From: Peter Zijlstra <pet...@infradead.org> A clang build reported an (obvious) double CLAC while a GCC build did not; it turns out we only re-visit instructions if the first visit was with AC=0. If OTOH the first visit was with AC=1, we completely ignore 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 <jpoim...@redhat.com> Reported-by: Thomas Gleixner <t...@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Reported-by: Sedat Dilek <sedat.di...@gmail.com> Tested-by: Nathan Chancellor <natechancel...@gmail.com> Tested-by: Nick Desaulniers <ndesaulni...@google.com> Tested-by: Sedat Dilek <sedat.di...@gmail.com> Link: https://github.com/ClangBuiltLinux/linux/issues/617 Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com> --- tools/objtool/check.c | 7 ++++--- tools/objtool/check.h | 3 ++- 2 files changed, 6 insertions(+), 4 deletions(-) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 5f26620f13f5..176f2f084060 100644 --- 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 index b881fafcf55d..6d875ca6fce0 100644 --- 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; -- 2.20.1
