From 2215d38d1231284cced64d94b4430e92c9e2c017 Mon Sep 17 00:00:00 2001 From: David Gibson Date: Tue, 5 Feb 2019 04:47:56 +0000 Subject: [PATCH 2/8] mmap-alloc: unfold qemu_ram_mmap() RH-Author: David Gibson Message-id: <20190205044757.13591-2-dgibson@redhat.com> Patchwork-id: 84234 O-Subject: [RHELAV-8.0 qemu-kvm PATCH 1/2] mmap-alloc: unfold qemu_ram_mmap() Bugzilla: 1671519 RH-Acked-by: Pankaj Gupta RH-Acked-by: Laurent Vivier RH-Acked-by: Serhii Popovych 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) Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1671519 Signed-off-by: David Gibson 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 fd329ec..f71ea03 100644 --- a/util/mmap-alloc.c +++ b/util/mmap-alloc.c @@ -77,11 +77,19 @@ size_t qemu_mempath_getpagesize(const char *mem_path) void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared) { + 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 @@ -91,16 +99,22 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared) * 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; } @@ -108,19 +122,20 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared) /* 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); } /* @@ -129,10 +144,10 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared) */ 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