Messages in this thread | | | Subject | Re: [PATCH RFC] riscv: Map the kernel with correct permissions the first time | From | Alex Ghiti <> | Date | Thu, 20 May 2021 07:11:34 +0200 |
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Hi Jisheng,
On 19/05/2021 18:29, Jisheng Zhang wrote: > On Tue, 18 May 2021 17:21:34 +0200 > Alexandre Ghiti <alex@ghiti.fr> wrote: > >> For 64b kernels, we map all the kernel with write and execute permissions >> and afterwards remove writability from text and executability from data. >> >> For 32b kernels, the kernel mapping resides in the linear mapping, so we >> map all the linear mapping as writable and executable and afterwards we >> remove those properties for unused memory and kernel mapping as >> described above. >> >> Change this behavior to directly map the kernel with correct permissions >> and avoid going through the whole mapping to fix the permissions. >> >> At the same time, this fixes an issue introduced by commit 2bfc6cd81bd1 >> ("riscv: Move kernel mapping outside of linear mapping") as reported >> here https://github.com/starfive-tech/linux/issues/17. >> >> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> >> --- >> >> This patchset was tested on: >> >> * kernel: >> - rv32 with CONFIG_STRICT_KERNEL_RWX: OK >> - rv32 without CONFIG_STRICT_KERNEL_RWX: OK >> - rv64 with CONFIG_STRICT_KERNEL_RWX: OK >> - rv64 without CONFIG_STRICT_KERNEL_RWX: OK >> >> * xipkernel: >> - rv32: build only >> - rv64: OK >> >> arch/riscv/include/asm/set_memory.h | 2 - >> arch/riscv/kernel/setup.c | 1 - >> arch/riscv/mm/init.c | 80 ++++++++++++++--------------- >> 3 files changed, 38 insertions(+), 45 deletions(-) >> >> diff --git a/arch/riscv/include/asm/set_memory.h b/arch/riscv/include/asm/set_memory.h >> index 086f757e8ba3..70154f012791 100644 >> --- a/arch/riscv/include/asm/set_memory.h >> +++ b/arch/riscv/include/asm/set_memory.h >> @@ -16,13 +16,11 @@ int set_memory_rw(unsigned long addr, int numpages); >> 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); >> #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; } >> static inline int set_memory_x(unsigned long addr, int numpages) { return 0; } >> static inline int set_memory_nx(unsigned long addr, int numpages) { return 0; } >> -static inline void protect_kernel_text_data(void) {} >> static inline int set_memory_rw_nx(unsigned long addr, int numpages) { return 0; } >> #endif >> >> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c >> index 03901d3a8b02..1eb50e512056 100644 >> --- a/arch/riscv/kernel/setup.c >> +++ b/arch/riscv/kernel/setup.c >> @@ -292,7 +292,6 @@ void __init setup_arch(char **cmdline_p) >> sbi_init(); >> >> if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)) { >> - protect_kernel_text_data(); >> protect_kernel_linear_mapping_text_rodata(); > > If we extend the idea a bit, I.E create the correct permission for alias line > mapping at the first time, we can remove protect_kernel_linear_mapping_text_rodata() >
Yes, I agree, I will do that.
> PS: No matter whether it's fine to extend, the set_memory_nx() calling in > protect_kernel_linear_mapping_text_rodata() is not necessary since the linear > mapping for 64bit is NX from the beginning.
You're totally right, that will be fixed when removing protect_kernel_linear_mapping_text_rodata() entirely.
> >> } >> >> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c >> index 4faf8bd157ea..92b3184420a2 100644 >> --- a/arch/riscv/mm/init.c >> +++ b/arch/riscv/mm/init.c >> @@ -436,6 +436,36 @@ asmlinkage void __init __copy_data(void) >> } >> #endif >> >> +#ifdef CONFIG_STRICT_KERNEL_RWX >> +#define is_text_va(va) ({ \ >> + unsigned long _va = va; \ >> + (_va < (unsigned long)__init_data_begin && _va >= (unsigned long)_start); \ >> + }) > > It's better if is_text_va() is a inline function >
Ok, will do.
>> + >> +static inline __init pgprot_t pgprot_from_kernel_va(uintptr_t va) > > I'm not sure whether it's necessary to put __init marker to inline functions > There are such issues in current riscv code, I planed to cook one patch > to remove __init from inline functions. > > >> +{ >> + return is_text_va(va) ? PAGE_KERNEL_READ_EXEC : PAGE_KERNEL; > > if we extend the idea, then here we may return PAGE_KERNEL_READ, PAGE_KERNEL > and PAGE_KERNEL_READ_EXEC correspondingly.
Again, I agree :)
I will come up with an enhanced v2 soon,
Thanks for your comments,
Alex
> > Thanks > >> +} >> + >> +void mark_rodata_ro(void) >> +{ >> + unsigned long rodata_start = (unsigned long)__start_rodata; >> + unsigned long data_start = (unsigned long)_data; >> + >> + set_memory_ro(rodata_start, (data_start - rodata_start) >> PAGE_SHIFT); >> + >> + debug_checkwx(); >> +} >> +#else >> +static inline __init pgprot_t pgprot_from_kernel_va(uintptr_t va) >> +{ >> + if (IS_ENABLED(CONFIG_32BIT)) >> + return PAGE_KERNEL_EXEC; >> + >> + return (va < kernel_virt_addr) ? PAGE_KERNEL : PAGE_KERNEL_EXEC; >> +} >> +#endif >> + >> /* >> * setup_vm() is called from head.S with MMU-off. >> * >> @@ -465,7 +495,8 @@ uintptr_t xiprom, xiprom_sz; >> #define xiprom_sz (*((uintptr_t *)XIP_FIXUP(&xiprom_sz))) >> #define xiprom (*((uintptr_t *)XIP_FIXUP(&xiprom))) >> >> -static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size) >> +static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size, >> + __always_unused bool early) >> { >> uintptr_t va, end_va; >> >> @@ -484,7 +515,7 @@ static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size) >> map_size, PAGE_KERNEL); >> } >> #else >> -static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size) >> +static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size, bool early) >> { >> uintptr_t va, end_va; >> >> @@ -492,7 +523,7 @@ static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size) >> 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); >> + map_size, early ? PAGE_KERNEL_EXEC : pgprot_from_kernel_va(va)); >> } >> #endif >> >> @@ -569,7 +600,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa) >> * us to reach paging_init(). We map all memory banks later >> * in setup_vm_final() below. >> */ >> - create_kernel_page_table(early_pg_dir, map_size); >> + create_kernel_page_table(early_pg_dir, map_size, true); >> >> #ifndef __PAGETABLE_PMD_FOLDED >> /* Setup early PMD for DTB */ >> @@ -693,21 +724,15 @@ static void __init setup_vm_final(void) >> map_size = best_map_size(start, end - start); >> for (pa = start; pa < end; pa += map_size) { >> va = (uintptr_t)__va(pa); >> - create_pgd_mapping(swapper_pg_dir, va, pa, >> - map_size, >> -#ifdef CONFIG_64BIT >> - PAGE_KERNEL >> -#else >> - PAGE_KERNEL_EXEC >> -#endif >> - ); >> >> + create_pgd_mapping(swapper_pg_dir, va, pa, map_size, >> + pgprot_from_kernel_va(va)); >> } >> } >> >> #ifdef CONFIG_64BIT >> /* Map the kernel */ >> - create_kernel_page_table(swapper_pg_dir, PMD_SIZE); >> + create_kernel_page_table(swapper_pg_dir, PMD_SIZE, false); >> #endif >> >> /* Clear fixmap PTE and PMD mappings */ >> @@ -738,35 +763,6 @@ static inline void setup_vm_final(void) >> } >> #endif /* CONFIG_MMU */ >> >> -#ifdef CONFIG_STRICT_KERNEL_RWX >> -void __init protect_kernel_text_data(void) >> -{ >> - unsigned long text_start = (unsigned long)_start; >> - unsigned long init_text_start = (unsigned long)__init_text_begin; >> - unsigned long init_data_start = (unsigned long)__init_data_begin; >> - unsigned long rodata_start = (unsigned long)__start_rodata; >> - unsigned long data_start = (unsigned long)_data; >> - unsigned long max_low = (unsigned long)(__va(PFN_PHYS(max_low_pfn))); >> - >> - set_memory_ro(text_start, (init_text_start - text_start) >> PAGE_SHIFT); >> - set_memory_ro(init_text_start, (init_data_start - init_text_start) >> PAGE_SHIFT); >> - set_memory_nx(init_data_start, (rodata_start - init_data_start) >> PAGE_SHIFT); >> - /* rodata section is marked readonly in mark_rodata_ro */ >> - set_memory_nx(rodata_start, (data_start - rodata_start) >> PAGE_SHIFT); >> - set_memory_nx(data_start, (max_low - data_start) >> PAGE_SHIFT); >> -} >> - >> -void mark_rodata_ro(void) >> -{ >> - unsigned long rodata_start = (unsigned long)__start_rodata; >> - unsigned long data_start = (unsigned long)_data; >> - >> - set_memory_ro(rodata_start, (data_start - rodata_start) >> PAGE_SHIFT); >> - >> - debug_checkwx(); >> -} >> -#endif >> - >> #ifdef CONFIG_KEXEC_CORE >> /* >> * reserve_crashkernel() - reserves memory for crash kernel > > > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv >
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