[Qemu-devel] [PATCH 3/4] elf-loader: add more return codes

[Alexey Kardashevskiy <aik@ozlabs.ru>]

The existing load_elf() just returns -1 if it fails to load ELF. However
it could be smarter than this and tell more about the failure such as
wrong endianness or incompatible platform.

This adds additional return codes for wrong architecture, wrong
endianness and if the image is not ELF at all.

This fixes handling of what load_elf() returns for s390x and moxie
architectures, other callers just check the return value for <0 and
this remains unchanged.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 hw/core/loader.c     | 12 ++++++------
 hw/s390x/ipl.c       |  4 ++--
 include/hw/elf_ops.h | 19 ++++++++++++++-----
 include/hw/loader.h  |  5 +++++
 4 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/hw/core/loader.c b/hw/core/loader.c
index 0634bee..f510260 100644
--- a/hw/core/loader.c
+++ b/hw/core/loader.c
@@ -289,7 +289,7 @@ int load_elf(const char *filename, uint64_t (*translate_fn)(void *, uint64_t),
              void *translate_opaque, uint64_t *pentry, uint64_t *lowaddr,
              uint64_t *highaddr, int big_endian, int elf_machine, int clear_lsb)
 {
-    int fd, data_order, target_data_order, must_swab, ret;
+    int fd, data_order, target_data_order, must_swab, ret = ELF_LOAD_FAILED;
     uint8_t e_ident[EI_NIDENT];
 
     fd = open(filename, O_RDONLY | O_BINARY);
@@ -302,8 +302,10 @@ int load_elf(const char *filename, uint64_t (*translate_fn)(void *, uint64_t),
     if (e_ident[0] != ELFMAG0 ||
         e_ident[1] != ELFMAG1 ||
         e_ident[2] != ELFMAG2 ||
-        e_ident[3] != ELFMAG3)
+        e_ident[3] != ELFMAG3) {
+        ret = ELF_LOAD_NOT_ELF;
         goto fail;
+    }
 #ifdef HOST_WORDS_BIGENDIAN
     data_order = ELFDATA2MSB;
 #else
@@ -317,6 +319,7 @@ int load_elf(const char *filename, uint64_t (*translate_fn)(void *, uint64_t),
     }
 
     if (target_data_order != e_ident[EI_DATA]) {
+        ret = ELF_LOAD_WRONG_ENDIAN;
         goto fail;
     }
 
@@ -329,12 +332,9 @@ int load_elf(const char *filename, uint64_t (*translate_fn)(void *, uint64_t),
                          pentry, lowaddr, highaddr, elf_machine, clear_lsb);
     }
 
-    close(fd);
-    return ret;
-
  fail:
     close(fd);
-    return -1;
+    return ret;
 }
 
 static void bswap_uboot_header(uboot_image_header_t *hdr)
diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
index 1a6397b..cff77ad 100644
--- a/hw/s390x/ipl.c
+++ b/hw/s390x/ipl.c
@@ -97,10 +97,10 @@ static int s390_ipl_init(SysBusDevice *dev)
     } else {
         kernel_size = load_elf(ipl->kernel, NULL, NULL, NULL, NULL,
                                NULL, 1, ELF_MACHINE, 0);
-        if (kernel_size == -1) {
+        if (kernel_size < 0) {
             kernel_size = load_image_targphys(ipl->kernel, 0, ram_size);
         }
-        if (kernel_size == -1) {
+        if (kernel_size < 0) {
             fprintf(stderr, "could not load kernel '%s'\n", ipl->kernel);
             return -1;
         }
diff --git a/include/hw/elf_ops.h b/include/hw/elf_ops.h
index acc701e..b7e7b36 100644
--- a/include/hw/elf_ops.h
+++ b/include/hw/elf_ops.h
@@ -201,6 +201,7 @@ static int glue(load_elf, SZ)(const char *name, int fd,
     uint64_t addr, low = (uint64_t)-1, high = 0;
     uint8_t *data = NULL;
     char label[128];
+    int ret = ELF_LOAD_FAILED;
 
     if (read(fd, &ehdr, sizeof(ehdr)) != sizeof(ehdr))
         goto fail;
@@ -210,23 +211,31 @@ static int glue(load_elf, SZ)(const char *name, int fd,
 
     switch (elf_machine) {
         case EM_PPC64:
-            if (EM_PPC64 != ehdr.e_machine)
+            if (EM_PPC64 != ehdr.e_machine) {
                 if (EM_PPC != ehdr.e_machine)
+                    ret = ELF_LOAD_WRONG_ARCH;
                     goto fail;
+                }
             break;
         case EM_X86_64:
             if (EM_X86_64 != ehdr.e_machine)
-                if (EM_386 != ehdr.e_machine)
+                if (EM_386 != ehdr.e_machine) {
+                    ret = ELF_LOAD_WRONG_ARCH;
                     goto fail;
+                }
             break;
         case EM_MICROBLAZE:
             if (EM_MICROBLAZE != ehdr.e_machine)
-                if (EM_MICROBLAZE_OLD != ehdr.e_machine)
+                if (EM_MICROBLAZE_OLD != ehdr.e_machine) {
+                    ret = ELF_LOAD_WRONG_ARCH;
                     goto fail;
+                }
             break;
         default:
-            if (elf_machine != ehdr.e_machine)
+            if (elf_machine != ehdr.e_machine) {
+                ret = ELF_LOAD_WRONG_ARCH;
                 goto fail;
+            }
     }
 
     if (pentry)
@@ -305,5 +314,5 @@ static int glue(load_elf, SZ)(const char *name, int fd,
  fail:
     g_free(data);
     g_free(phdr);
-    return -1;
+    return ret;
 }
diff --git a/include/hw/loader.h b/include/hw/loader.h
index 7a23d6b..6c9d762 100644
--- a/include/hw/loader.h
+++ b/include/hw/loader.h
@@ -8,6 +8,11 @@ int get_image_size(const char *filename);
 int load_image(const char *filename, uint8_t *addr); /* deprecated */
 int load_image_targphys(const char *filename, hwaddr,
                         uint64_t max_sz);
+
+#define ELF_LOAD_FAILED       -1
+#define ELF_LOAD_NOT_ELF      -2
+#define ELF_LOAD_WRONG_ARCH   -3
+#define ELF_LOAD_WRONG_ENDIAN -4
 int load_elf(const char *filename, uint64_t (*translate_fn)(void *, uint64_t),
              void *translate_opaque, uint64_t *pentry, uint64_t *lowaddr,
              uint64_t *highaddr, int big_endian, int elf_machine,
-- 
1.8.4.rc4