From 7dd968163f7c12bcb2132792bf873133b397a2d2 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Wed, 25 May 2016 09:32:20 +0200 Subject: bitmap: bitmap_equal memcmp optimization The bitmap_equal function has optimized code for small bitmaps with less than BITS_PER_LONG bits. For larger bitmaps the out-of-line function __bitmap_equal is called. For a constant number of bits divisible by BITS_PER_LONG the memcmp function can be used. For s390 gcc knows how to optimize this function, memcmp calls with up to 256 bytes / 2048 bits are translated into a single instruction. Reviewed-by: David Hildenbrand Signed-off-by: Martin Schwidefsky --- include/linux/bitmap.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include') diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index e9b0b9ab07e5..27bfc0b631a9 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -267,6 +267,10 @@ static inline int bitmap_equal(const unsigned long *src1, { if (small_const_nbits(nbits)) return ! ((*src1 ^ *src2) & BITMAP_LAST_WORD_MASK(nbits)); +#ifdef CONFIG_S390 + else if (__builtin_constant_p(nbits) && (nbits % BITS_PER_LONG) == 0) + return !memcmp(src1, src2, nbits / 8); +#endif else return __bitmap_equal(src1, src2, nbits); } -- cgit v1.2.3 From 32fb2fc5c357fb99616bbe100dbcb27bc7f5d045 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Tue, 7 Jun 2016 12:20:51 +0200 Subject: vmlinux.lds.h: allow arch specific handling of ro_after_init data section commit c74ba8b3480d ("arch: Introduce post-init read-only memory") introduced the __ro_after_init attribute which allows to add variables to the ro_after_init data section. This new section was added to rodata, even though it contains writable data. This in turn causes problems on architectures which mark the page table entries read-only that point to rodata very early. This patch allows architectures to implement an own handling of the .data..ro_after_init section. Usually that would be: - mark the rodata section read-only very early - mark the ro_after_init section read-only within mark_rodata_ro Signed-off-by: Heiko Carstens Reviewed-by: Kees Cook Signed-off-by: Martin Schwidefsky --- include/asm-generic/vmlinux.lds.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 6a67ab94b553..c4436d072d37 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -249,6 +249,14 @@ *(.data..init_task) \ VMLINUX_SYMBOL(__end_init_task) = .; +/* + * Allow architectures to handle ro_after_init data on their + * own by defining an empty RO_AFTER_INIT_DATA. + */ +#ifndef RO_AFTER_INIT_DATA +#define RO_AFTER_INIT_DATA *(.data..ro_after_init) +#endif + /* * Read only Data */ @@ -257,7 +265,7 @@ .rodata : AT(ADDR(.rodata) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start_rodata) = .; \ *(.rodata) *(.rodata.*) \ - *(.data..ro_after_init) /* Read only after init */ \ + RO_AFTER_INIT_DATA /* Read only after init */ \ *(__vermagic) /* Kernel version magic */ \ . = ALIGN(8); \ VMLINUX_SYMBOL(__start___tracepoints_ptrs) = .; \ -- cgit v1.2.3