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Sat, 21 Dec 2019 09:32:29 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id aeRrlaLRdQ6v; Sat, 21 Dec 2019 09:32:28 +0100 (CET) Received: from localhost.localdomain (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id BFC7A8B752; Sat, 21 Dec 2019 09:32:28 +0100 (CET) Received: by localhost.localdomain (Postfix, from userid 0) id 88DD0637B6; Sat, 21 Dec 2019 08:32:28 +0000 (UTC) Message-Id: <60e9ae86b7d2cdcf21468787076d345663648f46.1576916812.git.christophe.leroy@c-s.fr> In-Reply-To: References: From: Christophe Leroy Subject: [PATCH v5 07/17] powerpc: align stack to 2 * THREAD_SIZE with VMAP_STACK To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , dja@axtens.net Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org Date: Sat, 21 Dec 2019 08:32:28 +0000 (UTC) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: In order to ease stack overflow detection, align stack to 2 * THREAD_SIZE when using VMAP_STACK. This allows overflow detection using a single bit check. Signed-off-by: Christophe Leroy --- arch/powerpc/include/asm/thread_info.h | 13 +++++++++++++ arch/powerpc/kernel/setup_32.c | 2 +- arch/powerpc/kernel/setup_64.c | 2 +- arch/powerpc/kernel/vmlinux.lds.S | 2 +- 4 files changed, 16 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h index 488d5c4670ff..a2270749b282 100644 --- a/arch/powerpc/include/asm/thread_info.h +++ b/arch/powerpc/include/asm/thread_info.h @@ -22,6 +22,19 @@ #define THREAD_SIZE (1 << THREAD_SHIFT) +/* + * By aligning VMAP'd stacks to 2 * THREAD_SIZE, we can detect overflow by + * checking sp & (1 << THREAD_SHIFT), which we can do cheaply in the entry + * assembly. + */ +#ifdef CONFIG_VMAP_STACK +#define THREAD_ALIGN_SHIFT (THREAD_SHIFT + 1) +#else +#define THREAD_ALIGN_SHIFT THREAD_SHIFT +#endif + +#define THREAD_ALIGN (1 << THREAD_ALIGN_SHIFT) + #ifndef __ASSEMBLY__ #include #include diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c index dcffe927f5b9..f014c4f7a337 100644 --- a/arch/powerpc/kernel/setup_32.c +++ b/arch/powerpc/kernel/setup_32.c @@ -140,7 +140,7 @@ arch_initcall(ppc_init); static void *__init alloc_stack(void) { - void *ptr = memblock_alloc(THREAD_SIZE, THREAD_SIZE); + void *ptr = memblock_alloc(THREAD_SIZE, THREAD_ALIGN); if (!ptr) panic("cannot allocate %d bytes for stack at %pS\n", diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index 6104917a282d..e05e6dd67ae6 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -633,7 +633,7 @@ static void *__init alloc_stack(unsigned long limit, int cpu) BUILD_BUG_ON(STACK_INT_FRAME_SIZE % 16); - ptr = memblock_alloc_try_nid(THREAD_SIZE, THREAD_SIZE, + ptr = memblock_alloc_try_nid(THREAD_SIZE, THREAD_ALIGN, MEMBLOCK_LOW_LIMIT, limit, early_cpu_to_node(cpu)); if (!ptr) diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S index 8834220036a5..b4c89a1acebb 100644 --- a/arch/powerpc/kernel/vmlinux.lds.S +++ b/arch/powerpc/kernel/vmlinux.lds.S @@ -323,7 +323,7 @@ SECTIONS #endif /* The initial task and kernel stack */ - INIT_TASK_DATA_SECTION(THREAD_SIZE) + INIT_TASK_DATA_SECTION(THREAD_ALIGN) .data..page_aligned : AT(ADDR(.data..page_aligned) - LOAD_OFFSET) { PAGE_ALIGNED_DATA(PAGE_SIZE)