objtool: Update Retpoline validation

commit 9bb2ec608a209018080ca262f771e6a9ff203b6f upstream.

Update retpoline validation with the new CONFIG_RETPOLINE requirement of
not having bare naked RET instructions.

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>
[cascardo: conflict fixup at arch/x86/xen/xen-head.S]
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index af35428..8c0da9b 100644 (file)
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -76,6 +76,12 @@
 .endm
 
 /*
+ * (ab)use RETPOLINE_SAFE on RET to annotate away 'bare' RET instructions
+ * vs RETBleed validation.
+ */
+#define ANNOTATE_UNRET_SAFE ANNOTATE_RETPOLINE_SAFE
+
+/*
  * JMP_NOSPEC and CALL_NOSPEC macros can be used instead of a simple
  * indirect jmp/call which may be susceptible to the Spectre variant 2
  * attack.

diff --git a/arch/x86/mm/mem_encrypt_boot.S b/arch/x86/mm/mem_encrypt_boot.S
index d94dea4..9de3d90 100644 (file)
--- a/arch/x86/mm/mem_encrypt_boot.S
+++ b/arch/x86/mm/mem_encrypt_boot.S
@@ -66,6 +66,7 @@ SYM_FUNC_START(sme_encrypt_execute)
        pop     %rbp
 
        /* Offset to __x86_return_thunk would be wrong here */
+       ANNOTATE_UNRET_SAFE
        ret
        int3
 SYM_FUNC_END(sme_encrypt_execute)
@@ -154,6 +155,7 @@ SYM_FUNC_START(__enc_copy)
        pop     %r15
 
        /* Offset to __x86_return_thunk would be wrong here */
+       ANNOTATE_UNRET_SAFE
        ret
        int3
 .L__enc_copy_end:

diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
index 5650629..38b73e7 100644 (file)
--- a/arch/x86/xen/xen-head.S
+++ b/arch/x86/xen/xen-head.S
@@ -70,6 +70,7 @@ SYM_CODE_START(hypercall_page)
        .rept (PAGE_SIZE / 32)
                UNWIND_HINT_FUNC
                .skip 31, 0x90
+               ANNOTATE_UNRET_SAFE
                RET
        .endr
 

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index a90f0d6..6cc7e31 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1894,8 +1894,9 @@ static int read_retpoline_hints(struct objtool_file *file)
                }
 
                if (insn->type != INSN_JUMP_DYNAMIC &&
-                   insn->type != INSN_CALL_DYNAMIC) {
-                       WARN_FUNC("retpoline_safe hint not an indirect jump/call",
+                   insn->type != INSN_CALL_DYNAMIC &&
+                   insn->type != INSN_RETURN) {
+                       WARN_FUNC("retpoline_safe hint not an indirect jump/call/ret",
                                  insn->sec, insn->offset);
                        return -1;
                }
@@ -3229,7 +3230,8 @@ static int validate_retpoline(struct objtool_file *file)
 
        for_each_insn(file, insn) {
                if (insn->type != INSN_JUMP_DYNAMIC &&
-                   insn->type != INSN_CALL_DYNAMIC)
+                   insn->type != INSN_CALL_DYNAMIC &&
+                   insn->type != INSN_RETURN)
                        continue;
 
                if (insn->retpoline_safe)
@@ -3244,9 +3246,14 @@ static int validate_retpoline(struct objtool_file *file)
                if (!strcmp(insn->sec->name, ".init.text") && !module)
                        continue;
 
-               WARN_FUNC("indirect %s found in RETPOLINE build",
-                         insn->sec, insn->offset,
-                         insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
+               if (insn->type == INSN_RETURN) {
+                       WARN_FUNC("'naked' return found in RETPOLINE build",
+                                 insn->sec, insn->offset);
+               } else {
+                       WARN_FUNC("indirect %s found in RETPOLINE build",
+                                 insn->sec, insn->offset,
+                                 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
+               }
 
                warnings++;
        }