x86, realmode: 16-bit real-mode code support for relocs tool
H. Peter Anvin [Tue, 8 May 2012 18:22:24 +0000 (21:22 +0300)]
A new option is added to the relocs tool called '--realmode'.
This option causes the generation of 16-bit segment relocations
and 32-bit linear relocations for the real-mode code. When
the real-mode code is moved to the low-memory during kernel
initialization, these relocation entries can be used to
relocate the code properly.

In the assembly code 16-bit segment relocations must be relative
to the 'real_mode_seg' absolute symbol. Linear relocations must be
relative to a symbol prefixed with 'pa_'.

16-bit segment relocation is used to load cs:ip in 16-bit code.
Linear relocations are used in the 32-bit code for relocatable
data references. They are declared in the linker script of the
real-mode code.

The relocs tool is moved to arch/x86/tools/relocs.c, and added new
target archscripts that can be used to build scripts needed building
an architecture.  be compiled before building the arch/x86 tree.

[ hpa: accelerating this because it detects invalid absolute
  relocations, a serious bug in binutils 2.22.52.0.x which currently
  produces bad kernels. ]

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1336501366-28617-2-git-send-email-jarkko.sakkinen@intel.com
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: <stable@vger.kernel.org>

Makefile
arch/x86/Makefile
arch/x86/boot/compressed/Makefile
arch/x86/tools/.gitignore [new file with mode: 0644]
arch/x86/tools/Makefile
arch/x86/tools/relocs.c [moved from arch/x86/boot/compressed/relocs.c with 77% similarity]
scripts/Makefile

index 48bd1f5..db2bcf3 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -442,7 +442,7 @@ asm-generic:
 
 no-dot-config-targets := clean mrproper distclean \
                         cscope gtags TAGS tags help %docs check% coccicheck \
-                        include/linux/version.h headers_% archheaders \
+                        include/linux/version.h headers_% archheaders archscripts \
                         kernelversion %src-pkg
 
 config-targets := 0
@@ -979,7 +979,7 @@ prepare1: prepare2 include/linux/version.h include/generated/utsrelease.h \
                    include/config/auto.conf
        $(cmd_crmodverdir)
 
-archprepare: archheaders prepare1 scripts_basic
+archprepare: archheaders archscripts prepare1 scripts_basic
 
 prepare0: archprepare FORCE
        $(Q)$(MAKE) $(build)=.
@@ -1049,8 +1049,11 @@ hdr-dst = $(if $(KBUILD_HEADERS), dst=include/asm-$(hdr-arch), dst=include/asm)
 PHONY += archheaders
 archheaders:
 
+PHONY += archscripts
+archscripts:
+
 PHONY += __headers
-__headers: include/linux/version.h scripts_basic asm-generic archheaders FORCE
+__headers: include/linux/version.h scripts_basic asm-generic archheaders archscripts FORCE
        $(Q)$(MAKE) $(build)=scripts build_unifdef
 
 PHONY += headers_install_all
index 41a7237..94e91e4 100644 (file)
@@ -134,6 +134,9 @@ KBUILD_CFLAGS += $(call cc-option,-mno-avx,)
 KBUILD_CFLAGS += $(mflags-y)
 KBUILD_AFLAGS += $(mflags-y)
 
+archscripts:
+       $(Q)$(MAKE) $(build)=arch/x86/tools relocs
+
 ###
 # Syscall table generation
 
index fd55a2f..e398bb5 100644 (file)
@@ -40,13 +40,12 @@ OBJCOPYFLAGS_vmlinux.bin :=  -R .comment -S
 $(obj)/vmlinux.bin: vmlinux FORCE
        $(call if_changed,objcopy)
 
+targets += vmlinux.bin.all vmlinux.relocs
 
-targets += vmlinux.bin.all vmlinux.relocs relocs
-hostprogs-$(CONFIG_X86_NEED_RELOCS) += relocs
-
+CMD_RELOCS = arch/x86/tools/relocs
 quiet_cmd_relocs = RELOCS  $@
-      cmd_relocs = $(obj)/relocs $< > $@;$(obj)/relocs --abs-relocs $<
-$(obj)/vmlinux.relocs: vmlinux $(obj)/relocs FORCE
+      cmd_relocs = $(CMD_RELOCS) $< > $@;$(CMD_RELOCS) --abs-relocs $<
+$(obj)/vmlinux.relocs: vmlinux FORCE
        $(call if_changed,relocs)
 
 vmlinux.bin.all-y := $(obj)/vmlinux.bin
diff --git a/arch/x86/tools/.gitignore b/arch/x86/tools/.gitignore
new file mode 100644 (file)
index 0000000..be0ed06
--- /dev/null
@@ -0,0 +1 @@
+relocs
index d511aa9..733057b 100644 (file)
@@ -36,3 +36,7 @@ HOSTCFLAGS_insn_sanity.o := -Wall -I$(objtree)/arch/x86/lib/ -I$(srctree)/arch/x
 $(obj)/test_get_len.o: $(srctree)/arch/x86/lib/insn.c $(srctree)/arch/x86/lib/inat.c $(srctree)/arch/x86/include/asm/inat_types.h $(srctree)/arch/x86/include/asm/inat.h $(srctree)/arch/x86/include/asm/insn.h $(objtree)/arch/x86/lib/inat-tables.c
 
 $(obj)/insn_sanity.o: $(srctree)/arch/x86/lib/insn.c $(srctree)/arch/x86/lib/inat.c $(srctree)/arch/x86/include/asm/inat_types.h $(srctree)/arch/x86/include/asm/inat.h $(srctree)/arch/x86/include/asm/insn.h $(objtree)/arch/x86/lib/inat-tables.c
+
+HOST_EXTRACFLAGS += -I$(srctree)/tools/include
+hostprogs-y    += relocs
+relocs: $(obj)/relocs
similarity index 77%
rename from arch/x86/boot/compressed/relocs.c
rename to arch/x86/tools/relocs.c
index fb7117a..0291470 100644 (file)
@@ -18,6 +18,8 @@ static void die(char *fmt, ...);
 static Elf32_Ehdr ehdr;
 static unsigned long reloc_count, reloc_idx;
 static unsigned long *relocs;
+static unsigned long reloc16_count, reloc16_idx;
+static unsigned long *relocs16;
 
 struct section {
        Elf32_Shdr     shdr;
@@ -28,52 +30,82 @@ struct section {
 };
 static struct section *secs;
 
+enum symtype {
+       S_ABS,
+       S_REL,
+       S_SEG,
+       S_LIN,
+       S_NSYMTYPES
+};
+
+static const char * const sym_regex_kernel[S_NSYMTYPES] = {
 /*
  * Following symbols have been audited. There values are constant and do
  * not change if bzImage is loaded at a different physical address than
  * the address for which it has been compiled. Don't warn user about
  * absolute relocations present w.r.t these symbols.
  */
-static const char abs_sym_regex[] =
+       [S_ABS] =
        "^(xen_irq_disable_direct_reloc$|"
        "xen_save_fl_direct_reloc$|"
        "VDSO|"
-       "__crc_)";
-static regex_t abs_sym_regex_c;
-static int is_abs_reloc(const char *sym_name)
-{
-       return !regexec(&abs_sym_regex_c, sym_name, 0, NULL, 0);
-}
+       "__crc_)",
 
 /*
  * These symbols are known to be relative, even if the linker marks them
  * as absolute (typically defined outside any section in the linker script.)
  */
-static const char rel_sym_regex[] =
-       "^_end$";
-static regex_t rel_sym_regex_c;
-static int is_rel_reloc(const char *sym_name)
+       [S_REL] =
+       "^_end$",
+};
+
+
+static const char * const sym_regex_realmode[S_NSYMTYPES] = {
+/*
+ * These are 16-bit segment symbols when compiling 16-bit code.
+ */
+       [S_SEG] =
+       "^real_mode_seg$",
+
+/*
+ * These are offsets belonging to segments, as opposed to linear addresses,
+ * when compiling 16-bit code.
+ */
+       [S_LIN] =
+       "^pa_",
+};
+
+static const char * const *sym_regex;
+
+static regex_t sym_regex_c[S_NSYMTYPES];
+static int is_reloc(enum symtype type, const char *sym_name)
 {
-       return !regexec(&rel_sym_regex_c, sym_name, 0, NULL, 0);
+       return sym_regex[type] &&
+               !regexec(&sym_regex_c[type], sym_name, 0, NULL, 0);
 }
 
-static void regex_init(void)
+static void regex_init(int use_real_mode)
 {
         char errbuf[128];
         int err;
-       
-        err = regcomp(&abs_sym_regex_c, abs_sym_regex,
-                      REG_EXTENDED|REG_NOSUB);
-        if (err) {
-                regerror(err, &abs_sym_regex_c, errbuf, sizeof errbuf);
-                die("%s", errbuf);
-        }
+       int i;
 
-        err = regcomp(&rel_sym_regex_c, rel_sym_regex,
-                      REG_EXTENDED|REG_NOSUB);
-        if (err) {
-                regerror(err, &rel_sym_regex_c, errbuf, sizeof errbuf);
-                die("%s", errbuf);
+       if (use_real_mode)
+               sym_regex = sym_regex_realmode;
+       else
+               sym_regex = sym_regex_kernel;
+
+       for (i = 0; i < S_NSYMTYPES; i++) {
+               if (!sym_regex[i])
+                       continue;
+
+               err = regcomp(&sym_regex_c[i], sym_regex[i],
+                             REG_EXTENDED|REG_NOSUB);
+
+               if (err) {
+                       regerror(err, &sym_regex_c[i], errbuf, sizeof errbuf);
+                       die("%s", errbuf);
+               }
         }
 }
 
@@ -154,6 +186,10 @@ static const char *rel_type(unsigned type)
                REL_TYPE(R_386_RELATIVE),
                REL_TYPE(R_386_GOTOFF),
                REL_TYPE(R_386_GOTPC),
+               REL_TYPE(R_386_8),
+               REL_TYPE(R_386_PC8),
+               REL_TYPE(R_386_16),
+               REL_TYPE(R_386_PC16),
 #undef REL_TYPE
        };
        const char *name = "unknown type rel type name";
@@ -189,7 +225,7 @@ static const char *sym_name(const char *sym_strtab, Elf32_Sym *sym)
                name = sym_strtab + sym->st_name;
        }
        else {
-               name = sec_name(secs[sym->st_shndx].shdr.sh_name);
+               name = sec_name(sym->st_shndx);
        }
        return name;
 }
@@ -472,7 +508,7 @@ static void print_absolute_relocs(void)
                         * Before warning check if this absolute symbol
                         * relocation is harmless.
                         */
-                       if (is_abs_reloc(name) || is_rel_reloc(name))
+                       if (is_reloc(S_ABS, name) || is_reloc(S_REL, name))
                                continue;
 
                        if (!printed) {
@@ -496,7 +532,8 @@ static void print_absolute_relocs(void)
                printf("\n");
 }
 
-static void walk_relocs(void (*visit)(Elf32_Rel *rel, Elf32_Sym *sym))
+static void walk_relocs(void (*visit)(Elf32_Rel *rel, Elf32_Sym *sym),
+                       int use_real_mode)
 {
        int i;
        /* Walk through the relocations */
@@ -521,30 +558,62 @@ static void walk_relocs(void (*visit)(Elf32_Rel *rel, Elf32_Sym *sym))
                        Elf32_Rel *rel;
                        Elf32_Sym *sym;
                        unsigned r_type;
+                       const char *symname;
                        rel = &sec->reltab[j];
                        sym = &sh_symtab[ELF32_R_SYM(rel->r_info)];
                        r_type = ELF32_R_TYPE(rel->r_info);
-                       /* Don't visit relocations to absolute symbols */
-                       if (sym->st_shndx == SHN_ABS &&
-                           !is_rel_reloc(sym_name(sym_strtab, sym))) {
-                               continue;
-                       }
+
                        switch (r_type) {
                        case R_386_NONE:
                        case R_386_PC32:
+                       case R_386_PC16:
+                       case R_386_PC8:
                                /*
                                 * NONE can be ignored and and PC relative
                                 * relocations don't need to be adjusted.
                                 */
                                break;
+
+                       case R_386_16:
+                               symname = sym_name(sym_strtab, sym);
+                               if (!use_real_mode)
+                                       goto bad;
+                               if (sym->st_shndx == SHN_ABS) {
+                                       if (is_reloc(S_ABS, symname))
+                                               break;
+                                       else if (!is_reloc(S_SEG, symname))
+                                               goto bad;
+                               } else {
+                                       if (is_reloc(S_LIN, symname))
+                                               goto bad;
+                                       else
+                                               break;
+                               }
+                               visit(rel, sym);
+                               break;
+
                        case R_386_32:
-                               /* Visit relocations that need to be adjusted */
+                               symname = sym_name(sym_strtab, sym);
+                               if (sym->st_shndx == SHN_ABS) {
+                                       if (is_reloc(S_ABS, symname))
+                                               break;
+                                       else if (!is_reloc(S_REL, symname))
+                                               goto bad;
+                               } else {
+                                       if (use_real_mode &&
+                                           !is_reloc(S_LIN, symname))
+                                               break;
+                               }
                                visit(rel, sym);
                                break;
                        default:
                                die("Unsupported relocation type: %s (%d)\n",
                                    rel_type(r_type), r_type);
                                break;
+                       bad:
+                               symname = sym_name(sym_strtab, sym);
+                               die("Invalid %s relocation: %s\n",
+                                   rel_type(r_type), symname);
                        }
                }
        }
@@ -552,13 +621,19 @@ static void walk_relocs(void (*visit)(Elf32_Rel *rel, Elf32_Sym *sym))
 
 static void count_reloc(Elf32_Rel *rel, Elf32_Sym *sym)
 {
-       reloc_count += 1;
+       if (ELF32_R_TYPE(rel->r_info) == R_386_16)
+               reloc16_count++;
+       else
+               reloc_count++;
 }
 
 static void collect_reloc(Elf32_Rel *rel, Elf32_Sym *sym)
 {
        /* Remember the address that needs to be adjusted. */
-       relocs[reloc_idx++] = rel->r_offset;
+       if (ELF32_R_TYPE(rel->r_info) == R_386_16)
+               relocs16[reloc16_idx++] = rel->r_offset;
+       else
+               relocs[reloc_idx++] = rel->r_offset;
 }
 
 static int cmp_relocs(const void *va, const void *vb)
@@ -568,23 +643,41 @@ static int cmp_relocs(const void *va, const void *vb)
        return (*a == *b)? 0 : (*a > *b)? 1 : -1;
 }
 
-static void emit_relocs(int as_text)
+static int write32(unsigned int v, FILE *f)
+{
+       unsigned char buf[4];
+
+       put_unaligned_le32(v, buf);
+       return fwrite(buf, 1, 4, f) == 4 ? 0 : -1;
+}
+
+static void emit_relocs(int as_text, int use_real_mode)
 {
        int i;
        /* Count how many relocations I have and allocate space for them. */
        reloc_count = 0;
-       walk_relocs(count_reloc);
+       walk_relocs(count_reloc, use_real_mode);
        relocs = malloc(reloc_count * sizeof(relocs[0]));
        if (!relocs) {
                die("malloc of %d entries for relocs failed\n",
                        reloc_count);
        }
+
+       relocs16 = malloc(reloc16_count * sizeof(relocs[0]));
+       if (!relocs16) {
+               die("malloc of %d entries for relocs16 failed\n",
+                       reloc16_count);
+       }
        /* Collect up the relocations */
        reloc_idx = 0;
-       walk_relocs(collect_reloc);
+       walk_relocs(collect_reloc, use_real_mode);
+
+       if (reloc16_count && !use_real_mode)
+               die("Segment relocations found but --realmode not specified\n");
 
        /* Order the relocations for more efficient processing */
        qsort(relocs, reloc_count, sizeof(relocs[0]), cmp_relocs);
+       qsort(relocs16, reloc16_count, sizeof(relocs16[0]), cmp_relocs);
 
        /* Print the relocations */
        if (as_text) {
@@ -593,58 +686,83 @@ static void emit_relocs(int as_text)
                 */
                printf(".section \".data.reloc\",\"a\"\n");
                printf(".balign 4\n");
-               for (i = 0; i < reloc_count; i++) {
-                       printf("\t .long 0x%08lx\n", relocs[i]);
+               if (use_real_mode) {
+                       printf("\t.long %lu\n", reloc16_count);
+                       for (i = 0; i < reloc16_count; i++)
+                               printf("\t.long 0x%08lx\n", relocs16[i]);
+                       printf("\t.long %lu\n", reloc_count);
+                       for (i = 0; i < reloc_count; i++) {
+                               printf("\t.long 0x%08lx\n", relocs[i]);
+                       }
+               } else {
+                       /* Print a stop */
+                       printf("\t.long 0x%08lx\n", (unsigned long)0);
+                       for (i = 0; i < reloc_count; i++) {
+                               printf("\t.long 0x%08lx\n", relocs[i]);
+                       }
                }
+
                printf("\n");
        }
        else {
-               unsigned char buf[4];
-               /* Print a stop */
-               fwrite("\0\0\0\0", 4, 1, stdout);
-               /* Now print each relocation */
-               for (i = 0; i < reloc_count; i++) {
-                       put_unaligned_le32(relocs[i], buf);
-                       fwrite(buf, 4, 1, stdout);
+               if (use_real_mode) {
+                       write32(reloc16_count, stdout);
+                       for (i = 0; i < reloc16_count; i++)
+                               write32(relocs16[i], stdout);
+                       write32(reloc_count, stdout);
+
+                       /* Now print each relocation */
+                       for (i = 0; i < reloc_count; i++)
+                               write32(relocs[i], stdout);
+               } else {
+                       /* Print a stop */
+                       write32(0, stdout);
+
+                       /* Now print each relocation */
+                       for (i = 0; i < reloc_count; i++) {
+                               write32(relocs[i], stdout);
+                       }
                }
        }
 }
 
 static void usage(void)
 {
-       die("relocs [--abs-syms |--abs-relocs | --text] vmlinux\n");
+       die("relocs [--abs-syms|--abs-relocs|--text|--realmode] vmlinux\n");
 }
 
 int main(int argc, char **argv)
 {
        int show_absolute_syms, show_absolute_relocs;
-       int as_text;
+       int as_text, use_real_mode;
        const char *fname;
        FILE *fp;
        int i;
 
-       regex_init();
-
        show_absolute_syms = 0;
        show_absolute_relocs = 0;
        as_text = 0;
+       use_real_mode = 0;
        fname = NULL;
        for (i = 1; i < argc; i++) {
                char *arg = argv[i];
                if (*arg == '-') {
-                       if (strcmp(argv[1], "--abs-syms") == 0) {
+                       if (strcmp(arg, "--abs-syms") == 0) {
                                show_absolute_syms = 1;
                                continue;
                        }
-
-                       if (strcmp(argv[1], "--abs-relocs") == 0) {
+                       if (strcmp(arg, "--abs-relocs") == 0) {
                                show_absolute_relocs = 1;
                                continue;
                        }
-                       else if (strcmp(argv[1], "--text") == 0) {
+                       if (strcmp(arg, "--text") == 0) {
                                as_text = 1;
                                continue;
                        }
+                       if (strcmp(arg, "--realmode") == 0) {
+                               use_real_mode = 1;
+                               continue;
+                       }
                }
                else if (!fname) {
                        fname = arg;
@@ -655,6 +773,7 @@ int main(int argc, char **argv)
        if (!fname) {
                usage();
        }
+       regex_init(use_real_mode);
        fp = fopen(fname, "r");
        if (!fp) {
                die("Cannot open %s: %s\n",
@@ -673,6 +792,6 @@ int main(int argc, char **argv)
                print_absolute_relocs();
                return 0;
        }
-       emit_relocs(as_text);
+       emit_relocs(as_text, use_real_mode);
        return 0;
 }
index df7678f..3626666 100644 (file)
@@ -8,6 +8,8 @@
 # conmakehash:  Create arrays for initializing the kernel console tables
 # docproc:       Used in Documentation/DocBook
 
+HOST_EXTRACFLAGS += -I$(srctree)/tools/include
+
 hostprogs-$(CONFIG_KALLSYMS)     += kallsyms
 hostprogs-$(CONFIG_LOGO)         += pnmtologo
 hostprogs-$(CONFIG_VT)           += conmakehash