Commit eeaaa96a authored Jun 06, 2012 by Don Zickus Committed by Ingo Molnar Jun 08, 2012

x86/nmi: Fix section mismatch warnings on 32-bit



It was reported that compiling for 32-bit caused a bunch of
section mismatch warnings:

 VDSOSYM arch/x86/vdso/vdso32-syms.lds
  LD      arch/x86/vdso/built-in.o
  LD      arch/x86/built-in.o

 WARNING: arch/x86/built-in.o(.data+0x5af0): Section mismatch in
 reference from the variable test_nmi_ipi_callback_na.10451 to
 the function .init.text:test_nmi_ipi_callback() [...]

 WARNING: arch/x86/built-in.o(.data+0x5b04): Section mismatch in
 reference from the variable nmi_unk_cb_na.10399 to the function
 .init.text:nmi_unk_cb() The variable nmi_unk_cb_na.10399
 references the function __init nmi_unk_cb() [...]

Both of these are attributed to the internal representation of
the nmiaction struct created during register_nmi_handler.  The
reason for this is that those structs are not defined in the
init section whereas the rest of the code in nmi_selftest.c is.

To resolve this, I created a new #define,
register_nmi_handler_initonly, that tags the struct as
__initdata to resolve the mismatch.  This #define should only be
used in rare situations where the register/unregister is called
during init of the kernel.

Big thanks to Jan Beulich for decoding this for me as I didn't
have a clue what was going on.

Reported-by: Witold Baryluk <baryluk@smp.if.uj.edu.pl>
Tested-by: Witold Baryluk <baryluk@smp.if.uj.edu.pl>
Cc: Jan Beulich <JBeulich@suse.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Link: http://lkml.kernel.org/r/1338991542-23000-1-git-send-email-dzickus@redhat.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent d5d2d2ee

arch/x86/include/asm/nmi.h

+14 −0

Original line number	Diff line number	Diff line
		@@ -54,6 +54,20 @@ struct nmiaction {
		__register_nmi_handler((t), &fn##_na); \
		})

		/*
		* For special handlers that register/unregister in the
		* init section only. This should be considered rare.
		*/
		#define register_nmi_handler_initonly(t, fn, fg, n) \
		({ \
		static struct nmiaction fn##_na __initdata = { \
		.handler = (fn), \
		.name = (n), \
		.flags = (fg), \
		}; \
		__register_nmi_handler((t), &fn##_na); \
		})

		int __register_nmi_handler(unsigned int, struct nmiaction *);

		void unregister_nmi_handler(unsigned int, const char *);

arch/x86/kernel/nmi_selftest.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -42,7 +42,7 @@ static int __init nmi_unk_cb(unsigned int val, struct pt_regs *regs)
		static void __init init_nmi_testsuite(void)
		{
		/* trap all the unknown NMIs we may generate */
		register_nmi_handler(NMI_UNKNOWN, nmi_unk_cb, 0, "nmi_selftest_unk");
		register_nmi_handler_initonly(NMI_UNKNOWN, nmi_unk_cb, 0, "nmi_selftest_unk");
		}

		static void __init cleanup_nmi_testsuite(void)
		@@ -64,7 +64,7 @@ static void __init test_nmi_ipi(struct cpumask *mask)
		{
		unsigned long timeout;

		if (register_nmi_handler(NMI_LOCAL, test_nmi_ipi_callback,
		if (register_nmi_handler_initonly(NMI_LOCAL, test_nmi_ipi_callback,
		NMI_FLAG_FIRST, "nmi_selftest")) {
		nmi_fail = FAILURE;
		return;