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binfmt_elf32.c

/*
 * IA-32 ELF support.
 *
 * Copyright (C) 1999 Arun Sharma <arun.sharma@intel.com>
 * Copyright (C) 2001 Hewlett-Packard Co
 *    David Mosberger-Tang <davidm@hpl.hp.com>
 *
 * 06/16/00 A. Mallick  initialize csd/ssd/tssd/cflg for ia32_load_state
 * 04/13/01 D. Mosberger      dropped saving tssd in ar.k1---it's not needed
 * 09/14/01 D. Mosberger      fixed memory management for gdt/tss page
 */

#include <linux/types.h>
#include <linux/mm.h>
#include <linux/security.h>

#include <asm/param.h>
#include <asm/signal.h>

#include "ia32priv.h"
#include "elfcore32.h"

/* Override some function names */
#undef start_thread
#define start_thread                ia32_start_thread
#define elf_format                  elf32_format
#define init_elf_binfmt             init_elf32_binfmt
#define exit_elf_binfmt             exit_elf32_binfmt

#undef CLOCKS_PER_SEC
#define CLOCKS_PER_SEC  IA32_CLOCKS_PER_SEC

extern void ia64_elf32_init (struct pt_regs *regs);

static void elf32_set_personality (void);

static unsigned long __attribute ((unused))
randomize_stack_top(unsigned long stack_top);

#define setup_arg_pages(bprm,tos,exec)          ia32_setup_arg_pages(bprm,exec)
#define elf_map                     elf32_map

#undef SET_PERSONALITY
#define SET_PERSONALITY(ex)   elf32_set_personality()

#define elf_read_implies_exec(ex, have_pt_gnu_stack)  (!(have_pt_gnu_stack))

/* Ugly but avoids duplication */
#include "../../../fs/binfmt_elf.c"

extern struct page *ia32_shared_page[];
extern unsigned long *ia32_gdt;
extern struct page *ia32_gate_page;

int
ia32_install_shared_page (struct vm_area_struct *vma, struct vm_fault *vmf)
{
      vmf->page = ia32_shared_page[smp_processor_id()];
      get_page(vmf->page);
      return 0;
}

int
ia32_install_gate_page (struct vm_area_struct *vma, struct vm_fault *vmf)
{
      vmf->page = ia32_gate_page;
      get_page(vmf->page);
      return 0;
}


static const struct vm_operations_struct ia32_shared_page_vm_ops = {
      .fault = ia32_install_shared_page
};

static const struct vm_operations_struct ia32_gate_page_vm_ops = {
      .fault = ia32_install_gate_page
};

void
ia64_elf32_init (struct pt_regs *regs)
{
      struct vm_area_struct *vma;

      /*
       * Map GDT below 4GB, where the processor can find it.  We need to map
       * it with privilege level 3 because the IVE uses non-privileged accesses to these
       * tables.  IA-32 segmentation is used to protect against IA-32 accesses to them.
       */
      vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
      if (vma) {
            vma->vm_mm = current->mm;
            vma->vm_start = IA32_GDT_OFFSET;
            vma->vm_end = vma->vm_start + PAGE_SIZE;
            vma->vm_page_prot = PAGE_SHARED;
            vma->vm_flags = VM_READ|VM_MAYREAD|VM_RESERVED;
            vma->vm_ops = &ia32_shared_page_vm_ops;
            down_write(&current->mm->mmap_sem);
            {
                  if (insert_vm_struct(current->mm, vma)) {
                        kmem_cache_free(vm_area_cachep, vma);
                        up_write(&current->mm->mmap_sem);
                        BUG();
                  }
            }
            up_write(&current->mm->mmap_sem);
      }

      /*
       * When user stack is not executable, push sigreturn code to stack makes
       * segmentation fault raised when returning to kernel. So now sigreturn
       * code is locked in specific gate page, which is pointed by pretcode
       * when setup_frame_ia32
       */
      vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
      if (vma) {
            vma->vm_mm = current->mm;
            vma->vm_start = IA32_GATE_OFFSET;
            vma->vm_end = vma->vm_start + PAGE_SIZE;
            vma->vm_page_prot = PAGE_COPY_EXEC;
            vma->vm_flags = VM_READ | VM_MAYREAD | VM_EXEC
                        | VM_MAYEXEC | VM_RESERVED;
            vma->vm_ops = &ia32_gate_page_vm_ops;
            down_write(&current->mm->mmap_sem);
            {
                  if (insert_vm_struct(current->mm, vma)) {
                        kmem_cache_free(vm_area_cachep, vma);
                        up_write(&current->mm->mmap_sem);
                        BUG();
                  }
            }
            up_write(&current->mm->mmap_sem);
      }

      /*
       * Install LDT as anonymous memory.  This gives us all-zero segment descriptors
       * until a task modifies them via modify_ldt().
       */
      vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
      if (vma) {
            vma->vm_mm = current->mm;
            vma->vm_start = IA32_LDT_OFFSET;
            vma->vm_end = vma->vm_start + PAGE_ALIGN(IA32_LDT_ENTRIES*IA32_LDT_ENTRY_SIZE);
            vma->vm_page_prot = PAGE_SHARED;
            vma->vm_flags = VM_READ|VM_WRITE|VM_MAYREAD|VM_MAYWRITE;
            down_write(&current->mm->mmap_sem);
            {
                  if (insert_vm_struct(current->mm, vma)) {
                        kmem_cache_free(vm_area_cachep, vma);
                        up_write(&current->mm->mmap_sem);
                        BUG();
                  }
            }
            up_write(&current->mm->mmap_sem);
      }

      ia64_psr(regs)->ac = 0;       /* turn off alignment checking */
      regs->loadrs = 0;
      /*
       *  According to the ABI %edx points to an `atexit' handler.  Since we don't have
       *  one we'll set it to 0 and initialize all the other registers just to make
       *  things more deterministic, ala the i386 implementation.
       */
      regs->r8 = 0;     /* %eax */
      regs->r11 = 0;    /* %ebx */
      regs->r9 = 0;     /* %ecx */
      regs->r10 = 0;    /* %edx */
      regs->r13 = 0;    /* %ebp */
      regs->r14 = 0;    /* %esi */
      regs->r15 = 0;    /* %edi */

      current->thread.eflag = IA32_EFLAG;
      current->thread.fsr = IA32_FSR_DEFAULT;
      current->thread.fcr = IA32_FCR_DEFAULT;
      current->thread.fir = 0;
      current->thread.fdr = 0;

      /*
       * Setup GDTD.  Note: GDTD is the descrambled version of the pseudo-descriptor
       * format defined by Figure 3-11 "Pseudo-Descriptor Format" in the IA-32
       * architecture manual. Also note that the only fields that are not ignored are
       * `base', `limit', 'G', `P' (must be 1) and `S' (must be 0).
       */
      regs->r31 = IA32_SEG_UNSCRAMBLE(IA32_SEG_DESCRIPTOR(IA32_GDT_OFFSET, IA32_PAGE_SIZE - 1,
                                              0, 0, 0, 1, 0, 0, 0));
      /* Setup the segment selectors */
      regs->r16 = (__USER_DS << 16) | __USER_DS; /* ES == DS, GS, FS are zero */
      regs->r17 = (__USER_DS << 16) | __USER_CS; /* SS, CS; ia32_load_state() sets TSS and LDT */

      ia32_load_segment_descriptors(current);
      ia32_load_state(current);
}

/*
 * Undo the override of setup_arg_pages() without this ia32_setup_arg_pages()
 * will suffer infinite self recursion.
 */
#undef setup_arg_pages

int
ia32_setup_arg_pages (struct linux_binprm *bprm, int executable_stack)
{
      int ret;

      ret = setup_arg_pages(bprm, IA32_STACK_TOP, executable_stack);
      if (!ret) {
            /*
             * Can't do it in ia64_elf32_init(). Needs to be done before
             * calls to elf32_map()
             */
            current->thread.ppl = ia32_init_pp_list();
      }

      return ret;
}

static void
elf32_set_personality (void)
{
      set_personality(PER_LINUX32);
      current->thread.map_base  = IA32_PAGE_OFFSET/3;
}

static unsigned long
elf32_map(struct file *filep, unsigned long addr, struct elf_phdr *eppnt,
            int prot, int type, unsigned long unused)
{
      unsigned long pgoff = (eppnt->p_vaddr) & ~IA32_PAGE_MASK;

      return ia32_do_mmap(filep, (addr & IA32_PAGE_MASK), eppnt->p_filesz + pgoff, prot, type,
                      eppnt->p_offset - pgoff);
}

#define cpu_uses_ia32el()     (local_cpu_data->family > 0x1f)

static int __init check_elf32_binfmt(void)
{
      if (cpu_uses_ia32el()) {
            printk("Please use IA-32 EL for executing IA-32 binaries\n");
            unregister_binfmt(&elf_format);
      }
      return 0;
}

module_init(check_elf32_binfmt)

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