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objtool: Add support for intra-function calls

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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>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200414103618.12657-4-alexandre.chartre@oracle.com
This commit is contained in:
Alexandre Chartre
2020-04-14 12:36:12 +02:00
committed by Peter Zijlstra
parent b490f45362
commit 8aa8eb2a8f
4 changed files with 102 additions and 4 deletions
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79
tools/objtool/check.c
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@@ -674,6 +674,16 @@ static int add_jump_destinations(struct objtool_file *file)
return 0;
}
static void remove_insn_ops(struct instruction *insn)
{
struct stack_op *op, *tmp;
list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
list_del(&op->list);
free(op);
}
}
/*
* Find the destination instructions for all calls.
*/
@@ -699,10 +709,7 @@ static int add_call_destinations(struct objtool_file *file)
continue;
if (!insn->call_dest) {
WARN_FUNC("unsupported intra-function call",
insn->sec, insn->offset);
if (retpoline)
WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
return -1;
}
@@ -725,6 +732,15 @@ static int add_call_destinations(struct objtool_file *file)
}
} else
insn->call_dest = rela->sym;
/*
* Whatever stack impact regular CALLs have, should be undone
* by the RETURN of the called function.
*
* Annotated intra-function calls retain the stack_ops but
* are converted to JUMP, see read_intra_function_calls().
*/
remove_insn_ops(insn);
}
return 0;
@@ -1404,6 +1420,57 @@ static int read_instr_hints(struct objtool_file *file)
return 0;
}
static int read_intra_function_calls(struct objtool_file *file)
{
struct instruction *insn;
struct section *sec;
struct rela *rela;
sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
if (!sec)
return 0;
list_for_each_entry(rela, &sec->rela_list, list) {
unsigned long dest_off;
if (rela->sym->type != STT_SECTION) {
WARN("unexpected relocation symbol type in %s",
sec->name);
return -1;
}
insn = find_insn(file, rela->sym->sec, rela->addend);
if (!insn) {
WARN("bad .discard.intra_function_call entry");
return -1;
}
if (insn->type != INSN_CALL) {
WARN_FUNC("intra_function_call not a direct call",
insn->sec, insn->offset);
return -1;
}
/*
* Treat intra-function CALLs as JMPs, but with a stack_op.
* See add_call_destinations(), which strips stack_ops from
* normal CALLs.
*/
insn->type = INSN_JUMP_UNCONDITIONAL;
dest_off = insn->offset + insn->len + insn->immediate;
insn->jump_dest = find_insn(file, insn->sec, dest_off);
if (!insn->jump_dest) {
WARN_FUNC("can't find call dest at %s+0x%lx",
insn->sec, insn->offset,
insn->sec->name, dest_off);
return -1;
}
}
return 0;
}
static void mark_rodata(struct objtool_file *file)
{
struct section *sec;
@@ -1459,6 +1526,10 @@ static int decode_sections(struct objtool_file *file)
if (ret)
return ret;
ret = read_intra_function_calls(file);
if (ret)
return ret;
ret = add_call_destinations(file);
if (ret)
return ret;