linux-kernel - [PATCH 5/8] objtool: Rewrite add

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Date:   Thu, 28 Feb 2019 15:54:55 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     torvalds@...ux-foundation.org, tglx@...utronix.de, hpa@...or.com,
        julien.thierry@....com, will.deacon@....com, luto@...capital.net,
        mingo@...nel.org, catalin.marinas@....com, james.morse@....com,
        valentin.schneider@....com, brgerst@...il.com, jpoimboe@...hat.com,
        luto@...nel.org, bp@...en8.de, dvlasenk@...hat.com
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org
Subject: [PATCH 5/8] objtool: Rewrite add_ignores()

The whole add_ignores() thing was wildly weird; rewrite it according
to 'modern' ways.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 tools/objtool/check.c |   51 +++++++++++++++++++-------------------------------
 tools/objtool/check.h |    1 
 2 files changed, 20 insertions(+), 32 deletions(-)

--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -105,29 +105,6 @@ static struct instruction *next_insn_sam
 	     insn = next_insn_same_sec(file, insn))
 
 /*
- * Check if the function has been manually whitelisted with the
- * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted
- * due to its use of a context switching instruction.
- */
-static bool ignore_func(struct objtool_file *file, struct symbol *func)
-{
-	struct rela *rela;
-
-	/* check for STACK_FRAME_NON_STANDARD */
-	if (file->whitelist && file->whitelist->rela)
-		list_for_each_entry(rela, &file->whitelist->rela->rela_list, list) {
-			if (rela->sym->type == STT_SECTION &&
-			    rela->sym->sec == func->sec &&
-			    rela->addend == func->offset)
-				return true;
-			if (rela->sym->type == STT_FUNC && rela->sym == func)
-				return true;
-		}
-
-	return false;
-}
-
-/*
  * This checks to see if the given function is a "noreturn" function.
  *
  * For global functions which are outside the scope of this object file, we
@@ -436,18 +413,31 @@ static void add_ignores(struct objtool_f
 	struct instruction *insn;
 	struct section *sec;
 	struct symbol *func;
+	struct rela *rela;
 
-	for_each_sec(file, sec) {
-		list_for_each_entry(func, &sec->symbol_list, list) {
-			if (func->type != STT_FUNC)
-				continue;
+	sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
+	if (!sec)
+		return;
 
-			if (!ignore_func(file, func))
+	list_for_each_entry(rela, &sec->rela_list, list) {
+		switch (rela->sym->type) {
+		case STT_FUNC:
+			func = rela->sym;
+			break;
+
+		case STT_SECTION:
+			func = find_symbol_by_offset(rela->sym->sec, rela->addend);
+			if (!func || func->type != STT_FUNC)
 				continue;
+			break;
 
-			func_for_each_insn_all(file, func, insn)
-				insn->ignore = true;
+		default:
+			WARN("unexpected relation symbol type in %s: %d", sec->name, rela->sym->type);
+			continue;
 		}
+
+		func_for_each_insn_all(file, func, insn)
+			insn->ignore = true;
 	}
 }
 
@@ -2198,7 +2188,6 @@ int check(const char *_objname, bool orc
 
 	INIT_LIST_HEAD(&file.insn_list);
 	hash_init(file.insn_hash);
-	file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard");
 	file.c_file = find_section_by_name(file.elf, ".comment");
 	file.ignore_unreachables = no_unreachable;
 	file.hints = false;
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -60,7 +60,6 @@ struct objtool_file {
 	struct elf *elf;
 	struct list_head insn_list;
 	DECLARE_HASHTABLE(insn_hash, 16);
-	struct section *whitelist;
 	bool ignore_unreachables, c_file, hints, rodata;
 };