From nobody Tue Feb 10 10:22:11 2026 Received: from m.syntacore.com (m.syntacore.com [178.249.69.228]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 89A6E290D80; Wed, 4 Jun 2025 15:13:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.249.69.228 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749050030; cv=none; b=poy5lmqdvwJyCEqpwYP8L3wkm3pUyzleWmNqJohrmY+H3+M/RUVINIliBVLEpboyQ5G81H9aggfRjtYCASmyjQXC92WaLbVNiMC3e5IclB1pxcn79IS61ruTgOY+N5jHt2rl4FAE56l1TLu4G4eHw4szUXRwybMmBVK1elUgjlc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749050030; c=relaxed/simple; bh=Bz52cWmM5E063diqhU/tvNAwMpsAg2SFm+DiQ9Dj94Y=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=PCnX9oz5riIH1R9aeAsmkbYoCehd7Uh2Ih/ECs19I68IeS42h/H30wy/MD7z0zDR7tZ5KkiRYUF1pGsGw9jTdKvTOpV5n6ugReWebZXjXb18pNKfWh6uAVb6GmS5wmhQCTtsJppppBySPnuDkAveswjQLM0CTK9A/5VH8bFrGP4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=syntacore.com; spf=pass smtp.mailfrom=syntacore.com; dkim=pass (2048-bit key) header.d=syntacore.com header.i=@syntacore.com header.b=qFFBj5JE; arc=none smtp.client-ip=178.249.69.228 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=syntacore.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=syntacore.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=syntacore.com header.i=@syntacore.com header.b="qFFBj5JE" Received: from MRN-SC-KSMG-01.corp.syntacore.com (localhost [127.0.0.1]) by m.syntacore.com (Postfix) with ESMTP id 386171A0004; Wed, 4 Jun 2025 15:07:43 +0000 (UTC) DKIM-Filter: OpenDKIM Filter v2.11.0 m.syntacore.com 386171A0004 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=syntacore.com; s=m; t=1749049663; bh=cFvYaW2WkbtOra3S0g7FSljIzV4LxrpuqkAbvhUZRVI=; h=From:To:Subject:Date:Message-ID:MIME-Version:Content-Type:From; b=qFFBj5JEyV6NX3EeyzhabNsOKCgp9jJ9AFkzUYTr7lX9o+e4rwwXk5S81XGzUfEi1 LNQDEBsNDZs6a6o1xuli/VYrLGk4xDpdU11Z8sRU9LiqoRrk/sjtVcJDUm3rMlPP6F 6xFw521QT9wRVQVhk1boOFiMCUOHRs1gXCSxK+bMJyLcQ7sGz9hkWl42jKqdkBrIAv IVZpAhBMUcCFAVLRde+a/IgzLNAKMTuWC3JYRG9wJ9wDKHrROMXu95QlNFG6ZyDZ7l GpqCr/eSzO4xhWXg3rxXh6nlXf8urJZZKLfcFQceCqN1gNzeTvzzfyjeLHaKHVYOU5 gAdYVUb0Ohnmg== Received: from S-SC-EXCH-01.corp.syntacore.com (exchange.syntacore.com [10.76.202.20]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by m.syntacore.com (Postfix) with ESMTPS; Wed, 4 Jun 2025 15:07:41 +0000 (UTC) Received: from localhost (10.199.25.251) by S-SC-EXCH-01.corp.syntacore.com (10.76.202.20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 4 Jun 2025 18:06:55 +0300 From: Svetlana Parfenova To: Kees Cook , CC: Svetlana Parfenova , Alexander Viro , Christian Brauner , Jan Kara , Andrew Morton , , Subject: [RFC] binfmt_elf: preserve original ELF e_flags in core dumps Date: Wed, 4 Jun 2025 22:05:02 +0700 Message-ID: <20250604150502.622178-1-svetlana.parfenova@syntacore.com> X-Mailer: git-send-email 2.39.5 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: S-SC-EXCH-01.corp.syntacore.com (10.76.202.20) To S-SC-EXCH-01.corp.syntacore.com (10.76.202.20) X-KSMG-AntiPhishing: not scanned, disabled by settings X-KSMG-AntiSpam-Interceptor-Info: not scanned X-KSMG-AntiSpam-Status: not scanned, disabled by settings X-KSMG-AntiVirus: Kaspersky Secure Mail Gateway, version 2.1.1.8310, bases: 2025/06/04 12:53:00 #27536686 X-KSMG-AntiVirus-Status: NotDetected, skipped X-KSMG-LinksScanning: NotDetected X-KSMG-Message-Action: skipped X-KSMG-Rule-ID: 5 Content-Type: text/plain; charset="utf-8" Preserve the original ELF e_flags from the executable in the core dump header instead of relying on compile-time defaults (ELF_CORE_EFLAGS or value from the regset view). This ensures that ABI-specific flags in the dump file match the actual binary being executed. Save the e_flags field during ELF binary loading (in load_elf_binary()) into the mm_struct, and later retrieve it during core dump generation (in fill_note_info()). Use this saved value to populate the e_flags in the core dump ELF header. Add a new Kconfig option, CONFIG_CORE_DUMP_USE_PROCESS_EFLAGS, to guard this behavior. Although motivated by a RISC-V use case, the mechanism is generic and can be applied to all architectures. This change is needed to resolve a debugging issue encountered when analyzing core dumps with GDB for RISC-V systems. GDB inspects the e_flags field to determine whether optional register sets such as the floating-point unit are supported. Without correct flags, GDB may warn and ignore valid register data: warning: Unexpected size of section '.reg2/213' in core file. As a result, floating-point registers are not accessible in the debugger, even though they were dumped. Preserving the original e_flags enables GDB and other tools to properly interpret the dump contents. Signed-off-by: Svetlana Parfenova --- fs/Kconfig.binfmt | 9 +++++++++ fs/binfmt_elf.c | 26 ++++++++++++++++++++------ include/linux/mm_types.h | 5 +++++ 3 files changed, 34 insertions(+), 6 deletions(-) diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt index bd2f530e5740..45bed2041542 100644 --- a/fs/Kconfig.binfmt +++ b/fs/Kconfig.binfmt @@ -184,4 +184,13 @@ config EXEC_KUNIT_TEST This builds the exec KUnit tests, which tests boundary conditions of various aspects of the exec internals. =20 +config CORE_DUMP_USE_PROCESS_EFLAGS + bool "Preserve ELF e_flags from executable in core dumps" + depends on BINFMT_ELF && ELF_CORE && RISCV + default n + help + Save the ELF e_flags from the process executable at load time + and use it in the core dump header. This ensures the dump reflects + the original binary ABI. + endmenu diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 4c1ea6b52a53..baf749e431a1 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1297,6 +1297,11 @@ static int load_elf_binary(struct linux_binprm *bprm) mm->end_data =3D end_data; mm->start_stack =3D bprm->p; =20 +#ifdef CONFIG_CORE_DUMP_USE_PROCESS_EFLAGS + /* stash e_flags for use in core dumps */ + mm->saved_e_flags =3D elf_ex->e_flags; +#endif + /** * DOC: "brk" handling * @@ -1870,6 +1875,8 @@ static int fill_note_info(struct elfhdr *elf, int phd= rs, struct elf_thread_core_info *t; struct elf_prpsinfo *psinfo; struct core_thread *ct; + u16 machine; + u32 flags; =20 psinfo =3D kmalloc(sizeof(*psinfo), GFP_KERNEL); if (!psinfo) @@ -1897,17 +1904,24 @@ static int fill_note_info(struct elfhdr *elf, int p= hdrs, return 0; } =20 - /* - * Initialize the ELF file header. - */ - fill_elf_header(elf, phdrs, - view->e_machine, view->e_flags); + machine =3D view->e_machine; + flags =3D view->e_flags; #else view =3D NULL; info->thread_notes =3D 2; - fill_elf_header(elf, phdrs, ELF_ARCH, ELF_CORE_EFLAGS); + machine =3D ELF_ARCH; + flags =3D ELF_CORE_EFLAGS; #endif =20 +#ifdef CONFIG_CORE_DUMP_USE_PROCESS_EFLAGS + flags =3D dump_task->mm->saved_e_flags; +#endif + + /* + * Initialize the ELF file header. + */ + fill_elf_header(elf, phdrs, machine, flags); + /* * Allocate a structure for each thread. */ diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 56d07edd01f9..5487d6ba6fcb 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -1059,6 +1059,11 @@ struct mm_struct { =20 unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */ =20 +#ifdef CONFIG_CORE_DUMP_USE_PROCESS_EFLAGS + /* the ABI-related flags from the ELF header. Used for core dump */ + unsigned long saved_e_flags; +#endif + struct percpu_counter rss_stat[NR_MM_COUNTERS]; =20 struct linux_binfmt *binfmt; --=20 2.39.5