elf-loader: Provide the possibility to relocate s390 ELF files

On s390, we would like to load our "BIOS" s390-ccw.img to the end of the
RAM. Therefor we need the possibility to relocate the ELF file so that
it can also run from different addresses. This patch adds the necessary
code to the QEMU ELF loader function.

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Message-Id: <1425895973-15239-2-git-send-email-thuth@linux.vnet.ibm.com>
Acked-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

1 files changed, 78 insertions, 0 deletions

diff --git a/include/hw/elf_ops.h b/include/hw/elf_ops.h
index a517753..16a627b 100644
--- a/include/hw/elf_ops.h
+++ b/include/hw/elf_ops.h
@@ -49,6 +49,13 @@ static void glue(bswap_sym, SZ)(struct elf_sym *sym)
     bswap16s(&sym->st_shndx);
 }
 
+static void glue(bswap_rela, SZ)(struct elf_rela *rela)
+{
+    bswapSZs(&rela->r_offset);
+    bswapSZs(&rela->r_info);
+    bswapSZs((elf_word *)&rela->r_addend);
+}
+
 static struct elf_shdr *glue(find_section, SZ)(struct elf_shdr *shdr_table,
                                                int n, int type)
 {
@@ -182,6 +189,75 @@ static int glue(load_symbols, SZ)(struct elfhdr *ehdr, int fd, int must_swab,
     return -1;
 }
 
+static int glue(elf_reloc, SZ)(struct elfhdr *ehdr, int fd, int must_swab,
+                               uint64_t (*translate_fn)(void *, uint64_t),
+                               void *translate_opaque, uint8_t *data,
+                               struct elf_phdr *ph, int elf_machine)
+{
+    struct elf_shdr *reltab, *shdr_table = NULL;
+    struct elf_rela *rels = NULL;
+    int nrels, i, ret = -1;
+    elf_word wordval;
+    void *addr;
+
+    shdr_table = load_at(fd, ehdr->e_shoff,
+                         sizeof(struct elf_shdr) * ehdr->e_shnum);
+    if (!shdr_table) {
+        return -1;
+    }
+    if (must_swab) {
+        for (i = 0; i < ehdr->e_shnum; i++) {
+            glue(bswap_shdr, SZ)(&shdr_table[i]);
+        }
+    }
+
+    reltab = glue(find_section, SZ)(shdr_table, ehdr->e_shnum, SHT_RELA);
+    if (!reltab) {
+        goto fail;
+    }
+    rels = load_at(fd, reltab->sh_offset, reltab->sh_size);
+    if (!rels) {
+        goto fail;
+    }
+    nrels = reltab->sh_size / sizeof(struct elf_rela);
+
+    for (i = 0; i < nrels; i++) {
+        if (must_swab) {
+            glue(bswap_rela, SZ)(&rels[i]);
+        }
+        if (rels[i].r_offset < ph->p_vaddr ||
+            rels[i].r_offset >= ph->p_vaddr + ph->p_filesz) {
+            continue;
+        }
+        addr = &data[rels[i].r_offset - ph->p_vaddr];
+        switch (elf_machine) {
+        case EM_S390:
+            switch (rels[i].r_info) {
+            case R_390_RELATIVE:
+                wordval = *(elf_word *)addr;
+                if (must_swab) {
+                    bswapSZs(&wordval);
+                }
+                wordval = translate_fn(translate_opaque, wordval);
+                if (must_swab) {
+                    bswapSZs(&wordval);
+                }
+                *(elf_word *)addr = wordval;
+                break;
+            default:
+                fprintf(stderr, "Unsupported relocation type %i!\n",
+                        (int)rels[i].r_info);
+            }
+        }
+    }
+
+    ret = 0;
+fail:
+    g_free(rels);
+    g_free(shdr_table);
+    return ret;
+}
+
 static int glue(load_elf, SZ)(const char *name, int fd,
                               uint64_t (*translate_fn)(void *, uint64_t),
                               void *translate_opaque,
@@ -271,6 +347,8 @@ static int glue(load_elf, SZ)(const char *name, int fd,
                linked at the wrong physical address.  */
             if (translate_fn) {
                 addr = translate_fn(translate_opaque, ph->p_paddr);
+                glue(elf_reloc, SZ)(&ehdr, fd, must_swab,  translate_fn,
+                                    translate_opaque, data, ph, elf_machine);
             } else {
                 addr = ph->p_paddr;
             }