# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 32c3658d73916f127e19e8c77ca34ec49b9ab64c
# Parent f1abe953e4019c023cccec46560052df7261828d
Xen-friendly glibc selection: appropriate ld-linux can parse
the vsyscall page ELF notes and use the "nosegneg" glibc variant
to ensure that things work fine.
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Roland McGrath <roland@xxxxxxxxxx>
diff -r f1abe953e401 -r 32c3658d7391
linux-2.6-xen-sparse/arch/xen/i386/kernel/Makefile
--- a/linux-2.6-xen-sparse/arch/xen/i386/kernel/Makefile Fri Oct 7
22:36:26 2005
+++ b/linux-2.6-xen-sparse/arch/xen/i386/kernel/Makefile Sat Oct 8
08:49:28 2005
@@ -86,7 +86,7 @@
$(call if_changed,syscall)
c-link :=
-s-link := vsyscall-int80.o vsyscall-sysenter.o vsyscall-sigreturn.o
vsyscall.lds.o vsyscall-note.o
+s-link := vsyscall-int80.o vsyscall-sysenter.o vsyscall-sigreturn.o
vsyscall.lds.o
$(patsubst %.o,$(obj)/%.c,$(c-obj-y) $(c-obj-m) $(c-link)) $(patsubst
%.o,$(obj)/%.S,$(s-obj-y) $(s-link)):
@ln -fsn $(srctree)/arch/i386/kernel/$(notdir $@) $@
diff -r f1abe953e401 -r 32c3658d7391
linux-2.6-xen-sparse/arch/xen/i386/kernel/vsyscall-note.S
--- /dev/null Fri Oct 7 22:36:26 2005
+++ b/linux-2.6-xen-sparse/arch/xen/i386/kernel/vsyscall-note.S Sat Oct 8
08:49:28 2005
@@ -0,0 +1,32 @@
+/*
+ * This supplies .note.* sections to go into the PT_NOTE inside the vDSO text.
+ * Here we can supply some information useful to userland.
+ * First we get the vanilla i386 note that supplies the kernel version info.
+ */
+
+#include "../../../i386/kernel/vsyscall-note.S"
+
+/*
+ * Now we add a special note telling glibc's dynamic linker a fake hardware
+ * flavor that it will use to choose the search path for libraries in the
+ * same way it uses real hardware capabilities like "mmx".
+ * We supply "nosegneg" as the fake capability, to indicate that we
+ * do not like negative offsets in instructions using segment overrides,
+ * since we implement those inefficiently. This makes it possible to
+ * install libraries optimized to avoid those access patterns in someplace
+ * like /lib/i686/tls/nosegneg. Note that an /etc/ld.so.conf.d/file
+ * corresponding to the bits here is needed to make ldconfig work right.
+ * It should contain:
+ * hwcap 0 nosegneg
+ * to match the mapping of bit to name that we give here.
+ */
+#define NOTE_KERNELCAP_BEGIN(ncaps, mask) \
+ ASM_ELF_NOTE_BEGIN(".note.kernelcap", "a", "GNU", 2) \
+ .long ncaps, mask
+#define NOTE_KERNELCAP(bit, name) \
+ .byte bit; .asciz name
+#define NOTE_KERNELCAP_END ASM_ELF_NOTE_END
+
+NOTE_KERNELCAP_BEGIN(1, 1)
+NOTE_KERNELCAP(1, "nosegneg") /* Change 1 back to 0 when glibc is fixed! */
+NOTE_KERNELCAP_END
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