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authorJosh Poimboeuf <jpoimboe@redhat.com>2020-04-01 13:23:27 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-11-05 11:08:31 +0100
commit319b324649db73987723eae30af1f9c3157ec0d2 (patch)
treedc86b046ca6c21af8d235938b68fef097565e794 /tools
parentf5d8eef067acee3fda37137f4a08c0d3f6427a8e (diff)
objtool: Support Clang non-section symbols in ORC generation
commit e81e0724432542af8d8c702c31e9d82f57b1ff31 upstream. When compiling the kernel with AS=clang, objtool produces a lot of warnings: warning: objtool: missing symbol for section .text warning: objtool: missing symbol for section .init.text warning: objtool: missing symbol for section .ref.text It then fails to generate the ORC table. The problem is that objtool assumes text section symbols always exist. But the Clang assembler is aggressive about removing them. When generating relocations for the ORC table, objtool always tries to reference instructions by their section symbol offset. If the section symbol doesn't exist, it bails. Do a fallback: when a section symbol isn't available, reference a function symbol instead. Reported-by: Dmitry Golovin <dima@golovin.in> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Borislav Petkov <bp@suse.de> Tested-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://github.com/ClangBuiltLinux/linux/issues/669 Link: https://lkml.kernel.org/r/9a9cae7fcf628843aabe5a086b1a3c5bf50f42e8.1585761021.git.jpoimboe@redhat.com Cc: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'tools')
-rw-r--r--tools/objtool/orc_gen.c33
1 files changed, 26 insertions, 7 deletions
diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
index 3f98dcfbc177..0b1ba8e7d18a 100644
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -100,11 +100,6 @@ static int create_orc_entry(struct section *u_sec, struct section *ip_relasec,
struct orc_entry *orc;
struct rela *rela;
- if (!insn_sec->sym) {
- WARN("missing symbol for section %s", insn_sec->name);
- return -1;
- }
-
/* populate ORC data */
orc = (struct orc_entry *)u_sec->data->d_buf + idx;
memcpy(orc, o, sizeof(*orc));
@@ -117,8 +112,32 @@ static int create_orc_entry(struct section *u_sec, struct section *ip_relasec,
}
memset(rela, 0, sizeof(*rela));
- rela->sym = insn_sec->sym;
- rela->addend = insn_off;
+ if (insn_sec->sym) {
+ rela->sym = insn_sec->sym;
+ rela->addend = insn_off;
+ } else {
+ /*
+ * The Clang assembler doesn't produce section symbols, so we
+ * have to reference the function symbol instead:
+ */
+ rela->sym = find_symbol_containing(insn_sec, insn_off);
+ if (!rela->sym) {
+ /*
+ * Hack alert. This happens when we need to reference
+ * the NOP pad insn immediately after the function.
+ */
+ rela->sym = find_symbol_containing(insn_sec,
+ insn_off - 1);
+ }
+ if (!rela->sym) {
+ WARN("missing symbol for insn at offset 0x%lx\n",
+ insn_off);
+ return -1;
+ }
+
+ rela->addend = insn_off - rela->sym->offset;
+ }
+
rela->type = R_X86_64_PC32;
rela->offset = idx * sizeof(int);