Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756990AbbFCMXu (ORCPT ); Wed, 3 Jun 2015 08:23:50 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:58222 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756094AbbFCMUP (ORCPT ); Wed, 3 Jun 2015 08:20:15 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Paul Burton , Markos Chandras , Matthew Fortune , Ralf Baechle , linux-mips@linux-mips.org Subject: [PATCH 4.0 122/148] MIPS: fix FP mode selection in lieu of .MIPS.abiflags data Date: Wed, 3 Jun 2015 21:09:52 +0900 Message-Id: <20150603114210.701244562@linuxfoundation.org> X-Mailer: git-send-email 2.4.2 In-Reply-To: <20150603114205.337615117@linuxfoundation.org> References: <20150603114205.337615117@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4197 Lines: 112 4.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Paul Burton commit 620b155034570f577470cf5309f741bac6a6e32b upstream. Commit 46490b572544 ("MIPS: kernel: elf: Improve the overall ABI and FPU mode checks") reworked the ELF FP ABI mode selection logic, but when CONFIG_MIPS_O32_FP64_SUPPORT is enabled it breaks the use of binaries which have no PT_MIPS_ABIFLAGS program header & associated .MIPS.abiflags section. A default mode is selected based upon whether the ELF contains MIPS32 or MIPS64 code, but that selection is made in arch_elf_pt_proc. arch_elf_pt_proc only executes when a PT_MIPS_ABIFLAGS program header is found. If one is not found then arch_elf_pt_proc is never called, and no default overall_fp_mode value is selected. When arch_check_elf is called, both abi0 & abi1 are MIPS_ABI_FP_UNKNOWN which leads to both prog_req & interp_req being set to none_req. none_req matches none of the conditions for mode selection at the end of arch_check_elf, so overall_fp_mode is left untouched. Finally once mips_set_personality_fp is called the BUG() in the default case is then hit & the kernel likely panics. Fix this by moving the selection of a default overall mode to the start of arch_check_elf, which runs once per ELF executed regardless of whether it has a PT_MIPS_ABIFLAGS program header. Signed-off-by: Paul Burton Cc: Markos Chandras Cc: Matthew Fortune Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Patchwork: http://patchwork.linux-mips.org/patch/9978/ Signed-off-by: Ralf Baechle Signed-off-by: Greg Kroah-Hartman --- arch/mips/kernel/elf.c | 32 +++++++++++++++++--------------- 1 file changed, 17 insertions(+), 15 deletions(-) --- a/arch/mips/kernel/elf.c +++ b/arch/mips/kernel/elf.c @@ -76,14 +76,6 @@ int arch_elf_pt_proc(void *_ehdr, void * /* Lets see if this is an O32 ELF */ if (ehdr32->e_ident[EI_CLASS] == ELFCLASS32) { - /* FR = 1 for N32 */ - if (ehdr32->e_flags & EF_MIPS_ABI2) - state->overall_fp_mode = FP_FR1; - else - /* Set a good default FPU mode for O32 */ - state->overall_fp_mode = cpu_has_mips_r6 ? - FP_FRE : FP_FR0; - if (ehdr32->e_flags & EF_MIPS_FP64) { /* * Set MIPS_ABI_FP_OLD_64 for EF_MIPS_FP64. We will override it @@ -104,9 +96,6 @@ int arch_elf_pt_proc(void *_ehdr, void * (char *)&abiflags, sizeof(abiflags)); } else { - /* FR=1 is really the only option for 64-bit */ - state->overall_fp_mode = FP_FR1; - if (phdr64->p_type != PT_MIPS_ABIFLAGS) return 0; if (phdr64->p_filesz < sizeof(abiflags)) @@ -147,6 +136,7 @@ int arch_check_elf(void *_ehdr, bool has struct elf32_hdr *ehdr = _ehdr; struct mode_req prog_req, interp_req; int fp_abi, interp_fp_abi, abi0, abi1, max_abi; + bool is_mips64; if (!config_enabled(CONFIG_MIPS_O32_FP64_SUPPORT)) return 0; @@ -162,10 +152,22 @@ int arch_check_elf(void *_ehdr, bool has abi0 = abi1 = fp_abi; } - /* ABI limits. O32 = FP_64A, N32/N64 = FP_SOFT */ - max_abi = ((ehdr->e_ident[EI_CLASS] == ELFCLASS32) && - (!(ehdr->e_flags & EF_MIPS_ABI2))) ? - MIPS_ABI_FP_64A : MIPS_ABI_FP_SOFT; + is_mips64 = (ehdr->e_ident[EI_CLASS] == ELFCLASS64) || + (ehdr->e_flags & EF_MIPS_ABI2); + + if (is_mips64) { + /* MIPS64 code always uses FR=1, thus the default is easy */ + state->overall_fp_mode = FP_FR1; + + /* Disallow access to the various FPXX & FP64 ABIs */ + max_abi = MIPS_ABI_FP_SOFT; + } else { + /* Default to a mode capable of running code expecting FR=0 */ + state->overall_fp_mode = cpu_has_mips_r6 ? FP_FRE : FP_FR0; + + /* Allow all ABIs we know about */ + max_abi = MIPS_ABI_FP_64A; + } if ((abi0 > max_abi && abi0 != MIPS_ABI_FP_UNKNOWN) || (abi1 > max_abi && abi1 != MIPS_ABI_FP_UNKNOWN)) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/