On Mon, Mar 16, 2020 at 09:42:32AM +0000, Vincenzo Frascino wrote:

you should not really work on Sunday ;-)

I was getting bored ;).

On 3/15/20 6:30 PM, Catalin Marinas wrote:

quoted

On Fri, Mar 13, 2020 at 03:43:37PM +0000, Vincenzo Frascino wrote:

quoted

--- /dev/null
+++ b/arch/arm64/include/asm/vdso/processor.h

@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 ARM Ltd.
+ */
+#ifndef __ASM_VDSO_PROCESSOR_H
+#define __ASM_VDSO_PROCESSOR_H
+
+#ifndef __ASSEMBLY__
+
+#include <asm/page-def.h>
+
+#ifdef CONFIG_COMPAT
+#if defined(CONFIG_ARM64_64K_PAGES) && defined(CONFIG_KUSER_HELPERS)
+/*
+ * With CONFIG_ARM64_64K_PAGES enabled, the last page is occupied
+ * by the compat vectors page.
+ */
+#define TASK_SIZE_32		UL(0x100000000)
+#else
+#define TASK_SIZE_32		(UL(0x100000000) - PAGE_SIZE)
+#endif /* CONFIG_ARM64_64K_PAGES */
+#endif /* CONFIG_COMPAT */

Just curious, what's TASK_SIZE_32 used for in the vDSO code? You don't
seem to move TASK_SIZE.

I tried to fine grain the headers as much as I could in order to avoid
unneeded/unwanted inclusions:
 * TASK_SIZE_32 is used to verify ABI consistency on vdso32 (please refer to
   arch/arm64/kernel/vdso32/vgettimeofday.c).

I see. But the test is probably useless. With 4K pages, TASK_SIZE_32 is
1UL << 32, so you can't have a u32 greater than this. So I'd argue that
the ABI compatibility here doesn't matter.

With 16K or 64K pages, TASK_SIZE_32 is slightly smaller but arm32 never
supported it.

What's the side-effect of dropping this check altogether?

-- 
Catalin

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