powerpc: Simplify and move arch_randomize_brk()

arch_randomize_brk() is only needed for hash on book3s/64, for other
platforms the one provided by the default mmap layout is good enough.

Move it to hash_utils.c and use randomize_page() like the generic one.

And properly opt out the radix case instead of making an assumption
on mmu_highuser_ssize.

Also change to a 32M range like most other architectures instead of 8M.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/eafa4d18ec8ac7b98dd02b40181e61643707cc7c.1649523076.git.christophe.leroy@csgroup.eu

1 files changed, 0 insertions, 41 deletions

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 984813a4d5dc..e7f809bdd433 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -34,10 +34,8 @@
 #include <linux/ftrace.h>
 #include <linux/kernel_stat.h>
 #include <linux/personality.h>
-#include <linux/random.h>
 #include <linux/hw_breakpoint.h>
 #include <linux/uaccess.h>
-#include <linux/elf-randomize.h>
 #include <linux/pkeys.h>
 #include <linux/seq_buf.h>
 
@@ -2313,42 +2311,3 @@ unsigned long arch_align_stack(unsigned long sp)
 		sp -= get_random_int() & ~PAGE_MASK;
 	return sp & ~0xf;
 }
-
-static inline unsigned long brk_rnd(void)
-{
-        unsigned long rnd = 0;
-
-	/* 8MB for 32bit, 1GB for 64bit */
-	if (is_32bit_task())
-		rnd = (get_random_long() % (1UL<<(23-PAGE_SHIFT)));
-	else
-		rnd = (get_random_long() % (1UL<<(30-PAGE_SHIFT)));
-
-	return rnd << PAGE_SHIFT;
-}
-
-unsigned long arch_randomize_brk(struct mm_struct *mm)
-{
-	unsigned long base = mm->brk;
-	unsigned long ret;
-
-#ifdef CONFIG_PPC_BOOK3S_64
-	/*
-	 * If we are using 1TB segments and we are allowed to randomise
-	 * the heap, we can put it above 1TB so it is backed by a 1TB
-	 * segment. Otherwise the heap will be in the bottom 1TB
-	 * which always uses 256MB segments and this may result in a
-	 * performance penalty.
-	 */
-	if (!radix_enabled() && !is_32bit_task() && (mmu_highuser_ssize == MMU_SEGSIZE_1T))
-		base = max_t(unsigned long, mm->brk, 1UL << SID_SHIFT_1T);
-#endif
-
-	ret = PAGE_ALIGN(base + brk_rnd());
-
-	if (ret < mm->brk)
-		return mm->brk;
-
-	return ret;
-}
-