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: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Julien Thierry <jthierry@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>

diff --git a/tools/objtool/arch/x86/special.c b/tools/objtool/arch/x86/special.c
index 823561e..34e0e16 100644 (file)
--- a/tools/objtool/arch/x86/special.c
+++ b/tools/objtool/arch/x86/special.c
@@ -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));
+}

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 4afc2d5..1796a7c 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -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);

diff --git a/tools/objtool/check.h b/tools/objtool/check.h
index 6cac345..1de1188 100644 (file)
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -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);
 

diff --git a/tools/objtool/special.h b/tools/objtool/special.h
index 44da89a..1dc1bb3 100644 (file)
--- a/tools/objtool/special.h
+++ b/tools/objtool/special.h
@@ -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 */