2005-04-08 03:54:11

by Roland McGrath

Subject: [PATCH] i386 vDSO: add PT_NOTE segment

This patch adds an ELF note to the vDSO giving the LINUX_VERSION_CODE
value. Having this in the vDSO lets the dynamic linker avoid the `uname'
syscall it now always does at startup to ascertain the kernel ABI available.


Thanks,
Roland

Signed-off-by: Roland McGrath <[email protected]>

--- linux-2.6/arch/i386/kernel/Makefile
+++ linux-2.6/arch/i386/kernel/Makefile
@@ -56,7 +56,8 @@ SYSCFLAGS_vsyscall-sysenter.so = $(vsysc
SYSCFLAGS_vsyscall-int80.so = $(vsyscall-flags)

$(obj)/vsyscall-int80.so $(obj)/vsyscall-sysenter.so: \
-$(obj)/vsyscall-%.so: $(src)/vsyscall.lds $(obj)/vsyscall-%.o FORCE
+$(obj)/vsyscall-%.so: $(src)/vsyscall.lds \
+ $(obj)/vsyscall-%.o $(obj)/vsyscall-note.o FORCE
$(call if_changed,syscall)

# We also create a special relocatable object that should mirror the symbol
@@ -67,5 +68,6 @@ $(obj)/built-in.o: $(obj)/vsyscall-syms.
$(obj)/built-in.o: ld_flags += -R $(obj)/vsyscall-syms.o

SYSCFLAGS_vsyscall-syms.o = -r
-$(obj)/vsyscall-syms.o: $(src)/vsyscall.lds $(obj)/vsyscall-sysenter.o FORCE
+$(obj)/vsyscall-syms.o: $(src)/vsyscall.lds \
+ $(obj)/vsyscall-sysenter.o $(obj)/vsyscall-note.o FORCE
$(call if_changed,syscall)
--- linux-2.6/arch/i386/kernel/vsyscall.lds.S
+++ linux-2.6/arch/i386/kernel/vsyscall.lds.S
@@ -23,7 +23,7 @@ SECTIONS
. = VSYSCALL_BASE + 0x400;

.text : { *(.text) } :text =0x90909090
-
+ .note : { *(.note.*) } :text :note
.eh_frame_hdr : { *(.eh_frame_hdr) } :text :eh_frame_hdr
.eh_frame : { KEEP (*(.eh_frame)) } :text
.dynamic : { *(.dynamic) } :text :dynamic
@@ -43,6 +43,7 @@ PHDRS
{
text PT_LOAD FILEHDR PHDRS FLAGS(5); /* PF_R|PF_X */
dynamic PT_DYNAMIC FLAGS(4); /* PF_R */
+ note PT_NOTE FLAGS(4); /* PF_R */
eh_frame_hdr 0x6474e550; /* PT_GNU_EH_FRAME, but ld doesn't match the name */
}

--- linux-2.6/arch/i386/kernel/vsyscall-note.S
+++ linux-2.6/arch/i386/kernel/vsyscall-note.S
@@ -0,0 +1,25 @@
+/*
+ * This supplies .note.* sections to go into the PT_NOTE inside the vDSO text.
+ * Here we can supply some information useful to userland.
+ */
+
+#include <linux/uts.h>
+#include <linux/version.h>
+
+#define ASM_ELF_NOTE_BEGIN(name, flags, vendor, type) \
+ .section name, flags; \
+ .balign 4; \
+ .long 1f - 0f; /* name length */ \
+ .long 3f - 2f; /* data length */ \
+ .long type; /* note type */ \
+0: .asciz vendor; /* vendor name */ \
+1: .balign 4; \
+2:
+
+#define ASM_ELF_NOTE_END \
+3: .balign 4; /* pad out section */ \
+ .previous
+
+ ASM_ELF_NOTE_BEGIN(".note.kernel-version", "a", UTS_SYSNAME, 0)
+ .long LINUX_VERSION_CODE
+ ASM_ELF_NOTE_END

2005-04-08 03:55:59

by Roland McGrath

Subject: [PATCH] x86-64: i386 vDSO: add PT_NOTE segment

Assuming my previous patch goes into the native i386 vDSO,
this patch makes the x86_64's 32-bit vDSO match it.

Thanks,
Roland

Signed-off-by: Roland McGrath <[email protected]>

--- linux-2.6/arch/x86_64/ia32/vsyscall-sigreturn.S
+++ linux-2.6/arch/x86_64/ia32/vsyscall-sigreturn.S
@@ -118,3 +118,6 @@ __kernel_rt_sigreturn:

.align 4
.LENDFDE3:
+
+#include "../../i386/kernel/vsyscall-note.S"
+