powerpc/vdso: Don't map VDSO at a fixed address on PPC32
PPC64 removed default mapping address from VDSO in
commit 30d0b3682887 ("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: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/cba76f5a5b01fcc49415e632d92c11c1c5998cab.1660843877.git.christophe.leroy@csgroup.eu
diff --git a/arch/powerpc/include/asm/vdso.h b/arch/powerpc/include/asm/vdso.h
index 8542e9b..7650b6c 100644
--- a/arch/powerpc/include/asm/vdso.h
+++ b/arch/powerpc/include/asm/vdso.h
@@ -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__
diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index 0da2875..bf9574e 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -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;
