Save memory allocation in the elf loader

The current elf loader uses too much memory. For example, I have a
executable with a bss section of 400 MB and I set the ram size to 512
MB. Qemu uses about 780MB of RAM (which is fine), but there's a peak at
1.6 GB during initialization (this is not fine).

This patch fixes two things:
 1) do not allocate each elf program twice.
 2) do not allocate memory for areas that are only zeros.

For this we need a new field in Rom: "datasize" which is the size of the
allocated data. If datasize is less than romsize, it means that the area
from datasize to romsize is filled with zeros.

Signed-off-by: Fabien Chouteau <chouteau@adacore.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 11 insertions, 8 deletions

diff --git a/hw/elf_ops.h b/hw/elf_ops.h
index 531a42553b..acc701e3a4 100644
--- a/hw/elf_ops.h
+++ b/hw/elf_ops.h
@@ -197,7 +197,7 @@ static int glue(load_elf, SZ)(const char *name, int fd,
     struct elfhdr ehdr;
     struct elf_phdr *phdr = NULL, *ph;
     int size, i, total_size;
-    elf_word mem_size;
+    elf_word mem_size, file_size;
     uint64_t addr, low = (uint64_t)-1, high = 0;
     uint8_t *data = NULL;
     char label[128];
@@ -252,14 +252,16 @@ static int glue(load_elf, SZ)(const char *name, int fd,
     for(i = 0; i < ehdr.e_phnum; i++) {
         ph = &phdr[i];
         if (ph->p_type == PT_LOAD) {
-            mem_size = ph->p_memsz;
-            /* XXX: avoid allocating */
-            data = g_malloc0(mem_size);
+            mem_size = ph->p_memsz; /* Size of the ROM */
+            file_size = ph->p_filesz; /* Size of the allocated data */
+            data = g_malloc0(file_size);
             if (ph->p_filesz > 0) {
-                if (lseek(fd, ph->p_offset, SEEK_SET) < 0)
+                if (lseek(fd, ph->p_offset, SEEK_SET) < 0) {
                     goto fail;
-                if (read(fd, data, ph->p_filesz) != ph->p_filesz)
+                }
+                if (read(fd, data, file_size) != file_size) {
                     goto fail;
+                }
             }
             /* address_offset is hack for kernel images that are
                linked at the wrong physical address.  */
@@ -281,7 +283,9 @@ static int glue(load_elf, SZ)(const char *name, int fd,
             }
 
             snprintf(label, sizeof(label), "phdr #%d: %s", i, name);
-            rom_add_blob_fixed(label, data, mem_size, addr);
+
+            /* rom_add_elf_program() seize the ownership of 'data' */
+            rom_add_elf_program(label, data, file_size, mem_size, addr);
 
             total_size += mem_size;
             if (addr < low)
@@ -289,7 +293,6 @@ static int glue(load_elf, SZ)(const char *name, int fd,
             if ((addr + mem_size) > high)
                 high = addr + mem_size;
 
-            g_free(data);
             data = NULL;
         }
     }