ( xen_mpumap[idx].refcount != 0 )
> + {
> + printk(XENLOG_ERR
> + "Cannot modify memory attributes for a region mapped
> multiple times\n");
and s/memory/RO,XN/ here.
> + return -EINVAL;
> + }
> +
> + /* Set new attributes */
> + xen_mpumap[idx].prbar.reg.ro = PAGE_RO_MASK(flags);
> + xen_mpumap[idx].prbar.reg.xn = PAGE_XN_MASK(flags);
> +
> + write_protection_region(&xen_mpumap[idx], idx);
> + return 0;
> + }
> +
> /* Check for overflow of refcount before incrementing. */
> if ( xen_mpumap[idx].refcount == 0xFF )
> {
> @@ -514,8 +532,7 @@ void __init setup_mm_helper(void)
>
> int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf)
> {
> - BUG_ON("unimplemented");
> - return -EINVAL;
> + return xen_mpumap_update(s, e, nf);
> }
>
> void dump_hyp_walk(vaddr_t addr)
> @@ -526,7 +543,53 @@ void dump_hyp_walk(vaddr_t addr)
> /* Release all __init and __initdata ranges to be reused */
> void free_init_memory(void)
> {
> - BUG_ON("unimplemented");
> + unsigned long inittext_end = (unsigned long)__init_data_begin;
> + unsigned long len = __init_end - __init_begin;
> + uint8_t idx;
> + int rc;
> +
> + /* Modify inittext region to be read/write instead of read/execute. */
> + rc = modify_xen_mappings((unsigned long)__init_begin, inittext_end,
> + PAGE_HYPERVISOR_RW);
> + if ( rc )
> + panic("Unable to map RW the init text section (rc = %d)\n", rc);
> +
> + /*
> + * From now on, init will not be used for execution anymore,
> + * so nuke the instruction cache to remove entries related to init.
> + */
> + invalidate_icache_local();
> +
> + /*
> + * The initdata region already has read/write attributes so it can just
> be
> + * zeroed out.
> + */
> + memset(__init_begin, 0, len);
> +
> + rc = destroy_xen_mappings((unsigned long)__init_begin, inittext_end);
> + if ( rc )
> + panic("Unable to remove init text section (rc = %d)\n", rc);
> +
> + /*
> + * The initdata and bss sections are mapped using a single MPU region, so
> + * modify the start of this region to remove the initdata section.
> + */
> + spin_lock(&xen_mpumap_lock);
> +
> + rc = mpumap_contains_region(xen_mpumap, max_mpu_regions,
> + (unsigned long)__init_data_begin,
> + (unsigned long)__bss_end,
NIT: I'm thinking if it would not make sense to add some sanity checks in the
future to make sure the layout is as expected. For example, what if a new
section appeared between __init_end and __bss_start in the future?
For this patch with the printk adjustments:
Reviewed-by: Michal Orzel <[email protected]>
~Michal
