objtool: Fix infinite loop in find_jump_table()

Kristen found a hang in objtool when building with -ffunction-sections.

It was caused by evergreen_pcie_gen2_enable.cold() being laid out
immediately before evergreen_pcie_gen2_enable().  Since their "pfunc" is
always the same, find_jump_table() got into an infinite loop because it
didn't recognize the boundary between the two functions.

Fix that with a new prev_insn_same_sym() helper, which doesn't cross
subfunction boundaries.

Reported-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/378b51c9d9c894dc3294bc460b4b0869e950b7c5.1588110291.git.jpoimboe@redhat.com

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 4b170fd..0e8f9a3 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -72,6 +72,17 @@ static struct instruction *next_insn_same_func(struct objtool_file *file,
        return find_insn(file, func->cfunc->sec, func->cfunc->offset);
 }
 
+static struct instruction *prev_insn_same_sym(struct objtool_file *file,
+                                              struct instruction *insn)
+{
+       struct instruction *prev = list_prev_entry(insn, list);
+
+       if (&prev->list != &file->insn_list && prev->func == insn->func)
+               return prev;
+
+       return NULL;
+}
+
 #define func_for_each_insn(file, func, insn)                           \
        for (insn = find_insn(file, func->sec, func->offset);           \
             insn;                                                      \
@@ -1050,8 +1061,8 @@ static struct rela *find_jump_table(struct objtool_file *file,
         * it.
         */
        for (;
-            &insn->list != &file->insn_list && insn->func && insn->func->pfunc == func;
-            insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
+            insn && insn->func && insn->func->pfunc == func;
+            insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
 
                if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
                        break;