From 0c1ddd33177530feb3685a800bba1ac4cc58cc4b Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Wed, 17 Jul 2019 20:36:52 -0500 Subject: [PATCH] objtool: Refactor sibling call detection logic Simplify the sibling call detection logic a bit. Signed-off-by: Josh Poimboeuf Signed-off-by: Thomas Gleixner Tested-by: Nick Desaulniers Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/8357dbef9e7f5512e76bf83a76c81722fc09eb5e.1563413318.git.jpoimboe@redhat.com --- tools/objtool/check.c | 65 ++++++++++++++++++++++--------------------- 1 file changed, 33 insertions(+), 32 deletions(-) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 0d2a8e54a82e..7fe31e0f8afe 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -97,6 +97,20 @@ static struct instruction *next_insn_same_func(struct objtool_file *file, for (insn = next_insn_same_sec(file, insn); insn; \ insn = next_insn_same_sec(file, insn)) +static bool is_sibling_call(struct instruction *insn) +{ + /* An indirect jump is either a sibling call or a jump to a table. */ + if (insn->type == INSN_JUMP_DYNAMIC) + return list_empty(&insn->alts); + + if (insn->type != INSN_JUMP_CONDITIONAL && + insn->type != INSN_JUMP_UNCONDITIONAL) + return false; + + /* add_jump_destinations() sets insn->call_dest for sibling calls. */ + return !!insn->call_dest; +} + /* * This checks to see if the given function is a "noreturn" function. * @@ -167,34 +181,25 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func, * of the sibling call returns. */ func_for_each_insn_all(file, func, insn) { - if (insn->type == INSN_JUMP_UNCONDITIONAL) { + if (is_sibling_call(insn)) { struct instruction *dest = insn->jump_dest; if (!dest) /* sibling call to another file */ return false; - if (dest->func && dest->func->pfunc != insn->func->pfunc) { - - /* local sibling call */ - if (recursion == 5) { - /* - * Infinite recursion: two functions - * have sibling calls to each other. - * This is a very rare case. It means - * they aren't dead ends. - */ - return false; - } - - return __dead_end_function(file, dest->func, - recursion + 1); + /* local sibling call */ + if (recursion == 5) { + /* + * Infinite recursion: two functions have + * sibling calls to each other. This is a very + * rare case. It means they aren't dead ends. + */ + return false; } - } - if (insn->type == INSN_JUMP_DYNAMIC && list_empty(&insn->alts)) - /* sibling call */ - return false; + return __dead_end_function(file, dest->func, recursion+1); + } } return true; @@ -581,9 +586,8 @@ static int add_jump_destinations(struct objtool_file *file) insn->retpoline_safe = true; continue; } else { - /* sibling call */ + /* external sibling call */ insn->call_dest = rela->sym; - insn->jump_dest = NULL; continue; } @@ -633,9 +637,8 @@ static int add_jump_destinations(struct objtool_file *file) } else if (insn->jump_dest->func->pfunc != insn->func->pfunc && insn->jump_dest->offset == insn->jump_dest->func->offset) { - /* sibling class */ + /* internal sibling call */ insn->call_dest = insn->jump_dest->func; - insn->jump_dest = NULL; } } } @@ -1889,7 +1892,7 @@ static inline bool func_uaccess_safe(struct symbol *func) return false; } -static inline const char *insn_dest_name(struct instruction *insn) +static inline const char *call_dest_name(struct instruction *insn) { if (insn->call_dest) return insn->call_dest->name; @@ -1901,13 +1904,13 @@ static int validate_call(struct instruction *insn, struct insn_state *state) { if (state->uaccess && !func_uaccess_safe(insn->call_dest)) { WARN_FUNC("call to %s() with UACCESS enabled", - insn->sec, insn->offset, insn_dest_name(insn)); + insn->sec, insn->offset, call_dest_name(insn)); return 1; } if (state->df) { WARN_FUNC("call to %s() with DF set", - insn->sec, insn->offset, insn_dest_name(insn)); + insn->sec, insn->offset, call_dest_name(insn)); return 1; } @@ -2088,14 +2091,12 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, case INSN_JUMP_CONDITIONAL: case INSN_JUMP_UNCONDITIONAL: - if (func && !insn->jump_dest) { + if (func && is_sibling_call(insn)) { ret = validate_sibling_call(insn, &state); if (ret) return ret; - } else if (insn->jump_dest && - (!func || !insn->jump_dest->func || - insn->jump_dest->func->pfunc == func)) { + } else if (insn->jump_dest) { ret = validate_branch(file, func, insn->jump_dest, state); if (ret) { @@ -2111,7 +2112,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, break; case INSN_JUMP_DYNAMIC: - if (func && list_empty(&insn->alts)) { + if (func && is_sibling_call(insn)) { ret = validate_sibling_call(insn, &state); if (ret) return ret;