[Qemu-devel] [PATCH 1/2] linux-user: Build vdso for x64.

[Richard Henderson]

... Well, sortof.  The Makefile bits are broken.
Patch to load the vdso into the running program to follow.

Signed-off-by: Richard Henderson <address@hidden>
---
 Makefile                  |   3 +-
 pc-bios/Makefile          |   5 +++
 pc-bios/vdso-linux-x64.S  | 100 ++++++++++++++++++++++++++++++++++++++++++++++
 pc-bios/vdso-linux-x64.ld |  79 ++++++++++++++++++++++++++++++++++++
 pc-bios/vdso-linux-x64.so | Bin 0 -> 7419 bytes
 5 files changed, 186 insertions(+), 1 deletion(-)
 create mode 100644 pc-bios/vdso-linux-x64.S
 create mode 100644 pc-bios/vdso-linux-x64.ld
 create mode 100755 pc-bios/vdso-linux-x64.so

diff --git a/Makefile b/Makefile
index c06bfab..0148da1 100644
--- a/Makefile
+++ b/Makefile
@@ -296,7 +296,8 @@ multiboot.bin linuxboot.bin kvmvapic.bin \
 s390-zipl.rom \
 s390-ccw.img \
 spapr-rtas.bin slof.bin \
-palcode-clipper
+palcode-clipper \
+vdso-linux-x64.so
 else
 BLOBS=
 endif
diff --git a/pc-bios/Makefile b/pc-bios/Makefile
index 315288d..70e2485 100644
--- a/pc-bios/Makefile
+++ b/pc-bios/Makefile
@@ -15,5 +15,10 @@ all: $(TARGETS)
 %.dtb: %.dts
        dtc -I dts -O dtb -o $@ $<
 
+vdso-linux-x64.so: vdso-linux-x64.o vdso-linux-x64.ld
+       $(CC) -nostdlib -shared -Wl,-T,vdso-linux-x64.ld \
+         -Wl,-h,linux-vdso.so.1 -Wl,--hash-style=both \
+         vdso-linux-x64.o -o $@
+
 clean:
        rm -f $(TARGETS) *.o *~
diff --git a/pc-bios/vdso-linux-x64.S b/pc-bios/vdso-linux-x64.S
new file mode 100644
index 0000000..92efcd1
--- /dev/null
+++ b/pc-bios/vdso-linux-x64.S
@@ -0,0 +1,100 @@
+/*
+ *  x86-64 linux replacement vdso.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#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_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_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/pc-bios/vdso-linux-x64.ld b/pc-bios/vdso-linux-x64.ld
new file mode 100644
index 0000000..9e7e2d1
--- /dev/null
+++ b/pc-bios/vdso-linux-x64.ld
@@ -0,0 +1,79 @@
+/*
+ * Linker script for linux x64 replacement vdso.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+VERSION {
+       LINUX_2.6 {
+       global:
+               clock_gettime;
+               __vdso_clock_gettime;
+               gettimeofday;
+               __vdso_gettimeofday;
+               getcpu;
+               __vdso_getcpu;
+       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);
+       note            PT_NOTE         FLAGS(4);
+       /* ??? Various versions of ld don't know PT_GNU_EH_FRAME. */
+       eh_frame_hdr    0x6474e550;
+}
+
+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.  */
+       .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.*)
+       }
+
+       . += 4096;
+       .hash           : { *(.hash) }          :text
+       .gnu.hash       : { *(.gnu.hash) }
+       .dynstr         : { *(.dynstr) }
+       .gnu.version    : { *(.gnu.version) }
+       .gnu.version_d  : { *(.gnu.version_d) }
+       .gnu.version_r  : { *(.gnu.version_r) }
+       .note           : { *(.note*) }         :text :note
+       .eh_frame_hdr   : { *(.eh_frame_hdr) }  :text :eh_frame_hdr
+       .eh_frame       : { *(.eh_frame) }      :text
+       .rodata         : { *(.rodata) }
+
+       . = ALIGN(0x100);
+       .text           : { *(.text*) }         :text   =0x90909090
+}
diff --git a/pc-bios/vdso-linux-x64.so b/pc-bios/vdso-linux-x64.so
new file mode 100755
index 
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GIT binary patch
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-- 
1.8.3.1