lkml.org 
[lkml]   [2021]   [Nov]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2 9/9] powerpc: Simplify and move arch_randomize_brk()
Date
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>
---
v2: New
---
arch/powerpc/kernel/process.c | 40 ---------------------------
arch/powerpc/mm/book3s64/hash_utils.c | 18 ++++++++++++
include/linux/sizes.h | 2 ++
3 files changed, 20 insertions(+), 40 deletions(-)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 406d7ee9e322..f1f2f17543d6 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -2274,43 +2274,3 @@ 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. We don't need to worry about radix. For
- * radix, mmu_highuser_ssize remains unchanged from 256MB.
- */
- if (!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 1d09d4aeddbf..3521fad6a479 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -37,6 +37,7 @@
#include <linux/cpu.h>
#include <linux/pgtable.h>
#include <linux/debugfs.h>
+#include <linux/random.h>

#include <asm/interrupt.h>
#include <asm/processor.h>
@@ -2072,3 +2073,20 @@ 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);
+}
diff --git a/include/linux/sizes.h b/include/linux/sizes.h
index 1ac79bcee2bb..84aa448d8bb3 100644
--- a/include/linux/sizes.h
+++ b/include/linux/sizes.h
@@ -47,6 +47,8 @@
#define SZ_8G _AC(0x200000000, ULL)
#define SZ_16G _AC(0x400000000, ULL)
#define SZ_32G _AC(0x800000000, ULL)
+
+#define SZ_1T _AC(0x10000000000, ULL)
#define SZ_64T _AC(0x400000000000, ULL)

#endif /* __LINUX_SIZES_H__ */
--
2.33.1
\
 
 \ /
  Last update: 2021-11-25 09:41    [W:0.174 / U:3.348 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site