Messages in this thread Patch in this message | | | Date | Sun, 01 Jul 2007 15:13:34 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: 2.6.22-rc6-mm1: Xen: WARNING: Absolute relocations present |
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Eric W. Biederman wrote: > Jeremy Fitzhardinge <jeremy@goop.org> writes: > > > >>>> Adrian Bunk wrote: >>>> >>>> >>>>> <-- snip --> >>>>> >>>>> ... >>>>> RELOCS arch/i386/boot/compressed/vmlinux.relocs >>>>> WARNING: Absolute relocations present >>>>> Offset Info Type Sym.Value Sym.Name >>>>> c0101f80 020c6501 R_386_32 00000000 xen_irq_disable_direct_reloc >>>>> c0101f9a 0221ea01 R_386_32 00000000 xen_save_fl_direct_reloc >>>>> > Actually I have to ask. How in the world are these absolute symbols > ok from a relocation perspective. > > If the kernel is not running at 0xc0100000 the offset value looks like > it will be completely bogus. >
Notice they're absolute 0.
> Maybe those are ok, but if you could please explain why those are > false positives I would appreciate it. (Especially in your patch > description). > > If these are indeed false positives the patch looks ok. >
Subject: xen: suppress abs symbol warnings for unused reloc pointers
arch/i386/xen/xen-asm.S defines some small pieces of code which are used to implement a few paravirt_ops. They're designed so they can be used either in-place, or be inline patched into their callsites if there's enough space.
Some of those operations need to make calls out (specifically, if you re-enable events [interrupts], and there's a pending event at that time). These calls need the call instruction to be relocated if the code is patched inline. In this case xen_foo_reloc is a section-relative symbol which points to xen_foo's required relocation.
Other operations have no need of a relocation, and so their corresponding xen_bar_reloc is absolute 0. These are the cases which are triggering the warning.
This patch adds those symbols to the list of safe abs symbols.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Cc: Adrian Bunk <bunk@stusta.de>
--- arch/i386/boot/compressed/relocs.c | 2 ++ 1 file changed, 2 insertions(+)
=================================================================== --- a/arch/i386/boot/compressed/relocs.c +++ b/arch/i386/boot/compressed/relocs.c @@ -31,6 +31,8 @@ static const char* safe_abs_relocs[] = { "__kernel_rt_sigreturn", "__kernel_sigreturn", "SYSENTER_RETURN", + "xen_irq_disable_direct_reloc", + "xen_save_fl_direct_reloc", }; static int is_safe_abs_reloc(const char* sym_name)
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