Messages in this thread | | | Date | Sun, 19 Apr 2020 11:41:50 -0500 | From | Josh Poimboeuf <> | Subject | Re: [RFC][PATCH 4/7] objtool: Add support for intra-function calls |
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On Thu, Apr 16, 2020 at 05:07:56PM +0200, Peter Zijlstra wrote: > From: Alexandre Chartre <alexandre.chartre@oracle.com> > > Change objtool to support intra-function calls. On x86, an intra-function > call is represented in objtool as a push onto the stack (of the return > address), and a jump to the destination address. That way the stack > information is correctly updated and the call flow is still accurate. > > Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Link: https://lkml.kernel.org/r/20200414103618.12657-4-alexandre.chartre@oracle.com > --- > include/linux/frame.h | 11 + > tools/objtool/Documentation/stack-validation.txt | 8 + > tools/objtool/arch/x86/decode.c | 17 ++- > tools/objtool/check.c | 129 ++++++++++++++++++----- > tools/objtool/check.h | 1 > 5 files changed, 140 insertions(+), 26 deletions(-) > > --- a/include/linux/frame.h > +++ b/include/linux/frame.h > @@ -15,9 +15,20 @@ > static void __used __section(.discard.func_stack_frame_non_standard) \ > *__func_stack_frame_non_standard_##func = func > > +/* > + * This macro indicates that the following intra-function call is valid. > + * Any non-annotated intra-function call will cause objtool to issue warning.
issue *a* warning
> +static int setup_call_dest(struct objtool_file *file, struct instruction *insn) > +{ > + unsigned long dest_off; > + > + dest_off = insn->offset + insn->len + insn->immediate; > + insn->call_dest = find_func_by_offset(insn->sec, dest_off); > + if (!insn->call_dest) > + insn->call_dest = find_symbol_by_offset(insn->sec, dest_off); > + > + if (!insn->call_dest) { > + /* intra-function call */ > + if (insn->intra_function_call) > + return 0; > + > + WARN_FUNC("intra-function call", insn->sec, insn->offset); > + return -1; > + } > + > + /* regular call */ > + if (insn->func && insn->call_dest->type != STT_FUNC) { > + WARN_FUNC("unsupported call to non-function", > + insn->sec, insn->offset); > + return -1; > + } > + > + return 0; > +} > +
This function should first be added in a separate patch which doesn't change functionality.
> @@ -2269,6 +2327,29 @@ static int validate_branch(struct objtoo > if (dead_end_function(file, insn->call_dest)) > return 0; > > + if (insn->intra_function_call) { > + /* > + * The call instruction can update the stack > + * state. Then make the intra-function call > + * behaves like and unconditional jump.
grammar fix: "behave like an unconditional jump".
> + */ > + ret = handle_insn_ops(insn, &state); > + if (ret) > + return ret;
validate_branch's callers aren't currently able to handle a negative return code.
> + > + ret = validate_branch(file, func, insn, > + insn->jump_dest, state); > + if (ret) { > + if (backtrace) { > + BT_FUNC("(intra-function call)", > + insn); > + } > + return ret; > + } > + > + return 0; > + } > +
Could this be cleaner if the insn->type were just changed to INSN_JUMP_UNCONDITIONAL? Then it could share the normal jump logic.
Also, now that more instructions are getting stack ops, I wonder if the ops can just be handled generically for every instruction, with a call to handle_insn_ops() above, before the switch statement.
-- Josh
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