2021-05-06 20:11:24

by Peter Zijlstra

Subject: [PATCH 11/13] objtool: Rewrite jump_label instructions

When a jump_entry::key has bit1 set, rewrite the instruction to be a
NOP. This allows the compiler/assembler to emit JMP (and thus decide
on which encoding to use).

Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
---
tools/objtool/check.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1223,6 +1223,20 @@ static int handle_jump_alt(struct objtoo
return -1;
}

+ if (special_alt->key_addend & 2) {
+ struct reloc *reloc = insn_reloc(file, orig_insn);
+
+ if (reloc) {
+ reloc->type = R_NONE;
+ elf_write_reloc(file->elf, reloc);
+ }
+ elf_write_insn(file->elf, orig_insn->sec,
+ orig_insn->offset, orig_insn->len,
+ arch_nop_insn(orig_insn->len));
+ orig_insn->type = INSN_NOP;
+ return 0;
+ }
+
*new_insn = list_next_entry(orig_insn, list);
return 0;
}

2021-05-12 13:22:16

by tip-bot2 for Haifeng Xu

Subject: [tip: objtool/core] objtool: Rewrite jump_label instructions

The following commit has been merged into the objtool/core branch of tip:

Commit-ID: 6d37b83c5d79ef5996cc49c3e3ac3d8ecd8c7050
Gitweb: https://git.kernel.org/tip/6d37b83c5d79ef5996cc49c3e3ac3d8ecd8c7050
Author: Peter Zijlstra <[email protected]>
AuthorDate: Thu, 06 May 2021 21:34:03 +02:00
Committer: Ingo Molnar <[email protected]>
CommitterDate: Wed, 12 May 2021 14:54:56 +02:00

objtool: Rewrite jump_label instructions

When a jump_entry::key has bit1 set, rewrite the instruction to be a
NOP. This allows the compiler/assembler to emit JMP (and thus decide
on which encoding to use).

Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
tools/objtool/check.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 9ed1a4c..98cf87f 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1234,6 +1234,20 @@ static int handle_jump_alt(struct objtool_file *file,
return -1;
}

+ if (special_alt->key_addend & 2) {
+ struct reloc *reloc = insn_reloc(file, orig_insn);
+
+ if (reloc) {
+ reloc->type = R_NONE;
+ elf_write_reloc(file->elf, reloc);
+ }
+ elf_write_insn(file->elf, orig_insn->sec,
+ orig_insn->offset, orig_insn->len,
+ arch_nop_insn(orig_insn->len));
+ orig_insn->type = INSN_NOP;
+ return 0;
+ }
+
*new_insn = list_next_entry(orig_insn, list);
return 0;
}