Commit 8a8f7866 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/vdso: Don't map VDSO at a fixed address on PPC32 



PPC64 removed default mapping address from VDSO in
commit 30d0b368 ("powerpc: Move 64bit VDSO to improve context
switch performance").

Do like PPC64 and let get_unmapped_area() place the VDSO mapping
at the address it wants, don't force a default address.

This allows randomisation of VDSO address.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/cba76f5a5b01fcc49415e632d92c11c1c5998cab.1660843877.git.christophe.leroy@csgroup.eu
parent c814bf95

arch/powerpc/include/asm/vdso.h

+0 −3
Original line number Diff line number Diff line
@@ -2,9 +2,6 @@ 
#ifndef _ASM_POWERPC_VDSO_H

#define _ASM_POWERPC_VDSO_H



/* Default map addresses for 32bit vDSO */

#define VDSO32_MBASE	0x100000



#define VDSO_VERSION_STRING	LINUX_2.6.15



#ifndef __ASSEMBLY__

arch/powerpc/kernel/vdso.c

+2 −11
Original line number Diff line number Diff line
@@ -200,28 +200,19 @@ static int __arch_setup_additional_pages(struct linux_binprm *bprm, int uses_int 
	if (is_32bit_task()) {

		vdso_spec = &vdso32_spec;

		vdso_size = &vdso32_end - &vdso32_start;

		vdso_base = VDSO32_MBASE;

	} else {

		vdso_spec = &vdso64_spec;

		vdso_size = &vdso64_end - &vdso64_start;

		/*

		 * On 64bit we don't have a preferred map address. This

		 * allows get_unmapped_area to find an area near other mmaps

		 * and most likely share a SLB entry.

		 */

		vdso_base = 0;

	}



	mappings_size = vdso_size + vvar_size;

	mappings_size += (VDSO_ALIGNMENT - 1) & PAGE_MASK;



	/*

	 * pick a base address for the vDSO in process space. We try to put it

	 * at vdso_base which is the "natural" base for it, but we might fail

	 * and end up putting it elsewhere.

	 * Pick a base address for the vDSO in process space.

	 * Add enough to the size so that the result can be aligned.

	 */

	vdso_base = get_unmapped_area(NULL, vdso_base, mappings_size, 0, 0);

	vdso_base = get_unmapped_area(NULL, 0, mappings_size, 0, 0);

	if (IS_ERR_VALUE(vdso_base))

		return vdso_base;