linux-user: introduce functions to detect CPU type

Add a function to return ELF e_flags and use it
to select the CPU model.

Signed-off-by: YunQiang Su <syq@debian.org>
[lv: split the patch and some cleanup in get_elf_eflags()]
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20180220173307.25125-3-laurent@vivier.eu>

1 files changed, 35 insertions, 0 deletions

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 8bb9a2c3e8..0208022445 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -2396,6 +2396,41 @@ give_up:
     g_free(syms);
 }
 
+uint32_t get_elf_eflags(int fd)
+{
+    struct elfhdr ehdr;
+    off_t offset;
+    int ret;
+
+    /* Read ELF header */
+    offset = lseek(fd, 0, SEEK_SET);
+    if (offset == (off_t) -1) {
+        return 0;
+    }
+    ret = read(fd, &ehdr, sizeof(ehdr));
+    if (ret < sizeof(ehdr)) {
+        return 0;
+    }
+    offset = lseek(fd, offset, SEEK_SET);
+    if (offset == (off_t) -1) {
+        return 0;
+    }
+
+    /* Check ELF signature */
+    if (!elf_check_ident(&ehdr)) {
+        return 0;
+    }
+
+    /* check header */
+    bswap_ehdr(&ehdr);
+    if (!elf_check_ehdr(&ehdr)) {
+        return 0;
+    }
+
+    /* return architecture id */
+    return ehdr.e_flags;
+}
+
 int load_elf_binary(struct linux_binprm *bprm, struct image_info *info)
 {
     struct image_info interp_info;