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Commit b0b49f26 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by H. Peter Anvin
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x86, vdso: Remove compat vdso support 



The compat vDSO is a complicated hack that's needed to maintain
compatibility with a small range of glibc versions.

This removes it and replaces it with a much simpler hack: a config
option to disable the 32-bit vDSO by default.

This also changes the default value of CONFIG_COMPAT_VDSO to n --
users configuring kernels from scratch almost certainly want that
choice.

Signed-off-by: default avatarAndy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/4bb4690899106eb11430b1186d5cc66ca9d1660c.1394751608.git.luto@amacapital.net


Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent fa389e22

Documentation/kernel-parameters.txt

+16 −6
Original line number Original line Diff line number Diff line
@@ -3409,14 +3409,24 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
					of CONFIG_HIGHPTE.

					of CONFIG_HIGHPTE.





	vdso=		[X86,SH]

	vdso=		[X86,SH]

			vdso=2: enable compat VDSO (default with COMPAT_VDSO)

			On X86_32, this is an alias for vdso32=.  Otherwise:

			vdso=1: enable VDSO (default)



			vdso=1: enable VDSO (the default)

			vdso=0: disable VDSO mapping

			vdso=0: disable VDSO mapping





	vdso32=		[X86]

	vdso32=		[X86] Control the 32-bit vDSO

			vdso32=2: enable compat VDSO (default with COMPAT_VDSO)

			vdso32=1: enable 32-bit VDSO

			vdso32=1: enable 32-bit VDSO (default)

			vdso32=0 or vdso32=2: disable 32-bit VDSO

			vdso32=0: disable 32-bit VDSO mapping



			See the help text for CONFIG_COMPAT_VDSO for more

			details.  If CONFIG_COMPAT_VDSO is set, the default is

			vdso32=0; otherwise, the default is vdso32=1.



			For compatibility with older kernels, vdso32=2 is an

			alias for vdso32=0.



			Try vdso32=0 if you encounter an error that says:

			dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!





	vector=		[IA-64,SMP]

	vector=		[IA-64,SMP]

			vector=percpu: enable percpu vector domain

			vector=percpu: enable percpu vector domain

arch/x86/Kconfig

+19 −7
Original line number Original line Diff line number Diff line
@@ -1836,17 +1836,29 @@ config DEBUG_HOTPLUG_CPU0 
	  If unsure, say N.

	  If unsure, say N.





config COMPAT_VDSO

config COMPAT_VDSO

	def_bool y

	def_bool n

	prompt "Compat VDSO support"

	prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"

	depends on X86_32 || IA32_EMULATION

	depends on X86_32 || IA32_EMULATION

	---help---

	---help---

	  Map the 32-bit VDSO to the predictable old-style address too.

	  Certain buggy versions of glibc will crash if they are

	  presented with a 32-bit vDSO that is not mapped at the address

	  indicated in its segment table.





	  Say N here if you are running a sufficiently recent glibc

	  The bug was introduced by f866314b89d56845f55e6f365e18b31ec978ec3a

	  version (2.3.3 or later), to remove the high-mapped

	  and fixed by 3b3ddb4f7db98ec9e912ccdf54d35df4aa30e04a and

	  VDSO mapping and to exclusively use the randomized VDSO.

	  49ad572a70b8aeb91e57483a11dd1b77e31c4468.  Glibc 2.3.3 is

	  the only released version with the bug, but OpenSUSE 9

	  contains a buggy "glibc 2.3.2".





	  If unsure, say Y.

	  The symptom of the bug is that everything crashes on startup, saying:

	  dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!



	  Saying Y here changes the default value of the vdso32 boot

	  option from 1 to 0, which turns off the 32-bit vDSO entirely.

	  This works around the glibc bug but hurts performance.



	  If unsure, say N: if you are compiling your own kernel, you

	  are unlikely to be using a buggy version of glibc.





config CMDLINE_BOOL

config CMDLINE_BOOL

	bool "Built-in kernel command line"

	bool "Built-in kernel command line"

arch/x86/include/asm/elf.h

+0 −4
Original line number Original line Diff line number Diff line
@@ -281,16 +281,12 @@ do { \ 




#define STACK_RND_MASK (0x7ff)

#define STACK_RND_MASK (0x7ff)





#define VDSO_HIGH_BASE		(__fix_to_virt(FIX_VDSO))



#define ARCH_DLINFO		ARCH_DLINFO_IA32(vdso_enabled)

#define ARCH_DLINFO		ARCH_DLINFO_IA32(vdso_enabled)





/* update AT_VECTOR_SIZE_ARCH if the number of NEW_AUX_ENT entries changes */

/* update AT_VECTOR_SIZE_ARCH if the number of NEW_AUX_ENT entries changes */





#else /* CONFIG_X86_32 */

#else /* CONFIG_X86_32 */





#define VDSO_HIGH_BASE		0xffffe000U /* CONFIG_COMPAT_VDSO address */



/* 1GB for 64bit, 8MB for 32bit */

/* 1GB for 64bit, 8MB for 32bit */

#define STACK_RND_MASK (test_thread_flag(TIF_ADDR32) ? 0x7ff : 0x3fffff)

#define STACK_RND_MASK (test_thread_flag(TIF_ADDR32) ? 0x7ff : 0x3fffff)

arch/x86/include/asm/fixmap.h

+0 −8
Original line number Original line Diff line number Diff line
@@ -40,15 +40,8 @@ 
 */

 */

extern unsigned long __FIXADDR_TOP;

extern unsigned long __FIXADDR_TOP;

#define FIXADDR_TOP	((unsigned long)__FIXADDR_TOP)

#define FIXADDR_TOP	((unsigned long)__FIXADDR_TOP)



#define FIXADDR_USER_START     __fix_to_virt(FIX_VDSO)

#define FIXADDR_USER_END       __fix_to_virt(FIX_VDSO - 1)

#else

#else

#define FIXADDR_TOP	(VSYSCALL_END-PAGE_SIZE)

#define FIXADDR_TOP	(VSYSCALL_END-PAGE_SIZE)



/* Only covers 32bit vsyscalls currently. Need another set for 64bit. */

#define FIXADDR_USER_START	((unsigned long)VSYSCALL32_VSYSCALL)

#define FIXADDR_USER_END	(FIXADDR_USER_START + PAGE_SIZE)

#endif

#endif
@@ -74,7 +67,6 @@ extern unsigned long __FIXADDR_TOP; 
enum fixed_addresses {

enum fixed_addresses {

#ifdef CONFIG_X86_32

#ifdef CONFIG_X86_32

	FIX_HOLE,

	FIX_HOLE,

	FIX_VDSO,

#else

#else

	VSYSCALL_LAST_PAGE,

	VSYSCALL_LAST_PAGE,

	VSYSCALL_FIRST_PAGE = VSYSCALL_LAST_PAGE

	VSYSCALL_FIRST_PAGE = VSYSCALL_LAST_PAGE

arch/x86/include/asm/vdso.h

+1 −4
Original line number Original line Diff line number Diff line
@@ -2,8 +2,6 @@ 
#define _ASM_X86_VDSO_H

#define _ASM_X86_VDSO_H





#if defined CONFIG_X86_32 || defined CONFIG_COMPAT

#if defined CONFIG_X86_32 || defined CONFIG_COMPAT

extern const char VDSO32_PRELINK[];



/*

/*

 * Given a pointer to the vDSO image, find the pointer to VDSO32_name

 * Given a pointer to the vDSO image, find the pointer to VDSO32_name

 * as that symbol is defined in the vDSO sources or linker script.

 * as that symbol is defined in the vDSO sources or linker script.
@@ -11,8 +9,7 @@ extern const char VDSO32_PRELINK[]; 
#define VDSO32_SYMBOL(base, name)					\

#define VDSO32_SYMBOL(base, name)					\

({									\

({									\

	extern const char VDSO32_##name[];				\

	extern const char VDSO32_##name[];				\

	(void __user *)(VDSO32_##name - VDSO32_PRELINK +		\

	(void __user *)(VDSO32_##name + (unsigned long)(base));		\

			(unsigned long)(base));				\

})

})

#endif

#endif