From 7aecdc2e7a46a8b9663af019636b226fe2ca5823 Mon Sep 17 00:00:00 2001 From: "kaf24@firebug.cl.cam.ac.uk" Date: Sat, 8 Oct 2005 09:49:28 +0100 Subject: [PATCH] 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 Signed-off-by: Roland McGrath --- .../arch/xen/i386/kernel/Makefile | 2 +- .../arch/xen/i386/kernel/vsyscall-note.S | 32 +++++++++++++++++++ 2 files changed, 33 insertions(+), 1 deletion(-) create mode 100644 linux-2.6-xen-sparse/arch/xen/i386/kernel/vsyscall-note.S diff --git a/linux-2.6-xen-sparse/arch/xen/i386/kernel/Makefile b/linux-2.6-xen-sparse/arch/xen/i386/kernel/Makefile index 8f73398b41..a5bc95512f 100644 --- a/linux-2.6-xen-sparse/arch/xen/i386/kernel/Makefile +++ b/linux-2.6-xen-sparse/arch/xen/i386/kernel/Makefile @@ -86,7 +86,7 @@ $(obj)/vsyscall-syms.o: $(src)/vsyscall.lds \ $(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 --git a/linux-2.6-xen-sparse/arch/xen/i386/kernel/vsyscall-note.S b/linux-2.6-xen-sparse/arch/xen/i386/kernel/vsyscall-note.S new file mode 100644 index 0000000000..cdb81edf74 --- /dev/null +++ b/linux-2.6-xen-sparse/arch/xen/i386/kernel/vsyscall-note.S @@ -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 -- 2.30.2