elf-ops.h: Map into memory the ELF to load
In order to reduce the memory footprint we map into memory the ELF to load using g_mapped_file_new_from_fd() instead of reading each sections. In this way we can share the ELF pages between multiple instances of QEMU. Suggested-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> Message-Id: <20190724143105.307042-3-sgarzare@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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@ -323,8 +323,9 @@ static int glue(load_elf, SZ)(const char *name, int fd,
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struct elfhdr ehdr;
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struct elf_phdr *phdr = NULL, *ph;
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int size, i, total_size;
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elf_word mem_size, file_size;
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elf_word mem_size, file_size, data_offset;
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uint64_t addr, low = (uint64_t)-1, high = 0;
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GMappedFile *mapped_file = NULL;
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uint8_t *data = NULL;
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char label[128];
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int ret = ELF_LOAD_FAILED;
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@ -409,20 +410,32 @@ static int glue(load_elf, SZ)(const char *name, int fd,
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}
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}
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/*
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* Since we want to be able to modify the mapped buffer, we set the
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* 'writeble' parameter to 'true'. Modifications to the buffer are not
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* written back to the file.
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*/
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mapped_file = g_mapped_file_new_from_fd(fd, true, NULL);
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if (!mapped_file) {
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goto fail;
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}
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total_size = 0;
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for(i = 0; i < ehdr.e_phnum; i++) {
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ph = &phdr[i];
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if (ph->p_type == PT_LOAD) {
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mem_size = ph->p_memsz; /* Size of the ROM */
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file_size = ph->p_filesz; /* Size of the allocated data */
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data = g_malloc0(file_size);
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if (ph->p_filesz > 0) {
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if (lseek(fd, ph->p_offset, SEEK_SET) < 0) {
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goto fail;
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}
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if (read(fd, data, file_size) != file_size) {
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data_offset = ph->p_offset; /* Offset where the data is located */
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if (file_size > 0) {
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if (g_mapped_file_get_length(mapped_file) <
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file_size + data_offset) {
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goto fail;
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}
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data = (uint8_t *)g_mapped_file_get_contents(mapped_file);
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data += data_offset;
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}
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/* The ELF spec is somewhat vague about the purpose of the
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@ -513,25 +526,25 @@ static int glue(load_elf, SZ)(const char *name, int fd,
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*pentry = ehdr.e_entry - ph->p_vaddr + ph->p_paddr;
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}
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if (mem_size == 0) {
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/* Some ELF files really do have segments of zero size;
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* just ignore them rather than trying to create empty
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* ROM blobs, because the zero-length blob can falsely
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* trigger the overlapping-ROM-blobs check.
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*/
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g_free(data);
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} else {
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/* Some ELF files really do have segments of zero size;
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* just ignore them rather than trying to create empty
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* ROM blobs, because the zero-length blob can falsely
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* trigger the overlapping-ROM-blobs check.
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*/
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if (mem_size != 0) {
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if (load_rom) {
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snprintf(label, sizeof(label), "phdr #%d: %s", i, name);
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/* rom_add_elf_program() seize the ownership of 'data' */
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rom_add_elf_program(label, NULL, data, file_size, mem_size,
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addr, as);
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/*
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* rom_add_elf_program() takes its own reference to
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* 'mapped_file'.
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*/
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rom_add_elf_program(label, mapped_file, data, file_size,
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mem_size, addr, as);
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} else {
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address_space_write(as ? as : &address_space_memory,
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addr, MEMTXATTRS_UNSPECIFIED,
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data, file_size);
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g_free(data);
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}
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}
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@ -547,14 +560,16 @@ static int glue(load_elf, SZ)(const char *name, int fd,
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struct elf_note *nhdr = NULL;
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file_size = ph->p_filesz; /* Size of the range of ELF notes */
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data = g_malloc0(file_size);
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if (ph->p_filesz > 0) {
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if (lseek(fd, ph->p_offset, SEEK_SET) < 0) {
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goto fail;
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}
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if (read(fd, data, file_size) != file_size) {
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data_offset = ph->p_offset; /* Offset where the notes are located */
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if (file_size > 0) {
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if (g_mapped_file_get_length(mapped_file) <
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file_size + data_offset) {
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goto fail;
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}
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data = (uint8_t *)g_mapped_file_get_contents(mapped_file);
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data += data_offset;
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}
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/*
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@ -570,19 +585,17 @@ static int glue(load_elf, SZ)(const char *name, int fd,
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sizeof(struct elf_note) == sizeof(struct elf64_note);
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elf_note_fn((void *)nhdr, (void *)&ph->p_align, is64);
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}
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g_free(data);
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data = NULL;
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}
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}
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g_free(phdr);
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if (lowaddr)
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*lowaddr = (uint64_t)(elf_sword)low;
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if (highaddr)
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*highaddr = (uint64_t)(elf_sword)high;
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return total_size;
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ret = total_size;
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fail:
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g_free(data);
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g_mapped_file_unref(mapped_file);
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g_free(phdr);
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return ret;
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}
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