From b61d857b2ff3b0b099ef187d7ceebe26ea788578 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Stefan=20Br=C3=BCns?= Date: Sat, 1 Oct 2016 23:32:27 +0200 Subject: efi_loader: Readd freed pages to memory pool MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Currently each allocation creates a new mapping. Readding the mapping as free memory (EFI_CONVENTIONAL_MEMORY) potentially allows to hand out an existing mapping, thus limiting the number of mapping descriptors in the memory map. Mitigates a problem with current (4.8rc7) linux kernels when doing an efi_get_memory map, resulting in an infinite loop. Space for the memory map is reserved with allocate_pool (implicitly creating a new mapping) and filled. If there is insufficient slack space (8 entries) in the map, the space is freed and a new round is started, with space for one more entry. As each round increases requirement and allocation by exactly one, there is never enough slack space. (At least 32 entries are allocated, so as long as there are less than 24 entries, there is enough slack). Earlier kernels reserved no slack, and did less allocations, so this problem was not visible. Signed-off-by: Stefan Brüns Reviewed-by: Alexander Graf Signed-off-by: Alexander Graf --- include/efi_loader.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/efi_loader.h') diff --git a/include/efi_loader.h b/include/efi_loader.h index 3dad24e..94397af 100644 --- a/include/efi_loader.h +++ b/include/efi_loader.h @@ -117,7 +117,7 @@ void *efi_alloc(uint64_t len, int memory_type); /* More specific EFI memory allocator, called by EFI payloads */ efi_status_t efi_allocate_pages(int type, int memory_type, unsigned long pages, uint64_t *memory); -/* EFI memory free function. Not implemented today */ +/* EFI memory free function. */ efi_status_t efi_free_pages(uint64_t memory, unsigned long pages); /* EFI memory allocator for small allocations */ efi_status_t efi_allocate_pool(int pool_type, unsigned long size, -- cgit v1.1