[PATCH v3 1/3] riscv: Move kernel mapping to vmalloc zone
Alex Ghiti
alex at ghiti.fr
Thu May 28 23:07:34 AEST 2020
Hi Zong,
Le 5/27/20 à 3:29 AM, Alex Ghiti a écrit :
> Le 5/27/20 à 2:05 AM, Zong Li a écrit :
>> On Wed, May 27, 2020 at 1:06 AM Alex Ghiti <alex at ghiti.fr> wrote:
>>> Hi Zong,
>>>
>>> Le 5/26/20 à 5:43 AM, Zong Li a écrit :
>>>> On Sun, May 24, 2020 at 4:54 PM Alexandre Ghiti <alex at ghiti.fr> wrote:
>>>>> This is a preparatory patch for relocatable kernel.
>>>>>
>>>>> The kernel used to be linked at PAGE_OFFSET address and used to be
>>>>> loaded
>>>>> physically at the beginning of the main memory. Therefore, we
>>>>> could use
>>>>> the linear mapping for the kernel mapping.
>>>>>
>>>>> But the relocated kernel base address will be different from
>>>>> PAGE_OFFSET
>>>>> and since in the linear mapping, two different virtual addresses
>>>>> cannot
>>>>> point to the same physical address, the kernel mapping needs to
>>>>> lie outside
>>>>> the linear mapping.
>>>>>
>>>>> In addition, because modules and BPF must be close to the kernel
>>>>> (inside
>>>>> +-2GB window), the kernel is placed at the end of the vmalloc zone
>>>>> minus
>>>>> 2GB, which leaves room for modules and BPF. The kernel could not be
>>>>> placed at the beginning of the vmalloc zone since other vmalloc
>>>>> allocations from the kernel could get all the +-2GB window around the
>>>>> kernel which would prevent new modules and BPF programs to be loaded.
>>>>>
>>>>> Signed-off-by: Alexandre Ghiti <alex at ghiti.fr>
>>>>> ---
>>>>> arch/riscv/boot/loader.lds.S | 3 +-
>>>>> arch/riscv/include/asm/page.h | 10 +++++-
>>>>> arch/riscv/include/asm/pgtable.h | 37 +++++++++++++-------
>>>>> arch/riscv/kernel/head.S | 3 +-
>>>>> arch/riscv/kernel/module.c | 4 +--
>>>>> arch/riscv/kernel/vmlinux.lds.S | 3 +-
>>>>> arch/riscv/mm/init.c | 58
>>>>> +++++++++++++++++++++++++-------
>>>>> arch/riscv/mm/physaddr.c | 2 +-
>>>>> 8 files changed, 87 insertions(+), 33 deletions(-)
>>>>>
>>>>> diff --git a/arch/riscv/boot/loader.lds.S
>>>>> b/arch/riscv/boot/loader.lds.S
>>>>> index 47a5003c2e28..62d94696a19c 100644
>>>>> --- a/arch/riscv/boot/loader.lds.S
>>>>> +++ b/arch/riscv/boot/loader.lds.S
>>>>> @@ -1,13 +1,14 @@
>>>>> /* SPDX-License-Identifier: GPL-2.0 */
>>>>>
>>>>> #include <asm/page.h>
>>>>> +#include <asm/pgtable.h>
>>>>>
>>>>> OUTPUT_ARCH(riscv)
>>>>> ENTRY(_start)
>>>>>
>>>>> SECTIONS
>>>>> {
>>>>> - . = PAGE_OFFSET;
>>>>> + . = KERNEL_LINK_ADDR;
>>>>>
>>>>> .payload : {
>>>>> *(.payload)
>>>>> diff --git a/arch/riscv/include/asm/page.h
>>>>> b/arch/riscv/include/asm/page.h
>>>>> index 2d50f76efe48..48bb09b6a9b7 100644
>>>>> --- a/arch/riscv/include/asm/page.h
>>>>> +++ b/arch/riscv/include/asm/page.h
>>>>> @@ -90,18 +90,26 @@ typedef struct page *pgtable_t;
>>>>>
>>>>> #ifdef CONFIG_MMU
>>>>> extern unsigned long va_pa_offset;
>>>>> +extern unsigned long va_kernel_pa_offset;
>>>>> extern unsigned long pfn_base;
>>>>> #define ARCH_PFN_OFFSET (pfn_base)
>>>>> #else
>>>>> #define va_pa_offset 0
>>>>> +#define va_kernel_pa_offset 0
>>>>> #define ARCH_PFN_OFFSET (PAGE_OFFSET >> PAGE_SHIFT)
>>>>> #endif /* CONFIG_MMU */
>>>>>
>>>>> extern unsigned long max_low_pfn;
>>>>> extern unsigned long min_low_pfn;
>>>>> +extern unsigned long kernel_virt_addr;
>>>>>
>>>>> #define __pa_to_va_nodebug(x) ((void *)((unsigned long) (x) +
>>>>> va_pa_offset))
>>>>> -#define __va_to_pa_nodebug(x) ((unsigned long)(x) - va_pa_offset)
>>>>> +#define linear_mapping_va_to_pa(x) ((unsigned long)(x) -
>>>>> va_pa_offset)
>>>>> +#define kernel_mapping_va_to_pa(x) \
>>>>> + ((unsigned long)(x) - va_kernel_pa_offset)
>>>>> +#define __va_to_pa_nodebug(x) \
>>>>> + (((x) >= PAGE_OFFSET) ? \
>>>>> + linear_mapping_va_to_pa(x) :
>>>>> kernel_mapping_va_to_pa(x))
>>>>>
>>>>> #ifdef CONFIG_DEBUG_VIRTUAL
>>>>> extern phys_addr_t __virt_to_phys(unsigned long x);
>>>>> diff --git a/arch/riscv/include/asm/pgtable.h
>>>>> b/arch/riscv/include/asm/pgtable.h
>>>>> index 35b60035b6b0..25213cfaf680 100644
>>>>> --- a/arch/riscv/include/asm/pgtable.h
>>>>> +++ b/arch/riscv/include/asm/pgtable.h
>>>>> @@ -11,23 +11,29 @@
>>>>>
>>>>> #include <asm/pgtable-bits.h>
>>>>>
>>>>> -#ifndef __ASSEMBLY__
>>>>> -
>>>>> -/* Page Upper Directory not used in RISC-V */
>>>>> -#include <asm-generic/pgtable-nopud.h>
>>>>> -#include <asm/page.h>
>>>>> -#include <asm/tlbflush.h>
>>>>> -#include <linux/mm_types.h>
>>>>> -
>>>>> -#ifdef CONFIG_MMU
>>>>> +#ifndef CONFIG_MMU
>>>>> +#define KERNEL_VIRT_ADDR PAGE_OFFSET
>>>>> +#define KERNEL_LINK_ADDR PAGE_OFFSET
>>>>> +#else
>>>>> +/*
>>>>> + * Leave 2GB for modules and BPF that must lie within a 2GB range
>>>>> around
>>>>> + * the kernel.
>>>>> + */
>>>>> +#define KERNEL_VIRT_ADDR (VMALLOC_END - SZ_2G + 1)
>>>>> +#define KERNEL_LINK_ADDR KERNEL_VIRT_ADDR
>>>>>
>>>>> #define VMALLOC_SIZE (KERN_VIRT_SIZE >> 1)
>>>>> #define VMALLOC_END (PAGE_OFFSET - 1)
>>>>> #define VMALLOC_START (PAGE_OFFSET - VMALLOC_SIZE)
>>>>>
>>>>> #define BPF_JIT_REGION_SIZE (SZ_128M)
>>>>> -#define BPF_JIT_REGION_START (PAGE_OFFSET - BPF_JIT_REGION_SIZE)
>>>>> -#define BPF_JIT_REGION_END (VMALLOC_END)
>>>>> +#define BPF_JIT_REGION_START (kernel_virt_addr)
>>>>> +#define BPF_JIT_REGION_END (kernel_virt_addr +
>>>>> BPF_JIT_REGION_SIZE)
>>>> It seems to have a potential risk here, the region of bpf is
>>>> overlapping with kernel mapping, so if kernel size is bigger than
>>>> 128MB, bpf region would be occupied and run out by kernel mapping.
>> Is there the risk as I mentioned?
>
>
> Sorry I forgot to answer this one: I was confident that 128MB was
> large enough for kernel
> and BPF. But I see no reason to leave this risk so I'll change
> kernel_virt_addr for _end so
> BPF will have its 128MB reserved.
>
> Thanks !
>
> Alex
>
>
>>
>>>>> +
>>>>> +#ifdef CONFIG_64BIT
>>>>> +#define VMALLOC_MODULE_START BPF_JIT_REGION_END
>>>>> +#define VMALLOC_MODULE_END VMALLOC_END
>>>>> +#endif
>>>>>
>>>> Although kernel_virt_addr is a fixed address now, I think it could be
>>>> changed for the purpose of relocatable or KASLR, so if
>>>> kernel_virt_addr is moved to far from VMALLOC_END than 2G, the region
>>>> of module would be too big.
>>>
>>> Yes you're right, that's wrong to allow modules to lie outside
>>> the 2G window, thanks for noticing.
>>>
>>>
>>>> In addition, the region of module could be
>>>> +-2G around the kernel, so we don't be limited in one direction as
>>>> before. It seems to me that the region of the module could be decided
>>>> at runtime, for example, VMALLOC_MODULE_START is "&_end - 2G" and
>>>> VMLLOC_MODULE_END is "&_start + 2G".
>>>
>>> I had tried that, but as we need to make sure BPF region is different
>>> from the module's
>>> that makes the macro definitions really cumbersome. I'll give a try
>>> again anyway. And
>>> I tried to use _end and _start here but it failed, I have to debug
>>> this.
I gave more thought about that and it is actually not possible to use
the 2GB
before and after the kernel: modules can call exported functions from
each other,
so we need to make sure that the "distance" between 2 modules is at most
2GB.
And I assume BPF comes with the same restrictions with respect to
modules so the
kernel + BPF + modules must live in the same 2GB region.
I'll come with a v4 quickly,
Thanks,
Alex
>>>
>>>
>>>> I'm not sure whether the size of
>>>> region of bpf has to be 128MB for some particular reason, if not,
>>>> maybe the region of bpf could be the same with module to avoid being
>>>> run out by module.
>>>
>>> On the contrary, BPF region must not be the same as module's since in
>>> that case,
>>> modules could take all the space and make BPF fail.
>> ok, I got it. Thanks for the explaining.
>>
>>
>>>
>>> Thanks for your review Zong,
>>>
>>>
>>> Alex
>>>
>>>
>>>>> /*
>>>>> * Roughly size the vmemmap space to be large enough to fit enough
>>>>> @@ -57,9 +63,16 @@
>>>>> #define FIXADDR_SIZE PGDIR_SIZE
>>>>> #endif
>>>>> #define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
>>>>> -
>>>>> #endif
>>>>>
>>>>> +#ifndef __ASSEMBLY__
>>>>> +
>>>>> +/* Page Upper Directory not used in RISC-V */
>>>>> +#include <asm-generic/pgtable-nopud.h>
>>>>> +#include <asm/page.h>
>>>>> +#include <asm/tlbflush.h>
>>>>> +#include <linux/mm_types.h>
>>>>> +
>>>>> #ifdef CONFIG_64BIT
>>>>> #include <asm/pgtable-64.h>
>>>>> #else
>>>>> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
>>>>> index 98a406474e7d..8f5bb7731327 100644
>>>>> --- a/arch/riscv/kernel/head.S
>>>>> +++ b/arch/riscv/kernel/head.S
>>>>> @@ -49,7 +49,8 @@ ENTRY(_start)
>>>>> #ifdef CONFIG_MMU
>>>>> relocate:
>>>>> /* Relocate return address */
>>>>> - li a1, PAGE_OFFSET
>>>>> + la a1, kernel_virt_addr
>>>>> + REG_L a1, 0(a1)
>>>>> la a2, _start
>>>>> sub a1, a1, a2
>>>>> add ra, ra, a1
>>>>> diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
>>>>> index 8bbe5dbe1341..1a8fbe05accf 100644
>>>>> --- a/arch/riscv/kernel/module.c
>>>>> +++ b/arch/riscv/kernel/module.c
>>>>> @@ -392,12 +392,10 @@ int apply_relocate_add(Elf_Shdr *sechdrs,
>>>>> const char *strtab,
>>>>> }
>>>>>
>>>>> #if defined(CONFIG_MMU) && defined(CONFIG_64BIT)
>>>>> -#define VMALLOC_MODULE_START \
>>>>> - max(PFN_ALIGN((unsigned long)&_end - SZ_2G), VMALLOC_START)
>>>>> void *module_alloc(unsigned long size)
>>>>> {
>>>>> return __vmalloc_node_range(size, 1, VMALLOC_MODULE_START,
>>>>> - VMALLOC_END, GFP_KERNEL,
>>>>> + VMALLOC_MODULE_END, GFP_KERNEL,
>>>>> PAGE_KERNEL_EXEC, 0,
>>>>> NUMA_NO_NODE,
>>>>> __builtin_return_address(0));
>>>>> }
>>>>> diff --git a/arch/riscv/kernel/vmlinux.lds.S
>>>>> b/arch/riscv/kernel/vmlinux.lds.S
>>>>> index 0339b6bbe11a..a9abde62909f 100644
>>>>> --- a/arch/riscv/kernel/vmlinux.lds.S
>>>>> +++ b/arch/riscv/kernel/vmlinux.lds.S
>>>>> @@ -4,7 +4,8 @@
>>>>> * Copyright (C) 2017 SiFive
>>>>> */
>>>>>
>>>>> -#define LOAD_OFFSET PAGE_OFFSET
>>>>> +#include <asm/pgtable.h>
>>>>> +#define LOAD_OFFSET KERNEL_LINK_ADDR
>>>>> #include <asm/vmlinux.lds.h>
>>>>> #include <asm/page.h>
>>>>> #include <asm/cache.h>
>>>>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>>>>> index 27a334106708..17f108baec4f 100644
>>>>> --- a/arch/riscv/mm/init.c
>>>>> +++ b/arch/riscv/mm/init.c
>>>>> @@ -22,6 +22,9 @@
>>>>>
>>>>> #include "../kernel/head.h"
>>>>>
>>>>> +unsigned long kernel_virt_addr = KERNEL_VIRT_ADDR;
>>>>> +EXPORT_SYMBOL(kernel_virt_addr);
>>>>> +
>>>>> unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
>>>>> __page_aligned_bss;
>>>>> EXPORT_SYMBOL(empty_zero_page);
>>>>> @@ -178,8 +181,12 @@ void __init setup_bootmem(void)
>>>>> }
>>>>>
>>>>> #ifdef CONFIG_MMU
>>>>> +/* Offset between linear mapping virtual address and kernel load
>>>>> address */
>>>>> unsigned long va_pa_offset;
>>>>> EXPORT_SYMBOL(va_pa_offset);
>>>>> +/* Offset between kernel mapping virtual address and kernel load
>>>>> address */
>>>>> +unsigned long va_kernel_pa_offset;
>>>>> +EXPORT_SYMBOL(va_kernel_pa_offset);
>>>>> unsigned long pfn_base;
>>>>> EXPORT_SYMBOL(pfn_base);
>>>>>
>>>>> @@ -271,7 +278,7 @@ static phys_addr_t __init alloc_pmd(uintptr_t va)
>>>>> if (mmu_enabled)
>>>>> return memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE);
>>>>>
>>>>> - pmd_num = (va - PAGE_OFFSET) >> PGDIR_SHIFT;
>>>>> + pmd_num = (va - kernel_virt_addr) >> PGDIR_SHIFT;
>>>>> BUG_ON(pmd_num >= NUM_EARLY_PMDS);
>>>>> return (uintptr_t)&early_pmd[pmd_num * PTRS_PER_PMD];
>>>>> }
>>>>> @@ -372,14 +379,30 @@ static uintptr_t __init
>>>>> best_map_size(phys_addr_t base, phys_addr_t size)
>>>>> #error "setup_vm() is called from head.S before relocate so it
>>>>> should not use absolute addressing."
>>>>> #endif
>>>>>
>>>>> +static uintptr_t load_pa, load_sz;
>>>>> +
>>>>> +void create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
>>>>> +{
>>>>> + uintptr_t va, end_va;
>>>>> +
>>>>> + end_va = kernel_virt_addr + load_sz;
>>>>> + for (va = kernel_virt_addr; va < end_va; va += map_size)
>>>>> + create_pgd_mapping(pgdir, va,
>>>>> + load_pa + (va - kernel_virt_addr),
>>>>> + map_size, PAGE_KERNEL_EXEC);
>>>>> +}
>>>>> +
>>>>> asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>>>> {
>>>>> uintptr_t va, end_va;
>>>>> - uintptr_t load_pa = (uintptr_t)(&_start);
>>>>> - uintptr_t load_sz = (uintptr_t)(&_end) - load_pa;
>>>>> uintptr_t map_size = best_map_size(load_pa,
>>>>> MAX_EARLY_MAPPING_SIZE);
>>>>>
>>>>> + load_pa = (uintptr_t)(&_start);
>>>>> + load_sz = (uintptr_t)(&_end) - load_pa;
>>>>> +
>>>>> va_pa_offset = PAGE_OFFSET - load_pa;
>>>>> + va_kernel_pa_offset = kernel_virt_addr - load_pa;
>>>>> +
>>>>> pfn_base = PFN_DOWN(load_pa);
>>>>>
>>>>> /*
>>>>> @@ -402,26 +425,22 @@ asmlinkage void __init setup_vm(uintptr_t
>>>>> dtb_pa)
>>>>> create_pmd_mapping(fixmap_pmd, FIXADDR_START,
>>>>> (uintptr_t)fixmap_pte, PMD_SIZE,
>>>>> PAGE_TABLE);
>>>>> /* Setup trampoline PGD and PMD */
>>>>> - create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET,
>>>>> + create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>>>>> (uintptr_t)trampoline_pmd,
>>>>> PGDIR_SIZE, PAGE_TABLE);
>>>>> - create_pmd_mapping(trampoline_pmd, PAGE_OFFSET,
>>>>> + create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
>>>>> load_pa, PMD_SIZE, PAGE_KERNEL_EXEC);
>>>>> #else
>>>>> /* Setup trampoline PGD */
>>>>> - create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET,
>>>>> + create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>>>>> load_pa, PGDIR_SIZE, PAGE_KERNEL_EXEC);
>>>>> #endif
>>>>>
>>>>> /*
>>>>> - * Setup early PGD covering entire kernel which will allows
>>>>> + * Setup early PGD covering entire kernel which will allow
>>>>> * us to reach paging_init(). We map all memory banks later
>>>>> * in setup_vm_final() below.
>>>>> */
>>>>> - end_va = PAGE_OFFSET + load_sz;
>>>>> - for (va = PAGE_OFFSET; va < end_va; va += map_size)
>>>>> - create_pgd_mapping(early_pg_dir, va,
>>>>> - load_pa + (va - PAGE_OFFSET),
>>>>> - map_size, PAGE_KERNEL_EXEC);
>>>>> + create_kernel_page_table(early_pg_dir, map_size);
>>>>>
>>>>> /* Create fixed mapping for early FDT parsing */
>>>>> end_va = __fix_to_virt(FIX_FDT) + FIX_FDT_SIZE;
>>>>> @@ -441,6 +460,7 @@ static void __init setup_vm_final(void)
>>>>> uintptr_t va, map_size;
>>>>> phys_addr_t pa, start, end;
>>>>> struct memblock_region *reg;
>>>>> + static struct vm_struct vm_kernel = { 0 };
>>>>>
>>>>> /* Set mmu_enabled flag */
>>>>> mmu_enabled = true;
>>>>> @@ -467,10 +487,22 @@ static void __init setup_vm_final(void)
>>>>> for (pa = start; pa < end; pa += map_size) {
>>>>> va = (uintptr_t)__va(pa);
>>>>> create_pgd_mapping(swapper_pg_dir, va, pa,
>>>>> - map_size,
>>>>> PAGE_KERNEL_EXEC);
>>>>> + map_size, PAGE_KERNEL);
>>>>> }
>>>>> }
>>>>>
>>>>> + /* Map the kernel */
>>>>> + create_kernel_page_table(swapper_pg_dir, PMD_SIZE);
>>>>> +
>>>>> + /* Reserve the vmalloc area occupied by the kernel */
>>>>> + vm_kernel.addr = (void *)kernel_virt_addr;
>>>>> + vm_kernel.phys_addr = load_pa;
>>>>> + vm_kernel.size = (load_sz + PMD_SIZE) & ~(PMD_SIZE - 1);
>>>>> + vm_kernel.flags = VM_MAP | VM_NO_GUARD;
>>>>> + vm_kernel.caller = __builtin_return_address(0);
>>>>> +
>>>>> + vm_area_add_early(&vm_kernel);
>>>>> +
>>>>> /* Clear fixmap PTE and PMD mappings */
>>>>> clear_fixmap(FIX_PTE);
>>>>> clear_fixmap(FIX_PMD);
>>>>> diff --git a/arch/riscv/mm/physaddr.c b/arch/riscv/mm/physaddr.c
>>>>> index e8e4dcd39fed..35703d5ef5fd 100644
>>>>> --- a/arch/riscv/mm/physaddr.c
>>>>> +++ b/arch/riscv/mm/physaddr.c
>>>>> @@ -23,7 +23,7 @@ EXPORT_SYMBOL(__virt_to_phys);
>>>>>
>>>>> phys_addr_t __phys_addr_symbol(unsigned long x)
>>>>> {
>>>>> - unsigned long kernel_start = (unsigned long)PAGE_OFFSET;
>>>>> + unsigned long kernel_start = (unsigned long)kernel_virt_addr;
>>>>> unsigned long kernel_end = (unsigned long)_end;
>>>>>
>>>>> /*
>>>>> --
>>>>> 2.20.1
>>>>>
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