From 2e45474ab14f0f17c1091c503a13ff2fe2a84486 Mon Sep 17 00:00:00 2001 From: "Mike Rapoport (Microsoft)" Date: Wed, 23 Oct 2024 19:27:10 +0300 Subject: execmem: add support for cache of large ROX pages Using large pages to map text areas reduces iTLB pressure and improves performance. Extend execmem_alloc() with an ability to use huge pages with ROX permissions as a cache for smaller allocations. To populate the cache, a writable large page is allocated from vmalloc with VM_ALLOW_HUGE_VMAP, filled with invalid instructions and then remapped as ROX. The direct map alias of that large page is exculded from the direct map. Portions of that large page are handed out to execmem_alloc() callers without any changes to the permissions. When the memory is freed with execmem_free() it is invalidated again so that it won't contain stale instructions. An architecture has to implement execmem_fill_trapping_insns() callback and select ARCH_HAS_EXECMEM_ROX configuration option to be able to use the ROX cache. The cache is enabled on per-range basis when an architecture sets EXECMEM_ROX_CACHE flag in definition of an execmem_range. Link: https://lkml.kernel.org/r/20241023162711.2579610-8-rppt@kernel.org Signed-off-by: Mike Rapoport (Microsoft) Reviewed-by: Luis Chamberlain Tested-by: kdevops Cc: Andreas Larsson Cc: Andy Lutomirski Cc: Ard Biesheuvel Cc: Arnd Bergmann Cc: Borislav Petkov (AMD) Cc: Brian Cain Cc: Catalin Marinas Cc: Christophe Leroy Cc: Christoph Hellwig Cc: Dave Hansen Cc: Dinh Nguyen Cc: Geert Uytterhoeven Cc: Guo Ren Cc: Helge Deller Cc: Huacai Chen Cc: Ingo Molnar Cc: Johannes Berg Cc: John Paul Adrian Glaubitz Cc: Kent Overstreet Cc: Liam R. Howlett Cc: Mark Rutland Cc: Masami Hiramatsu (Google) Cc: Matt Turner Cc: Max Filippov Cc: Michael Ellerman Cc: Michal Simek Cc: Oleg Nesterov Cc: Palmer Dabbelt Cc: Peter Zijlstra Cc: Richard Weinberger Cc: Russell King Cc: Song Liu Cc: Stafford Horne Cc: Steven Rostedt (Google) Cc: Suren Baghdasaryan Cc: Thomas Bogendoerfer Cc: Thomas Gleixner Cc: Uladzislau Rezki (Sony) Cc: Vineet Gupta Cc: Will Deacon Signed-off-by: Andrew Morton --- include/linux/execmem.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'include/linux') diff --git a/include/linux/execmem.h b/include/linux/execmem.h index dfdf19f8a5e8..1517fa196bf7 100644 --- a/include/linux/execmem.h +++ b/include/linux/execmem.h @@ -53,6 +53,20 @@ enum execmem_range_flags { EXECMEM_ROX_CACHE = (1 << 1), }; +#ifdef CONFIG_ARCH_HAS_EXECMEM_ROX +/** + * execmem_fill_trapping_insns - set memory to contain instructions that + * will trap + * @ptr: pointer to memory to fill + * @size: size of the range to fill + * @writable: is the memory poited by @ptr is writable or ROX + * + * A hook for architecures to fill execmem ranges with invalid instructions. + * Architectures that use EXECMEM_ROX_CACHE must implement this. + */ +void execmem_fill_trapping_insns(void *ptr, size_t size, bool writable); +#endif + /** * struct execmem_range - definition of an address space suitable for code and * related data allocations -- cgit v1.2.3