From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 1944) id 7FBF9385E453; Wed, 14 Feb 2024 15:27:51 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 7FBF9385E453 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1707924471; bh=why2m733xIP09xCV9aTdB0jduvCtdQKcKWmV7l24mno=; h=From:To:Subject:Date:From; b=RKm+7e+ESq1zUAKU9PysoOeO/fnVy/8t4qsg7pRRYwyHAXn3y9QqW43JtHfIUPP7T XKo4v88Qza6smr7l7W98U8Ox6U9pkUVK6/vjzHtPvU5rK1KbYTFlnh2rtKvd7CfkyS 3j8DM3ED3To1CHHMPOjsKI8pSJjrHrrpXoVcHe6c= Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Szabolcs Nagy To: gcc-cvs@gcc.gnu.org Subject: [gcc(refs/vendors/ARM/heads/gcs)] aarch64: Introduce indirect_return attribute X-Act-Checkin: gcc X-Git-Author: Szabolcs Nagy X-Git-Refname: refs/vendors/ARM/heads/gcs X-Git-Oldrev: af7a4e5f397dfbb9496d8a6710ea90696ab0e355 X-Git-Newrev: 7f952ecef184a5b8c0ba40ba5fb31e6ac687329a Message-Id: <20240214152751.7FBF9385E453@sourceware.org> Date: Wed, 14 Feb 2024 15:27:51 +0000 (GMT) List-Id: https://gcc.gnu.org/g:7f952ecef184a5b8c0ba40ba5fb31e6ac687329a commit 7f952ecef184a5b8c0ba40ba5fb31e6ac687329a Author: Szabolcs Nagy Date: Thu Dec 28 13:37:38 2023 +0000 aarch64: Introduce indirect_return attribute Tail calls of indirect_return functions from non-indirect_return functions are disallowed even if BTI is disabled, since the call site may have BTI enabled. Following x86, mismatching attribute on function pointers is not a type error even though this can lead to bugs. Needed for swapcontext within the same function when GCS is enabled. TODO: arm? docs, tests. feature detection? gcc/ChangeLog: * config/aarch64/aarch64.cc (aarch64_gnu_attributes): Add indirect_return. (aarch64_function_ok_for_sibcall): Disallow tail calls if caller is non-indirect_return but callee is indirect_return. (aarch64_comp_type_attributes): Check indirect_return attribute. * config/arm/aarch-bti-insert.cc (call_needs_bti_j): New. (rest_of_insert_bti): Use call_needs_bti_j. Diff: --- gcc/config/aarch64/aarch64.cc | 11 +++++++++++ gcc/config/arm/aarch-bti-insert.cc | 36 ++++++++++++++++++++++++++++++++---- 2 files changed, 43 insertions(+), 4 deletions(-) diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc index 09374409fe07..975a7a7d533d 100644 --- a/gcc/config/aarch64/aarch64.cc +++ b/gcc/config/aarch64/aarch64.cc @@ -848,6 +848,7 @@ static const attribute_spec aarch64_gnu_attributes[] = affects_type_identity, handler, exclude } */ { "aarch64_vector_pcs", 0, 0, false, true, true, true, handle_aarch64_vector_pcs_attribute, NULL }, + { "indirect_return", 0, 0, false, true, true, false, NULL, NULL }, { "arm_sve_vector_bits", 1, 1, false, true, false, true, aarch64_sve::handle_arm_sve_vector_bits_attribute, NULL }, @@ -6314,6 +6315,14 @@ aarch64_function_ok_for_sibcall (tree, tree exp) return false; if (aarch64_fntype_pstate_za (fntype) != aarch64_cfun_incoming_pstate_za ()) return false; + + /* BTI J is needed where indirect_return functions may return + if bti is enabled there. */ + if (lookup_attribute ("indirect_return", TYPE_ATTRIBUTES (fntype)) + && !lookup_attribute ("indirect_return", + TYPE_ATTRIBUTES (TREE_TYPE (cfun->decl)))) + return false; + return true; } @@ -28849,6 +28858,8 @@ aarch64_comp_type_attributes (const_tree type1, const_tree type2) if (!check_attr ("gnu", "aarch64_vector_pcs")) return 0; + if (!check_attr ("gnu", "indirect_return")) + return 0; if (!check_attr ("gnu", "Advanced SIMD type")) return 0; if (!check_attr ("gnu", "SVE type")) diff --git a/gcc/config/arm/aarch-bti-insert.cc b/gcc/config/arm/aarch-bti-insert.cc index 14d36971cd40..403afff91209 100644 --- a/gcc/config/arm/aarch-bti-insert.cc +++ b/gcc/config/arm/aarch-bti-insert.cc @@ -92,6 +92,35 @@ const pass_data pass_data_insert_bti = 0, /* todo_flags_finish. */ }; +/* Decide if BTI J is needed after a call instruction. */ +static bool +call_needs_bti_j (rtx_insn *insn) +{ + /* Call returns twice, one of which may be indirect. */ + if (find_reg_note (insn, REG_SETJMP, NULL)) + return true; + + /* Tail call does not return. */ + if (SIBLING_CALL_P (insn)) + return false; + + /* Check if the function is marked to return indirectly. */ + rtx call = get_call_rtx_from (insn); + rtx fnaddr = XEXP (call, 0); + tree fndecl = NULL_TREE; + if (GET_CODE (XEXP (fnaddr, 0)) == SYMBOL_REF) + fndecl = SYMBOL_REF_DECL (XEXP (fnaddr, 0)); + if (fndecl == NULL_TREE) + fndecl = MEM_EXPR (fnaddr); + if (!fndecl) + return false; + if (TREE_CODE (TREE_TYPE (fndecl)) != FUNCTION_TYPE + && TREE_CODE (TREE_TYPE (fndecl)) != METHOD_TYPE) + return false; + tree fntype = TREE_TYPE (fndecl); + return lookup_attribute ("indirect_return", TYPE_ATTRIBUTES (fntype)); +} + /* Insert the BTI instruction. */ /* This is implemented as a late RTL pass that runs before branch shortening and does the following. */ @@ -147,10 +176,9 @@ rest_of_insert_bti (void) } } - /* Also look for calls to setjmp () which would be marked with - REG_SETJMP note and put a BTI J after. This is where longjump () - will return. */ - if (CALL_P (insn) && (find_reg_note (insn, REG_SETJMP, NULL))) + /* Also look for calls that may return indirectly, such as setjmp, + and put a BTI J after them. */ + if (CALL_P (insn) && call_needs_bti_j (insn)) { bti_insn = aarch_gen_bti_j (); emit_insn_after (bti_insn, insn);