Messages in this thread Patch in this message | | | From | Marek Szyprowski <> | Subject | [RFC 2/2] arm64: compat: cacheflush syscall: process only pages that are in the memory | Date | Fri, 26 Jan 2018 12:14:41 +0100 |
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glibc in ARM 32bit mode calls cacheflush syscall on the whole textrels section of the relocated binaries. However, relocation usually doesn't touch all pages of that section, so not all of them are read to memory when calling this syscall. However flush_cache_user_range() function will unconditionally touch all pages from the provided range, resulting additional overhead related to reading all clean pages. Optimize this by calling flush_cache_user_range() only on the pages that are already in the memory.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> --- arch/arm64/kernel/sys_compat.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-)
diff --git a/arch/arm64/kernel/sys_compat.c b/arch/arm64/kernel/sys_compat.c index 8b8bbd3eaa52..4a047db3fdd4 100644 --- a/arch/arm64/kernel/sys_compat.c +++ b/arch/arm64/kernel/sys_compat.c @@ -25,6 +25,7 @@ #include <linux/slab.h> #include <linux/syscalls.h> #include <linux/uaccess.h> +#include <linux/mm.h> #include <asm/cacheflush.h> #include <asm/unistd.h> @@ -32,23 +33,36 @@ static long __do_compat_cache_op(unsigned long start, unsigned long end) { - long ret; + struct vm_area_struct *vma = NULL; + long ret = 0; + down_read(¤t->mm->mmap_sem); do { unsigned long chunk = min(PAGE_SIZE, end - start); + if (!vma || vma->vm_end <= start) { + vma = find_vma(current->mm, start); + if (!vma) { + ret = -EFAULT; + goto done; + } + } + if (fatal_signal_pending(current)) - return 0; + goto done; - ret = __flush_cache_user_range(start, start + chunk); - if (ret) - return ret; + if (follow_page(vma, start, 0)) { + ret = __flush_cache_user_range(start, start + chunk); + if (ret) + goto done; + } cond_resched(); start += chunk; } while (start < end); - - return 0; +done: + up_read(¤t->mm->mmap_sem); + return ret; } static inline long -- 2.15.0
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