linux-user/s390x: Add vdso

Acked-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

linux-user/elfload.c

@@ -1894,6 +1894,8 @@ static void elf_core_copy_regs(target_elf_gregset_t *regs,
 #define USE_ELF_CORE_DUMP
 #define ELF_EXEC_PAGESIZE 4096
 
+#define VDSO_HEADER "vdso.c.inc"
+
 #endif /* TARGET_S390X */
 
 #ifdef TARGET_RISCV

linux-user/s390x/Makefile.vdso

@@ -0,0 +1,11 @@
+include $(BUILD_DIR)/tests/tcg/s390x-linux-user/config-target.mak
+
+SUBDIR = $(SRC_PATH)/linux-user/s390x
+VPATH += $(SUBDIR)
+
+all: $(SUBDIR)/vdso.so
+
+$(SUBDIR)/vdso.so: vdso.S vdso.ld vdso-asmoffset.h
+	$(CC) -o $@ -nostdlib -shared -Wl,-h,linux-vdso64.so.1 \
+	  -Wl,--build-id=sha1 -Wl,--hash-style=both \
+	  -Wl,-T,$(SUBDIR)/vdso.ld $<

linux-user/s390x/meson.build

@@ -3,3 +3,9 @@ syscall_nr_generators += {
                      arguments: [ meson.current_source_dir() / 'syscallhdr.sh', '@INPUT@', '@OUTPUT@', '@EXTRA_ARGS@' ],
                      output: '@BASENAME@_nr.h')
 }
+
+vdso_inc = gen_vdso.process('vdso.so', extra_args: [
+                                '-s', '__kernel_sigreturn',
+                                '-r', '__kernel_rt_sigreturn'
+                            ])
+linux_user_ss.add(when: 'TARGET_S390X', if_true: vdso_inc)

linux-user/s390x/signal.c

@@ -21,14 +21,12 @@
 #include "user-internals.h"
 #include "signal-common.h"
 #include "linux-user/trace.h"
+#include "vdso-asmoffset.h"
 
 #define __NUM_GPRS 16
 #define __NUM_FPRS 16
 #define __NUM_ACRS 16
 
-/* Minimum stack frame size */
-#define STACK_FRAME_OVERHEAD    160
-
 #define _SIGCONTEXT_NSIG        64
 #define _SIGCONTEXT_NSIG_BPW    64 /* FIXME: 31-bit mode -> 32 */
 #define _SIGCONTEXT_NSIG_WORDS  (_SIGCONTEXT_NSIG / _SIGCONTEXT_NSIG_BPW)

linux-user/s390x/vdso-asmoffset.h

@@ -0,0 +1,2 @@
+/* Minimum stack frame size */
+#define STACK_FRAME_OVERHEAD    160

linux-user/s390x/vdso.S

@@ -0,0 +1,61 @@
+/*
+ * s390x linux replacement vdso.
+ *
+ * Copyright 2023 Linaro, Ltd.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include <asm/unistd.h>
+#include "vdso-asmoffset.h"
+
+.macro endf name
+	.globl	\name
+	.type	\name, @function
+	.size	\name, . - \name
+.endm
+
+.macro raw_syscall n
+        .ifne	\n < 0x100
+	svc	\n
+	.else
+	lghi	%r1, \n
+	svc	0
+        .endif
+.endm
+
+.macro vdso_syscall name, nr
+\name:
+	.cfi_startproc
+	aghi	%r15, -(STACK_FRAME_OVERHEAD + 16)
+	.cfi_adjust_cfa_offset STACK_FRAME_OVERHEAD + 16
+	stg	%r14, STACK_FRAME_OVERHEAD(%r15)
+	.cfi_rel_offset %r14, STACK_FRAME_OVERHEAD
+	raw_syscall \nr
+	lg	%r14, STACK_FRAME_OVERHEAD(%r15)
+	aghi	%r15, STACK_FRAME_OVERHEAD + 16
+	.cfi_restore %r14
+	.cfi_adjust_cfa_offset -(STACK_FRAME_OVERHEAD + 16)
+	br	%r14
+	.cfi_endproc
+endf	\name
+.endm
+
+vdso_syscall __kernel_gettimeofday, __NR_gettimeofday
+vdso_syscall __kernel_clock_gettime, __NR_clock_gettime
+vdso_syscall __kernel_clock_getres, __NR_clock_getres
+vdso_syscall __kernel_getcpu, __NR_getcpu
+
+/*
+ * TODO unwind info, though we're ok without it.
+ * The kernel supplies bogus empty unwind info, and it is likely ignored
+ * by all users.  Without it we get the fallback signal frame handling.
+ */
+
+__kernel_sigreturn:
+	raw_syscall __NR_sigreturn
+endf	__kernel_sigreturn
+
+__kernel_rt_sigreturn:
+	raw_syscall __NR_rt_sigreturn
+endf	__kernel_rt_sigreturn

linux-user/s390x/vdso.ld

@@ -0,0 +1,72 @@
+/*
+ * Linker script for linux s390x replacement vdso.
+ *
+ * Copyright 2023 Linaro, Ltd.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+VERSION {
+        LINUX_2.6.29 {
+        global:
+                __kernel_gettimeofday;
+                __kernel_clock_gettime;
+                __kernel_clock_getres;
+                __kernel_getcpu;
+                __kernel_rt_sigreturn;
+                __kernel_sigreturn;
+                /*
+                 * QEMU handles syscall restart internally, so we don't
+                 * need the __kernel_restart_syscall entry point.
+                 */
+        local: *;
+        };
+}
+
+
+PHDRS {
+        phdr            PT_PHDR         FLAGS(4) PHDRS;
+        load            PT_LOAD         FLAGS(7) FILEHDR PHDRS; /* FLAGS=RWX */
+        dynamic         PT_DYNAMIC      FLAGS(4);
+        eh_frame_hdr    PT_GNU_EH_FRAME;
+        note            PT_NOTE         FLAGS(4);
+}
+
+SECTIONS {
+        . = 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
+}