From 369d6dc4de45b8e5e35a851f5719e7fd59a0462f Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Mon, 4 Jan 2021 17:13:18 +0000 Subject: memory: add readonly support to memory_region_init_ram_from_file() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit There is currently no way to open(O_RDONLY) and mmap(PROT_READ) when creating a memory region from a file. This functionality is needed since the underlying host file may not allow writing. Add a bool readonly argument to memory_region_init_ram_from_file() and the APIs it calls. Extend memory_region_init_ram_from_file() rather than introducing a memory_region_init_rom_from_file() API so that callers can easily make a choice between read/write and read-only at runtime without calling different APIs. No new RAMBlock flag is introduced for read-only because it's unclear whether RAMBlocks need to know that they are read-only. Pass a bool readonly argument instead. Both of these design decisions can be changed in the future. It just seemed like the simplest approach to me. Signed-off-by: Stefan Hajnoczi Reviewed-by: Philippe Mathieu-Daudé Reviewed-by: Igor Mammedov Reviewed-by: Liam Merwick Acked-by: Michael S. Tsirkin Message-Id: <20210104171320.575838-2-stefanha@redhat.com> Signed-off-by: Eduardo Habkost --- softmmu/physmem.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) (limited to 'softmmu/physmem.c') diff --git a/softmmu/physmem.c b/softmmu/physmem.c index cdcd197..60760a3 100644 --- a/softmmu/physmem.c +++ b/softmmu/physmem.c @@ -1398,6 +1398,7 @@ static int64_t get_file_align(int fd) static int file_ram_open(const char *path, const char *region_name, + bool readonly, bool *created, Error **errp) { @@ -1408,7 +1409,7 @@ static int file_ram_open(const char *path, *created = false; for (;;) { - fd = open(path, O_RDWR); + fd = open(path, readonly ? O_RDONLY : O_RDWR); if (fd >= 0) { /* @path names an existing file, use it */ break; @@ -1460,6 +1461,7 @@ static int file_ram_open(const char *path, static void *file_ram_alloc(RAMBlock *block, ram_addr_t memory, int fd, + bool readonly, bool truncate, Error **errp) { @@ -1510,7 +1512,7 @@ static void *file_ram_alloc(RAMBlock *block, perror("ftruncate"); } - area = qemu_ram_mmap(fd, memory, block->mr->align, + area = qemu_ram_mmap(fd, memory, block->mr->align, readonly, block->flags & RAM_SHARED, block->flags & RAM_PMEM); if (area == MAP_FAILED) { error_setg_errno(errp, errno, @@ -1942,7 +1944,7 @@ static void ram_block_add(RAMBlock *new_block, Error **errp, bool shared) #ifdef CONFIG_POSIX RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, - uint32_t ram_flags, int fd, + uint32_t ram_flags, int fd, bool readonly, Error **errp) { RAMBlock *new_block; @@ -1996,7 +1998,8 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, new_block->used_length = size; new_block->max_length = size; new_block->flags = ram_flags; - new_block->host = file_ram_alloc(new_block, size, fd, !file_size, errp); + new_block->host = file_ram_alloc(new_block, size, fd, readonly, + !file_size, errp); if (!new_block->host) { g_free(new_block); return NULL; @@ -2015,18 +2018,19 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr, RAMBlock *qemu_ram_alloc_from_file(ram_addr_t size, MemoryRegion *mr, uint32_t ram_flags, const char *mem_path, - Error **errp) + bool readonly, Error **errp) { int fd; bool created; RAMBlock *block; - fd = file_ram_open(mem_path, memory_region_name(mr), &created, errp); + fd = file_ram_open(mem_path, memory_region_name(mr), readonly, &created, + errp); if (fd < 0) { return NULL; } - block = qemu_ram_alloc_from_fd(size, mr, ram_flags, fd, errp); + block = qemu_ram_alloc_from_fd(size, mr, ram_flags, fd, readonly, errp); if (!block) { if (created) { unlink(mem_path); -- cgit v1.1