Re: [PATCH v5 1/3] riscv: Move kernel mapping outside of linear mapping
From: Alex Ghiti
Date: Thu Apr 15 2021 - 14:00:35 EST
Le 4/15/21 à 12:54 AM, Alex Ghiti a écrit :
Le 4/15/21 à 12:20 AM, Palmer Dabbelt a écrit :
On Sun, 11 Apr 2021 09:41:44 PDT (-0700), alex@xxxxxxxx wrote:
This is a preparatory patch for relocatable kernel and sv48 support.
The kernel used to be linked at PAGE_OFFSET address 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 so that we
don't
have to copy it at the same physical offset.
The kernel mapping is moved to the last 2GB of the address space, BPF
is now always after the kernel and modules use the 2GB memory range
right
before the kernel, so BPF and modules regions do not overlap. KASLR
implementation will simply have to move the kernel in the last 2GB range
and just take care of leaving enough space for BPF.
In addition, by moving the kernel to the end of the address space, both
sv39 and sv48 kernels will be exactly the same without needing to be
relocated at runtime.
Suggested-by: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: Alexandre Ghiti <alex@xxxxxxxx>
---
arch/riscv/boot/loader.lds.S | 3 +-
arch/riscv/include/asm/page.h | 17 +++++-
arch/riscv/include/asm/pgtable.h | 37 ++++++++----
arch/riscv/include/asm/set_memory.h | 1 +
arch/riscv/kernel/head.S | 3 +-
arch/riscv/kernel/module.c | 6 +-
arch/riscv/kernel/setup.c | 5 ++
arch/riscv/kernel/vmlinux.lds.S | 3 +-
arch/riscv/mm/fault.c | 13 +++++
arch/riscv/mm/init.c | 87 ++++++++++++++++++++++-------
arch/riscv/mm/kasan_init.c | 9 +++
arch/riscv/mm/physaddr.c | 2 +-
12 files changed, 146 insertions(+), 40 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 adc9d26f3d75..22cfb2be60dc 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -90,15 +90,28 @@ 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 */
-#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)
+extern unsigned long kernel_virt_addr;
+
+#define linear_mapping_pa_to_va(x) ((void *)((unsigned long)(x) +
va_pa_offset))
+#define kernel_mapping_pa_to_va(x) ((void *)((unsigned long)(x) +
va_kernel_pa_offset))
+#define __pa_to_va_nodebug(x) linear_mapping_pa_to_va(x)
+
+#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) ({ \
+ unsigned long _x = x; \
+ (_x < kernel_virt_addr) ? \
+ 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 ebf817c1bdf4..80e63a93e903 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -11,23 +11,30 @@
#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>
+#ifndef CONFIG_MMU
+#define KERNEL_LINK_ADDR PAGE_OFFSET
+#else
-#ifdef CONFIG_MMU
+#define ADDRESS_SPACE_END (UL(-1))
+/*
+ * Leave 2GB for kernel and BPF at the end of the address space
+ */
+#define KERNEL_LINK_ADDR (ADDRESS_SPACE_END - SZ_2G + 1)
#define VMALLOC_SIZE (KERN_VIRT_SIZE >> 1)
#define VMALLOC_END (PAGE_OFFSET - 1)
#define VMALLOC_START (PAGE_OFFSET - VMALLOC_SIZE)
+/* KASLR should leave at least 128MB for BPF after the kernel */
#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 PFN_ALIGN((unsigned long)&_end)
+#define BPF_JIT_REGION_END (BPF_JIT_REGION_START +
BPF_JIT_REGION_SIZE)
+
+/* Modules always live before the kernel */
+#ifdef CONFIG_64BIT
+#define MODULES_VADDR (PFN_ALIGN((unsigned long)&_end) - SZ_2G)
+#define MODULES_END (PFN_ALIGN((unsigned long)&_start))
+#endif
/*
* Roughly size the vmemmap space to be large enough to fit enough
@@ -57,9 +64,16 @@
#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
@@ -484,6 +498,7 @@ static inline int ptep_clear_flush_young(struct
vm_area_struct *vma,
#define kern_addr_valid(addr) (1) /* FIXME */
+extern char _start[];
extern void *dtb_early_va;
extern uintptr_t dtb_early_pa;
void setup_bootmem(void);
diff --git a/arch/riscv/include/asm/set_memory.h
b/arch/riscv/include/asm/set_memory.h
index 6887b3d9f371..a9c56776fa0e 100644
--- a/arch/riscv/include/asm/set_memory.h
+++ b/arch/riscv/include/asm/set_memory.h
@@ -17,6 +17,7 @@ int set_memory_x(unsigned long addr, int numpages);
int set_memory_nx(unsigned long addr, int numpages);
int set_memory_rw_nx(unsigned long addr, int numpages);
void protect_kernel_text_data(void);
+void protect_kernel_linear_mapping_text_rodata(void);
#else
static inline int set_memory_ro(unsigned long addr, int numpages) {
return 0; }
static inline int set_memory_rw(unsigned long addr, int numpages) {
return 0; }
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index f5a9bad86e58..6cb05f22e52a 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -69,7 +69,8 @@ pe_head_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 104fba889cf7..ce153771e5e9 100644
--- a/arch/riscv/kernel/module.c
+++ b/arch/riscv/kernel/module.c
@@ -408,12 +408,10 @@ 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,
+ return __vmalloc_node_range(size, 1, MODULES_VADDR,
+ MODULES_END, GFP_KERNEL,
PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
__builtin_return_address(0));
}
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index e85bacff1b50..30e4af0fd50c 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -265,6 +265,11 @@ void __init setup_arch(char **cmdline_p)
if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
protect_kernel_text_data();
+
+#if defined(CONFIG_64BIT) && defined(CONFIG_MMU)
+ protect_kernel_linear_mapping_text_rodata();
+#endif
+
#ifdef CONFIG_SWIOTLB
swiotlb_init(1);
#endif
diff --git a/arch/riscv/kernel/vmlinux.lds.S
b/arch/riscv/kernel/vmlinux.lds.S
index de03cb22d0e9..0726c05e0336 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/fault.c b/arch/riscv/mm/fault.c
index 8f17519208c7..1b14d523a95c 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -231,6 +231,19 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
return;
}
+#ifdef CONFIG_64BIT
+ /*
+ * Modules in 64bit kernels lie in their own virtual region
which is not
+ * in the vmalloc region, but dealing with page faults in this
region
+ * or the vmalloc region amounts to doing the same thing:
checking that
+ * the mapping exists in init_mm.pgd and updating user page
table, so
+ * just use vmalloc_fault.
+ */
+ if (unlikely(addr >= MODULES_VADDR && addr < MODULES_END)) {
+ vmalloc_fault(regs, code, addr);
+ return;
+ }
+#endif
/* Enable interrupts if they were enabled in the parent context. */
if (likely(regs->status & SR_PIE))
local_irq_enable();
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 7f5036fbee8c..093f3a96ecfc 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -25,6 +25,9 @@
#include "../kernel/head.h"
+unsigned long kernel_virt_addr = KERNEL_LINK_ADDR;
+EXPORT_SYMBOL(kernel_virt_addr);
+
unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
__page_aligned_bss;
EXPORT_SYMBOL(empty_zero_page);
@@ -88,6 +91,8 @@ static void print_vm_layout(void)
(unsigned long)VMALLOC_END);
print_mlm("lowmem", (unsigned long)PAGE_OFFSET,
(unsigned long)high_memory);
+ print_mlm("kernel", (unsigned long)KERNEL_LINK_ADDR,
+ (unsigned long)ADDRESS_SPACE_END);
}
#else
static void print_vm_layout(void) { }
@@ -116,8 +121,13 @@ void __init setup_bootmem(void)
/* The maximal physical memory size is -PAGE_OFFSET. */
memblock_enforce_memory_limit(-PAGE_OFFSET);
- /* Reserve from the start of the kernel to the end of the kernel */
- memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);
+ /*
+ * Reserve from the start of the kernel to the end of the kernel
+ * and make sure we align the reservation on PMD_SIZE since we will
+ * map the kernel in the linear mapping as read-only: we do not
want
+ * any allocation to happen between _end and the next pmd
aligned page.
+ */
+ memblock_reserve(vmlinux_start, (vmlinux_end - vmlinux_start +
PMD_SIZE - 1) & PMD_MASK);
/*
* memblock allocator is not aware of the fact that last 4K
bytes of
@@ -152,8 +162,12 @@ void __init setup_bootmem(void)
#ifdef CONFIG_MMU
static struct pt_alloc_ops pt_ops;
+/* 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);
@@ -257,7 +271,7 @@ static pmd_t *get_pmd_virt_late(phys_addr_t pa)
static phys_addr_t __init alloc_pmd_early(uintptr_t va)
{
- BUG_ON((va - PAGE_OFFSET) >> PGDIR_SHIFT);
+ BUG_ON((va - kernel_virt_addr) >> PGDIR_SHIFT);
return (uintptr_t)early_pmd;
}
@@ -372,17 +386,32 @@ 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
+uintptr_t load_pa, load_sz;
+
+static void __init 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, pa, end_va;
- uintptr_t load_pa = (uintptr_t)(&_start);
- uintptr_t load_sz = (uintptr_t)(&_end) - load_pa;
+ uintptr_t pa;
uintptr_t map_size;
#ifndef __PAGETABLE_PMD_FOLDED
pmd_t fix_bmap_spmd, fix_bmap_epmd;
#endif
+ 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);
/*
@@ -410,26 +439,22 @@ 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);
#ifndef __PAGETABLE_PMD_FOLDED
/* Setup early PMD for DTB */
@@ -444,7 +469,12 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
pa + PMD_SIZE, PMD_SIZE, PAGE_KERNEL);
dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PMD_SIZE -
1));
#else /* CONFIG_BUILTIN_DTB */
- dtb_early_va = __va(dtb_pa);
+ /*
+ * __va can't be used since it would return a linear mapping
address
+ * whereas dtb_early_va will be used before setup_vm_final installs
+ * the linear mapping.
+ */
+ dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
#endif /* CONFIG_BUILTIN_DTB */
#else
#ifndef CONFIG_BUILTIN_DTB
@@ -456,7 +486,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
pa + PGDIR_SIZE, PGDIR_SIZE, PAGE_KERNEL);
dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PGDIR_SIZE
- 1));
#else /* CONFIG_BUILTIN_DTB */
- dtb_early_va = __va(dtb_pa);
+ dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
#endif /* CONFIG_BUILTIN_DTB */
#endif
dtb_early_pa = dtb_pa;
@@ -492,6 +522,22 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
#endif
}
+#ifdef CONFIG_64BIT
+void protect_kernel_linear_mapping_text_rodata(void)
+{
+ unsigned long text_start = (unsigned long)lm_alias(_start);
+ unsigned long init_text_start = (unsigned
long)lm_alias(__init_text_begin);
+ unsigned long rodata_start = (unsigned
long)lm_alias(__start_rodata);
+ unsigned long data_start = (unsigned long)lm_alias(_data);
+
+ set_memory_ro(text_start, (init_text_start - text_start) >>
PAGE_SHIFT);
+ set_memory_nx(text_start, (init_text_start - text_start) >>
PAGE_SHIFT);
+
+ set_memory_ro(rodata_start, (data_start - rodata_start) >>
PAGE_SHIFT);
+ set_memory_nx(rodata_start, (data_start - rodata_start) >>
PAGE_SHIFT);
+}
+#endif
+
static void __init setup_vm_final(void)
{
uintptr_t va, map_size;
@@ -513,7 +559,7 @@ static void __init setup_vm_final(void)
__pa_symbol(fixmap_pgd_next),
PGDIR_SIZE, PAGE_TABLE);
- /* Map all memory banks */
+ /* Map all memory banks in the linear mapping */
for_each_mem_range(i, &start, &end) {
if (start >= end)
break;
@@ -525,10 +571,13 @@ 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);
+
/* Clear fixmap PTE and PMD mappings */
clear_fixmap(FIX_PTE);
clear_fixmap(FIX_PMD);
diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
index 2c39f0386673..28f4d52cf17e 100644
--- a/arch/riscv/mm/kasan_init.c
+++ b/arch/riscv/mm/kasan_init.c
@@ -171,6 +171,10 @@ void __init kasan_init(void)
phys_addr_t _start, _end;
u64 i;
+ /*
+ * Populate all kernel virtual address space with
kasan_early_shadow_page
+ * except for the linear mapping and the modules/kernel/BPF
mapping.
+ */
kasan_populate_early_shadow((void *)KASAN_SHADOW_START,
(void *)kasan_mem_to_shadow((void *)
VMEMMAP_END));
@@ -183,6 +187,7 @@ void __init kasan_init(void)
(void *)kasan_mem_to_shadow((void *)VMALLOC_START),
(void *)kasan_mem_to_shadow((void *)VMALLOC_END));
+ /* Populate the linear mapping */
for_each_mem_range(i, &_start, &_end) {
void *start = (void *)__va(_start);
void *end = (void *)__va(_end);
@@ -193,6 +198,10 @@ void __init kasan_init(void)
kasan_populate(kasan_mem_to_shadow(start),
kasan_mem_to_shadow(end));
};
+ /* Populate kernel, BPF, modules mapping */
+ kasan_populate(kasan_mem_to_shadow((const void *)MODULES_VADDR),
+ kasan_mem_to_shadow((const void *)BPF_JIT_REGION_END));
+
for (i = 0; i < PTRS_PER_PTE; i++)
set_pte(&kasan_early_shadow_pte[i],
mk_pte(virt_to_page(kasan_early_shadow_page),
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;
/*
This is breaking boot for me with CONFIG_STRICT_KERNEL_RWX=n. I'm not
even really convinced that's a useful config to support, but it's
currently optional and I'd prefer to avoid breaking it if possible.
I can't quite figure out what's going on here and I'm pretty much
tired out for tonight. LMK if you don't have time to look at it and
I'll try to give it another shot.
I'm taking a look at that.
Just to make sure you don't miss it, I fixed this issue in
https://patchwork.kernel.org/project/linux-riscv/patch/20210415110426.2238-1-alex@xxxxxxxx/
Thanks,
Alex
Thanks,
Alex
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