Commit ef47cc01 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

objtool: Add elf_create_reloc() helper 



We have 4 instances of adding a relocation. Create a common helper
to avoid growing even more.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarMiroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/20210326151259.817438847@infradead.org
parent 3a647607

tools/objtool/check.c

+16 −62
Original line number Diff line number Diff line
@@ -433,8 +433,7 @@ static int add_dead_ends(struct objtool_file *file) 


static int create_static_call_sections(struct objtool_file *file)

{

	struct section *sec, *reloc_sec;

	struct reloc *reloc;

	struct section *sec;

	struct static_call_site *site;

	struct instruction *insn;

	struct symbol *key_sym;
@@ -460,8 +459,7 @@ static int create_static_call_sections(struct objtool_file *file) 
	if (!sec)

		return -1;



	reloc_sec = elf_create_reloc_section(file->elf, sec, SHT_RELA);

	if (!reloc_sec)

	if (!elf_create_reloc_section(file->elf, sec, SHT_RELA))

		return -1;



	idx = 0;
@@ -471,25 +469,11 @@ static int create_static_call_sections(struct objtool_file *file) 
		memset(site, 0, sizeof(struct static_call_site));



		/* populate reloc for 'addr' */

		reloc = malloc(sizeof(*reloc));



		if (!reloc) {

			perror("malloc");

			return -1;

		}

		memset(reloc, 0, sizeof(*reloc));



		insn_to_reloc_sym_addend(insn->sec, insn->offset, reloc);

		if (!reloc->sym) {

			WARN_FUNC("static call tramp: missing containing symbol",

				  insn->sec, insn->offset);

		if (elf_add_reloc_to_insn(file->elf, sec,

					  idx * sizeof(struct static_call_site),

					  R_X86_64_PC32,

					  insn->sec, insn->offset))

			return -1;

		}



		reloc->type = R_X86_64_PC32;

		reloc->offset = idx * sizeof(struct static_call_site);

		reloc->sec = reloc_sec;

		elf_add_reloc(file->elf, reloc);



		/* find key symbol */

		key_name = strdup(insn->call_dest->name);
@@ -526,18 +510,11 @@ static int create_static_call_sections(struct objtool_file *file) 
		free(key_name);



		/* populate reloc for 'key' */

		reloc = malloc(sizeof(*reloc));

		if (!reloc) {

			perror("malloc");

		if (elf_add_reloc(file->elf, sec,

				  idx * sizeof(struct static_call_site) + 4,

				  R_X86_64_PC32, key_sym,

				  is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))

			return -1;

		}

		memset(reloc, 0, sizeof(*reloc));

		reloc->sym = key_sym;

		reloc->addend = is_sibling_call(insn) ? STATIC_CALL_SITE_TAIL : 0;

		reloc->type = R_X86_64_PC32;

		reloc->offset = idx * sizeof(struct static_call_site) + 4;

		reloc->sec = reloc_sec;

		elf_add_reloc(file->elf, reloc);



		idx++;

	}
@@ -547,8 +524,7 @@ static int create_static_call_sections(struct objtool_file *file) 


static int create_mcount_loc_sections(struct objtool_file *file)

{

	struct section *sec, *reloc_sec;

	struct reloc *reloc;

	struct section *sec;

	unsigned long *loc;

	struct instruction *insn;

	int idx;
@@ -571,8 +547,7 @@ static int create_mcount_loc_sections(struct objtool_file *file) 
	if (!sec)

		return -1;



	reloc_sec = elf_create_reloc_section(file->elf, sec, SHT_RELA);

	if (!reloc_sec)

	if (!elf_create_reloc_section(file->elf, sec, SHT_RELA))

		return -1;



	idx = 0;
@@ -581,32 +556,11 @@ static int create_mcount_loc_sections(struct objtool_file *file) 
		loc = (unsigned long *)sec->data->d_buf + idx;

		memset(loc, 0, sizeof(unsigned long));



		reloc = malloc(sizeof(*reloc));

		if (!reloc) {

			perror("malloc");

			return -1;

		}

		memset(reloc, 0, sizeof(*reloc));



		if (insn->sec->sym) {

			reloc->sym = insn->sec->sym;

			reloc->addend = insn->offset;

		} else {

			reloc->sym = find_symbol_containing(insn->sec, insn->offset);



			if (!reloc->sym) {

				WARN("missing symbol for insn at offset 0x%lx\n",

				     insn->offset);

		if (elf_add_reloc_to_insn(file->elf, sec,

					  idx * sizeof(unsigned long),

					  R_X86_64_64,

					  insn->sec, insn->offset))

			return -1;

			}



			reloc->addend = insn->offset - reloc->sym->offset;

		}



		reloc->type = R_X86_64_64;

		reloc->offset = idx * sizeof(unsigned long);

		reloc->sec = reloc_sec;

		elf_add_reloc(file->elf, reloc);



		idx++;

	}

tools/objtool/elf.c

+56 −30
Original line number Diff line number Diff line
@@ -211,32 +211,6 @@ struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, uns 
	return find_reloc_by_dest_range(elf, sec, offset, 1);

}



void insn_to_reloc_sym_addend(struct section *sec, unsigned long offset,

			      struct reloc *reloc)

{

	if (sec->sym) {

		reloc->sym = sec->sym;

		reloc->addend = offset;

		return;

	}



	/*

	 * The Clang assembler strips section symbols, so we have to reference

	 * the function symbol instead:

	 */

	reloc->sym = find_symbol_containing(sec, offset);

	if (!reloc->sym) {

		/*

		 * Hack alert.  This happens when we need to reference the NOP

		 * pad insn immediately after the function.

		 */

		reloc->sym = find_symbol_containing(sec, offset - 1);

	}



	if (reloc->sym)

		reloc->addend = offset - reloc->sym->offset;

}



static int read_sections(struct elf *elf)

{

	Elf_Scn *s = NULL;
@@ -473,14 +447,66 @@ static int read_symbols(struct elf *elf) 
	return -1;

}



void elf_add_reloc(struct elf *elf, struct reloc *reloc)

int elf_add_reloc(struct elf *elf, struct section *sec, unsigned long offset,

		  unsigned int type, struct symbol *sym, int addend)

{

	struct section *sec = reloc->sec;

	struct reloc *reloc;



	list_add_tail(&reloc->list, &sec->reloc_list);

	reloc = malloc(sizeof(*reloc));

	if (!reloc) {

		perror("malloc");

		return -1;

	}

	memset(reloc, 0, sizeof(*reloc));



	reloc->sec = sec->reloc;

	reloc->offset = offset;

	reloc->type = type;

	reloc->sym = sym;

	reloc->addend = addend;



	list_add_tail(&reloc->list, &sec->reloc->reloc_list);

	elf_hash_add(elf->reloc_hash, &reloc->hash, reloc_hash(reloc));



	sec->changed = true;

	sec->reloc->changed = true;



	return 0;

}



int elf_add_reloc_to_insn(struct elf *elf, struct section *sec,

			  unsigned long offset, unsigned int type,

			  struct section *insn_sec, unsigned long insn_off)

{

	struct symbol *sym;

	int addend;



	if (insn_sec->sym) {

		sym = insn_sec->sym;

		addend = insn_off;



	} else {

		/*

		 * The Clang assembler strips section symbols, so we have to

		 * reference the function symbol instead:

		 */

		sym = find_symbol_containing(insn_sec, insn_off);

		if (!sym) {

			/*

			 * Hack alert.  This happens when we need to reference

			 * the NOP pad insn immediately after the function.

			 */

			sym = find_symbol_containing(insn_sec, insn_off - 1);

		}



		if (!sym) {

			WARN("can't find symbol containing %s+0x%lx", insn_sec->name, insn_off);

			return -1;

		}



		addend = insn_off - sym->offset;

	}



	return elf_add_reloc(elf, sec, offset, type, sym, addend);

}



static int read_rel_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx)

tools/objtool/include/objtool/elf.h

+7 −3
Original line number Diff line number Diff line
@@ -123,7 +123,13 @@ static inline u32 reloc_hash(struct reloc *reloc) 
struct elf *elf_open_read(const char *name, int flags);

struct section *elf_create_section(struct elf *elf, const char *name, unsigned int sh_flags, size_t entsize, int nr);

struct section *elf_create_reloc_section(struct elf *elf, struct section *base, int reltype);

void elf_add_reloc(struct elf *elf, struct reloc *reloc);



int elf_add_reloc(struct elf *elf, struct section *sec, unsigned long offset,

		  unsigned int type, struct symbol *sym, int addend);

int elf_add_reloc_to_insn(struct elf *elf, struct section *sec,

			  unsigned long offset, unsigned int type,

			  struct section *insn_sec, unsigned long insn_off);



int elf_write_insn(struct elf *elf, struct section *sec,

		   unsigned long offset, unsigned int len,

		   const char *insn);
@@ -140,8 +146,6 @@ struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, uns 
struct reloc *find_reloc_by_dest_range(const struct elf *elf, struct section *sec,

				     unsigned long offset, unsigned int len);

struct symbol *find_func_containing(struct section *sec, unsigned long offset);

void insn_to_reloc_sym_addend(struct section *sec, unsigned long offset,

			      struct reloc *reloc);



#define for_each_sec(file, sec)						\

	list_for_each_entry(sec, &file->elf->sections, list)

tools/objtool/orc_gen.c

+6 −24
Original line number Diff line number Diff line
@@ -82,12 +82,11 @@ static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi) 
}



static int write_orc_entry(struct elf *elf, struct section *orc_sec,

			   struct section *ip_rsec, unsigned int idx,

			   struct section *ip_sec, unsigned int idx,

			   struct section *insn_sec, unsigned long insn_off,

			   struct orc_entry *o)

{

	struct orc_entry *orc;

	struct reloc *reloc;



	/* populate ORC data */

	orc = (struct orc_entry *)orc_sec->data->d_buf + idx;
@@ -96,25 +95,9 @@ static int write_orc_entry(struct elf *elf, struct section *orc_sec, 
	orc->bp_offset = bswap_if_needed(orc->bp_offset);



	/* populate reloc for ip */

	reloc = malloc(sizeof(*reloc));

	if (!reloc) {

		perror("malloc");

	if (elf_add_reloc_to_insn(elf, ip_sec, idx * sizeof(int), R_X86_64_PC32,

				  insn_sec, insn_off))

		return -1;

	}

	memset(reloc, 0, sizeof(*reloc));



	insn_to_reloc_sym_addend(insn_sec, insn_off, reloc);

	if (!reloc->sym) {

		WARN("missing symbol for insn at offset 0x%lx",

		     insn_off);

		return -1;

	}



	reloc->type = R_X86_64_PC32;

	reloc->offset = idx * sizeof(int);

	reloc->sec = ip_rsec;



	elf_add_reloc(elf, reloc);



	return 0;

}
@@ -153,7 +136,7 @@ static unsigned long alt_group_len(struct alt_group *alt_group) 


int orc_create(struct objtool_file *file)

{

	struct section *sec, *ip_rsec, *orc_sec;

	struct section *sec, *orc_sec;

	unsigned int nr = 0, idx = 0;

	struct orc_list_entry *entry;

	struct list_head orc_list;
@@ -242,13 +225,12 @@ int orc_create(struct objtool_file *file) 
	sec = elf_create_section(file->elf, ".orc_unwind_ip", 0, sizeof(int), nr);

	if (!sec)

		return -1;

	ip_rsec = elf_create_reloc_section(file->elf, sec, SHT_RELA);

	if (!ip_rsec)

	if (!elf_create_reloc_section(file->elf, sec, SHT_RELA))

		return -1;



	/* Write ORC entries to sections: */

	list_for_each_entry(entry, &orc_list, list) {

		if (write_orc_entry(file->elf, orc_sec, ip_rsec, idx++,

		if (write_orc_entry(file->elf, orc_sec, sec, idx++,

				    entry->insn_sec, entry->insn_off,

				    &entry->orc))

			return -1;