From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail02.kasm.eu (unknown [46.227.67.101]) (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 6120D4779BC for ; Tue, 11 Aug 2026 20:48:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=46.227.67.101 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786481312; cv=none; b=fDQqnE+V3q8OkLScYj4prtGjKF4zPHA86BE+RBgxni4Jce/LJYH3eIS9VsG58mkmf93PaHdnyu34HHKzy4t1HUb0hyE7102CA3sFepdWl5NDDFVXf+1j2MB+bf92VR2zNa4rVnMr0tDa8Mln5S5fOECMsoV9s5f5Eot8azOwulM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786481312; c=relaxed/simple; bh=HzCsdjXOl07TBdcf1JVpgBjz4KRdhAtdc0V5Bj5044U=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=K8tXPJRqvuUVhU2uf+7hODltlcsKoX3Y/dYIXcN+VtkSh/6L5Y4DJ3VKDNKoRYS3cCBabs6tVeCp+6rjTugfw1E2AlohkyYbXJAdGkgMwwZMaKZ98ncBGDlSl5QgSl4XN5eVAkqIfTKDMbMnrWLnnc4dTEbO6qE3oaKSqr01UHA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=kasm.eu; spf=pass smtp.mailfrom=kasm.eu; dkim=pass (1024-bit key) header.d=kasm.eu header.i=@kasm.eu header.b=vVUawmid; arc=none smtp.client-ip=46.227.67.101 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=kasm.eu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kasm.eu Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=kasm.eu header.i=@kasm.eu header.b="vVUawmid" Received: from localhost (soda.int.kasm.eu [IPv6:2001:678:a5c:1202:7b92:9ac1:b9ef:5287]) by mail02.kasm.eu (Postfix) with ESMTPSA id DF9712548DE; Tue, 11 Aug 2026 22:39:38 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kasm.eu; s=default; t=1786480779; bh=HzCsdjXOl07TBdcf1JVpgBjz4KRdhAtdc0V5Bj5044U=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=vVUawmidp9WCzBxaGy2k/Fm3REpQfFT8mjY23q/otlXT2L26nY+HkTvPPOiE/wK5H 94y/+qgNGsDMiYHhLuQOkgtTDQL1yDzLDJlBexCvNz3S9Cycuv1IyLJLf8PcRCHxJ2 rhDXN4Z2P4H1PgjMyd1e2q9yYl0hoNjcock6QCbc= Date: Tue, 11 Aug 2026 22:39:38 +0200 From: Klara Modin To: Xiaofeng Yuan Cc: Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Nam Cao , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 2/2] riscv: patch: skip fixmap mapping when kernel text is already writable Message-ID: References: <20260720032258.5188-1-xiaofengmian@163.com> <20260720032258.5188-3-xiaofengmian@163.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260720032258.5188-3-xiaofengmian@163.com> Hi, On 2026-07-20 03:22:57 +0000, Xiaofeng Yuan wrote: > Currently patch_map() always creates a temporary writable mapping via > fixmap for kernel text addresses, even when CONFIG_STRICT_MODULE_RWX > is disabled and the kernel text is already mapped with _PAGE_WRITE. > > This is unnecessary overhead at best, and on minimal configurations > it can cause page faults. > > Skip the fixmap path for kernel text when CONFIG_STRICT_MODULE_RWX > is not enabled, since the text pages are already writable in this case. > > Signed-off-by: Xiaofeng Yuan > --- > v2: add commit description > v3: early return when !CONFIG_STRICT_MODULE_RWX (per Nam Cao's suggestion) > diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c > index 16b243376f..caef41d5ef 100644 > --- a/arch/riscv/kernel/patch.c > +++ b/arch/riscv/kernel/patch.c > @@ -44,15 +44,16 @@ static __always_inline void *patch_map(void *addr, const unsigned int fixmap) > uintptr_t uintaddr = (uintptr_t) addr; > phys_addr_t phys; > > + if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) > + return addr; Is this correct when STRICT_KERNEL_RWX is set and not STRICT_MODULE_RWX (e.g. when modules are not enabled)? > + > if (core_kernel_text(uintaddr) || is_kernel_exittext(uintaddr)) { > phys = __pa_symbol(addr); > - } else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) { > + } else { > struct page *page = vmalloc_to_page(addr); > > BUG_ON(!page); > phys = page_to_phys(page) + offset_in_page(addr); > - } else { > - return addr; > } > > return (void *)set_fixmap_offset(fixmap, phys); > -- > 2.43.0 > This patch causes the following oops on my BPI-F3: Unable to handle kernel paging request at virtual address 0000006789abce0b Current swapper/0 pgtable: 4K pagesize, 39-bit VAs, pgdp=0x000000000269d000 [0000006789abce0b] pgd=0000000040031c01, p4d=0000000040031c01, pud=0000000040031c01, pmd=0000000000000000 Oops [#1] Tainted: [W]=WARN Hardware name: Banana Pi BPI-F3 (DT) epc : kmem_cache_alloc_lru_noprof (/home/klara/git/linux/trees/bisect/mm/slub.c:4941) ra : __d_alloc (/home/klara/git/linux/trees/bisect/fs/dcache.c:1902) epc : ffffffff8038379e ra : ffffffff804053b2 sp : ffffffff82203ab0 gp : ffffffff8248da18 tp : ffffffff822200c0 t0 : ffffffd7010660e8 t1 : ffffffff921904d0 t2 : 000000005d6ccc9e s0 : ffffffff82203b30 s1 : 0000000000000000 a0 : 0123456789abcdef a1 : ffffffd700b3f510 a2 : 0000000000000cc0 a3 : 0000000000000002 a4 : 0000000000000000 a5 : 0123456700000000 a6 : 00ffffffff899275 a7 : ffffffff82203918 s2 : 0000000000000000 s3 : ffffffd700b3f000 s4 : ffffffff81a0d848 s5 : ffffffff82492018 s6 : 0000000000000000 s7 : 00000000000003e8 s8 : ffffffff814010e0 s9 : 0000000000000000 s10: 0000000000200000 s11: 00000000024910d8 t3 : 0000000000000014 t4 : 0000000000000026 t5 : 000000003137ae71 t6 : ffffffff82203b18 ssp : 0000000000000000 status: 0000000200000120 badaddr: 0000006789abce0b cause: 000000000000000d kmem_cache_alloc_lru_noprof (/home/klara/git/linux/trees/bisect/mm/slub.c:4941) __d_alloc (/home/klara/git/linux/trees/bisect/fs/dcache.c:1902) d_make_root (/home/klara/git/linux/trees/bisect/fs/dcache.c:1999 /home/klara/git/linux/trees/bisect/fs/dcache.c:2213) shmem_fill_super (/home/klara/git/linux/trees/bisect/mm/shmem.c:5050) get_tree_nodev (/home/klara/git/linux/trees/bisect/fs/super.c:1273 /home/klara/git/linux/trees/bisect/fs/super.c:1292) shmem_get_tree (/home/klara/git/linux/trees/bisect/mm/shmem.c:5062) vfs_get_tree (/home/klara/git/linux/trees/bisect/fs/super.c:1700) fc_mount (/home/klara/git/linux/trees/bisect/fs/namespace.c:1198) vfs_kern_mount.part.0 (/home/klara/git/linux/trees/bisect/fs/namespace.c:1236) kern_mount (/home/klara/git/linux/trees/bisect/fs/namespace.c:6290 /home/klara/git/linux/trees/bisect/fs/namespace.c:6292) shmem_init (/home/klara/git/linux/trees/bisect/mm/shmem.c:5367) mnt_init (/home/klara/git/linux/trees/bisect/fs/namespace.c:6274) vfs_caches_init (/home/klara/git/linux/trees/bisect/fs/dcache.c:3517) start_kernel (/home/klara/git/linux/trees/bisect/init/main.c:1157) Code: 0001 0001 0001 7119 f8a2 f4a6 0100 f0ca ecce fc86 (6703) 01c5 All code ======== 0: 0001 .insn 2, 0x0001 2: 0001 .insn 2, 0x0001 4: 0001 .insn 2, 0x0001 6: 7119 .insn 2, 0x7119 8: f8a2 .insn 2, 0xf8a2 a: f4a6 .insn 2, 0xf4a6 c: 0100 .insn 2, 0x0100 e: f0ca .insn 2, 0xf0ca 10: ecce .insn 2, 0xecce 12: fc86 .insn 2, 0xfc86 14:* 01c56703 lwu a4,28(a0) <-- trapping instruction Code starting with the faulting instruction =========================================== 0: 01c56703 lwu a4,28(a0) ---[ end trace 0000000000000000 ]--- Kernel panic - not syncing: Attempted to kill the idle task! I have MODULES disabled and thus also STRICT_MODULE_RWX disabled, but still STRICT_KERNEL_RWX enabled. I saw that an earlier version of this patch[1] instead gated the first branch behind STRICT_KERNEL_RWX. That version works fine for me. Regards, Klara Modin Link: https://lore.kernel.org/lkml/20260719081037.5749-3-xiaofengmian@163.com [1] # bad: [66566bdc5a42d707d4c3f54587333db00e955268] Merge branch 'unstable/spacemit-k1-wdt' into unstable/next-local git bisect start 'HEAD' # status: waiting for 'good' commit(s), 'bad' commit known # good: [f5bbbfec59b4e2fb7520a91de3df8a6174325d6a] Merge tag 'probes-fixes-v7.2-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace git bisect good f5bbbfec59b4e2fb7520a91de3df8a6174325d6a # bad: [9eba0000697167ff6960428f7401e9f65f7abba3] Merge branch 'libcrypto-next' of https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git git bisect bad 9eba0000697167ff6960428f7401e9f65f7abba3 # bad: [6a66dbb2b9b0a0a5b1225052267c0eaedf34492d] Merge branch 'xtensa-for-next' of https://github.com/jcmvbkbc/linux-xtensa.git git bisect bad 6a66dbb2b9b0a0a5b1225052267c0eaedf34492d # good: [3787df98a48a0e699f6a06d4a42fc20597368db1] Merge branch 'for-next/core' of https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux git bisect good 3787df98a48a0e699f6a06d4a42fc20597368db1 # good: [aeba6e4f8ace1a3f016feb64c0a417c7ddcbcf6b] Merge tag 'qcom-arm64-for-7.3-2' of https://git.kernel.org/pub/scm/linux/kernel/git/qcom/linux into soc/dt git bisect good aeba6e4f8ace1a3f016feb64c0a417c7ddcbcf6b # good: [15213090630d0a4417dbcdef0de776cd2fac0fac] Merge branch 'for-next' of https://git.kernel.org/pub/scm/linux/kernel/git/khilman/linux-omap.git git bisect good 15213090630d0a4417dbcdef0de776cd2fac0fac # good: [e347a696fd95bc9b47e23e3d8ac7f6263ee502b2] Merge branch 'for-next' of https://git.kernel.org/pub/scm/linux/kernel/git/abelvesa/linux.git git bisect good e347a696fd95bc9b47e23e3d8ac7f6263ee502b2 # good: [b7307ccce8238c792fb3a6412ca5cac9ba8784bc] Merge branch 'next' of https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git git bisect good b7307ccce8238c792fb3a6412ca5cac9ba8784bc # good: [b5d4268affa543793ccaf838a10915c2c9f0db1c] Merge branch 'features' into for-next git bisect good b5d4268affa543793ccaf838a10915c2c9f0db1c # good: [ebdec8d2c156b8e662cb350ce05b0f92275f6ffd] RISC-V: Add Ssccfg/Smcdeleg ISA extension definition and parsing git bisect good ebdec8d2c156b8e662cb350ce05b0f92275f6ffd # good: [f61959a3a8b5522eb43cf71f293e091417bbf11c] riscv: Add Ziccamoa, Ziccif, Ziccrse, and Za64rs to cpufeature and hwprobe git bisect good f61959a3a8b5522eb43cf71f293e091417bbf11c # bad: [54fefa110db4a407d96625b66a76d874713ddae2] riscv: patch: skip fixmap mapping when kernel text is already writable git bisect bad 54fefa110db4a407d96625b66a76d874713ddae2 # good: [42cd1e1fc8995ec7ed5cc61957fc503eb065e0eb] riscv: alternative: Also patch the compat vDSO git bisect good 42cd1e1fc8995ec7ed5cc61957fc503eb065e0eb # good: [83ba459c9b5893590fd47177363b08b453a86168] riscv: mm: make EXECMEM_KPROBES writable without CONFIG_STRICT_MODULE_RWX git bisect good 83ba459c9b5893590fd47177363b08b453a86168 # first 'bad' commit: [54fefa110db4a407d96625b66a76d874713ddae2] riscv: patch: skip fixmap mapping when kernel text is already writable