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authorPeter Zijlstra <peterz@infradead.org>2022-06-14 23:15:38 +0200
committerBorislav Petkov <bp@suse.de>2022-06-27 10:33:58 +0200
commitd9e9d2300681d68a775c28de6aa6e5290ae17796 (patch)
treef67d4b228c6c59ba6ec95aa48099040dbbb6fc3b /tools/objtool
parent15e67227c49a57837108acfe1c80570e1bd9f962 (diff)
downloadlinux-d9e9d2300681d68a775c28de6aa6e5290ae17796.tar.bz2
x86,objtool: Create .return_sites
Find all the return-thunk sites and record them in a .return_sites section such that the kernel can undo this. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Borislav Petkov <bp@suse.de>
Diffstat (limited to 'tools/objtool')
-rw-r--r--tools/objtool/arch/x86/decode.c5
-rw-r--r--tools/objtool/check.c74
-rw-r--r--tools/objtool/include/objtool/arch.h1
-rw-r--r--tools/objtool/include/objtool/elf.h1
-rw-r--r--tools/objtool/include/objtool/objtool.h1
-rw-r--r--tools/objtool/objtool.c1
6 files changed, 83 insertions, 0 deletions
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 8b990a52aada..c260006106be 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -787,3 +787,8 @@ bool arch_is_retpoline(struct symbol *sym)
{
return !strncmp(sym->name, "__x86_indirect_", 15);
}
+
+bool arch_is_rethunk(struct symbol *sym)
+{
+ return !strcmp(sym->name, "__x86_return_thunk");
+}
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 864bb9dd3584..f6d4ffa82432 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -749,6 +749,52 @@ static int create_retpoline_sites_sections(struct objtool_file *file)
return 0;
}
+static int create_return_sites_sections(struct objtool_file *file)
+{
+ struct instruction *insn;
+ struct section *sec;
+ int idx;
+
+ sec = find_section_by_name(file->elf, ".return_sites");
+ if (sec) {
+ WARN("file already has .return_sites, skipping");
+ return 0;
+ }
+
+ idx = 0;
+ list_for_each_entry(insn, &file->return_thunk_list, call_node)
+ idx++;
+
+ if (!idx)
+ return 0;
+
+ sec = elf_create_section(file->elf, ".return_sites", 0,
+ sizeof(int), idx);
+ if (!sec) {
+ WARN("elf_create_section: .return_sites");
+ return -1;
+ }
+
+ idx = 0;
+ list_for_each_entry(insn, &file->return_thunk_list, call_node) {
+
+ int *site = (int *)sec->data->d_buf + idx;
+ *site = 0;
+
+ if (elf_add_reloc_to_insn(file->elf, sec,
+ idx * sizeof(int),
+ R_X86_64_PC32,
+ insn->sec, insn->offset)) {
+ WARN("elf_add_reloc_to_insn: .return_sites");
+ return -1;
+ }
+
+ idx++;
+ }
+
+ return 0;
+}
+
static int create_ibt_endbr_seal_sections(struct objtool_file *file)
{
struct instruction *insn;
@@ -1083,6 +1129,11 @@ __weak bool arch_is_retpoline(struct symbol *sym)
return false;
}
+__weak bool arch_is_rethunk(struct symbol *sym)
+{
+ return false;
+}
+
#define NEGATIVE_RELOC ((void *)-1L)
static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
@@ -1250,6 +1301,18 @@ static void add_retpoline_call(struct objtool_file *file, struct instruction *in
annotate_call_site(file, insn, false);
}
+static void add_return_call(struct objtool_file *file, struct instruction *insn)
+{
+ /*
+ * Return thunk tail calls are really just returns in disguise,
+ * so convert them accordingly.
+ */
+ insn->type = INSN_RETURN;
+ insn->retpoline_safe = true;
+
+ list_add_tail(&insn->call_node, &file->return_thunk_list);
+}
+
static bool same_function(struct instruction *insn1, struct instruction *insn2)
{
return insn1->func->pfunc == insn2->func->pfunc;
@@ -1302,6 +1365,9 @@ static int add_jump_destinations(struct objtool_file *file)
} else if (reloc->sym->retpoline_thunk) {
add_retpoline_call(file, insn);
continue;
+ } else if (reloc->sym->return_thunk) {
+ add_return_call(file, insn);
+ continue;
} else if (insn->func) {
/*
* External sibling call or internal sibling call with
@@ -2184,6 +2250,9 @@ static int classify_symbols(struct objtool_file *file)
if (arch_is_retpoline(func))
func->retpoline_thunk = true;
+ if (arch_is_rethunk(func))
+ func->return_thunk = true;
+
if (!strcmp(func->name, "__fentry__"))
func->fentry = true;
@@ -3972,6 +4041,11 @@ int check(struct objtool_file *file)
if (ret < 0)
goto out;
warnings += ret;
+
+ ret = create_return_sites_sections(file);
+ if (ret < 0)
+ goto out;
+ warnings += ret;
}
if (opts.mcount) {
diff --git a/tools/objtool/include/objtool/arch.h b/tools/objtool/include/objtool/arch.h
index 9b19cc304195..beb2f3aa94ff 100644
--- a/tools/objtool/include/objtool/arch.h
+++ b/tools/objtool/include/objtool/arch.h
@@ -89,6 +89,7 @@ const char *arch_ret_insn(int len);
int arch_decode_hint_reg(u8 sp_reg, int *base);
bool arch_is_retpoline(struct symbol *sym);
+bool arch_is_rethunk(struct symbol *sym);
int arch_rewrite_retpolines(struct objtool_file *file);
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index adebfbc2b518..16f4067b82ae 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -57,6 +57,7 @@ struct symbol {
u8 uaccess_safe : 1;
u8 static_call_tramp : 1;
u8 retpoline_thunk : 1;
+ u8 return_thunk : 1;
u8 fentry : 1;
u8 profiling_func : 1;
struct list_head pv_target;
diff --git a/tools/objtool/include/objtool/objtool.h b/tools/objtool/include/objtool/objtool.h
index a6e72d916807..7f2d1b095333 100644
--- a/tools/objtool/include/objtool/objtool.h
+++ b/tools/objtool/include/objtool/objtool.h
@@ -24,6 +24,7 @@ struct objtool_file {
struct list_head insn_list;
DECLARE_HASHTABLE(insn_hash, 20);
struct list_head retpoline_call_list;
+ struct list_head return_thunk_list;
struct list_head static_call_list;
struct list_head mcount_loc_list;
struct list_head endbr_list;
diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c
index 512669ce064c..a7ecc32e3512 100644
--- a/tools/objtool/objtool.c
+++ b/tools/objtool/objtool.c
@@ -102,6 +102,7 @@ struct objtool_file *objtool_open_read(const char *_objname)
INIT_LIST_HEAD(&file.insn_list);
hash_init(file.insn_hash);
INIT_LIST_HEAD(&file.retpoline_call_list);
+ INIT_LIST_HEAD(&file.return_thunk_list);
INIT_LIST_HEAD(&file.static_call_list);
INIT_LIST_HEAD(&file.mcount_loc_list);
INIT_LIST_HEAD(&file.endbr_list);