[Qemu-devel] [PATCH v3 0/4] elf loader: exit if incompatible architecture is detected

[Qemu-devel] [PATCH v3 0/4] elf loader: exit if incompatible architecture is detected

[Alexey Kardashevskiy]

The aim of this set is to print reasonable error if ELF cannot be loaded.
While we are here, also fix some other bits.

Changes:
v3:
* added a helper to convert error codes to strings

Alexey Kardashevskiy (4):
  spapr: support only ELF kernel images
  moxie: fix load_elf() usage
  elf-loader: add more return codes
  spapr: print more detailed error message on failed load_elf()

 hw/core/loader.c     | 30 ++++++++++++++++++++++++------
 hw/moxie/moxiesim.c  |  2 +-
 hw/ppc/spapr.c       | 11 +++--------
 hw/s390x/ipl.c       |  4 ++--
 include/hw/elf_ops.h | 19 ++++++++++++++-----
 include/hw/loader.h  |  6 ++++++
 6 files changed, 50 insertions(+), 22 deletions(-)

-- 
1.8.4.rc4

[Qemu-devel] [PATCH v3 1/4] spapr: support only ELF kernel images

[Alexey Kardashevskiy]

Currently everybody uses ELF kernel images with "-kernel" option on
pseries machine but QEMU still tries to boot from an image even it
fails to recognize it is ELF. This produces undefined behaviour if
the user tries a kernel image compiled for another architecture.

This removes support of raw kernel images.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 hw/ppc/spapr.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 5b21562..851ce4b 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1313,11 +1313,6 @@ static void ppc_spapr_init(QEMUMachineInitArgs *args)
             kernel_le = kernel_size > 0;
         }
         if (kernel_size < 0) {
-            kernel_size = load_image_targphys(kernel_filename,
-                                              KERNEL_LOAD_ADDR,
-                                              load_limit - KERNEL_LOAD_ADDR);
-        }
-        if (kernel_size < 0) {
             fprintf(stderr, "qemu: could not load kernel '%s'\n",
                     kernel_filename);
             exit(1);
-- 
1.8.4.rc4

[Qemu-devel] [PATCH v3 2/4] moxie: fix load_elf() usage

[Alexey Kardashevskiy]

At the moment in the case of error, load_elf() returns -1 so load_kernel()
will not signal error at all.

Cc: green@moxielogic.com
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 hw/moxie/moxiesim.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/moxie/moxiesim.c b/hw/moxie/moxiesim.c
index ef4f3a8..a87ca6d 100644
--- a/hw/moxie/moxiesim.c
+++ b/hw/moxie/moxiesim.c
@@ -55,7 +55,7 @@ static void load_kernel(MoxieCPU *cpu, LoaderParams *loader_params)
                            &entry, &kernel_low, &kernel_high, 1,
                            ELF_MACHINE, 0);
 
-    if (!kernel_size) {
+    if (kernel_size <= 0) {
         fprintf(stderr, "qemu: could not load kernel '%s'\n",
                 loader_params->kernel_filename);
         exit(1);
-- 
1.8.4.rc4

[Qemu-devel] [PATCH v3 3/4] elf-loader: add more return codes

[Alexey Kardashevskiy]

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 adds a load_elf_strerror() helper to convert return codes into
string messages.

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

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
Changes:
v3:
* added load_elf_strerror() helper
---
 hw/core/loader.c     | 30 ++++++++++++++++++++++++------
 hw/s390x/ipl.c       |  4 ++--
 include/hw/elf_ops.h | 19 ++++++++++++++-----
 include/hw/loader.h  |  6 ++++++
 4 files changed, 46 insertions(+), 13 deletions(-)

diff --git a/hw/core/loader.c b/hw/core/loader.c
index 0634bee..8a9bb5a 100644
--- a/hw/core/loader.c
+++ b/hw/core/loader.c
@@ -284,12 +284,30 @@ static void *load_at(int fd, int offset, int size)
 #define SZ		64
 #include "hw/elf_ops.h"
 
+const char *load_elf_strerror(int error)
+{
+    switch (error) {
+    case 0:
+        return "No error";
+    case ELF_LOAD_FAILED:
+        return "Failed to load ELF";
+    case ELF_LOAD_NOT_ELF:
+        return "The image is not ELF";
+    case ELF_LOAD_WRONG_ARCH:
+        return "The image is from incompatible architecture";
+    case ELF_LOAD_WRONG_ENDIAN:
+        return "The image has incorrect endianness";
+    default:
+        return "Unknown error";
+    }
+}
+
 /* return < 0 if error, otherwise the number of bytes loaded in memory */
 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 +320,10 @@ 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 +337,7 @@ 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 +350,9 @@ 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..c6b5129 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;
@@ -211,22 +212,30 @@ 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_PPC != 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..3f4335c 100644
--- a/include/hw/loader.h
+++ b/include/hw/loader.h
@@ -8,6 +8,12 @@ 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
+const char *load_elf_strerror(int error);
 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

[Qemu-devel] [PATCH v3 4/4] spapr: print more detailed error message on failed load_elf()

[Alexey Kardashevskiy]

This makes use of new error codes which load_elf() can return and
prints more informative error message.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 hw/ppc/spapr.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 851ce4b..c9dfc6c 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1306,15 +1306,15 @@ static void ppc_spapr_init(QEMUMachineInitArgs *args)
 
         kernel_size = load_elf(kernel_filename, translate_kernel_address, NULL,
                                NULL, &lowaddr, NULL, 1, ELF_MACHINE, 0);
-        if (kernel_size < 0) {
+        if (kernel_size == ELF_LOAD_WRONG_ENDIAN) {
             kernel_size = load_elf(kernel_filename,
                                    translate_kernel_address, NULL,
                                    NULL, &lowaddr, NULL, 0, ELF_MACHINE, 0);
             kernel_le = kernel_size > 0;
         }
         if (kernel_size < 0) {
-            fprintf(stderr, "qemu: could not load kernel '%s'\n",
-                    kernel_filename);
+            fprintf(stderr, "qemu: error loading %s: %s\n",
+                    kernel_filename, load_elf_strerror(kernel_size));
             exit(1);
         }
 
-- 
1.8.4.rc4

Re: [Qemu-devel] [PATCH v3 0/4] elf loader: exit if incompatible architecture is detected

[Alexander Graf]

On 04.02.2014, at 05:04, Alexey Kardashevskiy <aik@ozlabs.ru> wrote:

> The aim of this set is to print reasonable error if ELF cannot be loaded.
> While we are here, also fix some other bits.
> 
> Changes:
> v3:
> * added a helper to convert error codes to strings

Thanks, applied all to ppc-next.


Alex