[PATCH v3 08/17] x86/efi: Allow ranges_to_free array to grow beyond initial size

Ard Biesheuvel
2026-04-23T15:21:10Z

In order to avoid the need to mangle the EFI memory map, which is being
done to keep track of which boot services data regions are really really
reserved, and which ones are only reserved temporarily, this information
needs to be recorded in a different manner.

The temporary ranges_to_free array is a suitable candidate, as it is
specifically intended to capture which boot services data regions should
be handed back to the page allocator once deferred struct page
initialization is done.

This requires that boot services data regions are intersected with the
memblock reserved list, and this may result in more ranges_to_free
elements than the current upper bound of the number of EFI memory map
entries.

So reallocate the array when running out of slots.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/x86/platform/efi/quirks.c | 40 ++++++++++++++++----
1 file changed, 32 insertions(+), 8 deletions(-)

diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
index 1d10277796b7..ce452e5c2f0a 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -401,23 +401,46 @@ struct efi_freeable_range {
u64 end;
};

-static struct efi_freeable_range *ranges_to_free;
+static struct efi_freeable_range *ranges_to_free __initdata;
+static int num_to_free __initdata;
+
+static int __init efi_add_range_to_free(u64 range_start, u64 range_end)
+{
+ static int idx __initdata;
+
+ ranges_to_free[idx].start = range_start;
+ ranges_to_free[idx].end = range_end;
+
+ if (++idx >= num_to_free) {
+ num_to_free *= 2;
+ ranges_to_free = krealloc_array(ranges_to_free,
+ num_to_free,
+ sizeof(ranges_to_free[0]),
+ GFP_KERNEL);
+ if (!ranges_to_free)
+ return -ENOMEM;
+ }
+
+ /* add a terminating entry at the end */
+ ranges_to_free[idx].start = ranges_to_free[idx].end = 0;
+
+ return 0;
+}

void __init efi_unmap_boot_services(void)
{
struct efi_memory_map_data data = { 0 };
efi_memory_desc_t *md;
int num_entries = 0;
- int idx = 0;
- size_t sz;
void *new, *new_md;

/* Keep all regions for /sys/kernel/debug/efi */
if (efi_enabled(EFI_DBG))
return;

- sz = sizeof(*ranges_to_free) * (efi.memmap.nr_map + 1);
- ranges_to_free = kzalloc(sz, GFP_KERNEL);
+ num_to_free = efi.memmap.nr_map;
+ ranges_to_free = kmalloc_array(num_to_free, sizeof(ranges_to_free[0]),
+ GFP_KERNEL);
if (!ranges_to_free) {
pr_err("Failed to allocate storage for freeable EFI regions\n");
return;
@@ -452,9 +475,10 @@ void __init efi_unmap_boot_services(void)
* memory here.
* Queue the ranges to free at a later point.
*/
- ranges_to_free[idx].start = start;
- ranges_to_free[idx].end = start + size;
- idx++;
+ if (efi_add_range_to_free(start, start + size)) {
+ pr_err("Failed to reallocate storage for freeable EFI regions\n");
+ return;
+ }
}

if (!num_entries)