Commit 433de739 authored by H. Peter Anvin's avatar H. Peter Anvin
Browse files

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 scripts/x86-relocs.c so it will
be compiled before building the arch/x86 tree.

Signed-off-by: default avatarH. 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: default avatarJarkko Sakkinen <jarkko.sakkinen@intel.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent d48b97b4

arch/x86/boot/compressed/Makefile

+5 −6
Original line number Diff line number Diff line
@@ -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 = scripts/x86-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

scripts/.gitignore

+1 −0
Original line number Diff line number Diff line
@@ -9,3 +9,4 @@ unifdef 
ihex2fw

recordmcount

docproc

x86-relocs

scripts/Makefile

+3 −0
Original line number Diff line number Diff line
@@ -8,11 +8,14 @@ 
# 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

hostprogs-$(CONFIG_IKCONFIG)     += bin2c

hostprogs-$(BUILD_C_RECORDMCOUNT) += recordmcount

hostprogs-$(CONFIG_X86)          += x86-relocs



always		:= $(hostprogs-y) $(hostprogs-m)

arch/x86/boot/compressed/relocs.c→scripts/x86-relocs.c

+176 −57
Original line number Diff line number Diff line
@@ -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;
@@ -28,54 +30,84 @@ 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;

	int i;



        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);

        }

	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(&rel_sym_regex_c, rel_sym_regex,

		err = regcomp(&sym_regex_c[i], sym_regex[i],

			      REG_EXTENDED|REG_NOSUB);



		if (err) {

                regerror(err, &rel_sym_regex_c, errbuf, sizeof errbuf);

			regerror(err, &sym_regex_c[i], errbuf, sizeof errbuf);

			die("%s", errbuf);

		}

        }

}



static void die(char *fmt, ...)

{
@@ -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);

			}

		}

	}
@@ -552,12 +621,18 @@ 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. */

	if (ELF32_R_TYPE(rel->r_info) == R_386_16)

		relocs16[reloc16_idx++] = rel->r_offset;

	else

		relocs[reloc_idx++] = rel->r_offset;

}
@@ -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");

		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];

		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 */

		fwrite("\0\0\0\0", 4, 1, stdout);

			write32(0, stdout);



			/* Now print each relocation */

			for (i = 0; i < reloc_count; i++) {

			put_unaligned_le32(relocs[i], buf);

			fwrite(buf, 4, 1, stdout);

				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;

}

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