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

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 984813a..e7f809b 100644 (file)
--- 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;
-}
-

diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
index 43ecad8..72a3eca 100644 (file)
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -37,6 +37,8 @@
 #include <linux/cpu.h>
 #include <linux/pgtable.h>
 #include <linux/debugfs.h>
+#include <linux/random.h>
+#include <linux/elf-randomize.h>
 
 #include <asm/interrupt.h>
 #include <asm/processor.h>
@@ -2133,3 +2135,20 @@ void __init print_system_hash_info(void)
        if (htab_hash_mask)
                pr_info("htab_hash_mask    = 0x%lx\n", htab_hash_mask);
 }
+
+unsigned long arch_randomize_brk(struct mm_struct *mm)
+{
+       /*
+        * 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 (is_32bit_task())
+               return randomize_page(mm->brk, SZ_32M);
+       else if (!radix_enabled() && mmu_highuser_ssize == MMU_SEGSIZE_1T)
+               return randomize_page(max_t(unsigned long, mm->brk, SZ_1T), SZ_1G);
+       else
+               return randomize_page(mm->brk, SZ_1G);
+}