From patchwork Thu Oct 19 09:17:26 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nelson Chu X-Patchwork-Id: 78146 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id EC13B3858023 for ; Thu, 19 Oct 2023 09:17:45 +0000 (GMT) X-Original-To: binutils@sourceware.org Delivered-To: binutils@sourceware.org Received: from NelsondeMBP.localdomain (114-25-69-175.dynamic-ip.hinet.net [114.25.69.175]) by sourceware.org (Postfix) with ESMTP id 3B16C3858D1E for ; Thu, 19 Oct 2023 09:17:29 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 3B16C3858D1E Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=rivosinc.com Authentication-Results: sourceware.org; spf=none smtp.mailfrom=NelsondeMBP.localdomain ARC-Filter: OpenARC Filter v1.0.0 sourceware.org 3B16C3858D1E Authentication-Results: server2.sourceware.org; arc=none smtp.remote-ip=114.25.69.175 ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1697707051; cv=none; b=NoliPPEAe3aNygEUA8FHSv/xKmfKWqnkaG2ccYIRq5jWrtHXtColOZ+oXkj3TmRg08XADZJyCGjUjySKfy1G+PkQv9n1vcnyrvgtHvqbkx5RUmWtYOIi1ndGItPOwRgWViXEHi4X2YB2VMYQwYPmxV168E27oSOi3eYDc2hWaBo= ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1697707051; c=relaxed/simple; bh=V020BuRuOAFyaOFWM84hNS6EXVVBIS6h8f0j1wensc4=; h=From:To:Subject:Date:Message-Id:MIME-Version; b=vP3vyeaUivRUFSpxlXXWL+1WEtLN/CyGrafiZ0oWCxiR+wgTT7oddQLcvaeHnAyO6TOAKlET1hp+19Uy58YMtS7yi3V9tWGW4Q6rQP9JSv9E69X3Jpx0iPHSQoV9AA2+NtyUBUW9ei4lXNlb2X3kT20XVLFcDycaZhs5SbpK+C8= ARC-Authentication-Results: i=1; server2.sourceware.org Received: by NelsondeMBP.localdomain (Postfix, from userid 501) id 70E4512A2775; Thu, 19 Oct 2023 17:17:27 +0800 (CST) From: Nelson Chu To: binutils@sourceware.org, kito.cheng@sifive.com, palmer@rivosinc.com, charlie@rivosinc.com Cc: nelson@rivosinc.com Subject: [PATCH] RISC-V: Clarify the behaviors of SET/ADD/SUB relocations. Date: Thu, 19 Oct 2023 17:17:26 +0800 Message-Id: <20231019091726.69380-1-nelson@rivosinc.com> X-Mailer: git-send-email 2.39.3 (Apple Git-145) MIME-Version: 1.0 X-Spam-Status: No, score=-7.2 required=5.0 tests=BAYES_00, GIT_PATCH_0, HEADER_FROM_DIFFERENT_DOMAINS, KAM_DMARC_STATUS, KAM_LAZY_DOMAIN_SECURITY, KHOP_HELO_FCRDNS, NO_DNS_FOR_FROM, RCVD_IN_PBL, RCVD_IN_SORBS_DUL, RDNS_DYNAMIC, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: binutils@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Binutils mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: binutils-bounces+patchwork=sourceware.org@sourceware.org We are used to generate these kinds of relocations by data directives. Considering the following example, .word (A + 3) - (B + 2) The GAS will generate a pair of ADD/SUB for this, R_RISCV_ADD, A + 1 R_RISCV_SUB, 0 The addend of R_RISCV_SUB will always be zero, and the summary of the constants will be stored in the addend of R_RISCV_ADD/SET. Therefore, we can always add the addend of these data relocations when doing relocations. But unfortunately, I had heard that if we are using .reloc to generate the data relocations will make the relocations failed. Refer to this, .reloc offset, R_RISCV_ADD32, A + 3 .reloc offset, R_RISCV_SUB32, B + 2 .word 0 Then we can get the relocations as follows, R_RISCV_ADD, A + 3 R_RISCV_SUB, B + 2 Then... Current LD does the relocation, B - A + 3 + 2, which is wrong obviously... So first of all, this patch fixes the wrong relocation behavior of R_RISCV_SUB* relocations. Afterwards, considering the uleb128 direcitve, we will get a pair of SET_ULEB128/SUB_ULEB128 relocations for it for now, .uleb128 (A + 3) - (B + 2) R_RISCV_SET_ULEB128, A + 1 R_RISCV_SUB_ULEB128, B + 1 Which looks also wrong obviously, the summary of the constants should only be stored into the addend of SET_ULEB128, and the addend of SUB_ULEB128 should be zero like other SUB relocations. But the current LD will still get the right relocation values since we only add the addend of SUB_ULEB128 by accident... Anyway, this patch also fixes the behaviors above, to make sure that no matter using .uleb128 or .reloc directives, we should always get the right values. bfd/ * elfnn-riscv.c (perform_relocation): Clarify that SUB relocations should substract the addend, rather than add. (riscv_elf_relocate_section): Since SET_ULEB128 won't go into perform_relocation, we should add it's addend here in advance. gas/ * config/tc-riscv.c (riscv_insert_uleb128_fixes): Set the addend of SUB_ULEB128 to zero since it should already be added into the addend of SET_ULEB128. Acked-by: Charlie Jenkins --- bfd/elfnn-riscv.c | 22 ++++++++++++++++------ gas/config/tc-riscv.c | 1 + 2 files changed, 17 insertions(+), 6 deletions(-) diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c index 3edf68e3e30..00e5c69dbec 100644 --- a/bfd/elfnn-riscv.c +++ b/bfd/elfnn-riscv.c @@ -1737,7 +1737,20 @@ perform_relocation (const reloc_howto_type *howto, { if (howto->pc_relative) value -= sec_addr (input_section) + rel->r_offset; - value += rel->r_addend; + + switch (ELFNN_R_TYPE (rel->r_info)) + { + case R_RISCV_SUB6: + case R_RISCV_SUB8: + case R_RISCV_SUB16: + case R_RISCV_SUB32: + case R_RISCV_SUB64: + case R_RISCV_SUB_ULEB128: + value -= rel->r_addend; + break; + default: + value += rel->r_addend; + } switch (ELFNN_R_TYPE (rel->r_info)) { @@ -1818,10 +1831,7 @@ perform_relocation (const reloc_howto_type *howto, value = ENCODE_CITYPE_LUI_IMM (RISCV_CONST_HIGH_PART (value)); break; - /* SUB_ULEB128 must be applied after SET_ULEB128, so we only write the - value back for SUB_ULEB128 should be enough. */ - case R_RISCV_SET_ULEB128: - break; + /* R_RISCV_SET_ULEB128 won't go into here. */ case R_RISCV_SUB_ULEB128: { unsigned int len = 0; @@ -2523,7 +2533,7 @@ riscv_elf_relocate_section (bfd *output_bfd, if (uleb128_set_rel != NULL && uleb128_set_rel->r_offset == rel->r_offset) { - relocation = uleb128_set_vma - relocation; + relocation = uleb128_set_vma - relocation + uleb128_set_rel->r_addend; uleb128_set_vma = 0; uleb128_set_rel = NULL; } diff --git a/gas/config/tc-riscv.c b/gas/config/tc-riscv.c index 5759d3a5fc4..09f2ea17c17 100644 --- a/gas/config/tc-riscv.c +++ b/gas/config/tc-riscv.c @@ -4999,6 +4999,7 @@ riscv_insert_uleb128_fixes (bfd *abfd ATTRIBUTE_UNUSED, fix_new_exp (fragP, fragP->fr_fix, 0, exp_dup, 0, BFD_RELOC_RISCV_SET_ULEB128); exp_dup->X_add_symbol = exp->X_op_symbol; + exp_dup->X_add_number = 0; /* Set addend of SUB_ULEB128 to zero. */ fix_new_exp (fragP, fragP->fr_fix, 0, exp_dup, 0, BFD_RELOC_RISCV_SUB_ULEB128); free ((void *) exp_dup);