linux-user/aarch64: Add vdso

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

linux-user/aarch64/Makefile.vdso

@@ -0,0 +1,15 @@
+include $(BUILD_DIR)/tests/tcg/aarch64-linux-user/config-target.mak
+
+SUBDIR = $(SRC_PATH)/linux-user/aarch64
+VPATH += $(SUBDIR)
+
+all: $(SUBDIR)/vdso-be.so $(SUBDIR)/vdso-le.so
+
+LDFLAGS = -nostdlib -shared -Wl,-h,linux-vdso.so.1 -Wl,--build-id=sha1 \
+	  -Wl,--hash-style=both -Wl,-T,$(SUBDIR)/vdso.ld
+
+$(SUBDIR)/vdso-be.so: vdso.S vdso.ld
+	$(CC) -o $@ $(LDFLAGS) -mbig-endian $<
+
+$(SUBDIR)/vdso-le.so: vdso.S vdso.ld
+	$(CC) -o $@ $(LDFLAGS) -mlittle-endian $<

linux-user/aarch64/meson.build

@@ -0,0 +1,11 @@
+# TARGET_BIG_ENDIAN is defined to 'n' for little-endian; which means it
+# is always true as far as source_set.apply() is concerned.  Always build
+# both header files and include the right one via #if.
+
+vdso_be_inc = gen_vdso.process('vdso-be.so',
+                               extra_args: ['-r', '__kernel_rt_sigreturn'])
+
+vdso_le_inc = gen_vdso.process('vdso-le.so',
+                               extra_args: ['-r', '__kernel_rt_sigreturn'])
+
+linux_user_ss.add(when: 'TARGET_AARCH64', if_true: [vdso_be_inc, vdso_le_inc])

linux-user/aarch64/vdso.S

@@ -0,0 +1,71 @@
+/*
+ * aarch64 linux replacement vdso.
+ *
+ * Copyright 2023 Linaro, Ltd.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include <asm/unistd.h>
+
+/* ??? These are in include/elf.h, which is not ready for inclusion in asm. */
+#define NT_GNU_PROPERTY_TYPE_0  5
+#define GNU_PROPERTY_AARCH64_FEATURE_1_AND      0xc0000000
+#define GNU_PROPERTY_AARCH64_FEATURE_1_BTI      (1U << 0)
+#define GNU_PROPERTY_AARCH64_FEATURE_1_PAC      (1U << 1)
+
+#define GNU_PROPERTY_AARCH64_FEATURE_1_DEFAULT \
+    (GNU_PROPERTY_AARCH64_FEATURE_1_BTI | GNU_PROPERTY_AARCH64_FEATURE_1_PAC)
+
+	.section .note.gnu.property
+	.align	3
+	.long	2f - 1f
+	.long	6f - 3f
+	.long	NT_GNU_PROPERTY_TYPE_0
+1:	.string	"GNU"
+2:	.align	3
+3:	.long	GNU_PROPERTY_AARCH64_FEATURE_1_AND
+	.long	5f - 4f
+4:	.long	GNU_PROPERTY_AARCH64_FEATURE_1_DEFAULT
+5:	.align	3
+6:
+
+	.text
+
+.macro endf name
+	.globl	\name
+	.type	\name, @function
+	.size	\name, . - \name
+.endm
+
+.macro vdso_syscall name, nr
+\name:
+	bti	c
+	mov	x8, #\nr
+	svc	#0
+	ret
+endf	\name
+.endm
+
+	.cfi_startproc
+
+vdso_syscall __kernel_gettimeofday, __NR_gettimeofday
+vdso_syscall __kernel_clock_gettime, __NR_clock_gettime
+vdso_syscall __kernel_clock_getres, __NR_clock_getres
+
+	.cfi_endproc
+
+
+/*
+ * TODO: The kernel makes a big deal of turning off the .cfi directives,
+ * because they cause libgcc to crash, but that's because they're wrong.
+ *
+ * For now, elide the unwind info for __kernel_rt_sigreturn and rely on
+ * the libgcc fallback routine as we have always done.  This requires
+ * that the code sequence used be exact.
+ */
+__kernel_rt_sigreturn:
+	/* No BTI C insn here -- we arrive via RET. */
+	mov	x8, #__NR_rt_sigreturn
+	svc	#0
+endf	__kernel_rt_sigreturn

linux-user/aarch64/vdso.ld

@@ -0,0 +1,72 @@
+/*
+ * Linker script for linux aarch64 replacement vdso.
+ *
+ * Copyright 2021 Linaro, Ltd.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+VERSION {
+        LINUX_2.6.39 {
+        global:
+                __kernel_rt_sigreturn;
+                __kernel_gettimeofday;
+                __kernel_clock_gettime;
+                __kernel_clock_getres;
+
+        local: *;
+        };
+}
+
+
+PHDRS {
+        phdr            PT_PHDR         FLAGS(4) PHDRS;
+        load            PT_LOAD         FLAGS(7) FILEHDR PHDRS;
+        dynamic         PT_DYNAMIC      FLAGS(4);
+        eh_frame_hdr    PT_GNU_EH_FRAME;
+        note            PT_NOTE         FLAGS(4);
+}
+
+SECTIONS {
+        /*
+         * We can't 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*) }         :load :note
+        .dynamic        : { *(.dynamic) }       :load :dynamic
+        .dynsym         : { *(.dynsym) }        :load
+        /*
+         * There ought not be any real read-write data.
+         * But since we manipulated the segment layout,
+         * we have to put these sections somewhere.
+         */
+        .data           : {
+                *(.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) }  :load :eh_frame_hdr
+        .eh_frame       : { *(.eh_frame) }      :load
+
+        .text           : { *(.text*) }         :load   =0xd503201f
+}

linux-user/elfload.c

@@ -944,6 +944,12 @@ const char *elf_hwcap2_str(uint32_t bit)
 
 #undef GET_FEATURE_ID
 
+#if TARGET_BIG_ENDIAN
+# define VDSO_HEADER  "vdso-be.c.inc"
+#else
+# define VDSO_HEADER  "vdso-le.c.inc"
+#endif
+
 #endif /* not TARGET_AARCH64 */
 #endif /* TARGET_ARM */
 

linux-user/meson.build

@@ -35,6 +35,7 @@ gen_vdso_exe = executable('gen-vdso', 'gen-vdso.c',
 gen_vdso = generator(gen_vdso_exe, output: '@BASENAME@.c.inc',
                      arguments: ['-o', '@OUTPUT@', '@EXTRA_ARGS@', '@INPUT@'])
 
+subdir('aarch64')
 subdir('alpha')
 subdir('arm')
 subdir('hppa')