From nobody Sat Feb 7 23:48:02 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 EEDBC325716 for ; Wed, 24 Dec 2025 11:21:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766575289; cv=none; b=cpZERew/Q4q32mM4G7hc/dn9CFxUElwtAVPbnlwQc3MQ4XP56lkfTkNWsytd5x2sIdbY/J+Vz7CK06znbOlDh0QD8p52taTSs1UyRJYUDNa11cmPMidm9Rh9UtSTueL+9Np6qmO2AeyJJ1CytpRUTHIDn2k9tvzCfdqJqM9Z+ac= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766575289; c=relaxed/simple; bh=wKTECL+uhV2GewMTUnLeAs+N2tpCOWuQ3qmRO31AzZU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hzAKqwP76mlDODflh3YABvCyimLwjvutik2eTbpiMWPExtWegTcf9vZv7vN2lKXydmltajhNU3raJDHvCmDtuLdfkHXYs6DXLqzeTd5TgOjB5BRHahh0j7VWBmWI7h2dSvx/JIpvC7mUM3WP5is/u04mMCwDPucDMrMgcjuvis4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iWPeDBA8; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="iWPeDBA8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 04B32C16AAE; Wed, 24 Dec 2025 11:21:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766575288; bh=wKTECL+uhV2GewMTUnLeAs+N2tpCOWuQ3qmRO31AzZU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=iWPeDBA8oLNW9eDp4PsxIG5ToDSE+K5B19Dz2tJYX9VEH8JjPH+TI2pohxIIc5kbm AqF9Vu/NaSMUZXvsMUUqzNM8HRHvocup8CUVTaYJ0cgtY8cz/s6/B0+67wDcRFE5HM 6wpguaQzAWUd1CMY6S43aBsW7lsFFtEc5KwFpuTvMEug/OnNVHQS7YGXhC+dI65pr5 jC6Mhrx7zRi93oWBKyLxFQ492l1i0RrmuAOurXYUgXn5+5pig4gUHQBRnaIykNjOtA u64SNV+s0cPd1Hx+hCMIm/4s5NgYBhbcs3u+qKhXWq5HwrWPMRvGxrDwrYvUWHUmkw dPN81g3JcMNOg== From: "Christophe Leroy (CS GROUP)" To: Michael Ellerman , Nicholas Piggin , Madhavan Srinivasan Cc: Christophe Leroy , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: [PATCH v5 6/7] powerpc/32: Automatically adapt TASK_SIZE based on constraints Date: Wed, 24 Dec 2025 12:20:54 +0100 Message-ID: <6a2575420770d075cd090b5a316730a2ffafdee4.1766574657.git.chleroy@kernel.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=6156; i=chleroy@kernel.org; h=from:subject:message-id; bh=9s+oMFBAX9h3xrMQNyahO4dDCw3Exg61uapF1kwcX3o=; b=owGbwMvMwCV2d0KB2p7V54MZT6slMWR6n5mj+b055mGMtUj/A/4S78f7Be3XHpMsCbjFHD3lK MuflRNXdJSyMIhxMciKKbIc/8+9a0bXl9T8qbv0YeawMoEMYeDiFICJKExl+GedeoltpqxiZg8D x/fJDt+tUnaxb+udzcm0dpP8f54b2y4yMrTrdOkvfvfGN8YkapY7j/px1hqHVy6sP555tx/ninp bww4A X-Developer-Key: i=chleroy@kernel.org; a=openpgp; fpr=10FFE6F8B390DE17ACC2632368A92FEB01B8DD78 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Christophe Leroy At the time being, TASK_SIZE can be customized by the user via Kconfig but it is not possible to check all constraints in Kconfig. Impossible setups are detected at compile time with BUILD_BUG() but that leads to build failure when setting crazy values. It is not a problem on its own because the user will usually either use the default value or set a well thought value. However build robots generate crazy random configs that lead to build failures, and build robots see it as a regression every time a patch adds such a constraint. So instead of failing the build when the custom TASK_SIZE is too big, just adjust it to the maximum possible value matching the setup. Several architectures already calculate TASK_SIZE based on other parameters and options. In order to do so, move MODULES_VADDR calculation into task_size_32.h and ensure that: - On book3s/32, userspace and module area have their own segments (256M) - On 8xx, userspace has its own full PGDIR entries (4M) Then TASK_SIZE is guaranteed to be correct so remove related BUILD_BUG()s. Signed-off-by: Christophe Leroy --- arch/powerpc/Kconfig | 3 +-- arch/powerpc/include/asm/book3s/32/pgtable.h | 4 --- arch/powerpc/include/asm/nohash/32/mmu-8xx.h | 4 --- arch/powerpc/include/asm/task_size_32.h | 26 ++++++++++++++++++++ arch/powerpc/mm/book3s32/mmu.c | 2 -- arch/powerpc/mm/mem.c | 2 -- arch/powerpc/mm/nohash/8xx.c | 2 -- 7 files changed, 27 insertions(+), 16 deletions(-) diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 9537a61ebae0..b8d36a261009 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -1293,9 +1293,8 @@ config TASK_SIZE_BOOL Say N here unless you know what you are doing. =20 config TASK_SIZE - hex "Size of user task space" if TASK_SIZE_BOOL + hex "Size of maximum user task space" if TASK_SIZE_BOOL default "0x80000000" if PPC_8xx - default "0xb0000000" if PPC_BOOK3S_32 && EXECMEM default "0xc0000000" =20 config MODULES_SIZE_BOOL diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/in= clude/asm/book3s/32/pgtable.h index 87dcca962be7..41ae404d0b7a 100644 --- a/arch/powerpc/include/asm/book3s/32/pgtable.h +++ b/arch/powerpc/include/asm/book3s/32/pgtable.h @@ -195,10 +195,6 @@ void unmap_kernel_page(unsigned long va); #define VMALLOC_END ioremap_bot #endif =20 -#define MODULES_END ALIGN_DOWN(PAGE_OFFSET, SZ_256M) -#define MODULES_SIZE (CONFIG_MODULES_SIZE * SZ_1M) -#define MODULES_VADDR (MODULES_END - MODULES_SIZE) - #ifndef __ASSEMBLER__ #include #include diff --git a/arch/powerpc/include/asm/nohash/32/mmu-8xx.h b/arch/powerpc/in= clude/asm/nohash/32/mmu-8xx.h index f19115db8072..74ad32e1588c 100644 --- a/arch/powerpc/include/asm/nohash/32/mmu-8xx.h +++ b/arch/powerpc/include/asm/nohash/32/mmu-8xx.h @@ -170,10 +170,6 @@ =20 #define mmu_linear_psize MMU_PAGE_8M =20 -#define MODULES_END PAGE_OFFSET -#define MODULES_SIZE (CONFIG_MODULES_SIZE * SZ_1M) -#define MODULES_VADDR (MODULES_END - MODULES_SIZE) - #ifndef __ASSEMBLER__ =20 #include diff --git a/arch/powerpc/include/asm/task_size_32.h b/arch/powerpc/include= /asm/task_size_32.h index 30edc21f71fb..42a64bbd1964 100644 --- a/arch/powerpc/include/asm/task_size_32.h +++ b/arch/powerpc/include/asm/task_size_32.h @@ -2,11 +2,37 @@ #ifndef _ASM_POWERPC_TASK_SIZE_32_H #define _ASM_POWERPC_TASK_SIZE_32_H =20 +#include + #if CONFIG_TASK_SIZE > CONFIG_KERNEL_START #error User TASK_SIZE overlaps with KERNEL_START address #endif =20 +#ifdef CONFIG_PPC_8xx +#define MODULES_END ASM_CONST(CONFIG_PAGE_OFFSET) +#define MODULES_SIZE (CONFIG_MODULES_SIZE * SZ_1M) +#define MODULES_VADDR (MODULES_END - MODULES_SIZE) +#define MODULES_BASE (MODULES_VADDR & ~(UL(SZ_4M) - 1)) +#define USER_TOP MODULES_BASE +#endif + +#ifdef CONFIG_PPC_BOOK3S_32 +#define MODULES_END (ASM_CONST(CONFIG_PAGE_OFFSET) & ~(UL(SZ_256M) - 1)) +#define MODULES_SIZE (CONFIG_MODULES_SIZE * SZ_1M) +#define MODULES_VADDR (MODULES_END - MODULES_SIZE) +#define MODULES_BASE (MODULES_VADDR & ~(UL(SZ_256M) - 1)) +#define USER_TOP MODULES_BASE +#endif + +#ifndef USER_TOP +#define USER_TOP ASM_CONST(CONFIG_PAGE_OFFSET) +#endif + +#if CONFIG_TASK_SIZE < USER_TOP #define TASK_SIZE ASM_CONST(CONFIG_TASK_SIZE) +#else +#define TASK_SIZE USER_TOP +#endif =20 /* * This decides where the kernel will search for a free chunk of vm space = during diff --git a/arch/powerpc/mm/book3s32/mmu.c b/arch/powerpc/mm/book3s32/mmu.c index 37eefc6786a7..07660e8badbd 100644 --- a/arch/powerpc/mm/book3s32/mmu.c +++ b/arch/powerpc/mm/book3s32/mmu.c @@ -223,8 +223,6 @@ int mmu_mark_initmem_nx(void) =20 update_bats(); =20 - BUILD_BUG_ON(ALIGN_DOWN(MODULES_VADDR, SZ_256M) < TASK_SIZE); - for (i =3D ALIGN(TASK_SIZE, SZ_256M) >> 28; i < 16; i++) { /* Do not set NX on VM space for modules */ if (is_module_segment(i << 28)) diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c index 3ddbfdbfa941..bc0f1a9eb0bc 100644 --- a/arch/powerpc/mm/mem.c +++ b/arch/powerpc/mm/mem.c @@ -401,8 +401,6 @@ struct execmem_info __init *execmem_arch_setup(void) #ifdef MODULES_VADDR unsigned long limit =3D (unsigned long)_etext - SZ_32M; =20 - BUILD_BUG_ON(TASK_SIZE > MODULES_VADDR); - /* First try within 32M limit from _etext to avoid branch trampolines */ if (MODULES_VADDR < PAGE_OFFSET && MODULES_END > limit) { start =3D limit; diff --git a/arch/powerpc/mm/nohash/8xx.c b/arch/powerpc/mm/nohash/8xx.c index ab1505cf42bf..a9d3f4729ead 100644 --- a/arch/powerpc/mm/nohash/8xx.c +++ b/arch/powerpc/mm/nohash/8xx.c @@ -209,8 +209,6 @@ void __init setup_initial_memory_limit(phys_addr_t firs= t_memblock_base, =20 /* 8xx can only access 32MB at the moment */ memblock_set_current_limit(min_t(u64, first_memblock_size, SZ_32M)); - - BUILD_BUG_ON(ALIGN_DOWN(MODULES_VADDR, PGDIR_SIZE) < TASK_SIZE); } =20 int pud_clear_huge(pud_t *pud) --=20 2.49.0