svn commit: r248121 - in head/sys/boot: common fdt

[Ian Lepore]

Author: ian
Date: Sun Mar 10 00:43:01 2013
New Revision: 248121
URL: http://svnweb.freebsd.org/changeset/base/248121

Log:
  Attach the elf section headers to the loaded kernel as metadata, so
  they can easily be used by later post-processing.  When searching for
  a compiled-in fdt blob, use the section headers to get the size and
  location of the .dynsym section to do a symbol search.
  
  This fixes a problem where the search could overshoot the symbol
  table and wander into the string table.  Sometimes that was harmless
  and sometimes it lead to spurious panic messages about an offset
  bigger than the module size.

Modified:
  head/sys/boot/common/load_elf.c
  head/sys/boot/fdt/fdt_loader_cmd.c

Modified: head/sys/boot/common/load_elf.c
==============================================================================
--- head/sys/boot/common/load_elf.c	Sun Mar 10 00:36:28 2013	(r248120)
+++ head/sys/boot/common/load_elf.c	Sun Mar 10 00:43:01 2013	(r248121)
@@ -397,6 +397,8 @@ __elfN(loadimage)(struct preloaded_file 
 	    "_loadimage: failed to read section headers");
 	goto nosyms;
     }
+    file_addmetadata(fp, MODINFOMD_SHDR, chunk, shdr);
+
     symtabindex = -1;
     symstrindex = -1;
     for (i = 0; i < ehdr->e_shnum; i++) {

Modified: head/sys/boot/fdt/fdt_loader_cmd.c
==============================================================================
--- head/sys/boot/fdt/fdt_loader_cmd.c	Sun Mar 10 00:36:28 2013	(r248120)
+++ head/sys/boot/fdt/fdt_loader_cmd.c	Sun Mar 10 00:43:01 2013	(r248121)
@@ -118,16 +118,17 @@ static char cwd[FDT_CWD_LEN] = "/";
 static vm_offset_t
 fdt_find_static_dtb()
 {
-	Elf_Dyn dyn;
+	Elf_Ehdr *ehdr;
+	Elf_Shdr *shdr;
 	Elf_Sym sym;
-	vm_offset_t dyntab, esym, strtab, symtab, fdt_start;
+	vm_offset_t strtab, symtab, fdt_start;
 	uint64_t offs;
 	struct preloaded_file *kfp;
 	struct file_metadata *md;
 	char *strp;
-	int sym_count;
+	int i, sym_count;
 
-	symtab = strtab = dyntab = esym = 0;
+	symtab = strtab = 0;
 	strp = NULL;
 
 	offs = __elfN(relocation_offset);
@@ -136,42 +137,26 @@ fdt_find_static_dtb()
 	if (kfp == NULL)
 		return (0);
 
-	md = file_findmetadata(kfp, MODINFOMD_ESYM);
+	/* Locate the dynamic symbols and strtab. */
+	md = file_findmetadata(kfp, MODINFOMD_ELFHDR);
 	if (md == NULL)
 		return (0);
-	bcopy(md->md_data, &esym, sizeof(esym));
-	/* esym is already offset */
+	ehdr = (Elf_Ehdr *)md->md_data;
 
-	md = file_findmetadata(kfp, MODINFOMD_DYNAMIC);
+	md = file_findmetadata(kfp, MODINFOMD_SHDR);
 	if (md == NULL)
 		return (0);
-	bcopy(md->md_data, &dyntab, sizeof(dyntab));
-	dyntab += offs;
+	shdr = (Elf_Shdr *)md->md_data;
 
-	/* Locate STRTAB and DYNTAB */
-	for (;;) {
-		COPYOUT(dyntab, &dyn, sizeof(dyn));
-		if (dyn.d_tag == DT_STRTAB) {
-			strtab = (vm_offset_t)(dyn.d_un.d_ptr) + offs;
-		} else if (dyn.d_tag == DT_SYMTAB) {
-			symtab = (vm_offset_t)(dyn.d_un.d_ptr) + offs;
-		} else if (dyn.d_tag == DT_NULL) {
-			break;
+	for (i = 0; i < ehdr->e_shnum; ++i) {
+		if (shdr[i].sh_type == SHT_DYNSYM && symtab == 0) {
+			symtab = shdr[i].sh_addr + offs;
+			sym_count = shdr[i].sh_size / sizeof(Elf_Sym);
+		} else if (shdr[i].sh_type == SHT_STRTAB && strtab == 0) {
+			strtab = shdr[i].sh_addr + offs;
 		}
-		dyntab += sizeof(dyn);
 	}
 
-	if (symtab == 0 || strtab == 0) {
-		/*
-		 * No symtab? No strtab? That should not happen here,
-		 * and should have been verified during __elfN(loadimage).
-		 * This must be some kind of a bug.
-		 */
-		return (0);
-	}
-
-	sym_count = (int)(esym - symtab) / sizeof(Elf_Sym);
-
 	/*
 	 * The most efficent way to find a symbol would be to calculate a
 	 * hash, find proper bucket and chain, and thus find a symbol.