Blame SOURCES/0256-nx-set-page-permissions-for-loaded-modules.patch

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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Peter Jones <pjones@redhat.com>
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Date: Mon, 21 Mar 2022 17:46:35 -0400
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Subject: [PATCH] nx: set page permissions for loaded modules.
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For NX, we need to set write and executable permissions on the sections
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of grub modules when we load them.
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On sections with SHF_ALLOC set, which is typically everything except
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.modname and the symbol and string tables, this patch clears the Read
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Only flag on sections that have the ELF flag SHF_WRITE set, and clears
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the No eXecute flag on sections with SHF_EXECINSTR set.  In all other
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cases it sets both flags.
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Signed-off-by: Peter Jones <pjones@redhat.com>
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[rharwood: arm tgptr -> tgaddr]
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Signed-off-by: Robbie Harwood <rharwood@redhat.com>
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---
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 grub-core/kern/dl.c | 120 +++++++++++++++++++++++++++++++++++++++-------------
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 include/grub/dl.h   |  44 +++++++++++++++++++
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 2 files changed, 134 insertions(+), 30 deletions(-)
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diff --git a/grub-core/kern/dl.c b/grub-core/kern/dl.c
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index 8c7aacef39..d5de80186f 100644
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--- a/grub-core/kern/dl.c
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+++ b/grub-core/kern/dl.c
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@@ -285,6 +285,8 @@ grub_dl_load_segments (grub_dl_t mod, const Elf_Ehdr *e)
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 #endif
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   char *ptr;
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+  grub_dprintf ("modules", "loading segments for \"%s\"\n", mod->name);
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+
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   arch_addralign = grub_arch_dl_min_alignment ();
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   for (i = 0, s = (const Elf_Shdr *)((const char *) e + e->e_shoff);
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@@ -384,6 +386,7 @@ grub_dl_load_segments (grub_dl_t mod, const Elf_Ehdr *e)
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   ptr += got;
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 #endif
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+  grub_dprintf ("modules", "done loading segments for \"%s\"\n", mod->name);
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   return GRUB_ERR_NONE;
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 }
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@@ -517,23 +520,6 @@ grub_dl_find_section (Elf_Ehdr *e, const char *name)
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       return s;
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   return NULL;
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 }
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-static long
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-grub_dl_find_section_index (Elf_Ehdr *e, const char *name)
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-{
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-  Elf_Shdr *s;
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-  const char *str;
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-  unsigned i;
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-
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-  s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shstrndx * e->e_shentsize);
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-  str = (char *) e + s->sh_offset;
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-
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-  for (i = 0, s = (Elf_Shdr *) ((char *) e + e->e_shoff);
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-       i < e->e_shnum;
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-       i++, s = (Elf_Shdr *) ((char *) s + e->e_shentsize))
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-    if (grub_strcmp (str + s->sh_name, name) == 0)
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-      return (long)i;
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-  return -1;
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-}
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 /* Me, Vladimir Serbinenko, hereby I add this module check as per new
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    GNU module policy. Note that this license check is informative only.
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@@ -662,6 +648,7 @@ grub_dl_relocate_symbols (grub_dl_t mod, void *ehdr)
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   Elf_Shdr *s;
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   unsigned i;
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+  grub_dprintf ("modules", "relocating symbols for \"%s\"\n", mod->name);
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   for (i = 0, s = (Elf_Shdr *) ((char *) e + e->e_shoff);
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        i < e->e_shnum;
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        i++, s = (Elf_Shdr *) ((char *) s + e->e_shentsize))
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@@ -670,24 +657,95 @@ grub_dl_relocate_symbols (grub_dl_t mod, void *ehdr)
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 	grub_dl_segment_t seg;
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 	grub_err_t err;
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-	/* Find the target segment.  */
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-	for (seg = mod->segment; seg; seg = seg->next)
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-	  if (seg->section == s->sh_info)
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-	    break;
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+	seg = grub_dl_find_segment(mod, s->sh_info);
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+        if (!seg)
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+	  continue;
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-	if (seg)
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-	  {
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-	    if (!mod->symtab)
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-	      return grub_error (GRUB_ERR_BAD_MODULE, "relocation without symbol table");
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+	if (!mod->symtab)
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+	  return grub_error (GRUB_ERR_BAD_MODULE, "relocation without symbol table");
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-	    err = grub_arch_dl_relocate_symbols (mod, ehdr, s, seg);
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-	    if (err)
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-	      return err;
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-	  }
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+	err = grub_arch_dl_relocate_symbols (mod, ehdr, s, seg);
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+	if (err)
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+	  return err;
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       }
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+  grub_dprintf ("modules", "done relocating symbols for \"%s\"\n", mod->name);
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   return GRUB_ERR_NONE;
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 }
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+
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+static grub_err_t
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+grub_dl_set_mem_attrs (grub_dl_t mod, void *ehdr)
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+{
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+  unsigned i;
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+  const Elf_Shdr *s;
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+  const Elf_Ehdr *e = ehdr;
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+#if !defined (__i386__) && !defined (__x86_64__) && !defined(__riscv)
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+  grub_size_t arch_addralign = grub_arch_dl_min_alignment ();
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+  grub_addr_t tgaddr;
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+  grub_uint64_t tgsz;
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+#endif
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+
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+  grub_dprintf ("modules", "updating memory attributes for \"%s\"\n",
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+		mod->name);
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+  for (i = 0, s = (const Elf_Shdr *)((const char *) e + e->e_shoff);
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+       i < e->e_shnum;
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+       i++, s = (const Elf_Shdr *)((const char *) s + e->e_shentsize))
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+    {
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+      grub_dl_segment_t seg;
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+      grub_uint64_t set_attrs = GRUB_MEM_ATTR_R;
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+      grub_uint64_t clear_attrs = GRUB_MEM_ATTR_W|GRUB_MEM_ATTR_X;
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+
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+      seg = grub_dl_find_segment(mod, i);
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+      if (!seg)
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+	continue;
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+
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+      if (seg->size == 0 || !(s->sh_flags & SHF_ALLOC))
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+	continue;
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+
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+      if (s->sh_flags & SHF_WRITE)
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+	{
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+	  set_attrs |= GRUB_MEM_ATTR_W;
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+	  clear_attrs &= ~GRUB_MEM_ATTR_W;
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+	}
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+
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+      if (s->sh_flags & SHF_EXECINSTR)
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+	{
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+	  set_attrs |= GRUB_MEM_ATTR_X;
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+	  clear_attrs &= ~GRUB_MEM_ATTR_X;
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+	}
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+
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+      grub_dprintf ("modules", "setting memory attrs for section \"%s\" to -%s%s%s+%s%s%s\n",
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+		    grub_dl_get_section_name(e, s),
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+		    (clear_attrs & GRUB_MEM_ATTR_R) ? "r" : "",
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+		    (clear_attrs & GRUB_MEM_ATTR_W) ? "w" : "",
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+		    (clear_attrs & GRUB_MEM_ATTR_X) ? "x" : "",
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+		    (set_attrs & GRUB_MEM_ATTR_R) ? "r" : "",
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+		    (set_attrs & GRUB_MEM_ATTR_W) ? "w" : "",
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+		    (set_attrs & GRUB_MEM_ATTR_X) ? "x" : "");
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+      grub_update_mem_attrs ((grub_addr_t)(seg->addr), seg->size, set_attrs, clear_attrs);
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+    }
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+
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+#if !defined (__i386__) && !defined (__x86_64__) && !defined(__riscv)
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+  tgaddr = grub_min((grub_addr_t)mod->tramp, (grub_addr_t)mod->got);
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+  tgsz = grub_max((grub_addr_t)mod->trampptr, (grub_addr_t)mod->gotptr) - tgaddr;
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+
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+  if (tgsz)
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+    {
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+      tgsz = ALIGN_UP(tgsz, arch_addralign);
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+
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+      grub_dprintf ("modules", "updating attributes for GOT and trampolines\n",
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+		    mod->name);
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+      grub_update_mem_attrs (tgaddr, tgsz, GRUB_MEM_ATTR_R|GRUB_MEM_ATTR_X,
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+			     GRUB_MEM_ATTR_W);
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+    }
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+#endif
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+
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+  grub_dprintf ("modules", "done updating module memory attributes for \"%s\"\n",
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+		mod->name);
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+
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+  return GRUB_ERR_NONE;
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+}
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+
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 static void
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 grub_dl_print_gdb_info (grub_dl_t mod, Elf_Ehdr *e)
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 {
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@@ -753,6 +811,7 @@ grub_dl_load_core_noinit (void *addr, grub_size_t size)
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   mod->ref_count = 1;
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   grub_dprintf ("modules", "relocating to %p\n", mod);
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+
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   /* Me, Vladimir Serbinenko, hereby I add this module check as per new
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      GNU module policy. Note that this license check is informative only.
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      Modules have to be licensed under GPLv3 or GPLv3+ (optionally
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@@ -766,7 +825,8 @@ grub_dl_load_core_noinit (void *addr, grub_size_t size)
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       || grub_dl_resolve_dependencies (mod, e)
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       || grub_dl_load_segments (mod, e)
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       || grub_dl_resolve_symbols (mod, e)
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-      || grub_dl_relocate_symbols (mod, e))
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+      || grub_dl_relocate_symbols (mod, e)
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+      || grub_dl_set_mem_attrs (mod, e))
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     {
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       mod->fini = 0;
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       grub_dl_unload (mod);
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diff --git a/include/grub/dl.h b/include/grub/dl.h
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index f36ed5cb17..45ac8e339f 100644
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--- a/include/grub/dl.h
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+++ b/include/grub/dl.h
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@@ -27,6 +27,7 @@
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 #include <grub/elf.h>
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 #include <grub/list.h>
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 #include <grub/misc.h>
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+#include <grub/mm.h>
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 #endif
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 /*
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@@ -268,6 +269,49 @@ grub_dl_is_persistent (grub_dl_t mod)
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   return mod->persistent;
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 }
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+static inline const char *
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+grub_dl_get_section_name (const Elf_Ehdr *e, const Elf_Shdr *s)
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+{
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+  Elf_Shdr *str_s;
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+  const char *str;
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+
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+  str_s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shstrndx * e->e_shentsize);
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+  str = (char *) e + str_s->sh_offset;
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+
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+  return str + s->sh_name;
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+}
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+
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+static inline long
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+grub_dl_find_section_index (Elf_Ehdr *e, const char *name)
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+{
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+  Elf_Shdr *s;
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+  const char *str;
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+  unsigned i;
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+
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+  s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shstrndx * e->e_shentsize);
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+  str = (char *) e + s->sh_offset;
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+
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+  for (i = 0, s = (Elf_Shdr *) ((char *) e + e->e_shoff);
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+       i < e->e_shnum;
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+       i++, s = (Elf_Shdr *) ((char *) s + e->e_shentsize))
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+    if (grub_strcmp (str + s->sh_name, name) == 0)
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+      return (long)i;
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+  return -1;
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+}
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+
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+/* Return the segment for a section of index N */
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+static inline grub_dl_segment_t
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+grub_dl_find_segment (grub_dl_t mod, unsigned n)
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+{
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+  grub_dl_segment_t seg;
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+
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+  for (seg = mod->segment; seg; seg = seg->next)
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+    if (seg->section == n)
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+      return seg;
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+
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+  return NULL;
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+}
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+
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 #endif
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 void * EXPORT_FUNC(grub_resolve_symbol) (const char *name);