Messages in this thread | | | Subject | Re: [PATCH v1 1/1] Add support for mm->mmap_legacy_base in legacy layout | From | Alex Ghiti <> | Date | Sun, 10 Oct 2021 17:33:22 +0200 |
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Hi Jinli,
Le 27/09/2021 à 13:11, Jinli Zheng a écrit : > Add support for mm->mmap_legacy_base in the legacy layout > of the process memory space for the riscv architecture >
Can you elaborate a bit more? What value does it bring? I remember I had spent some time to factorize this code with arm64 to offer ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT config and I had another patchset to get rid of mmap_legacy_base entirely at https://lkml.org/lkml/2019/6/19/18 (which never got merged though).
Thanks,
Alex
> Signed-off-by: Jinli Zheng <zhengdbu@gmail.com> > --- > arch/riscv/Kconfig | 2 +- > arch/riscv/include/asm/pgtable.h | 3 + > arch/riscv/include/asm/processor.h | 1 + > arch/riscv/mm/Makefile | 2 +- > arch/riscv/mm/mmap.c | 165 +++++++++++++++++++++++++++++ > 5 files changed, 171 insertions(+), 2 deletions(-) > create mode 100644 arch/riscv/mm/mmap.c > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > index 301a54233c7e..e64231592227 100644 > --- a/arch/riscv/Kconfig > +++ b/arch/riscv/Kconfig > @@ -37,7 +37,7 @@ config RISCV > select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU > select ARCH_SUPPORTS_HUGETLBFS if MMU > select ARCH_USE_MEMTEST > - select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU > + select ARCH_HAS_ELF_RANDOMIZE > select ARCH_WANT_FRAME_POINTERS > select ARCH_WANT_HUGE_PMD_SHARE if 64BIT > select BINFMT_FLAT_NO_DATA_START_OFFSET if !MMU > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h > index 39b550310ec6..107d61371272 100644 > --- a/arch/riscv/include/asm/pgtable.h > +++ b/arch/riscv/include/asm/pgtable.h > @@ -700,6 +700,9 @@ void misc_mem_init(void); > extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]; > #define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page)) > > +#define HAVE_ARCH_UNMAPPED_AREA > +#define HAVE_ARCH_UNMAPPED_AREA_TOPDOWN > + > #endif /* !__ASSEMBLY__ */ > > #endif /* _ASM_RISCV_PGTABLE_H */ > diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h > index 46b492c78cbb..e7dc7c1f820a 100644 > --- a/arch/riscv/include/asm/processor.h > +++ b/arch/riscv/include/asm/processor.h > @@ -56,6 +56,7 @@ static inline void arch_thread_struct_whitelist(unsigned long *offset, > #define KSTK_EIP(tsk) (task_pt_regs(tsk)->epc) > #define KSTK_ESP(tsk) (task_pt_regs(tsk)->sp) > > +#define HAVE_ARCH_PICK_MMAP_LAYOUT 1 > > /* Do necessary setup to start up a newly executed thread. */ > extern void start_thread(struct pt_regs *regs, > diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile > index 7ebaef10ea1b..123c67a2c24a 100644 > --- a/arch/riscv/mm/Makefile > +++ b/arch/riscv/mm/Makefile > @@ -10,7 +10,7 @@ KCOV_INSTRUMENT_init.o := n > > obj-y += init.o > obj-y += extable.o > -obj-$(CONFIG_MMU) += fault.o pageattr.o > +obj-$(CONFIG_MMU) += fault.o pageattr.o mmap.o > obj-y += cacheflush.o > obj-y += context.o > > diff --git a/arch/riscv/mm/mmap.c b/arch/riscv/mm/mmap.c > new file mode 100644 > index 000000000000..6c5818db5a65 > --- /dev/null > +++ b/arch/riscv/mm/mmap.c > @@ -0,0 +1,165 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Legacy and flexible mmap layout support > + * > + * Copyright (C) 2021 Jinli Zheng <zhengdbu@gmail.com> > + */ > + > +#include <linux/personality.h> > +#include <linux/mm.h> > +#include <linux/mman.h> > +#include <linux/random.h> > +#include <linux/limits.h> > +#include <linux/security.h> > +#include <linux/compat.h> > +#include <linux/sched/mm.h> > +#include <linux/sched.h> > +#include <linux/elf-randomize.h> > +#include <asm/pgtable.h> > +#include <asm/processor.h> > + > +#define SIZE_128M (128*1024*1024UL) > + > +/*gap between MMAP and STACK*/ > +#define GAP_MIN SIZE_128M > +#define GAP_MAX (((TASK_SIZE)/6)*5) > + > +static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack) > +{ > + unsigned long gap = rlim_stack->rlim_cur; > + > + if (gap < GAP_MIN) > + gap = GAP_MIN; > + else if (gap > GAP_MAX) > + gap = GAP_MAX; > + > + return PAGE_ALIGN(TASK_SIZE - gap - rnd); > +} > + > +unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, > + unsigned long len, unsigned long pgoff, unsigned long flags) > +{ > + struct mm_struct *mm = current->mm; > + struct vm_area_struct *vma, *prev; > + struct vm_unmapped_area_info info; > + > + if (len > TASK_SIZE) > + return -ENOMEM; > + > + if (flags & MAP_FIXED) > + return addr; > + > + if (addr) { > + addr = PAGE_ALIGN(addr); > + vma = find_vma_prev(mm, addr, &prev); > + if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && > + (!vma || addr + len <= vm_start_gap(vma)) && > + (!prev || addr >= vm_end_gap(prev))) > + return addr; > + } > + > + info.flags = 0; > + info.length = len; > + info.low_limit = mm->mmap_legacy_base; > + info.high_limit = TASK_SIZE; > + info.align_mask = 0; > + info.align_offset = 0; > + return vm_unmapped_area(&info); > +} > + > +unsigned long arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr, > + unsigned long len, unsigned long pgoff, unsigned long flags) > +{ > + struct mm_struct *mm = current->mm; > + struct vm_area_struct *vma, *prev; > + struct vm_unmapped_area_info info; > + > + if (len > TASK_SIZE) > + return -ENOMEM; > + > + if (flags & MAP_FIXED) > + return addr; > + > + if (addr) { > + addr = PAGE_ALIGN(addr); > + vma = find_vma_prev(mm, addr, &prev); > + if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && > + (!vma || addr + len <= vm_start_gap(vma)) && > + (!prev || addr >= vm_end_gap(prev))) > + return addr; > + } > + > + info.flags = VM_UNMAPPED_AREA_TOPDOWN; > + info.length = len; > + info.low_limit = max(PAGE_SIZE, mmap_min_addr); > + info.high_limit = mm->mmap_base; > + info.align_mask = 0; > + info.align_offset = 0; > + addr = vm_unmapped_area(&info); > + > + if (offset_in_page(addr)) { > + VM_BUG_ON(addr != -ENOMEM); > + info.flags = 0; > + info.low_limit = TASK_UNMAPPED_BASE; > + info.high_limit = TASK_SIZE; > + addr = vm_unmapped_area(&info); > + } > + > + return addr; > +} > + > +unsigned long arch_mmap_rnd(void) > +{ > + unsigned long rnd; > + > +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS > + if (is_compat_task()) > + rnd = get_random_int() & ((1UL << mmap_rnd_compat_bits) - 1); > + else > +#endif /*CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS*/ > + rnd = get_random_int() & ((1UL << mmap_rnd_bits) - 1); > + > + return rnd << PAGE_SHIFT; > +} > + > +static int mmap_is_legacy(struct rlimit *rlim_stack) > +{ > + if (current->personality & ADDR_COMPAT_LAYOUT) > + return 1; > + > + if (rlim_stack->rlim_cur == RLIM_INFINITY) > + return 1; > + > + return sysctl_legacy_va_layout; > +} > + > +static void arch_pick_mmap_base(struct mm_struct *mm, struct rlimit *rlim_stack) > +{ > + unsigned long random; > + > + random = (current->flags & PF_RANDOMIZE) ? > + arch_mmap_rnd() : 0UL; > + > + if (mmap_is_legacy(rlim_stack)) > + mm->mmap_legacy_base = TASK_UNMAPPED_BASE + random; > + else > + mm->mmap_base = mmap_base(random, rlim_stack); > +} > + > +void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) > +{ > + if (mmap_is_legacy(rlim_stack)) > + mm->get_unmapped_area = arch_get_unmapped_area; > + else > + mm->get_unmapped_area = arch_get_unmapped_area_topdown; > + > + arch_pick_mmap_base(mm, rlim_stack); > +} > + > +unsigned long arch_randomize_brk(struct mm_struct *mm) > +{ > + if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task()) > + return randomize_page(mm->brk, SZ_32M); > + > + return randomize_page(mm->brk, SZ_1G); > +} >
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