The following commit has been merged into the objtool/core branch of tip:
Commit-ID: 45245f51f9a4b9a883a8c94468473c1de9b88153
Gitweb: https://git.kernel.org/tip/45245f51f9a4b9a883a8c94468473c1de9b88153
Author: Julien Thierry <jthierry@xxxxxxxxxx>
AuthorDate: Fri, 04 Sep 2020 16:30:23 +01:00
Committer: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
CommitterDate: Thu, 10 Sep 2020 10:43:13 -05:00
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@xxxxxxx>
Signed-off-by: Julien Thierry <jthierry@xxxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
tools/objtool/arch/x86/special.c | 13 +++++++++++++
tools/objtool/check.c | 19 ++++++-------------
tools/objtool/check.h | 6 ++++++
tools/objtool/special.h | 4 ++++
4 files changed, 29 insertions(+), 13 deletions(-)
diff --git a/tools/objtool/arch/x86/special.c b/tools/objtool/arch/x86/special.c
index 823561e..34e0e16 100644
--- 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
--- 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
--- 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
--- 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 */
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