LoongArch: Add VDSO and VSYSCALL support

Add VDSO and VSYSCALL support (sigreturn, gettimeofday and its friends)
for LoongArch.

Reviewed-by: WANG Xuerui <git@xen0n.name>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

7 files changed, 267 insertions, 0 deletions

diff --git a/arch/loongarch/vdso/Makefile b/arch/loongarch/vdso/Makefile
new file mode 100644
index 000000000000..6b6e16732c60
--- /dev/null
+++ b/arch/loongarch/vdso/Makefile
@@ -0,0 +1,96 @@
+# SPDX-License-Identifier: GPL-2.0
+# Objects to go into the VDSO.
+
+# Absolute relocation type $(ARCH_REL_TYPE_ABS) needs to be defined before
+# the inclusion of generic Makefile.
+ARCH_REL_TYPE_ABS := R_LARCH_32|R_LARCH_64|R_LARCH_MARK_LA|R_LARCH_JUMP_SLOT
+include $(srctree)/lib/vdso/Makefile
+
+obj-vdso-y := elf.o vgettimeofday.o sigreturn.o
+
+# Common compiler flags between ABIs.
+ccflags-vdso := \
+	$(filter -I%,$(KBUILD_CFLAGS)) \
+	$(filter -E%,$(KBUILD_CFLAGS)) \
+	$(filter -march=%,$(KBUILD_CFLAGS)) \
+	$(filter -m%-float,$(KBUILD_CFLAGS)) \
+	-D__VDSO__
+
+ifeq ($(cc-name),clang)
+ccflags-vdso += $(filter --target=%,$(KBUILD_CFLAGS))
+endif
+
+cflags-vdso := $(ccflags-vdso) \
+	$(filter -W%,$(filter-out -Wa$(comma)%,$(KBUILD_CFLAGS))) \
+	-O2 -g -fno-strict-aliasing -fno-common -fno-builtin -G0 \
+	-fno-stack-protector -fno-jump-tables -DDISABLE_BRANCH_PROFILING \
+	$(call cc-option, -fno-asynchronous-unwind-tables) \
+	$(call cc-option, -fno-stack-protector)
+aflags-vdso := $(ccflags-vdso) \
+	-D__ASSEMBLY__ -Wa,-gdwarf-2
+
+ifneq ($(c-gettimeofday-y),)
+  CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
+endif
+
+# VDSO linker flags.
+ldflags-y := -Bsymbolic --no-undefined -soname=linux-vdso.so.1 \
+	$(filter -E%,$(KBUILD_CFLAGS)) -nostdlib -shared \
+	--hash-style=sysv --build-id -T
+
+GCOV_PROFILE := n
+
+#
+# Shared build commands.
+#
+
+quiet_cmd_vdsold_and_vdso_check = LD      $@
+      cmd_vdsold_and_vdso_check = $(cmd_ld); $(cmd_vdso_check)
+
+quiet_cmd_vdsoas_o_S = AS       $@
+      cmd_vdsoas_o_S = $(CC) $(a_flags) -c -o $@ $<
+
+# Generate VDSO offsets using helper script
+gen-vdsosym := $(srctree)/$(src)/gen_vdso_offsets.sh
+quiet_cmd_vdsosym = VDSOSYM $@
+      cmd_vdsosym = $(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@
+
+include/generated/vdso-offsets.h: $(obj)/vdso.so.dbg FORCE
+	$(call if_changed,vdsosym)
+
+#
+# Build native VDSO.
+#
+
+native-abi := $(filter -mabi=%,$(KBUILD_CFLAGS))
+
+targets += $(obj-vdso-y)
+targets += vdso.lds vdso.so.dbg vdso.so
+
+obj-vdso := $(obj-vdso-y:%.o=$(obj)/%.o)
+
+$(obj-vdso): KBUILD_CFLAGS := $(cflags-vdso) $(native-abi)
+$(obj-vdso): KBUILD_AFLAGS := $(aflags-vdso) $(native-abi)
+
+$(obj)/vdso.lds: KBUILD_CPPFLAGS := $(ccflags-vdso) $(native-abi)
+
+$(obj)/vdso.so.dbg: $(obj)/vdso.lds $(obj-vdso) FORCE
+	$(call if_changed,vdsold_and_vdso_check)
+
+$(obj)/vdso.so: OBJCOPYFLAGS := -S
+$(obj)/vdso.so: $(obj)/vdso.so.dbg FORCE
+	$(call if_changed,objcopy)
+
+obj-y += vdso.o
+
+$(obj)/vdso.o : $(obj)/vdso.so
+
+# 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/loongarch/vdso/elf.S b/arch/loongarch/vdso/elf.S
new file mode 100644
index 000000000000..9bb21b9f9583
--- /dev/null
+++ b/arch/loongarch/vdso/elf.S
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Author: Huacai Chen <chenhuacai@loongson.cn>
+ *
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+#include <asm/vdso/vdso.h>
+
+#include <linux/elfnote.h>
+#include <linux/version.h>
+
+ELFNOTE_START(Linux, 0, "a")
+	.long LINUX_VERSION_CODE
+ELFNOTE_END
diff --git a/arch/loongarch/vdso/gen_vdso_offsets.sh b/arch/loongarch/vdso/gen_vdso_offsets.sh
new file mode 100755
index 000000000000..1bb4e12642ff
--- /dev/null
+++ b/arch/loongarch/vdso/gen_vdso_offsets.sh
@@ -0,0 +1,13 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+#
+# Derived from RISC-V and ARM64:
+# Author: Will Deacon <will.deacon@arm.com>
+#
+# Match symbols in the DSO that look like VDSO_*; produce a header file
+# of constant offsets into the shared object.
+#
+
+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/loongarch/vdso/sigreturn.S b/arch/loongarch/vdso/sigreturn.S
new file mode 100644
index 000000000000..9cb3c58fad03
--- /dev/null
+++ b/arch/loongarch/vdso/sigreturn.S
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Author: Huacai Chen <chenhuacai@loongson.cn>
+ *
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+#include <asm/vdso/vdso.h>
+
+#include <linux/linkage.h>
+#include <uapi/asm/unistd.h>
+
+#include <asm/regdef.h>
+#include <asm/asm.h>
+
+	.section	.text
+	.cfi_sections	.debug_frame
+
+SYM_FUNC_START(__vdso_rt_sigreturn)
+
+	li.w	a7, __NR_rt_sigreturn
+	syscall	0
+
+SYM_FUNC_END(__vdso_rt_sigreturn)
diff --git a/arch/loongarch/vdso/vdso.S b/arch/loongarch/vdso/vdso.S
new file mode 100644
index 000000000000..46789bade6ff
--- /dev/null
+++ b/arch/loongarch/vdso/vdso.S
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ *
+ * Derived from RISC-V:
+ * Copyright (C) 2014 Regents of the University of California
+ */
+
+#include <linux/init.h>
+#include <linux/linkage.h>
+#include <asm/page.h>
+
+	__PAGE_ALIGNED_DATA
+
+	.globl vdso_start, vdso_end
+	.balign PAGE_SIZE
+vdso_start:
+	.incbin "arch/loongarch/vdso/vdso.so"
+	.balign PAGE_SIZE
+vdso_end:
+
+	.previous
diff --git a/arch/loongarch/vdso/vdso.lds.S b/arch/loongarch/vdso/vdso.lds.S
new file mode 100644
index 000000000000..955f02de4a2d
--- /dev/null
+++ b/arch/loongarch/vdso/vdso.lds.S
@@ -0,0 +1,72 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Author: Huacai Chen <chenhuacai@loongson.cn>
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+
+OUTPUT_FORMAT("elf64-loongarch", "elf64-loongarch", "elf64-loongarch")
+
+OUTPUT_ARCH(loongarch)
+
+SECTIONS
+{
+	PROVIDE(_start = .);
+	. = 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
+	PROVIDE (__etext = .);
+	PROVIDE (_etext = .);
+	PROVIDE (etext = .);
+
+	.eh_frame_hdr	: { *(.eh_frame_hdr) }		:text :eh_frame_hdr
+	.eh_frame	: { KEEP (*(.eh_frame)) }	:text
+
+	.dynamic	: { *(.dynamic) }		:text :dynamic
+
+	.rodata		: { *(.rodata*) }		:text
+
+	_end = .;
+	PROVIDE(end = .);
+
+	/DISCARD/	: {
+		*(.gnu.attributes)
+		*(.note.GNU-stack)
+		*(.data .data.* .gnu.linkonce.d.* .sdata*)
+		*(.bss .sbss .dynbss .dynsbss)
+	}
+}
+
+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;
+}
+
+VERSION
+{
+	LINUX_5.10 {
+	global:
+		__vdso_clock_getres;
+		__vdso_clock_gettime;
+		__vdso_gettimeofday;
+		__vdso_rt_sigreturn;
+	local: *;
+	};
+}
+
+/*
+ * Make the sigreturn code visible to the kernel.
+ */
+VDSO_sigreturn		= __vdso_rt_sigreturn;
diff --git a/arch/loongarch/vdso/vgettimeofday.c b/arch/loongarch/vdso/vgettimeofday.c
new file mode 100644
index 000000000000..b1f4548dae92
--- /dev/null
+++ b/arch/loongarch/vdso/vgettimeofday.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * LoongArch userspace implementations of gettimeofday() and similar.
+ *
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+#include <linux/types.h>
+
+int __vdso_clock_gettime(clockid_t clock,
+			 struct __kernel_timespec *ts)
+{
+	return __cvdso_clock_gettime(clock, ts);
+}
+
+int __vdso_gettimeofday(struct __kernel_old_timeval *tv,
+			struct timezone *tz)
+{
+	return __cvdso_gettimeofday(tv, tz);
+}
+
+int __vdso_clock_getres(clockid_t clock_id,
+			struct __kernel_timespec *res)
+{
+	return __cvdso_clock_getres(clock_id, res);
+}