[PATCH 5.10 031/130] objtool: Keep track of retpoline call sites

Greg Kroah-Hartman
2022-07-12T18:42:48Z

commit 43d5430ad74ef5156353af7aec352426ec7a8e57 upstream.

Provide infrastructure for architectures to rewrite/augment compiler
generated retpoline calls. Similar to what we do for static_call()s,
keep track of the instructions that are retpoline calls.

Use the same list_head, since a retpoline call cannot also be a
static_call.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/20210326151300.130805730@infradead.org
[bwh: Backported to 5.10: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/objtool/arch.h | 2 ++
tools/objtool/check.c | 34 +++++++++++++++++++++++++++++-----
tools/objtool/check.h | 2 +-
tools/objtool/objtool.c | 1 +
tools/objtool/objtool.h | 1 +
5 files changed, 34 insertions(+), 6 deletions(-)

--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -88,4 +88,6 @@ int arch_decode_hint_reg(struct instruct

bool arch_is_retpoline(struct symbol *sym);

+int arch_rewrite_retpolines(struct objtool_file *file);
+
#endif /* _ARCH_H */
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -451,7 +451,7 @@ static int create_static_call_sections(s
return 0;

idx = 0;
- list_for_each_entry(insn, &file->static_call_list, static_call_node)
+ list_for_each_entry(insn, &file->static_call_list, call_node)
idx++;

sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE,
@@ -460,7 +460,7 @@ static int create_static_call_sections(s
return -1;

idx = 0;
- list_for_each_entry(insn, &file->static_call_list, static_call_node) {
+ list_for_each_entry(insn, &file->static_call_list, call_node) {

site = (struct static_call_site *)sec->data->d_buf + idx;
memset(site, 0, sizeof(struct static_call_site));
@@ -786,13 +786,16 @@ static int add_jump_destinations(struct
else
insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;

+ list_add_tail(&insn->call_node,
+ &file->retpoline_call_list);
+
insn->retpoline_safe = true;
continue;
} else if (insn->func) {
/* internal or external sibling call (with reloc) */
insn->call_dest = reloc->sym;
if (insn->call_dest->static_call_tramp) {
- list_add_tail(&insn->static_call_node,
+ list_add_tail(&insn->call_node,
&file->static_call_list);
}
continue;
@@ -854,7 +857,7 @@ static int add_jump_destinations(struct
/* internal sibling call (without reloc) */
insn->call_dest = insn->jump_dest->func;
if (insn->call_dest->static_call_tramp) {
- list_add_tail(&insn->static_call_node,
+ list_add_tail(&insn->call_node,
&file->static_call_list);
}
}
@@ -938,6 +941,9 @@ static int add_call_destinations(struct
insn->type = INSN_CALL_DYNAMIC;
insn->retpoline_safe = true;

+ list_add_tail(&insn->call_node,
+ &file->retpoline_call_list);
+
remove_insn_ops(insn);
continue;

@@ -945,7 +951,7 @@ static int add_call_destinations(struct
insn->call_dest = reloc->sym;

if (insn->call_dest && insn->call_dest->static_call_tramp) {
- list_add_tail(&insn->static_call_node,
+ list_add_tail(&insn->call_node,
&file->static_call_list);
}

@@ -1655,6 +1661,11 @@ static void mark_rodata(struct objtool_f
file->rodata = found;
}

+__weak int arch_rewrite_retpolines(struct objtool_file *file)
+{
+ return 0;
+}
+
static int decode_sections(struct objtool_file *file)
{
int ret;
@@ -1683,6 +1694,10 @@ static int decode_sections(struct objtoo
if (ret)
return ret;

+ /*
+ * Must be before add_special_section_alts() as that depends on
+ * jump_dest being set.
+ */
ret = add_jump_destinations(file);
if (ret)
return ret;
@@ -1719,6 +1734,15 @@ static int decode_sections(struct objtoo
if (ret)
return ret;

+ /*
+ * Must be after add_special_section_alts(), since this will emit
+ * alternatives. Must be after add_{jump,call}_destination(), since
+ * those create the call insn lists.
+ */
+ ret = arch_rewrite_retpolines(file);
+ if (ret)
+ return ret;
+
return 0;
}

--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -39,7 +39,7 @@ struct alt_group {
struct instruction {
struct list_head list;
struct hlist_node hash;
- struct list_head static_call_node;
+ struct list_head call_node;
struct section *sec;
unsigned long offset;
unsigned int len;
--- a/tools/objtool/objtool.c
+++ b/tools/objtool/objtool.c
@@ -61,6 +61,7 @@ struct objtool_file *objtool_open_read(c

INIT_LIST_HEAD(&file.insn_list);
hash_init(file.insn_hash);
+ INIT_LIST_HEAD(&file.retpoline_call_list);
INIT_LIST_HEAD(&file.static_call_list);
file.c_file = !vmlinux && find_section_by_name(file.elf, ".comment");
file.ignore_unreachables = no_unreachable;
--- a/tools/objtool/objtool.h
+++ b/tools/objtool/objtool.h
@@ -18,6 +18,7 @@ struct objtool_file {
struct elf *elf;
struct list_head insn_list;
DECLARE_HASHTABLE(insn_hash, 20);
+ struct list_head retpoline_call_list;
struct list_head static_call_list;
bool ignore_unreachables, c_file, hints, rodata;
};