objtool: Improve UACCESS coverage

A clang build reported an (obvious) double CLAC while a GCC build did not; it turns out that objtool only re-visits instructions if the first visit was with AC=0. If OTOH the first visit was with AC=1, it completely ignores any subsequent visit, even when it has AC=0. Fix this by using a visited mask instead of a boolean, and (explicitly) mark the AC state. $ ./objtool check -b --no-fp --retpoline --uaccess drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x22: redundant UACCESS disable drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0xea: (alt) drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0xffffffffffffffff: (branch) drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0xd9: (alt) drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0xb2: (branch) drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0x39: (branch) drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0x0: <=== (func) Reported-by: Josh Poimboeuf <[email protected]> Reported-by: Thomas Gleixner <[email protected]> Reported-by: Sedat Dilek <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Signed-off-by: Josh Poimboeuf <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Tested-by: Nathan Chancellor <[email protected]> Tested-by: Nick Desaulniers <[email protected]> Tested-by: Sedat Dilek <[email protected]> Link: ClangBuiltLinux#617 Link: https://lkml.kernel.org/r/5359166aad2d53f3145cd442d83d0e5115e0cd17.1564007838.git.jpoimboe@redhat.com
laijs · Jul 25, 2019 · 882a0db · 882a0db
1 parent b68b990
commit 882a0db
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Showing 2 changed files with 6 additions and 4 deletions.
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
@@ -1946,6 +1946,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 	struct alternative *alt;
 	struct instruction *insn, *next_insn;
 	struct section *sec;
+	u8 visited;
 	int ret;
 
 	insn = first;
@@ -1972,12 +1973,12 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 			return 1;
 		}
 
+		visited = 1 << state.uaccess;
 		if (insn->visited) {
 			if (!insn->hint && !insn_state_match(insn, &state))
 				return 1;
 
-			/* If we were here with AC=0, but now have AC=1, go again */
-			if (insn->state.uaccess || !state.uaccess)
+			if (insn->visited & visited)
 				return 0;
 		}
 
@@ -2024,7 +2025,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 		} else
 			insn->state = state;
 
-		insn->visited = true;
+		insn->visited |= visited;
 
 		if (!insn->ignore_alts) {
 			bool skip_orig = false;

diff --git a/tools/objtool/check.h b/tools/objtool/check.h
@@ -33,8 +33,9 @@ struct instruction {
 	unsigned int len;
 	enum insn_type type;
 	unsigned long immediate;
-	bool alt_group, visited, dead_end, ignore, hint, save, restore, ignore_alts;
+	bool alt_group, dead_end, ignore, hint, save, restore, ignore_alts;
 	bool retpoline_safe;
+	u8 visited;
 	struct symbol *call_dest;
 	struct instruction *jump_dest;
 	struct instruction *first_jump_src;