RE: [PATCH] generic ELF loading

[Mao, Bibo]

   I do not know whether it is possible to add one element in structure
grub_elf_file structure to identify ELF type (ELFCLASS32/ELFCLASS64)
and ELF machine type, this element can be set at function grub_elf_open.

Thanks
Bibo,mao

>-----Original Message-----
>From: address@hidden
>[mailto:address@hidden On Behalf Of Hollis
>Blanchard
>Sent: 2006年10月14日 6:38
>To: grub-devel
>Subject: [PATCH] generic ELF loading
>
>This patch adds generic ELF loading infrastructure for both 32-bit and
>64-bit ELF. It provides an "iterate" function for program headers, and a
>"load" function for convenience.
>
>I have converted the PowerPC Linux loader to use this infrastructure
>(see next mail), and possibly the i386 multiboot loader as well (though
>I will need others to test it). The module loader looks a little more
>annoying because it actually loads *sections*, not segments.
>
>I will be away next week but intend to commit this soon after, so please
>review.
>
>This code is literally duplicated, once for 32-bit and once for 64-bit.
>I'm trying to come up with a better way of doing that, and I'm
>considering something like this:
>
>        elf32.c:
>        #define Elf_Ehdr Elf32_Ehdr
>        #define Elf_Phdr Elf32_Phdr
>        #include "elfclass.c"
>
>        elf64.c:
>        #define Elf_Ehdr Elf64_Ehdr
>        #define Elf_Phdr Elf64_Phdr
>        #include "elfclass.c"
>
>If you strongly object to #including C files, or have a better way of
>doing this, please speak up.
>
>-Hollis
>
>diff -r b53dfa2812ad include/grub/elfload.h
>--- /dev/null  Thu Jan 01 00:00:00 1970 +0000
>+++ b/include/grub/elfload.h   Fri Oct 13 16:23:22 2006 -0500
>@@ -0,0 +1,57 @@
>+/*
>+ *  GRUB  --  GRand Unified Bootloader
>+ *  Copyright (C) 2003, 2004, 2005, 2006  Free Software Foundation, Inc.
>+ *
>+ *  This program is free software; you can redistribute it and/or modify
>+ *  it under the terms of the GNU General Public License as published by
>+ *  the Free Software Foundation; either version 2 of the License, or
>+ *  (at your option) any later version.
>+ *
>+ *  This program is distributed in the hope that it will be useful,
>+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
>+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>+ *  GNU General Public License for more details.
>+ *
>+ *  You should have received a copy of the GNU General Public License
>+ *  along with this program; if not, write to the Free Software
>+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
>+ */
>+
>+#ifndef GRUB_ELFLOAD_HEADER
>+#define GRUB_ELFLOAD_HEADER   1
>+
>+#include <grub/err.h>
>+#include <grub/elf.h>
>+#include <grub/file.h>
>+#include <grub/symbol.h>
>+#include <grub/types.h>
>+
>+struct grub_elf_file
>+{
>+  grub_file_t file;
>+  union {
>+    Elf64_Ehdr ehdr64;
>+    Elf32_Ehdr ehdr32;
>+  } ehdr;
>+  void *phdrs;
>+};
>+typedef struct grub_elf_file *grub_elf_t;
>+
>+grub_elf_t EXPORT_FUNC(grub_elf_open) (const char *name);
>+grub_err_t EXPORT_FUNC(grub_elf_close) (grub_elf_t elf);
>+
>+int EXPORT_FUNC(grub_elf_is_elf32) (grub_elf_t elf);
>+grub_err_t EXPORT_FUNC(grub_elf32_phdr_iterate) (grub_elf_t elf,
>+                       int (*hook) (grub_elf_t, Elf32_Phdr *, void *),
>+                       void *hook_arg);
>+grub_err_t EXPORT_FUNC(grub_elf32_load) (grub_elf_t elf,
>+                                       int (*) (Elf32_Phdr *));
>+
>+int EXPORT_FUNC(grub_elf_is_elf64) (grub_elf_t elf);
>+grub_err_t EXPORT_FUNC(grub_elf64_phdr_iterate) (grub_elf_t elf,
>+                       int (*hook) (grub_elf_t, Elf64_Phdr *, void *),
>+                       void *hook_arg);
>+grub_err_t EXPORT_FUNC(grub_elf64_load) (grub_elf_t elf,
>+                                       int (*) (Elf64_Phdr *));
>+
>+#endif /* ! GRUB_ELFLOAD_HEADER */
>diff -r b53dfa2812ad kern/elf.c
>--- /dev/null  Thu Jan 01 00:00:00 1970 +0000
>+++ b/kern/elf.c       Fri Oct 13 16:23:22 2006 -0500
>@@ -0,0 +1,280 @@
>+/* elf.c - load ELF files */
>+/*
>+ *  GRUB  --  GRand Unified Bootloader
>+ *  Copyright (C) 2003, 2004, 2005, 2006  Free Software Foundation, Inc.
>+ *
>+ *  This program is free software; you can redistribute it and/or modify
>+ *  it under the terms of the GNU General Public License as published by
>+ *  the Free Software Foundation; either version 2 of the License, or
>+ *  (at your option) any later version.
>+ *
>+ *  This program is distributed in the hope that it will be useful,
>+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
>+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>+ *  GNU General Public License for more details.
>+ *
>+ *  You should have received a copy of the GNU General Public License
>+ *  along with this program; if not, write to the Free Software
>+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
>+ */
>+
>+#include <grub/err.h>
>+#include <grub/elf.h>
>+#include <grub/elfload.h>
>+#include <grub/file.h>
>+#include <grub/misc.h>
>+#include <grub/mm.h>
>+
>+/* Check if EHDR is a valid ELF header.  */
>+static grub_err_t
>+grub_elf_check_header (grub_elf_t elf)
>+{
>+  Elf32_Ehdr *e = &elf->ehdr.ehdr32;
>+
>+  if (e->e_ident[EI_MAG0] != ELFMAG0
>+      || e->e_ident[EI_MAG1] != ELFMAG1
>+      || e->e_ident[EI_MAG2] != ELFMAG2
>+      || e->e_ident[EI_MAG3] != ELFMAG3
>+      || e->e_ident[EI_VERSION] != EV_CURRENT
>+      || e->e_version != EV_CURRENT)
>+    return grub_error (GRUB_ERR_BAD_OS, "invalid arch independent ELF
>magic");
>+
>+  return GRUB_ERR_NONE;
>+}
>+
>+grub_err_t
>+grub_elf_close (grub_elf_t elf)
>+{
>+  grub_file_t file = elf->file;
>+
>+  grub_free (elf->phdrs);
>+  grub_free (elf);
>+
>+  if (file)
>+    grub_file_close (file);
>+
>+  return grub_errno;
>+}
>+
>+grub_elf_t
>+grub_elf_open (const char *name)
>+{
>+  grub_elf_t elf;
>+
>+  elf = grub_malloc (sizeof (*elf));
>+  if (! elf)
>+    return 0;
>+
>+  elf->file = 0;
>+  elf->phdrs = 0;
>+
>+  elf->file = grub_file_open (name);
>+  if (! elf->file)
>+    goto fail;
>+
>+  if (grub_file_read (elf->file, (char *) &elf->ehdr, sizeof (elf->ehdr))
>+      != sizeof (elf->ehdr))
>+    {
>+      grub_error (GRUB_ERR_READ_ERROR, "Cannot read ELF header.");
>+      goto fail;
>+    }
>+
>+  if (grub_elf_check_header (elf))
>+    goto fail;
>+
>+  return elf;
>+
>+fail:
>+  grub_elf_close (elf);
>+  return 0;
>+}
>+
>+
>
>
>+/* 32-bit */
>+
>+int
>+grub_elf_is_elf32 (grub_elf_t elf)
>+{
>+  return elf->ehdr.ehdr32.e_ident[EI_CLASS] == ELFCLASS32;
>+}
>+
>+typedef int (*grub_elf32_load_hook_t) (Elf32_Phdr *phdr);
>+
>+static int
>+grub_elf32_load_segment (grub_elf_t elf, Elf32_Phdr *phdr,
>+                       void *hook)
>+{
>+  grub_elf32_load_hook_t load_hook = (grub_elf32_load_hook_t) hook;
>+
>+  if (phdr->p_type != PT_LOAD)
>+    return 0;
>+
>+  if (load_hook && load_hook (phdr))
>+    return 1;
>+
>+  grub_dprintf ("loader", "Loading segment at %llx, size 0x%llx\n",
>+              (unsigned long long) phdr->p_paddr,
>+              (unsigned long long) phdr->p_filesz);
>+
>+  if (grub_file_seek (elf->file, phdr->p_offset) == (grub_off_t) -1)
>+    {
>+      return grub_error (GRUB_ERR_BAD_OS, "Invalid offset in program
>header");
>+    }
>+
>+  if (grub_file_read (elf->file, (void *) (long) phdr->p_paddr,
>phdr->p_filesz)
>+      != (grub_ssize_t) phdr->p_filesz)
>+    {
>+      return grub_error (GRUB_ERR_BAD_OS, "Couldn't load segment");
>+    }
>+
>+  if (phdr->p_filesz < phdr->p_memsz)
>+    grub_memset ((void *) (unsigned long) (phdr->p_paddr + phdr->p_filesz),
>+               0, phdr->p_memsz - phdr->p_filesz);
>+
>+  return 0;
>+}
>+
>+static grub_err_t
>+grub_elf32_load_phdrs (grub_elf_t elf)
>+{
>+  grub_ssize_t phdrs_size;
>+
>+  phdrs_size = elf->ehdr.ehdr32.e_phnum * elf->ehdr.ehdr32.e_phentsize;
>+
>+  grub_dprintf ("elf", "loading program headers: offset 0x%llx, size 0x%x\n",
>+              (unsigned long long) elf->ehdr.ehdr32.e_phoff,
>+              phdrs_size);
>+
>+  elf->phdrs = grub_malloc (phdrs_size);
>+  if (! elf->phdrs)
>+    return grub_errno;
>+
>+  if ((grub_file_seek (elf->file, elf->ehdr.ehdr32.e_phoff) == (grub_off_t)
>-1)
>+      || (grub_file_read (elf->file, elf->phdrs, phdrs_size) != phdrs_size))
>+    return grub_error (GRUB_ERR_READ_ERROR, "Cannot read program headers");
>+
>+  return GRUB_ERR_NONE;
>+}
>+
>+grub_err_t
>+grub_elf32_phdr_iterate (grub_elf_t elf,
>+                       int (*hook) (grub_elf_t, Elf32_Phdr *, void *),
>+                       void *hook_arg)
>+{
>+  Elf32_Phdr *phdrs;
>+  unsigned int i;
>+
>+  if (! elf->phdrs)
>+    if (grub_elf32_load_phdrs (elf))
>+      return grub_errno;
>+
>+  phdrs = (Elf32_Phdr *) elf->phdrs;
>+  for (i = 0; i < elf->ehdr.ehdr32.e_phnum; i++)
>+    if (hook (elf, phdrs + i, hook_arg))
>+      break;
>+
>+  return grub_errno;
>+}
>+
>+/* Load every loadable segment into memory.  */
>+grub_err_t
>+grub_elf32_load (grub_elf_t elf, int (*phdr_hook) (Elf32_Phdr *))
>+{
>+  return grub_elf32_phdr_iterate (elf, grub_elf32_load_segment,
>+                                phdr_hook);
>+}
>+
>+
>
>
>+/* 64-bit */
>+
>+int
>+grub_elf_is_elf64 (grub_elf_t elf)
>+{
>+  return elf->ehdr.ehdr64.e_ident[EI_CLASS] == ELFCLASS64;
>+}
>+
>+typedef int (*grub_elf64_load_hook_t) (Elf64_Phdr *phdr);
>+
>+static int
>+grub_elf64_load_segment (grub_elf_t elf, Elf64_Phdr *phdr,
>+                       void *hook)
>+{
>+  grub_elf64_load_hook_t load_hook = (grub_elf64_load_hook_t) hook;
>+
>+  if (phdr->p_type != PT_LOAD)
>+    return 0;
>+
>+  if (load_hook && load_hook (phdr))
>+    return 1;
>+
>+  grub_dprintf ("loader", "Loading segment at %llx, size 0x%llx\n",
>+              (unsigned long long) phdr->p_paddr,
>+              (unsigned long long) phdr->p_filesz);
>+
>+  if (grub_file_seek (elf->file, phdr->p_offset) == (grub_off_t) -1)
>+    {
>+      return grub_error (GRUB_ERR_BAD_OS, "Invalid offset in program
>header");
>+    }
>+
>+  if (grub_file_read (elf->file, (void *) (long) phdr->p_paddr,
>phdr->p_filesz)
>+      != (grub_ssize_t) phdr->p_filesz)
>+    {
>+      return grub_error (GRUB_ERR_BAD_OS, "Couldn't load segment");
>+    }
>+
>+  if (phdr->p_filesz < phdr->p_memsz)
>+    grub_memset ((void *) (unsigned long) (phdr->p_paddr + phdr->p_filesz),
>+               0, phdr->p_memsz - phdr->p_filesz);
>+
>+  return 0;
>+}
>+
>+static grub_err_t
>+grub_elf64_load_phdrs (grub_elf_t elf)
>+{
>+  grub_ssize_t phdrs_size;
>+
>+  phdrs_size = elf->ehdr.ehdr64.e_phnum * elf->ehdr.ehdr64.e_phentsize;
>+
>+  grub_dprintf ("elf", "loading program headers: offset 0x%llx, size 0x%x\n",
>+              (unsigned long long) elf->ehdr.ehdr64.e_phoff,
>+              phdrs_size);
>+
>+  elf->phdrs = grub_malloc (phdrs_size);
>+  if (! elf->phdrs)
>+    return grub_errno;
>+
>+  if ((grub_file_seek (elf->file, elf->ehdr.ehdr64.e_phoff) == (grub_off_t)
>-1)
>+      || (grub_file_read (elf->file, elf->phdrs, phdrs_size) != phdrs_size))
>+    return grub_error (GRUB_ERR_READ_ERROR, "Cannot read program headers");
>+
>+  return GRUB_ERR_NONE;
>+}
>+
>+grub_err_t
>+grub_elf64_phdr_iterate (grub_elf_t elf,
>+                       int (*hook) (grub_elf_t, Elf64_Phdr *, void *),
>+                       void *hook_arg)
>+{
>+  Elf64_Phdr *phdrs;
>+  unsigned int i;
>+
>+  if (! elf->phdrs)
>+    if (grub_elf64_load_phdrs (elf))
>+      return grub_errno;
>+
>+  phdrs = (Elf64_Phdr *) elf->phdrs;
>+  for (i = 0; i < elf->ehdr.ehdr64.e_phnum; i++)
>+    if (hook (elf, phdrs + i, hook_arg))
>+      break;
>+
>+  return grub_errno;
>+}
>+
>+/* Load every loadable segment into memory.  */
>+grub_err_t
>+grub_elf64_load (grub_elf_t elf, int (*phdr_hook) (Elf64_Phdr *))
>+{
>+  return grub_elf64_phdr_iterate (elf, grub_elf64_load_segment,
>+                                phdr_hook);
>+}
>
>
>
>
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