From 6b3478bb8b5718d86cb04f41043a8e0cce4df24c Mon Sep 17 00:00:00 2001 From: "plai@redhat.com" Date: Tue, 20 Aug 2019 16:12:49 +0100 Subject: [PATCH 02/11] mmap-alloc: unfold qemu_ram_mmap() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: plai@redhat.com Message-id: <1566317571-5697-3-git-send-email-plai@redhat.com> Patchwork-id: 90083 O-Subject: [RHEL8.2 qemu-kvm PATCH 2/4] mmap-alloc: unfold qemu_ram_mmap() Bugzilla: 1539282 RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Philippe Mathieu-Daudé RH-Acked-by: Pankaj Gupta RH-Acked-by: Eduardo Habkost From: Murilo Opsfelder Araujo Unfold parts of qemu_ram_mmap() for the sake of understanding, moving declarations to the top, and keeping architecture-specifics in the ifdef-else blocks. No changes in the function behaviour. Give ptr and ptr1 meaningful names: ptr -> guardptr : pointer to the PROT_NONE guard region ptr1 -> ptr : pointer to the mapped memory returned to caller Signed-off-by: Murilo Opsfelder Araujo Reviewed-by: Greg Kurz Signed-off-by: David Gibson (cherry picked from commit 2044c3e7116eeac0449dcb4a4130cc8f8b9310da) Signed-off-by: Paul Lai Signed-off-by: Danilo C. L. de Paula --- util/mmap-alloc.c | 53 ++++++++++++++++++++++++++++++++++------------------- 1 file changed, 34 insertions(+), 19 deletions(-) diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c index 55d1890..b29fcee 100644 --- a/util/mmap-alloc.c +++ b/util/mmap-alloc.c @@ -79,11 +79,19 @@ void *qemu_ram_mmap(int fd, bool shared, bool is_pmem) { + int flags; + int guardfd; + size_t offset; + size_t total; + void *guardptr; + void *ptr; + /* * Note: this always allocates at least one extra page of virtual address * space, even if size is already aligned. */ - size_t total = size + align; + total = size + align; + #if defined(__powerpc64__) && defined(__linux__) /* On ppc64 mappings in the same segment (aka slice) must share the same * page size. Since we will be re-allocating part of this segment @@ -93,16 +101,22 @@ void *qemu_ram_mmap(int fd, * We do this unless we are using the system page size, in which case * anonymous memory is OK. */ - int anonfd = fd == -1 || qemu_fd_getpagesize(fd) == getpagesize() ? -1 : fd; - int flags = anonfd == -1 ? MAP_ANONYMOUS : MAP_NORESERVE; - void *ptr = mmap(0, total, PROT_NONE, flags | MAP_PRIVATE, anonfd, 0); + flags = MAP_PRIVATE; + if (fd == -1 || qemu_fd_getpagesize(fd) == getpagesize()) { + guardfd = -1; + flags |= MAP_ANONYMOUS; + } else { + guardfd = fd; + flags |= MAP_NORESERVE; + } #else - void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + guardfd = -1; + flags = MAP_PRIVATE | MAP_ANONYMOUS; #endif - size_t offset; - void *ptr1; - if (ptr == MAP_FAILED) { + guardptr = mmap(0, total, PROT_NONE, flags, guardfd, 0); + + if (guardptr == MAP_FAILED) { return MAP_FAILED; } @@ -110,19 +124,20 @@ void *qemu_ram_mmap(int fd, /* Always align to host page size */ assert(align >= getpagesize()); - offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr; - ptr1 = mmap(ptr + offset, size, PROT_READ | PROT_WRITE, - MAP_FIXED | - (fd == -1 ? MAP_ANONYMOUS : 0) | - (shared ? MAP_SHARED : MAP_PRIVATE), - fd, 0); - if (ptr1 == MAP_FAILED) { - munmap(ptr, total); + flags = MAP_FIXED; + flags |= fd == -1 ? MAP_ANONYMOUS : 0; + flags |= shared ? MAP_SHARED : MAP_PRIVATE; + offset = QEMU_ALIGN_UP((uintptr_t)guardptr, align) - (uintptr_t)guardptr; + + ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE, flags, fd, 0); + + if (ptr == MAP_FAILED) { + munmap(guardptr, total); return MAP_FAILED; } if (offset > 0) { - munmap(ptr, offset); + munmap(guardptr, offset); } /* @@ -131,10 +146,10 @@ void *qemu_ram_mmap(int fd, */ total -= offset; if (total > size + getpagesize()) { - munmap(ptr1 + size + getpagesize(), total - size - getpagesize()); + munmap(ptr + size + getpagesize(), total - size - getpagesize()); } - return ptr1; + return ptr; } void qemu_ram_munmap(void *ptr, size_t size) -- 1.8.3.1