x86,objtool: Separate unret validation from unwind hints

The ENTRY unwind hint type is serving double duty as both an empty
unwind hint and an unret validation annotation.

Unret validation is unrelated to unwinding. Separate it out into its own
annotation.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/ff7448d492ea21b86d8a90264b105fbd0d751077.1677683419.git.jpoimboe@kernel.org

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index eccc3431e515a674b584f2984679aa8140bcc631..5b93eb7db0ab22f3c1326c312185b4bce4590b94 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -388,9 +388,9 @@ SYM_CODE_START(\asmsym)
 
        .if \vector == X86_TRAP_BP
                /* #BP advances %rip to the next instruction */
-               UNWIND_HINT_IRET_REGS offset=\has_error_code*8 signal=0
+               UNWIND_HINT_IRET_ENTRY offset=\has_error_code*8 signal=0
        .else
-               UNWIND_HINT_IRET_REGS offset=\has_error_code*8
+               UNWIND_HINT_IRET_ENTRY offset=\has_error_code*8
        .endif
 
        ENDBR
@@ -461,7 +461,7 @@ SYM_CODE_END(\asmsym)
  */
 .macro idtentry_mce_db vector asmsym cfunc
 SYM_CODE_START(\asmsym)
-       UNWIND_HINT_IRET_REGS
+       UNWIND_HINT_IRET_ENTRY
        ENDBR
        ASM_CLAC
        cld
@@ -518,7 +518,7 @@ SYM_CODE_END(\asmsym)
  */
 .macro idtentry_vc vector asmsym cfunc
 SYM_CODE_START(\asmsym)
-       UNWIND_HINT_IRET_REGS
+       UNWIND_HINT_IRET_ENTRY
        ENDBR
        ASM_CLAC
        cld
@@ -582,7 +582,7 @@ SYM_CODE_END(\asmsym)
  */
 .macro idtentry_df vector asmsym cfunc
 SYM_CODE_START(\asmsym)
-       UNWIND_HINT_IRET_REGS offset=8
+       UNWIND_HINT_IRET_ENTRY offset=8
        ENDBR
        ASM_CLAC
        cld
@@ -1107,7 +1107,7 @@ SYM_CODE_START(error_entry)
        FENCE_SWAPGS_KERNEL_ENTRY
        CALL_DEPTH_ACCOUNT
        leaq    8(%rsp), %rax                   /* return pt_regs pointer */
-       ANNOTATE_UNRET_END
+       VALIDATE_UNRET_END
        RET
 
 .Lbstep_iret:
@@ -1153,7 +1153,7 @@ SYM_CODE_END(error_return)
  *           when PAGE_TABLE_ISOLATION is in use.  Do not clobber.
  */
 SYM_CODE_START(asm_exc_nmi)
-       UNWIND_HINT_IRET_REGS
+       UNWIND_HINT_IRET_ENTRY
        ENDBR
 
        /*

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 78ed1546b7750d096fa46f18d85bb5b3c6169aa6..edb2b0cb8efe5d47ef84bddbba62d58ebbe72a3a 100644 (file)
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -210,8 +210,8 @@
  * Abuse ANNOTATE_RETPOLINE_SAFE on a NOP to indicate UNRET_END, should
  * eventually turn into it's own annotation.
  */
-.macro ANNOTATE_UNRET_END
-#ifdef CONFIG_DEBUG_ENTRY
+.macro VALIDATE_UNRET_END
+#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
        ANNOTATE_RETPOLINE_SAFE
        nop
 #endif
@@ -286,7 +286,7 @@
 .macro UNTRAIN_RET
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
        defined(CONFIG_CALL_DEPTH_TRACKING)
-       ANNOTATE_UNRET_END
+       VALIDATE_UNRET_END
        ALTERNATIVE_3 "",                                               \
                      CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET,          \
                      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,        \
@@ -297,7 +297,7 @@
 .macro UNTRAIN_RET_FROM_CALL
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
        defined(CONFIG_CALL_DEPTH_TRACKING)
-       ANNOTATE_UNRET_END
+       VALIDATE_UNRET_END
        ALTERNATIVE_3 "",                                               \
                      CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET,          \
                      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,        \

diff --git a/arch/x86/include/asm/unwind_hints.h b/arch/x86/include/asm/unwind_hints.h
index 97b392217c0f9150fd9284525b27081dd435bda7..4c0f28d665ebbe78ec6a76feea984288291611f0 100644 (file)
--- a/arch/x86/include/asm/unwind_hints.h
+++ b/arch/x86/include/asm/unwind_hints.h
@@ -12,7 +12,8 @@
 .endm
 
 .macro UNWIND_HINT_ENTRY
-       UNWIND_HINT type=UNWIND_HINT_TYPE_ENTRY end=1
+       VALIDATE_UNRET_BEGIN
+       UNWIND_HINT_EMPTY
 .endm
 
 .macro UNWIND_HINT_REGS base=%rsp offset=0 indirect=0 extra=1 partial=0 signal=1
@@ -52,6 +53,11 @@
        UNWIND_HINT_REGS base=\base offset=\offset partial=1 signal=\signal
 .endm
 
+.macro UNWIND_HINT_IRET_ENTRY base=%rsp offset=0 signal=1
+       VALIDATE_UNRET_BEGIN
+       UNWIND_HINT_IRET_REGS base=\base offset=\offset signal=\signal
+.endm
+
 .macro UNWIND_HINT_FUNC
        UNWIND_HINT sp_reg=ORC_REG_SP sp_offset=8 type=UNWIND_HINT_TYPE_FUNC
 .endm

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 222efd4a09bc8861b3871f4a175013c0730f8759..ee3ed15ee1f8fefa2b033120968b746760db668d 100644 (file)
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -390,8 +390,6 @@ SYM_CODE_START_NOALIGN(vc_boot_ghcb)
        UNWIND_HINT_IRET_REGS offset=8
        ENDBR
 
-       ANNOTATE_UNRET_END
-
        /* Build pt_regs */
        PUSH_AND_CLEAR_REGS
 
@@ -451,7 +449,6 @@ SYM_CODE_END(early_idt_handler_array)
 
 SYM_CODE_START_LOCAL(early_idt_handler_common)
        UNWIND_HINT_IRET_REGS offset=16
-       ANNOTATE_UNRET_END
        /*
         * The stack is the hardware frame, an error code or zero, and the
         * vector number.
@@ -501,8 +498,6 @@ SYM_CODE_START_NOALIGN(vc_no_ghcb)
        UNWIND_HINT_IRET_REGS offset=8
        ENDBR
 
-       ANNOTATE_UNRET_END
-
        /* Build pt_regs */
        PUSH_AND_CLEAR_REGS
 

diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 725d7f0b6748d301ac4762ac4f602e3912b77d29..5aa475118820fc181c4c1f084e9a98cbfa62898b 100644 (file)
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -124,6 +124,22 @@
        .popsection
 .endm
 
+/*
+ * Use objtool to validate the entry requirement that all code paths do
+ * VALIDATE_UNRET_END before RET.
+ *
+ * NOTE: The macro must be used at the beginning of a global symbol, otherwise
+ * it will be ignored.
+ */
+.macro VALIDATE_UNRET_BEGIN
+#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
+.Lhere_\@:
+       .pushsection .discard.validate_unret
+       .long   .Lhere_\@ - .
+       .popsection
+#endif
+.endm
+
 .macro REACHABLE
 .Lhere_\@:
        .pushsection .discard.reachable

diff --git a/include/linux/objtool_types.h b/include/linux/objtool_types.h
index 9a83468c00393e0a2d9c7da06a9b1d03ca9e7055..9787ad0f2ef4ebde8fc4e44027076f369b5a2038 100644 (file)
--- a/include/linux/objtool_types.h
+++ b/include/linux/objtool_types.h
@@ -42,8 +42,7 @@ struct unwind_hint {
 #define UNWIND_HINT_TYPE_REGS_PARTIAL  2
 /* The below hint types don't have corresponding ORC types */
 #define UNWIND_HINT_TYPE_FUNC          3
-#define UNWIND_HINT_TYPE_ENTRY         4
-#define UNWIND_HINT_TYPE_SAVE          5
-#define UNWIND_HINT_TYPE_RESTORE       6
+#define UNWIND_HINT_TYPE_SAVE          4
+#define UNWIND_HINT_TYPE_RESTORE       5
 
 #endif /* _LINUX_OBJTOOL_TYPES_H */

diff --git a/tools/include/linux/objtool_types.h b/tools/include/linux/objtool_types.h
index 9a83468c00393e0a2d9c7da06a9b1d03ca9e7055..9787ad0f2ef4ebde8fc4e44027076f369b5a2038 100644 (file)
--- a/tools/include/linux/objtool_types.h
+++ b/tools/include/linux/objtool_types.h
@@ -42,8 +42,7 @@ struct unwind_hint {
 #define UNWIND_HINT_TYPE_REGS_PARTIAL  2
 /* The below hint types don't have corresponding ORC types */
 #define UNWIND_HINT_TYPE_FUNC          3
-#define UNWIND_HINT_TYPE_ENTRY         4
-#define UNWIND_HINT_TYPE_SAVE          5
-#define UNWIND_HINT_TYPE_RESTORE       6
+#define UNWIND_HINT_TYPE_SAVE          4
+#define UNWIND_HINT_TYPE_RESTORE       5
 
 #endif /* _LINUX_OBJTOOL_TYPES_H */

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index efc2baa028837c28c6d994a14eb8615a07d4e3e8..10be80b3fe672c12b3b06506d409323a914d65de 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2307,16 +2307,9 @@ static int read_unwind_hints(struct objtool_file *file)
                                        WARN_FUNC("UNWIND_HINT_IRET_REGS without ENDBR",
                                                  insn->sec, insn->offset);
                                }
-
-                               insn->entry = 1;
                        }
                }
 
-               if (hint->type == UNWIND_HINT_TYPE_ENTRY) {
-                       hint->type = UNWIND_HINT_TYPE_CALL;
-                       insn->entry = 1;
-               }
-
                if (hint->type == UNWIND_HINT_TYPE_FUNC) {
                        insn->cfi = &func_cfi;
                        continue;
@@ -2449,6 +2442,34 @@ static int read_instr_hints(struct objtool_file *file)
        return 0;
 }
 
+static int read_validate_unret_hints(struct objtool_file *file)
+{
+       struct section *sec;
+       struct instruction *insn;
+       struct reloc *reloc;
+
+       sec = find_section_by_name(file->elf, ".rela.discard.validate_unret");
+       if (!sec)
+               return 0;
+
+       list_for_each_entry(reloc, &sec->reloc_list, list) {
+               if (reloc->sym->type != STT_SECTION) {
+                       WARN("unexpected relocation symbol type in %s", sec->name);
+                       return -1;
+               }
+
+               insn = find_insn(file, reloc->sym->sec, reloc->addend);
+               if (!insn) {
+                       WARN("bad .discard.instr_end entry");
+                       return -1;
+               }
+               insn->unret = 1;
+       }
+
+       return 0;
+}
+
+
 static int read_intra_function_calls(struct objtool_file *file)
 {
        struct instruction *insn;
@@ -2667,6 +2688,10 @@ static int decode_sections(struct objtool_file *file)
        if (ret)
                return ret;
 
+       ret = read_validate_unret_hints(file);
+       if (ret)
+               return ret;
+
        return 0;
 }
 
@@ -3863,10 +3888,10 @@ static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
 /*
  * Validate rethunk entry constraint: must untrain RET before the first RET.
  *
- * Follow every branch (intra-function) and ensure ANNOTATE_UNRET_END comes
+ * Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes
  * before an actual RET instruction.
  */
-static int validate_entry(struct objtool_file *file, struct instruction *insn)
+static int validate_unret(struct objtool_file *file, struct instruction *insn)
 {
        struct instruction *next, *dest;
        int ret, warnings = 0;
@@ -3874,10 +3899,10 @@ static int validate_entry(struct objtool_file *file, struct instruction *insn)
        for (;;) {
                next = next_insn_to_validate(file, insn);
 
-               if (insn->visited & VISITED_ENTRY)
+               if (insn->visited & VISITED_UNRET)
                        return 0;
 
-               insn->visited |= VISITED_ENTRY;
+               insn->visited |= VISITED_UNRET;
 
                if (!insn->ignore_alts && insn->alts) {
                        struct alternative *alt;
@@ -3887,7 +3912,7 @@ static int validate_entry(struct objtool_file *file, struct instruction *insn)
                                if (alt->skip_orig)
                                        skip_orig = true;
 
-                               ret = validate_entry(file, alt->insn);
+                               ret = validate_unret(file, alt->insn);
                                if (ret) {
                                        if (opts.backtrace)
                                                BT_FUNC("(alt)", insn);
@@ -3915,7 +3940,7 @@ static int validate_entry(struct objtool_file *file, struct instruction *insn)
                                                  insn->sec, insn->offset);
                                        return -1;
                                }
-                               ret = validate_entry(file, insn->jump_dest);
+                               ret = validate_unret(file, insn->jump_dest);
                                if (ret) {
                                        if (opts.backtrace) {
                                                BT_FUNC("(branch%s)", insn,
@@ -3940,7 +3965,7 @@ static int validate_entry(struct objtool_file *file, struct instruction *insn)
                                return -1;
                        }
 
-                       ret = validate_entry(file, dest);
+                       ret = validate_unret(file, dest);
                        if (ret) {
                                if (opts.backtrace)
                                        BT_FUNC("(call)", insn);
@@ -3976,19 +4001,19 @@ static int validate_entry(struct objtool_file *file, struct instruction *insn)
 }
 
 /*
- * Validate that all branches starting at 'insn->entry' encounter UNRET_END
- * before RET.
+ * Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter
+ * VALIDATE_UNRET_END before RET.
  */
-static int validate_unret(struct objtool_file *file)
+static int validate_unrets(struct objtool_file *file)
 {
        struct instruction *insn;
        int ret, warnings = 0;
 
        for_each_insn(file, insn) {
-               if (!insn->entry)
+               if (!insn->unret)
                        continue;
 
-               ret = validate_entry(file, insn);
+               ret = validate_unret(file, insn);
                if (ret < 0) {
                        WARN_FUNC("Failed UNRET validation", insn->sec, insn->offset);
                        return ret;
@@ -4607,7 +4632,7 @@ int check(struct objtool_file *file)
                 * Must be after validate_branch() and friends, it plays
                 * further games with insn->visited.
                 */
-               ret = validate_unret(file);
+               ret = validate_unrets(file);
                if (ret < 0)
                        return ret;
                warnings += ret;

diff --git a/tools/objtool/include/objtool/check.h b/tools/objtool/include/objtool/check.h
index 3e7c7004f7df27f6887369f7bd0b277f59a02669..daa46f1f0965ad7f390bef7c6dc2e1e9eb2fd2cd 100644 (file)
--- a/tools/objtool/include/objtool/check.h
+++ b/tools/objtool/include/objtool/check.h
@@ -61,7 +61,7 @@ struct instruction {
            restore             : 1,
            retpoline_safe      : 1,
            noendbr             : 1,
-           entry               : 1,
+           unret               : 1,
            visited             : 4,
            no_reloc            : 1;
                /* 10 bit hole */
@@ -92,7 +92,7 @@ static inline struct symbol *insn_func(struct instruction *insn)
 #define VISITED_BRANCH         0x01
 #define VISITED_BRANCH_UACCESS 0x02
 #define VISITED_BRANCH_MASK    0x03
-#define VISITED_ENTRY          0x04
+#define VISITED_UNRET          0x04
 
 static inline bool is_static_jump(struct instruction *insn)
 {