Re: [Xen-ia64-devel] Progress on RHEL4, but blocked at xlilo?

[takebe_akio@xxxxxxxxxxxxxx]

Hi All,

I'm still tried to boot RHEL4 + Xen.
But I have not been able to boot yet.

I confirmed to boot until the following point. 

fs/binfmt_elf.c
-------------------------
 static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
 {

 snip...

         for (i = 0; i < loc->elf_ex.e_phnum; i++) {
                 if (elf_ppnt->p_type == PT_INTERP) {
                         /* This is the program interpreter used for
                          * shared libraries - for now assume that this
                          * is an a.out format binary
                          */
 
                         retval = -ENOEXEC;
                         if (elf_ppnt->p_filesz > PATH_MAX || 
                             elf_ppnt->p_filesz < 2)
                                 goto out_free_file;
                         retval = -ENOMEM;
                         elf_interpreter = (char *) kmalloc(elf_ppnt->p_filesz,
                                                            GFP_KERNEL);
                         if (!elf_interpreter)
                                 goto out_free_file;
 
                         retval = kernel_read(bprm->file, elf_ppnt->p_offset,
                                            elf_interpreter,
                                            elf_ppnt->p_filesz);
                         if (retval != elf_ppnt->p_filesz) {
                                 if (retval >= 0)
                                         retval = -EIO;
                                 goto out_free_interp;
                         }
                         /* make sure path is NULL terminated */
                         retval = -ENOEXEC;
                         if (elf_interpreter[elf_ppnt->p_filesz - 1] != '\0')
                                 goto out_free_interp;
 
                         /* If the program interpreter is one of these two,
                          * then assume an iBCS2 image. Otherwise assume
                          * a native linux image.
                          */
                         if (strcmp(elf_interpreter,"/usr/lib/libc.so.1") == 0 
||
                             strcmp(elf_interpreter,"/usr/lib/ld.so.1") == 0)
                                 ibcs2_interpreter = 1;
 
                         /*
                          * The early SET_PERSONALITY here is so that the lookup
                          * for the interpreter happens in the namespace of the 
                          * to-be-execed image.  SET_PERSONALITY can select an
                          * alternate root.
                          *
                          * However, SET_PERSONALITY is NOT allowed to switch
                          * this task into the new images's memory mapping
                          * policy - that is, TASK_SIZE must still evaluate to
                          * that which is appropriate to the execing 
application.
                          * This is because exit_mmap() needs to have TASK_SIZE
                          * evaluate to the size of the old image.
                          *
                          * So if (say) a 64-bit application is execing a 32-bit
                          * application it is the architecture's responsibility
                          * to defer changing the value of TASK_SIZE until the
                          * switch really is going to happen - do this in
                          * flush_thread().      - akpm
                          */
                         SET_PERSONALITY(loc->elf_ex, ibcs2_interpreter);
 
                         interpreter = open_exec(elf_interpreter);
                         retval = PTR_ERR(interpreter);
                         if (IS_ERR(interpreter))
                                 goto out_free_interp;
                         retval = kernel_read(interpreter, 0, bprm->buf, 
BINPRM_BUF_SIZE);  <---HERE !!!!!
                         if (retval != BINPRM_BUF_SIZE) {
                                 if (retval >= 0)
                                         retval = -EIO;
                                 goto out_free_dentry;
                         }
 
                         /* Get the exec headers */
                         loc->interp_ex = *((struct exec *) bprm->buf);
                         loc->interp_elf_ex = *((struct elfhdr *) bprm->buf);
                         break;
                 }
                 elf_ppnt++;
         }
  snip...
-------------

The above for loop is available when there is .interp section in ELF binary.
.interp section is found, then enter if section and the following operation do.
 1. Check "if (elf_ppnt->p_filesz > PATH_MAX || elf_ppnt->p_filesz < 2)"
 2. Alloc memory for pasting a library path by using kmalloc().
 3. Read a library path from /sbin/init by using kernel_read()
 4. Check wheather /usr/lib/libc.so.1 or /usr/lib/ld.so.1
 5. Open the library by using open_exec()
 6. Read the library from head to BINPRM_BUF_SIZE(128)
 7. Substitute the library header and Break

contents of .interp section are below.
=====================
# LANG=C objdump -s -j .interp /sbin/init

/sbin/init:     file format elf64-ia64-little

Contents of section .interp:
 4000000000000200 2f6c6962 2f6c642d 6c696e75 782d6961  /lib/ld-linux-ia
 4000000000000210 36342e73 6f2e3200                    64.so.2.    
=====================

 /lib/ld-linux-ia64.so.2 is symbolic link
=====================
# LANG=C ls -l /lib/ld-linux-ia64.so.2
lrwxrwxrwx  1 root root 11 Oct 25 23:27 /lib/ld-linux-ia64.so.2 -> ld-2.3.4.so
=====================

I think 0 -> 128 byte of the ld-2.3.4.so is ELF header. 
The header of the ld-2.3.4.so is the below.
=====================
# readelf -h /lib/ld-2.3.4.so |less
ELF Header:
  Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF64
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              DYN (Shared object file)
  Machine:                           Intel IA-64
  Version:                           0x1
  Entry point address:               0x2c90
  Start of program headers:          64 (bytes into file)
  Start of section headers:          205448 (bytes into file)
  Flags:                             0x10, 64-bit
  Size of this header:               64 (bytes)
  Size of program headers:           56 (bytes)
  Number of program headers:         5
  Size of section headers:           64 (bytes)
  Number of section headers:         25
  Section header string table index: 22
=====================

Why the header cannot be read?
Any idea? It's very difficult. Hmmm.... :<

Best Regards,

Akio takebe


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