Commit 45245f51 authored by Julien Thierry's avatar Julien Thierry Committed by Josh Poimboeuf
Browse files

objtool: Make relocation in alternative handling arch dependent 



As pointed out by the comment in handle_group_alt(), support of
relocation for instructions in an alternative group depends on whether
arch specific kernel code handles it.

So, let objtool arch specific code decide whether a relocation for
the alternative section should be accepted.

Reviewed-by: default avatarMiroslav Benes <mbenes@suse.cz>
Signed-off-by: default avatarJulien Thierry <jthierry@redhat.com>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
parent eda3dc90

tools/objtool/arch/x86/special.c

+13 −0
Original line number Diff line number Diff line
@@ -35,3 +35,16 @@ void arch_handle_alternative(unsigned short feature, struct special_alt *alt) 
		break;

	}

}



bool arch_support_alt_relocation(struct special_alt *special_alt,

				 struct instruction *insn,

				 struct reloc *reloc)

{

	/*

	 * The x86 alternatives code adjusts the offsets only when it

	 * encounters a branch instruction at the very beginning of the

	 * replacement group.

	 */

	return insn->offset == special_alt->new_off &&

	       (insn->type == INSN_CALL || is_static_jump(insn));

}

tools/objtool/check.c

+6 −13
Original line number Diff line number Diff line
@@ -110,12 +110,6 @@ static struct instruction *prev_insn_same_sym(struct objtool_file *file, 
	for (insn = next_insn_same_sec(file, insn); insn;		\

	     insn = next_insn_same_sec(file, insn))



static bool is_static_jump(struct instruction *insn)

{

	return insn->type == INSN_JUMP_CONDITIONAL ||

	       insn->type == INSN_JUMP_UNCONDITIONAL;

}



static bool is_sibling_call(struct instruction *insn)

{

	/* An indirect jump is either a sibling call or a jump to a table. */
@@ -972,6 +966,8 @@ static int handle_group_alt(struct objtool_file *file, 
	alt_group = alt_group_next_index++;

	insn = *new_insn;

	sec_for_each_insn_from(file, insn) {

		struct reloc *alt_reloc;



		if (insn->offset >= special_alt->new_off + special_alt->new_len)

			break;
@@ -988,14 +984,11 @@ static int handle_group_alt(struct objtool_file *file, 
		 * .altinstr_replacement section, unless the arch's

		 * alternatives code can adjust the relative offsets

		 * accordingly.

		 *

		 * The x86 alternatives code adjusts the offsets only when it

		 * encounters a branch instruction at the very beginning of the

		 * replacement group.

		 */

		if ((insn->offset != special_alt->new_off ||

		    (insn->type != INSN_CALL && !is_static_jump(insn))) &&

		    find_reloc_by_dest_range(file->elf, insn->sec, insn->offset, insn->len)) {

		alt_reloc = find_reloc_by_dest_range(file->elf, insn->sec,

						   insn->offset, insn->len);

		if (alt_reloc &&

		    !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {



			WARN_FUNC("unsupported relocation in alternatives section",

				  insn->sec, insn->offset);

tools/objtool/check.h

+6 −0
Original line number Diff line number Diff line
@@ -48,6 +48,12 @@ struct instruction { 
#endif

};



static inline bool is_static_jump(struct instruction *insn)

{

	return insn->type == INSN_JUMP_CONDITIONAL ||

	       insn->type == INSN_JUMP_UNCONDITIONAL;

}



struct instruction *find_insn(struct objtool_file *file,

			      struct section *sec, unsigned long offset);

tools/objtool/special.h

+4 −0
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 
#define _SPECIAL_H



#include <stdbool.h>

#include "check.h"

#include "elf.h"



struct special_alt {
@@ -30,4 +31,7 @@ int special_get_alts(struct elf *elf, struct list_head *alts); 


void arch_handle_alternative(unsigned short feature, struct special_alt *alt);



bool arch_support_alt_relocation(struct special_alt *special_alt,

				 struct instruction *insn,

				 struct reloc *reloc);

#endif /* _SPECIAL_H */