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x86, realmode: 16-bit real-mode code support for relocs tool

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>
  • Loading branch information...
commit 6520fe5564acf07ade7b18a1272db1184835c487 1 parent 36be505
H. Peter Anvin authored
View
9 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
View
3  arch/x86/Makefile
@@ -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
View
9 arch/x86/boot/compressed/Makefile
@@ -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 := $(obj)/vmlinux.bin
View
1  arch/x86/tools/.gitignore
@@ -0,0 +1 @@
+relocs
View
4 arch/x86/tools/Makefile
@@ -36,3 +36,7 @@ HOSTCFLAGS_insn_sanity.o := -Wall -I$(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: $(obj)/relocs
View
233 arch/x86/boot/compressed/relocs.c → arch/x86/tools/relocs.c
@@ -18,6 +18,8 @@ static void die(char *fmt, ...);
static Elf32_Ehdr ehdr;
static unsigned long reloc_count, reloc_idx;
static unsigned long *relocs;
+static unsigned long reloc16_count, reloc16_idx;
+static unsigned long *relocs16;
struct section {
Elf32_Shdr shdr;
@@ -28,52 +30,82 @@ struct section {
};
static struct section *secs;
+enum symtype {
+ S_ABS,
+ S_REL,
+ S_SEG,
+ S_LIN,
+ S_NSYMTYPES
+};
+
+static const char * const sym_regex_kernel[S_NSYMTYPES] = {
/*
* Following symbols have been audited. There values are constant and do
* not change if bzImage is loaded at a different physical address than
* the address for which it has been compiled. Don't warn user about
* absolute relocations present w.r.t these symbols.
*/
-static const char abs_sym_regex[] =
+ [S_ABS] =
"^(xen_irq_disable_direct_reloc$|"
"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;
}
View
2  scripts/Makefile
@@ -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
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