arch/riscv/include/asm/page.h | 1 + arch/riscv/include/asm/pgtable.h | 2 +- arch/riscv/mm/init.c | 17 ++++++++++++++++- 3 files changed, 18 insertions(+), 2 deletions(-)
In sparse vmemmap model, the virtual address of vmemmap is calculated as:
((struct page *)VMEMMAP_START - (phys_ram_base >> PAGE_SHIFT)).
And the struct page's va can be calculated with an offset:
(vmemmap + (pfn)).
However, when initializing struct pages, kernel actually starts from the
first page from the same section that phys_ram_base belongs to. If the
first page's physical address is not (phys_ram_base >> PAGE_SHIFT), then
we get an va below VMEMMAP_START when calculating va for it's struct page.
For example, if phys_ram_base starts from 0x82000000 with pfn 0x82000, the
first page in the same section is actually pfn 0x80000. During
init_unavailable_range(), we will initialize struct page for pfn 0x80000
with virtual address ((struct page *)VMEMMAP_START - 0x2000), which is
below VMEMMAP_START as well as PCI_IO_END.
This commit fixes this bug by introducing a new variable
'vmemmap_start_pfn' which is aligned with memory section size and using
it to calculate vmemmap address instead of phys_ram_base.
Fixes: a11dd49dcb93 ("riscv: Sparse-Memory/vmemmap out-of-bounds fix")
Signed-off-by: Xu Lu <luxu.kernel@bytedance.com>
---
arch/riscv/include/asm/page.h | 1 +
arch/riscv/include/asm/pgtable.h | 2 +-
arch/riscv/mm/init.c | 17 ++++++++++++++++-
3 files changed, 18 insertions(+), 2 deletions(-)
diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
index 71aabc5c6713..125f5ecd9565 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -122,6 +122,7 @@ struct kernel_mapping {
extern struct kernel_mapping kernel_map;
extern phys_addr_t phys_ram_base;
+extern unsigned long vmemmap_start_pfn;
#define is_kernel_mapping(x) \
((x) >= kernel_map.virt_addr && (x) < (kernel_map.virt_addr + kernel_map.size))
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index d4e99eef90ac..050fdc49b5ad 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -87,7 +87,7 @@
* Define vmemmap for pfn_to_page & page_to_pfn calls. Needed if kernel
* is configured with CONFIG_SPARSEMEM_VMEMMAP enabled.
*/
-#define vmemmap ((struct page *)VMEMMAP_START - (phys_ram_base >> PAGE_SHIFT))
+#define vmemmap ((struct page *)VMEMMAP_START - vmemmap_start_pfn)
#define PCI_IO_SIZE SZ_16M
#define PCI_IO_END VMEMMAP_START
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 0e8c20adcd98..d93271cb97b1 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -33,6 +33,7 @@
#include <asm/pgtable.h>
#include <asm/sections.h>
#include <asm/soc.h>
+#include <asm/sparsemem.h>
#include <asm/tlbflush.h>
#include "../kernel/head.h"
@@ -62,6 +63,13 @@ EXPORT_SYMBOL(pgtable_l5_enabled);
phys_addr_t phys_ram_base __ro_after_init;
EXPORT_SYMBOL(phys_ram_base);
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+#define VMEMMAP_ADDR_ALIGN (1ULL << SECTION_SIZE_BITS)
+
+unsigned long vmemmap_start_pfn __ro_after_init;
+EXPORT_SYMBOL(vmemmap_start_pfn);
+#endif
+
unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
__page_aligned_bss;
EXPORT_SYMBOL(empty_zero_page);
@@ -240,8 +248,12 @@ static void __init setup_bootmem(void)
* Make sure we align the start of the memory on a PMD boundary so that
* at worst, we map the linear mapping with PMD mappings.
*/
- if (!IS_ENABLED(CONFIG_XIP_KERNEL))
+ if (!IS_ENABLED(CONFIG_XIP_KERNEL)) {
phys_ram_base = memblock_start_of_DRAM() & PMD_MASK;
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+ vmemmap_start_pfn = round_down(phys_ram_base, VMEMMAP_ADDR_ALIGN) >> PAGE_SHIFT;
+#endif
+ }
/*
* In 64-bit, any use of __va/__pa before this point is wrong as we
@@ -1101,6 +1113,9 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
kernel_map.xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
phys_ram_base = CONFIG_PHYS_RAM_BASE;
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+ vmemmap_start_pfn = round_down(phys_ram_base, VMEMMAP_ADDR_ALIGN) >> PAGE_SHIFT;
+#endif
kernel_map.phys_addr = (uintptr_t)CONFIG_PHYS_RAM_BASE;
kernel_map.size = (uintptr_t)(&_end) - (uintptr_t)(&_start);
--
2.20.1Xu Lu <luxu.kernel@bytedance.com> writes:
> In sparse vmemmap model, the virtual address of vmemmap is calculated as:
> ((struct page *)VMEMMAP_START - (phys_ram_base >> PAGE_SHIFT)).
> And the struct page's va can be calculated with an offset:
> (vmemmap + (pfn)).
>
> However, when initializing struct pages, kernel actually starts from the
> first page from the same section that phys_ram_base belongs to. If the
> first page's physical address is not (phys_ram_base >> PAGE_SHIFT), then
> we get an va below VMEMMAP_START when calculating va for it's struct page.
>
> For example, if phys_ram_base starts from 0x82000000 with pfn 0x82000, the
> first page in the same section is actually pfn 0x80000. During
> init_unavailable_range(), we will initialize struct page for pfn 0x80000
> with virtual address ((struct page *)VMEMMAP_START - 0x2000), which is
> below VMEMMAP_START as well as PCI_IO_END.
>
> This commit fixes this bug by introducing a new variable
> 'vmemmap_start_pfn' which is aligned with memory section size and using
> it to calculate vmemmap address instead of phys_ram_base.
>
> Fixes: a11dd49dcb93 ("riscv: Sparse-Memory/vmemmap out-of-bounds fix")
> Signed-off-by: Xu Lu <luxu.kernel@bytedance.com>
Verified that the kernel is not trying to access vmemmap/struct pages
below VMEMMAP_START.
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Hi Xu,
On Mon, Dec 9, 2024 at 1:26 PM Xu Lu <luxu.kernel@bytedance.com> wrote:
>
> In sparse vmemmap model, the virtual address of vmemmap is calculated as:
> ((struct page *)VMEMMAP_START - (phys_ram_base >> PAGE_SHIFT)).
> And the struct page's va can be calculated with an offset:
> (vmemmap + (pfn)).
>
> However, when initializing struct pages, kernel actually starts from the
> first page from the same section that phys_ram_base belongs to. If the
> first page's physical address is not (phys_ram_base >> PAGE_SHIFT), then
> we get an va below VMEMMAP_START when calculating va for it's struct page.
>
> For example, if phys_ram_base starts from 0x82000000 with pfn 0x82000, the
> first page in the same section is actually pfn 0x80000. During
> init_unavailable_range(), we will initialize struct page for pfn 0x80000
> with virtual address ((struct page *)VMEMMAP_START - 0x2000), which is
> below VMEMMAP_START as well as PCI_IO_END.
>
> This commit fixes this bug by introducing a new variable
> 'vmemmap_start_pfn' which is aligned with memory section size and using
> it to calculate vmemmap address instead of phys_ram_base.
>
> Fixes: a11dd49dcb93 ("riscv: Sparse-Memory/vmemmap out-of-bounds fix")
> Signed-off-by: Xu Lu <luxu.kernel@bytedance.com>
> ---
> arch/riscv/include/asm/page.h | 1 +
> arch/riscv/include/asm/pgtable.h | 2 +-
> arch/riscv/mm/init.c | 17 ++++++++++++++++-
> 3 files changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
> index 71aabc5c6713..125f5ecd9565 100644
> --- a/arch/riscv/include/asm/page.h
> +++ b/arch/riscv/include/asm/page.h
> @@ -122,6 +122,7 @@ struct kernel_mapping {
>
> extern struct kernel_mapping kernel_map;
> extern phys_addr_t phys_ram_base;
> +extern unsigned long vmemmap_start_pfn;
>
> #define is_kernel_mapping(x) \
> ((x) >= kernel_map.virt_addr && (x) < (kernel_map.virt_addr + kernel_map.size))
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index d4e99eef90ac..050fdc49b5ad 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -87,7 +87,7 @@
> * Define vmemmap for pfn_to_page & page_to_pfn calls. Needed if kernel
> * is configured with CONFIG_SPARSEMEM_VMEMMAP enabled.
> */
> -#define vmemmap ((struct page *)VMEMMAP_START - (phys_ram_base >> PAGE_SHIFT))
> +#define vmemmap ((struct page *)VMEMMAP_START - vmemmap_start_pfn)
>
> #define PCI_IO_SIZE SZ_16M
> #define PCI_IO_END VMEMMAP_START
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 0e8c20adcd98..d93271cb97b1 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -33,6 +33,7 @@
> #include <asm/pgtable.h>
> #include <asm/sections.h>
> #include <asm/soc.h>
> +#include <asm/sparsemem.h>
> #include <asm/tlbflush.h>
>
> #include "../kernel/head.h"
> @@ -62,6 +63,13 @@ EXPORT_SYMBOL(pgtable_l5_enabled);
> phys_addr_t phys_ram_base __ro_after_init;
> EXPORT_SYMBOL(phys_ram_base);
>
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> +#define VMEMMAP_ADDR_ALIGN (1ULL << SECTION_SIZE_BITS)
> +
> +unsigned long vmemmap_start_pfn __ro_after_init;
> +EXPORT_SYMBOL(vmemmap_start_pfn);
> +#endif
> +
> unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
> __page_aligned_bss;
> EXPORT_SYMBOL(empty_zero_page);
> @@ -240,8 +248,12 @@ static void __init setup_bootmem(void)
> * Make sure we align the start of the memory on a PMD boundary so that
> * at worst, we map the linear mapping with PMD mappings.
> */
> - if (!IS_ENABLED(CONFIG_XIP_KERNEL))
> + if (!IS_ENABLED(CONFIG_XIP_KERNEL)) {
> phys_ram_base = memblock_start_of_DRAM() & PMD_MASK;
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> + vmemmap_start_pfn = round_down(phys_ram_base, VMEMMAP_ADDR_ALIGN) >> PAGE_SHIFT;
> +#endif
> + }
>
> /*
> * In 64-bit, any use of __va/__pa before this point is wrong as we
> @@ -1101,6 +1113,9 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> kernel_map.xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
>
> phys_ram_base = CONFIG_PHYS_RAM_BASE;
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> + vmemmap_start_pfn = round_down(phys_ram_base, VMEMMAP_ADDR_ALIGN) >> PAGE_SHIFT;
> +#endif
> kernel_map.phys_addr = (uintptr_t)CONFIG_PHYS_RAM_BASE;
> kernel_map.size = (uintptr_t)(&_end) - (uintptr_t)(&_start);
>
> --
> 2.20.1
>
Thanks for the multiple revisions!
It looks good to me, so:
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Thanks again,
Alex
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