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mm/execmem: use VM_FLUSH_RESET_PERMS for ROX cache allocations

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Initially execmem completely removed direct map alias for the memory
allocated for the ROX cache in PMD_SIZE chunks.  When that memory was
freed, its direct map was restored also in PMD_SIZE chunks to avoid
fragmentation of the direct map caused by vmalloc::vm_reset_perms().

This required execmem to implement the wrappers for set_direct_map APIs
for proper sequencing of removal and restoration of the direct map
aliases.

Since then x86's CPA gained support for collapsing the direct map page
tables for ROX pages and execmem switched from removing ROX caches from
the direct map to making them ROX there, so execmem only needs to update
direct map alias permissions when freeing the ROX cache memory.

vmalloc already handles those updates for areas with VM_FLUSH_RESET_PERMS
set and vmalloc::vm_reset_perms() does not force split of the direct map
for PMD_SIZE chunks.

Set the area permissions with set_vm_flush_reset_perms() when populating
the execmem cache just before flipping the area to ROX.

This way freeing an allocated area on an error path won't incur two
updates of the direct map alias of that area and TLB flushing in
vm_reset_perms().

Link: https://lore.kernel.org/20260903-execmem-set-vm-perms-v0-2-v3-5-949b64a9f755@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: Brendan Jackman <brendan.jackman@linux.dev>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
This commit is contained in:
Mike Rapoport (Microsoft) 2026-09-03 12:28:31 +03:00 committed by Andrew Morton
parent 86dc0280b8
commit 4c4b2ed5b7
1 changed files with 7 additions and 33 deletions
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40
mm/execmem.c
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@ -113,28 +113,6 @@ static inline unsigned long mas_range_len(struct ma_state *mas)
return mas->last - mas->index + 1;
}
static int execmem_set_direct_map_valid(struct vm_struct *vm, bool valid)
{
unsigned int nr = (1 << get_vm_area_page_order(vm));
unsigned int updated = 0;
int err = 0;
for (int i = 0; i < vm->nr_pages; i += nr) {
err = set_direct_map_valid_noflush(vm->pages[i], nr, valid);
if (err)
goto err_restore;
updated += nr;
}
return 0;
err_restore:
for (int i = 0; i < updated; i += nr)
set_direct_map_valid_noflush(vm->pages[i], nr, !valid);
return err;
}
static int execmem_force_rw(void *ptr, size_t size)
{
unsigned int nr = PAGE_ALIGN(size) >> PAGE_SHIFT;
@ -169,9 +147,6 @@ static void execmem_cache_clean(struct work_struct *work)
if (IS_ALIGNED(size, PMD_SIZE) &&
IS_ALIGNED(mas.index, PMD_SIZE)) {
struct vm_struct *vm = find_vm_area(area);
execmem_set_direct_map_valid(vm, true);
mas_store_gfp(&mas, NULL, GFP_KERNEL);
vfree(area);
}
@ -301,6 +276,8 @@ static void *execmem_cache_populate_alloc(struct execmem_range *range, size_t si
/* fill memory with instructions that will trap */
execmem_fill_trapping_insns(p, alloc_size);
set_vm_flush_reset_perms(p);
err = set_memory_rox((unsigned long)p, vm->nr_pages);
if (err)
goto err_free_mem;
@ -312,18 +289,15 @@ static void *execmem_cache_populate_alloc(struct execmem_range *range, size_t si
*/
mutex_lock(mutex);
err = execmem_cache_add_locked(p, alloc_size, GFP_KERNEL);
if (err)
goto err_reset_direct_map;
p = execmem_cache_alloc_locked(range, size);
if (!err)
p = execmem_cache_alloc_locked(range, size);
mutex_unlock(mutex);
if (err)
goto err_free_mem;
return p;
err_reset_direct_map:
mutex_unlock(mutex);
execmem_set_direct_map_valid(vm, true);
err_free_mem:
vfree(p);
return NULL;