tile: implement gettimeofday() via vDSO

This change creates the framework for vDSO calls, makes the existing
rt_sigreturn() mechanism use it, and adds a fast gettimeofday().
Now that we need to expose the vDSO address to userspace, we add
AT_SYSINFO_EHDR to the set of aux entries provided to userspace.
(You can disable any extra vDSO support by booting with vdso=0,
but the rt_sigreturn vDSO page will still be provided.)

Note that glibc has supported the tile vDSO since release 2.17.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

7 files changed, 71 insertions, 5 deletions

diff --git a/arch/tile/include/asm/elf.h b/arch/tile/include/asm/elf.h
index ff8a93408823..31d854f1b83b 100644
--- a/arch/tile/include/asm/elf.h
+++ b/arch/tile/include/asm/elf.h
@@ -132,6 +132,11 @@ extern int dump_task_regs(struct task_struct *, elf_gregset_t *);
 struct linux_binprm;
 extern int arch_setup_additional_pages(struct linux_binprm *bprm,
 				       int executable_stack);
+#define ARCH_DLINFO \
+do { \
+	NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_BASE); \
+} while (0)
+
 #ifdef CONFIG_COMPAT
 
 #define COMPAT_ELF_PLATFORM "tilegx-m32"
diff --git a/arch/tile/include/asm/mmu.h b/arch/tile/include/asm/mmu.h
index e2c789096795..0cab1182bde1 100644
--- a/arch/tile/include/asm/mmu.h
+++ b/arch/tile/include/asm/mmu.h
@@ -22,6 +22,7 @@ struct mm_context {
 	 * semaphore but atomically, but it is conservatively set.
 	 */
 	unsigned long priority_cached;
+	unsigned long vdso_base;
 };
 
 typedef struct mm_context mm_context_t;
diff --git a/arch/tile/include/asm/page.h b/arch/tile/include/asm/page.h
index dd033a4fd627..b4f96c0024df 100644
--- a/arch/tile/include/asm/page.h
+++ b/arch/tile/include/asm/page.h
@@ -39,6 +39,12 @@
 #define HPAGE_MASK	(~(HPAGE_SIZE - 1))
 
 /*
+ * We do define AT_SYSINFO_EHDR to support vDSO,
+ * but don't use the gate mechanism.
+ */
+#define __HAVE_ARCH_GATE_AREA		1
+
+/*
  * If the Kconfig doesn't specify, set a maximum zone order that
  * is enough so that we can create huge pages from small pages given
  * the respective sizes of the two page types.  See <linux/mmzone.h>.
@@ -246,7 +252,7 @@ static inline __attribute_const__ int get_order(unsigned long size)
 
 #endif /* __tilegx__ */
 
-#ifndef __ASSEMBLY__
+#if !defined(__ASSEMBLY__) && !defined(VDSO_BUILD)
 
 #ifdef CONFIG_HIGHMEM
 
diff --git a/arch/tile/include/asm/processor.h b/arch/tile/include/asm/processor.h
index fed1c044fec8..461322b473b5 100644
--- a/arch/tile/include/asm/processor.h
+++ b/arch/tile/include/asm/processor.h
@@ -180,10 +180,10 @@ struct thread_struct {
 #define TASK_SIZE		TASK_SIZE_MAX
 #endif
 
-/* We provide a minimal "vdso" a la x86; just the sigreturn code for now. */
-#define VDSO_BASE		(TASK_SIZE - PAGE_SIZE)
+#define VDSO_BASE	((unsigned long)current->active_mm->context.vdso_base)
+#define VDSO_SYM(x)	(VDSO_BASE + (unsigned long)(x))
 
-#define STACK_TOP		VDSO_BASE
+#define STACK_TOP		TASK_SIZE
 
 /* STACK_TOP_MAX is used temporarily in execve and should not check COMPAT. */
 #define STACK_TOP_MAX		TASK_SIZE_MAX
diff --git a/arch/tile/include/asm/sections.h b/arch/tile/include/asm/sections.h
index cc95276ef9c9..5d5d3b739a6b 100644
--- a/arch/tile/include/asm/sections.h
+++ b/arch/tile/include/asm/sections.h
@@ -25,6 +25,10 @@ extern char _sinitdata[], _einitdata[];
 /* Write-once data is writable only till the end of initialization. */
 extern char __w1data_begin[], __w1data_end[];
 
+extern char vdso_start[], vdso_end[];
+#ifdef CONFIG_COMPAT
+extern char vdso32_start[], vdso32_end[];
+#endif
 
 /* Not exactly sections, but PC comparison points in the code. */
 extern char __rt_sigreturn[], __rt_sigreturn_end[];
diff --git a/arch/tile/include/asm/vdso.h b/arch/tile/include/asm/vdso.h
new file mode 100644
index 000000000000..9f6a78d665fa
--- /dev/null
+++ b/arch/tile/include/asm/vdso.h
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2012 Tilera Corporation. All Rights Reserved.
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful, but
+ *   WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ *   NON INFRINGEMENT.  See the GNU General Public License for
+ *   more details.
+ */
+
+#ifndef __TILE_VDSO_H__
+#define __TILE_VDSO_H__
+
+#include <linux/types.h>
+
+/*
+ * Note about the vdso_data structure:
+ *
+ * NEVER USE THEM IN USERSPACE CODE DIRECTLY. The layout of the
+ * structure is supposed to be known only to the function in the vdso
+ * itself and may change without notice.
+ */
+
+struct vdso_data {
+	__u64 tz_update_count;  /* Timezone atomicity ctr             */
+	__u64 tb_update_count;  /* Timebase atomicity ctr             */
+	__u64 xtime_tod_stamp;  /* TOD clock for xtime                */
+	__u64 xtime_clock_sec;  /* Kernel time second                 */
+	__u64 xtime_clock_nsec; /* Kernel time nanosecond             */
+	__u64 wtom_clock_sec;   /* Wall to monotonic clock second     */
+	__u64 wtom_clock_nsec;  /* Wall to monotonic clock nanosecond */
+	__u32 mult;             /* Cycle to nanosecond multiplier     */
+	__u32 shift;            /* Cycle to nanosecond divisor (power of two) */
+	__u32 tz_minuteswest;   /* Minutes west of Greenwich          */
+	__u32 tz_dsttime;       /* Type of dst correction             */
+};
+
+extern struct vdso_data *vdso_data;
+
+/* __vdso_rt_sigreturn is defined with the addresses in the vdso page. */
+extern void __vdso_rt_sigreturn(void);
+
+extern int setup_vdso_pages(void);
+
+#endif /* __TILE_VDSO_H__ */
diff --git a/arch/tile/include/uapi/asm/auxvec.h b/arch/tile/include/uapi/asm/auxvec.h
index 1d393edb0641..c93e92709f14 100644
--- a/arch/tile/include/uapi/asm/auxvec.h
+++ b/arch/tile/include/uapi/asm/auxvec.h
@@ -15,6 +15,7 @@
 #ifndef _ASM_TILE_AUXVEC_H
 #define _ASM_TILE_AUXVEC_H
 
-/* No extensions to auxvec */
+/* The vDSO location. */
+#define AT_SYSINFO_EHDR         33
 
 #endif /* _ASM_TILE_AUXVEC_H */