objtool: Move the IRET hack into the arch decoder

Quoting Julien:

  "And the other suggestion is my other email was that you don't even
  need to add INSN_EXCEPTION_RETURN. You can keep IRET as
  INSN_CONTEXT_SWITCH by default and x86 decoder lookups the symbol
  conaining an iret. If it's a function symbol, it can just set the type
  to INSN_OTHER so that it caries on to the next instruction after
  having handled the stack_op."

Suggested-by: Julien Thierry <jthierry@redhat.com>
Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200428191659.913283807@infradead.org

diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h
index 25dd4a9..cd118eb 100644 (file)
--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -19,7 +19,6 @@ enum insn_type {
        INSN_CALL,
        INSN_CALL_DYNAMIC,
        INSN_RETURN,
-       INSN_EXCEPTION_RETURN,
        INSN_CONTEXT_SWITCH,
        INSN_BUG,
        INSN_NOP,

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index e26bedb..d7b5d10 100644 (file)
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -94,6 +94,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
                      rex_x = 0, modrm = 0, modrm_mod = 0, modrm_rm = 0,
                      modrm_reg = 0, sib = 0;
        struct stack_op *op = NULL;
+       struct symbol *sym;
 
        x86_64 = is_x86_64(elf);
        if (x86_64 == -1)
@@ -469,17 +470,24 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
                break;
 
        case 0xcf: /* iret */
-               *type = INSN_EXCEPTION_RETURN;
-
-               ADD_OP(op) {
-                       /* add $40, %rsp */
-                       op->src.type = OP_SRC_ADD;
-                       op->src.reg = CFI_SP;
-                       op->src.offset = 5*8;
-                       op->dest.type = OP_DEST_REG;
-                       op->dest.reg = CFI_SP;
+               /*
+                * Handle sync_core(), which has an IRET to self.
+                * All other IRET are in STT_NONE entry code.
+                */
+               sym = find_symbol_containing(sec, offset);
+               if (sym && sym->type == STT_FUNC) {
+                       ADD_OP(op) {
+                               /* add $40, %rsp */
+                               op->src.type = OP_SRC_ADD;
+                               op->src.reg = CFI_SP;
+                               op->src.offset = 5*8;
+                               op->dest.type = OP_DEST_REG;
+                               op->dest.reg = CFI_SP;
+                       }
+                       break;
                }
-               break;
+
+               /* fallthrough */
 
        case 0xca: /* retf */
        case 0xcb: /* retf */

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 4f3db2f..d822858 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2320,17 +2320,6 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 
                        break;
 
-               case INSN_EXCEPTION_RETURN:
-                       /*
-                        * This handles x86's sync_core() case, where we use an
-                        * IRET to self. All 'normal' IRET instructions are in
-                        * STT_NOTYPE entry symbols.
-                        */
-                       if (func)
-                               break;
-
-                       return 0;
-
                case INSN_CONTEXT_SWITCH:
                        if (func && (!next_insn || !next_insn->hint)) {
                                WARN_FUNC("unsupported instruction in callable function",

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 453b723..b6349ca 100644 (file)
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -61,7 +61,7 @@ static void rb_add(struct rb_root *tree, struct rb_node *node,
        rb_insert_color(node, tree);
 }
 
-static struct rb_node *rb_find_first(struct rb_root *tree, const void *key,
+static struct rb_node *rb_find_first(const struct rb_root *tree, const void *key,
                               int (*cmp)(const void *key, const struct rb_node *))
 {
        struct rb_node *node = tree->rb_node;
@@ -189,7 +189,7 @@ struct symbol *find_func_by_offset(struct section *sec, unsigned long offset)
        return NULL;
 }
 
-struct symbol *find_symbol_containing(struct section *sec, unsigned long offset)
+struct symbol *find_symbol_containing(const struct section *sec, unsigned long offset)
 {
        struct rb_node *node;
 

diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index 5e76ac3..9d6bb07 100644 (file)
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -124,7 +124,7 @@ struct section *find_section_by_name(const struct elf *elf, const char *name);
 struct symbol *find_func_by_offset(struct section *sec, unsigned long offset);
 struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset);
 struct symbol *find_symbol_by_name(const struct elf *elf, const char *name);
-struct symbol *find_symbol_containing(struct section *sec, unsigned long offset);
+struct symbol *find_symbol_containing(const struct section *sec, unsigned long offset);
 struct rela *find_rela_by_dest(const struct elf *elf, struct section *sec, unsigned long offset);
 struct rela *find_rela_by_dest_range(const struct elf *elf, struct section *sec,
                                     unsigned long offset, unsigned int len);