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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
This commit is contained in:
Christophe Leroy 2022-04-09 19:17:37 +02:00 committed by Michael Ellerman
parent 36e5f9ee77
commit 3ba4289a3e
2 changed files with 19 additions and 41 deletions
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41
arch/powerpc/kernel/process.c
View File

@ -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;
}

19
arch/powerpc/mm/book3s64/hash_utils.c
View File

@ -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);
}