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elf-ops.h: Map into memory the ELF to load

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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>
This commit is contained in:
Stefano Garzarella 2019-07-24 16:31:04 +02:00 committed by Paolo Bonzini
parent fef28891aa
commit 816b9fe450
1 changed files with 42 additions and 29 deletions
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61
include/hw/elf_ops.h
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@ -323,8 +323,9 @@ static int glue(load_elf, SZ)(const char *name, int fd,
struct elfhdr ehdr; struct elfhdr ehdr;
struct elf_phdr *phdr = NULL, *ph; struct elf_phdr *phdr = NULL, *ph;
int size, i, total_size; int size, i, total_size;
elf_word mem_size, file_size; elf_word mem_size, file_size, data_offset;
uint64_t addr, low = (uint64_t)-1, high = 0; uint64_t addr, low = (uint64_t)-1, high = 0;
GMappedFile *mapped_file = NULL;
uint8_t *data = NULL; uint8_t *data = NULL;
char label[128]; char label[128];
int ret = ELF_LOAD_FAILED; int ret = ELF_LOAD_FAILED;
@ -409,20 +410,32 @@ static int glue(load_elf, SZ)(const char *name, int fd,
} }
} }
/*
* Since we want to be able to modify the mapped buffer, we set the
* 'writeble' parameter to 'true'. Modifications to the buffer are not
* written back to the file.
*/
mapped_file = g_mapped_file_new_from_fd(fd, true, NULL);
if (!mapped_file) {
goto fail;
}
total_size = 0; total_size = 0;
for(i = 0; i < ehdr.e_phnum; i++) { for(i = 0; i < ehdr.e_phnum; i++) {
ph = &phdr[i]; ph = &phdr[i];
if (ph->p_type == PT_LOAD) { if (ph->p_type == PT_LOAD) {
mem_size = ph->p_memsz; /* Size of the ROM */ mem_size = ph->p_memsz; /* Size of the ROM */
file_size = ph->p_filesz; /* Size of the allocated data */ file_size = ph->p_filesz; /* Size of the allocated data */
data = g_malloc0(file_size); data_offset = ph->p_offset; /* Offset where the data is located */
if (ph->p_filesz > 0) {
if (lseek(fd, ph->p_offset, SEEK_SET) < 0) { if (file_size > 0) {
goto fail; if (g_mapped_file_get_length(mapped_file) <
} file_size + data_offset) {
if (read(fd, data, file_size) != file_size) {
goto fail; goto fail;
} }
data = (uint8_t *)g_mapped_file_get_contents(mapped_file);
data += data_offset;
} }
/* The ELF spec is somewhat vague about the purpose of the /* The ELF spec is somewhat vague about the purpose of the
@ -513,25 +526,25 @@ static int glue(load_elf, SZ)(const char *name, int fd,
*pentry = ehdr.e_entry - ph->p_vaddr + ph->p_paddr; *pentry = ehdr.e_entry - ph->p_vaddr + ph->p_paddr;
} }
if (mem_size == 0) {
/* Some ELF files really do have segments of zero size; /* Some ELF files really do have segments of zero size;
* just ignore them rather than trying to create empty * just ignore them rather than trying to create empty
* ROM blobs, because the zero-length blob can falsely * ROM blobs, because the zero-length blob can falsely
* trigger the overlapping-ROM-blobs check. * trigger the overlapping-ROM-blobs check.
*/ */
g_free(data); if (mem_size != 0) {
} else {
if (load_rom) { if (load_rom) {
snprintf(label, sizeof(label), "phdr #%d: %s", i, name); snprintf(label, sizeof(label), "phdr #%d: %s", i, name);
/* rom_add_elf_program() seize the ownership of 'data' */ /*
rom_add_elf_program(label, NULL, data, file_size, mem_size, * rom_add_elf_program() takes its own reference to
addr, as); * 'mapped_file'.
*/
rom_add_elf_program(label, mapped_file, data, file_size,
mem_size, addr, as);
} else { } else {
address_space_write(as ? as : &address_space_memory, address_space_write(as ? as : &address_space_memory,
addr, MEMTXATTRS_UNSPECIFIED, addr, MEMTXATTRS_UNSPECIFIED,
data, file_size); data, file_size);
g_free(data);
} }
} }
@ -547,14 +560,16 @@ static int glue(load_elf, SZ)(const char *name, int fd,
struct elf_note *nhdr = NULL; struct elf_note *nhdr = NULL;
file_size = ph->p_filesz; /* Size of the range of ELF notes */ file_size = ph->p_filesz; /* Size of the range of ELF notes */
data = g_malloc0(file_size); data_offset = ph->p_offset; /* Offset where the notes are located */
if (ph->p_filesz > 0) {
if (lseek(fd, ph->p_offset, SEEK_SET) < 0) { if (file_size > 0) {
goto fail; if (g_mapped_file_get_length(mapped_file) <
} file_size + data_offset) {
if (read(fd, data, file_size) != file_size) {
goto fail; goto fail;
} }
data = (uint8_t *)g_mapped_file_get_contents(mapped_file);
data += data_offset;
} }
/* /*
@ -570,19 +585,17 @@ static int glue(load_elf, SZ)(const char *name, int fd,
sizeof(struct elf_note) == sizeof(struct elf64_note); sizeof(struct elf_note) == sizeof(struct elf64_note);
elf_note_fn((void *)nhdr, (void *)&ph->p_align, is64); elf_note_fn((void *)nhdr, (void *)&ph->p_align, is64);
} }
g_free(data);
data = NULL; data = NULL;
} }
} }
g_free(phdr);
if (lowaddr) if (lowaddr)
*lowaddr = (uint64_t)(elf_sword)low; *lowaddr = (uint64_t)(elf_sword)low;
if (highaddr) if (highaddr)
*highaddr = (uint64_t)(elf_sword)high; *highaddr = (uint64_t)(elf_sword)high;
return total_size; ret = total_size;
fail: fail:
g_free(data); g_mapped_file_unref(mapped_file);
g_free(phdr); g_free(phdr);
return ret; return ret;
} }