nds32: VDSO support

This patch adds VDSO support. The VDSO code is currently used for
sys_rt_sigreturn() and optimised gettimeofday() (using the SoC timer counter).

Signed-off-by: Vincent Chen <vincentc@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

8 files changed, 512 insertions, 0 deletions

diff --git a/arch/nds32/kernel/vdso/Makefile b/arch/nds32/kernel/vdso/Makefile
new file mode 100644
index 000000000000..e6c50a701313
--- /dev/null
+++ b/arch/nds32/kernel/vdso/Makefile
@@ -0,0 +1,82 @@
+#
+# Building a vDSO image for AArch64.
+#
+# Author: Will Deacon <will.deacon@arm.com>
+# Heavily based on the vDSO Makefiles for other archs.
+#
+
+obj-vdso := note.o datapage.o sigreturn.o gettimeofday.o
+
+# Build rules
+targets := $(obj-vdso) vdso.so vdso.so.dbg
+obj-vdso := $(addprefix $(obj)/, $(obj-vdso))
+
+ccflags-y := -shared -fno-common -fno-builtin
+ccflags-y += -nostdlib -Wl,-soname=linux-vdso.so.1 \
+		$(call cc-ldoption, -Wl$(comma)--hash-style=sysv)
+ccflags-y += -fPIC -Wl,-shared -g
+
+# Disable gcov profiling for VDSO code
+GCOV_PROFILE := n
+
+
+obj-y += vdso.o
+extra-y += vdso.lds
+CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
+
+# Force dependency
+$(obj)/vdso.o : $(obj)/vdso.so
+
+# Link rule for the .so file, .lds has to be first
+$(obj)/vdso.so.dbg: $(src)/vdso.lds $(obj-vdso)
+	$(call if_changed,vdsold)
+
+
+# Strip rule for the .so file
+$(obj)/%.so: OBJCOPYFLAGS := -S
+$(obj)/%.so: $(obj)/%.so.dbg FORCE
+	$(call if_changed,objcopy)
+
+# Generate VDSO offsets using helper script
+gen-vdsosym := $(srctree)/$(src)/gen_vdso_offsets.sh
+quiet_cmd_vdsosym = VDSOSYM $@
+define cmd_vdsosym
+	$(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@
+endef
+
+include/generated/vdso-offsets.h: $(obj)/vdso.so.dbg FORCE
+	$(call if_changed,vdsosym)
+
+
+
+# Assembly rules for the .S files
+
+sigreturn.o : sigreturn.S
+	$(call if_changed_dep,vdsoas)
+
+note.o : note.S
+	$(call if_changed_dep,vdsoas)
+
+datapage.o : datapage.S
+	$(call if_changed_dep,vdsoas)
+
+gettimeofday.o : gettimeofday.c FORCE
+	$(call if_changed_dep,vdsocc)
+
+# Actual build commands
+quiet_cmd_vdsold = VDSOL   $@
+      cmd_vdsold = $(CC) $(c_flags) -Wl,-n -Wl,-T $^ -o $@
+quiet_cmd_vdsoas = VDSOA   $@
+      cmd_vdsoas = $(CC) $(a_flags) -c -o $@ $<
+quiet_cmd_vdsocc = VDSOA   $@
+      cmd_vdsocc = $(CC) $(c_flags) -c -o $@ $<
+
+# Install commands for the unstripped file
+quiet_cmd_vdso_install = INSTALL $@
+      cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@
+
+vdso.so: $(obj)/vdso.so.dbg
+	@mkdir -p $(MODLIB)/vdso
+	$(call cmd,vdso_install)
+
+vdso_install: vdso.so
diff --git a/arch/nds32/kernel/vdso/datapage.S b/arch/nds32/kernel/vdso/datapage.S
new file mode 100644
index 000000000000..4a62c3cab1c8
--- /dev/null
+++ b/arch/nds32/kernel/vdso/datapage.S
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+#include <linux/linkage.h>
+#include <asm/page.h>
+
+ENTRY(__get_timerpage)
+	sethi	$r0, hi20(. + PAGE_SIZE + 8)
+	ori	$r0, $r0, lo12(. + PAGE_SIZE + 4)
+	mfusr	$r1, $pc
+	sub	$r0, $r1, $r0
+	ret
+ENDPROC(__get_timerpage)
+
+ENTRY(__get_datapage)
+	sethi	$r0, hi20(. + 2*PAGE_SIZE + 8)
+	ori	$r0, $r0, lo12(. + 2*PAGE_SIZE + 4)
+	mfusr	$r1, $pc
+	sub	$r0, $r1, $r0
+	ret
+ENDPROC(__get_datapage)
diff --git a/arch/nds32/kernel/vdso/gen_vdso_offsets.sh b/arch/nds32/kernel/vdso/gen_vdso_offsets.sh
new file mode 100755
index 000000000000..01924ff071ad
--- /dev/null
+++ b/arch/nds32/kernel/vdso/gen_vdso_offsets.sh
@@ -0,0 +1,15 @@
+#!/bin/sh
+
+#
+# Match symbols in the DSO that look like VDSO_*; produce a header file
+# of constant offsets into the shared object.
+#
+# Doing this inside the Makefile will break the $(filter-out) function,
+# causing Kbuild to rebuild the vdso-offsets header file every time.
+#
+# Author: Will Deacon <will.deacon@arm.com
+#
+
+LC_ALL=C
+sed -n -e 's/^00*/0/' -e \
+'s/^\([0-9a-fA-F]*\) . VDSO_\([a-zA-Z0-9_]*\)$/\#define vdso_offset_\2\t0x\1/p'
diff --git a/arch/nds32/kernel/vdso/gettimeofday.c b/arch/nds32/kernel/vdso/gettimeofday.c
new file mode 100644
index 000000000000..038721af40e3
--- /dev/null
+++ b/arch/nds32/kernel/vdso/gettimeofday.c
@@ -0,0 +1,270 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+#include <linux/compiler.h>
+#include <linux/hrtimer.h>
+#include <linux/time.h>
+#include <asm/io.h>
+#include <asm/barrier.h>
+#include <asm/bug.h>
+#include <asm/page.h>
+#include <asm/unistd.h>
+#include <asm/vdso_datapage.h>
+#include <asm/vdso_timer_info.h>
+#include <asm/asm-offsets.h>
+
+#define X(x) #x
+#define Y(x) X(x)
+
+extern struct vdso_data *__get_datapage(void);
+extern struct vdso_data *__get_timerpage(void);
+
+static notrace unsigned int __vdso_read_begin(const struct vdso_data *vdata)
+{
+	u32 seq;
+repeat:
+	seq = READ_ONCE(vdata->seq_count);
+	if (seq & 1) {
+		cpu_relax();
+		goto repeat;
+	}
+	return seq;
+}
+
+static notrace unsigned int vdso_read_begin(const struct vdso_data *vdata)
+{
+	unsigned int seq;
+
+	seq = __vdso_read_begin(vdata);
+
+	smp_rmb();		/* Pairs with smp_wmb in vdso_write_end */
+	return seq;
+}
+
+static notrace int vdso_read_retry(const struct vdso_data *vdata, u32 start)
+{
+	smp_rmb();		/* Pairs with smp_wmb in vdso_write_begin */
+	return vdata->seq_count != start;
+}
+
+static notrace long clock_gettime_fallback(clockid_t _clkid,
+					   struct timespec *_ts)
+{
+	register struct timespec *ts asm("$r1") = _ts;
+	register clockid_t clkid asm("$r0") = _clkid;
+	register long ret asm("$r0");
+
+	asm volatile ("movi	$r15, %3\n"
+		      "syscall 	0x0\n"
+		      :"=r" (ret)
+		      :"r"(clkid), "r"(ts), "i"(__NR_clock_gettime)
+		      :"$r15", "memory");
+
+	return ret;
+}
+
+static notrace int do_realtime_coarse(struct timespec *ts,
+				      struct vdso_data *vdata)
+{
+	u32 seq;
+
+	do {
+		seq = vdso_read_begin(vdata);
+
+		ts->tv_sec = vdata->xtime_coarse_sec;
+		ts->tv_nsec = vdata->xtime_coarse_nsec;
+
+	} while (vdso_read_retry(vdata, seq));
+	return 0;
+}
+
+static notrace int do_monotonic_coarse(struct timespec *ts,
+				       struct vdso_data *vdata)
+{
+	struct timespec tomono;
+	u32 seq;
+
+	do {
+		seq = vdso_read_begin(vdata);
+
+		ts->tv_sec = vdata->xtime_coarse_sec;
+		ts->tv_nsec = vdata->xtime_coarse_nsec;
+
+		tomono.tv_sec = vdata->wtm_clock_sec;
+		tomono.tv_nsec = vdata->wtm_clock_nsec;
+
+	} while (vdso_read_retry(vdata, seq));
+
+	ts->tv_sec += tomono.tv_sec;
+	timespec_add_ns(ts, tomono.tv_nsec);
+	return 0;
+}
+
+static notrace inline u64 vgetsns(struct vdso_data *vdso)
+{
+	u32 cycle_now;
+	u32 cycle_delta;
+	u32 *timer_cycle_base;
+
+	timer_cycle_base =
+	    (u32 *) ((char *)__get_timerpage() + vdso->cycle_count_offset);
+	cycle_now = readl_relaxed(timer_cycle_base);
+	if (true == vdso->cycle_count_down)
+		cycle_now = ~(*timer_cycle_base);
+	cycle_delta = cycle_now - (u32) vdso->cs_cycle_last;
+	return ((u64) cycle_delta & vdso->cs_mask) * vdso->cs_mult;
+}
+
+static notrace int do_realtime(struct timespec *ts, struct vdso_data *vdata)
+{
+	unsigned count;
+	u64 ns;
+	do {
+		count = vdso_read_begin(vdata);
+		ts->tv_sec = vdata->xtime_clock_sec;
+		ns = vdata->xtime_clock_nsec;
+		ns += vgetsns(vdata);
+		ns >>= vdata->cs_shift;
+	} while (vdso_read_retry(vdata, count));
+
+	ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
+	ts->tv_nsec = ns;
+
+	return 0;
+}
+
+static notrace int do_monotonic(struct timespec *ts, struct vdso_data *vdata)
+{
+	struct timespec tomono;
+	u64 nsecs;
+	u32 seq;
+
+	do {
+		seq = vdso_read_begin(vdata);
+
+		ts->tv_sec = vdata->xtime_clock_sec;
+		nsecs = vdata->xtime_clock_nsec;
+		nsecs += vgetsns(vdata);
+		nsecs >>= vdata->cs_shift;
+
+		tomono.tv_sec = vdata->wtm_clock_sec;
+		tomono.tv_nsec = vdata->wtm_clock_nsec;
+
+	} while (vdso_read_retry(vdata, seq));
+
+	ts->tv_sec += tomono.tv_sec;
+	ts->tv_nsec = 0;
+	timespec_add_ns(ts, nsecs + tomono.tv_nsec);
+	return 0;
+}
+
+notrace int __vdso_clock_gettime(clockid_t clkid, struct timespec *ts)
+{
+	struct vdso_data *vdata;
+	int ret = -1;
+
+	vdata = __get_datapage();
+	if (vdata->cycle_count_offset == EMPTY_REG_OFFSET)
+		return clock_gettime_fallback(clkid, ts);
+
+	switch (clkid) {
+	case CLOCK_REALTIME_COARSE:
+		ret = do_realtime_coarse(ts, vdata);
+		break;
+	case CLOCK_MONOTONIC_COARSE:
+		ret = do_monotonic_coarse(ts, vdata);
+		break;
+	case CLOCK_REALTIME:
+		ret = do_realtime(ts, vdata);
+		break;
+	case CLOCK_MONOTONIC:
+		ret = do_monotonic(ts, vdata);
+		break;
+	default:
+		break;
+	}
+
+	if (ret)
+		ret = clock_gettime_fallback(clkid, ts);
+
+	return ret;
+}
+
+static notrace int clock_getres_fallback(clockid_t _clk_id,
+					  struct timespec *_res)
+{
+	register clockid_t clk_id asm("$r0") = _clk_id;
+	register struct timespec *res asm("$r1") = _res;
+	register int ret asm("$r0");
+
+	asm volatile ("movi	$r15, %3\n"
+		      "syscall	0x0\n"
+		      :"=r" (ret)
+		      :"r"(clk_id), "r"(res), "i"(__NR_clock_getres)
+		      :"$r15", "memory");
+
+	return ret;
+}
+
+notrace int __vdso_clock_getres(clockid_t clk_id, struct timespec *res)
+{
+	if (res == NULL)
+		return 0;
+	switch (clk_id) {
+	case CLOCK_REALTIME:
+	case CLOCK_MONOTONIC:
+	case CLOCK_MONOTONIC_RAW:
+		res->tv_sec = 0;
+		res->tv_nsec = CLOCK_REALTIME_RES;
+		break;
+	case CLOCK_REALTIME_COARSE:
+	case CLOCK_MONOTONIC_COARSE:
+		res->tv_sec = 0;
+		res->tv_nsec = CLOCK_COARSE_RES;
+		break;
+	default:
+		return clock_getres_fallback(clk_id, res);
+	}
+	return 0;
+}
+
+static notrace inline int gettimeofday_fallback(struct timeval *_tv,
+						struct timezone *_tz)
+{
+	register struct timeval *tv asm("$r0") = _tv;
+	register struct timezone *tz asm("$r1") = _tz;
+	register int ret asm("$r0");
+
+	asm volatile ("movi	$r15, %3\n"
+		      "syscall	0x0\n"
+		      :"=r" (ret)
+		      :"r"(tv), "r"(tz), "i"(__NR_gettimeofday)
+		      :"$r15", "memory");
+
+	return ret;
+}
+
+notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
+{
+	struct timespec ts;
+	struct vdso_data *vdata;
+	int ret;
+
+	vdata = __get_datapage();
+
+	if (vdata->cycle_count_offset == EMPTY_REG_OFFSET)
+		return gettimeofday_fallback(tv, tz);
+
+	ret = do_realtime(&ts, vdata);
+
+	if (tv) {
+		tv->tv_sec = ts.tv_sec;
+		tv->tv_usec = ts.tv_nsec / 1000;
+	}
+	if (tz) {
+		tz->tz_minuteswest = vdata->tz_minuteswest;
+		tz->tz_dsttime = vdata->tz_dsttime;
+	}
+
+	return ret;
+}
diff --git a/arch/nds32/kernel/vdso/note.S b/arch/nds32/kernel/vdso/note.S
new file mode 100644
index 000000000000..0aeaa19b05f0
--- /dev/null
+++ b/arch/nds32/kernel/vdso/note.S
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2012 ARM Limited
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+#include <linux/uts.h>
+#include <linux/version.h>
+#include <linux/elfnote.h>
+
+ELFNOTE_START(Linux, 0, "a")
+	.long LINUX_VERSION_CODE
+ELFNOTE_END
diff --git a/arch/nds32/kernel/vdso/sigreturn.S b/arch/nds32/kernel/vdso/sigreturn.S
new file mode 100644
index 000000000000..67e4d1d1612a
--- /dev/null
+++ b/arch/nds32/kernel/vdso/sigreturn.S
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2012 ARM Limited
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+#include <linux/linkage.h>
+#include <asm/unistd.h>
+
+	.text
+
+ENTRY(__kernel_rt_sigreturn)
+	.cfi_startproc
+	movi $r15, __NR_rt_sigreturn
+	/*
+	 * The SWID of syscall should be __NR_rt_sigreturn to synchronize
+	 * the unwinding scheme in gcc
+	 */
+	syscall	__NR_rt_sigreturn
+	.cfi_endproc
+ENDPROC(__kernel_rt_sigreturn)
diff --git a/arch/nds32/kernel/vdso/vdso.S b/arch/nds32/kernel/vdso/vdso.S
new file mode 100644
index 000000000000..16737c11e55b
--- /dev/null
+++ b/arch/nds32/kernel/vdso/vdso.S
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2012 ARM Limited
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+#include <linux/init.h>
+#include <linux/linkage.h>
+#include <linux/const.h>
+#include <asm/page.h>
+
+	.globl vdso_start, vdso_end
+	.section .rodata
+	.balign PAGE_SIZE
+vdso_start:
+	.incbin "arch/nds32/kernel/vdso/vdso.so"
+	.balign PAGE_SIZE
+vdso_end:
+
+	.previous
diff --git a/arch/nds32/kernel/vdso/vdso.lds.S b/arch/nds32/kernel/vdso/vdso.lds.S
new file mode 100644
index 000000000000..36630352ee02
--- /dev/null
+++ b/arch/nds32/kernel/vdso/vdso.lds.S
@@ -0,0 +1,76 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0
+ * Copyright (C) 2005-2017 Andes Technology Corporation
+ */
+
+
+#include <linux/const.h>
+#include <asm/page.h>
+#include <asm/vdso.h>
+
+OUTPUT_FORMAT("elf32-nds32le-linux", "elf32-nds32be-linux", "elf32-nds32le-linux")
+OUTPUT_ARCH(nds32)
+
+SECTIONS
+{
+	. = SIZEOF_HEADERS;
+
+	.hash		: { *(.hash) }			:text
+	.gnu.hash	: { *(.gnu.hash) }
+	.dynsym		: { *(.dynsym) }
+	.dynstr		: { *(.dynstr) }
+	.gnu.version	: { *(.gnu.version) }
+	.gnu.version_d	: { *(.gnu.version_d) }
+	.gnu.version_r	: { *(.gnu.version_r) }
+
+	.note		: { *(.note.*) }		:text	:note
+
+
+	.text		: { *(.text*) }			:text
+
+	.eh_frame_hdr	: { *(.eh_frame_hdr) }		:text	:eh_frame_hdr
+	.eh_frame	: { KEEP (*(.eh_frame)) }	:text
+
+	.dynamic	: { *(.dynamic) }		:text	:dynamic
+
+	.rodata		: { *(.rodata*) }		:text
+
+
+	/DISCARD/	: {
+		*(.note.GNU-stack)
+		*(.data .data.* .gnu.linkonce.d.* .sdata*)
+		*(.bss .sbss .dynbss .dynsbss)
+	}
+}
+
+/*
+ * We must supply the ELF program headers explicitly to get just one
+ * PT_LOAD segment, and set the flags explicitly to make segments read-only.
+ */
+PHDRS
+{
+	text		PT_LOAD		FLAGS(5) FILEHDR PHDRS; /* PF_R|PF_X */
+	dynamic		PT_DYNAMIC	FLAGS(4);		/* PF_R */
+	note		PT_NOTE		FLAGS(4);		/* PF_R */
+	eh_frame_hdr	PT_GNU_EH_FRAME;
+}
+
+/*
+ * This controls what symbols we export from the DSO.
+ */
+VERSION
+{
+	LINUX_4 {
+	global:
+		__kernel_rt_sigreturn;
+		__vdso_gettimeofday;
+		__vdso_clock_getres;
+		__vdso_clock_gettime;
+	local: *;
+	};
+}
+
+/*
+ * Make the rt_sigreturn code visible to the kernel.
+ */
+VDSO_rt_sigtramp	= __kernel_rt_sigreturn;