[v2,23/36] linux-user/x86_64: Add vdso

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 7a598f9f76..43c985f318 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -284,12 +284,12 @@  static void elf_core_copy_regs(target_elf_gregset_t *regs, const CPUX86State *en
 #define DLINFO_ARCH_ITEMS 1
 #define ARCH_DLINFO       NEW_AUX_ENT(AT_SYSINFO, vdso_info->entry);
 
+#endif /* TARGET_X86_64 */
+
 #include "vdso.c.inc"
 
 #define vdso_image_info()    &vdso_image_info
 
-#endif /* TARGET_X86_64 */
-
 #define USE_ELF_CORE_DUMP
 #define ELF_EXEC_PAGESIZE       4096
 
diff --git a/linux-user/x86_64/Makefile.vdso b/linux-user/x86_64/Makefile.vdso
new file mode 100644
index 0000000000..532c9d6964
--- /dev/null
+++ b/linux-user/x86_64/Makefile.vdso
@@ -0,0 +1,5 @@ 
+CROSS_CC ?= $(CC)
+
+vdso.so: vdso.S vdso.ld Makefile.vdso
+	$(CROSS_CC) -nostdlib -shared -Wl,-T,vdso.ld -Wl,--build-id=sha1 \
+	  -Wl,-h,linux-vdso.so.1 -Wl,--hash-style=both vdso.S -o $@
diff --git a/linux-user/x86_64/meson.build b/linux-user/x86_64/meson.build
index 203af9a60c..f6a0015953 100644
--- a/linux-user/x86_64/meson.build
+++ b/linux-user/x86_64/meson.build
@@ -3,3 +3,9 @@  syscall_nr_generators += {
                       arguments: [ meson.current_source_dir() / 'syscallhdr.sh', '@INPUT@', '@OUTPUT@', '@EXTRA_ARGS@' ],
                       output: '@BASENAME@_nr.h')
 }
+
+gen = [
+  gen_vdso.process('vdso.so')
+]
+
+linux_user_ss.add(when: 'TARGET_X86_64', if_true: gen)
diff --git a/linux-user/x86_64/vdso.S b/linux-user/x86_64/vdso.S
new file mode 100644
index 0000000000..bbd75a79aa
--- /dev/null
+++ b/linux-user/x86_64/vdso.S
@@ -0,0 +1,122 @@ 
+/*
+ * x86-64 linux replacement vdso.
+ *
+ * Copyright 2021 Linaro, Ltd.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include <asm/unistd.h>
+
+	.globl	__vdso_clock_gettime
+	.type	__vdso_clock_gettime, @function
+	.balign	16
+	.cfi_startproc
+__vdso_clock_gettime:
+	mov	$__NR_clock_gettime, %eax
+	syscall
+	ret
+	.cfi_endproc
+	.size	__vdso_clock_gettime, . - __vdso_clock_gettime
+
+clock_gettime = __vdso_clock_gettime
+	.weak	clock_gettime
+
+	.globl	__vdso_clock_getres
+	.type	__vdso_clock_getres, @function
+	.balign	16
+	.cfi_startproc
+__vdso_clock_getres:
+	mov	$__NR_clock_getres, %eax
+	syscall
+	ret
+	.cfi_endproc
+	.size	__vdso_clock_getres, . - __vdso_clock_getres
+
+clock_getres = __vdso_clock_getres
+	.weak	clock_getres
+
+	.globl	__vdso_gettimeofday
+	.type	__vdso_gettimeofday, @function
+	.balign	16
+	.cfi_startproc
+__vdso_gettimeofday:
+	mov	$__NR_gettimeofday, %eax
+	syscall
+	ret
+	.cfi_endproc
+	.size	__vdso_gettimeofday, . - __vdso_gettimeofday
+
+gettimeofday = __vdso_gettimeofday
+	.weak	gettimeofday
+
+
+	.globl	__vdso_time
+	.type	__vdso_time, @function
+	.balign	16
+	.cfi_startproc
+__vdso_time:
+	mov	$__NR_time, %eax
+	syscall
+	ret
+	.cfi_endproc
+	.size	__vdso_time, . - __vdso_time
+
+time = __vdso_time
+	.weak	time
+
+
+	.globl	__vdso_getcpu
+	.type	__vdso_getcpu, @function
+	.balign	16
+	.cfi_startproc
+__vdso_getcpu:
+	/*
+         * ??? There is no syscall number for this allocated on x64.
+	 * We can handle this several ways:
+         *
+	 * (1) Invent a syscall number for use within qemu.
+         *     It should be easy enough to pick a number that
+         *     is well out of the way of the kernel numbers.
+         *
+         * (2) Force the emulated cpu to support the rdtscp insn,
+	 *     and initialize the TSC_AUX value the appropriate value.
+         *
+	 * (3) Pretend that we're always running on cpu 0.
+         *
+	 * This last is the one that's implemented here, with the
+	 * tiny bit of extra code to support rdtscp in place.
+         */
+	xor	%ecx, %ecx		/* rdtscp w/ tsc_aux = 0 */
+
+	/* if (cpu != NULL) *cpu = (ecx & 0xfff); */
+	test	%rdi, %rdi
+	jz	1f
+	mov	%ecx, %eax
+	and	$0xfff, %eax
+	mov	%eax, (%rdi)
+
+	/* if (node != NULL) *node = (ecx >> 12); */
+1:	test	%rsi, %rsi
+	jz	2f
+	shr	$12, %ecx
+	mov	%ecx, (%rsi)
+
+2:	xor	%eax, %eax
+	ret
+	.cfi_endproc
+	.size	__vdso_getcpu, . - __vdso_getcpu
+
+getcpu = __vdso_getcpu
+	.weak	getcpu
+
+/*
+ * ??? Perhaps add elf notes.  E.g.
+ *
+ * #include <linux/elfnote.h>
+ * ELFNOTE_START(Linux, 0, "a")
+ *   .long LINUX_VERSION_CODE
+ * ELFNOTE_END
+ *
+ * but what version number would we set for QEMU?
+ */
diff --git a/linux-user/x86_64/vdso.ld b/linux-user/x86_64/vdso.ld
new file mode 100644
index 0000000000..6630193079
--- /dev/null
+++ b/linux-user/x86_64/vdso.ld
@@ -0,0 +1,74 @@ 
+/*
+ * Linker script for linux x86-64 replacement vdso.
+ *
+ * Copyright 2021 Linaro, Ltd.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+VERSION {
+        LINUX_2.6 {
+        global:
+                clock_gettime;
+                __vdso_clock_gettime;
+                gettimeofday;
+                __vdso_gettimeofday;
+                getcpu;
+                __vdso_getcpu;
+                time;
+                __vdso_time;
+                clock_getres;
+                __vdso_clock_getres;
+
+        local: *;
+        };
+}
+
+
+PHDRS {
+        phdr            PT_PHDR         FLAGS(4) PHDRS;
+        data            PT_LOAD         FLAGS(6) FILEHDR PHDRS;
+        text            PT_LOAD         FLAGS(5);
+        dynamic         PT_DYNAMIC      FLAGS(4);
+        eh_frame_hdr    PT_GNU_EH_FRAME;
+        note            PT_NOTE         FLAGS(4);
+}
+
+SECTIONS {
+        /* ??? We can't really prelink to any address without knowing
+           something about the virtual memory space of the host, since
+           that leaks over into the available memory space of the guest.  */
+        . = SIZEOF_HEADERS;
+
+        /* The following, including the FILEHDRS and PHDRS, are modified
+           when we relocate the binary.  We want them to be initially
+           writable for the relocation; we'll force them read-only after.  */
+        .note           : { *(.note*) }         :data :note
+        .dynamic        : { *(.dynamic) }       :data :dynamic
+        .dynsym         : { *(.dynsym) }        :data
+        .data           : {
+                /* There ought not be any real read-write data.
+                   But since we manipulated the segment layout,
+                   we have to put these sections somewhere.  */
+                *(.data*)
+                *(.sdata*)
+                *(.got.plt) *(.got)
+                *(.gnu.linkonce.d.*)
+                *(.bss*)
+                *(.dynbss*)
+                *(.gnu.linkonce.b.*)
+        }
+
+        .rodata         : { *(.rodata*) }
+        .hash           : { *(.hash) }
+        .gnu.hash       : { *(.gnu.hash) }
+        .dynstr         : { *(.dynstr) }
+        .gnu.version    : { *(.gnu.version) }
+        .gnu.version_d  : { *(.gnu.version_d) }
+        .gnu.version_r  : { *(.gnu.version_r) }
+        .eh_frame_hdr   : { *(.eh_frame_hdr) }  :data :eh_frame_hdr
+        .eh_frame       : { *(.eh_frame) }      :data
+
+        . = ALIGN(4096);
+        .text           : { *(.text*) }         :text   =0x90909090
+}