Messages in this thread | | | Date | Thu, 25 Nov 2021 11:42:35 +0100 | Subject | Re: [PATCH v2 9/9] powerpc: Simplify and move arch_randomize_brk() | From | Christophe Leroy <> |
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Le 25/11/2021 à 09:23, Christophe Leroy a écrit : > 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>
Also need <linux/elf-randomize.h> to get the declaration of arch_randomize_brk() and make sparse happy :)
Michael can you add it if you apply this version ?
Thanks
> > #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__ */ >
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