Messages in this thread | | | Subject | Re: [PATCH RFC 6/8] riscv/kaslr: clear the original kernel image | From | Alex Ghiti <> | Date | Tue, 7 Apr 2020 01:11:48 -0400 |
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On 3/24/20 3:30 AM, Zong Li wrote: > After completing final page table, we can clear original kernel image > and remove executable permission. > > Signed-off-by: Zong Li <zong.li@sifive.com> > --- > arch/riscv/include/asm/kaslr.h | 12 ++++++++++++ > arch/riscv/kernel/kaslr.c | 12 ++++++++++++ > arch/riscv/mm/init.c | 6 ++++++ > 3 files changed, 30 insertions(+) > create mode 100644 arch/riscv/include/asm/kaslr.h > > diff --git a/arch/riscv/include/asm/kaslr.h b/arch/riscv/include/asm/kaslr.h > new file mode 100644 > index 000000000000..b165fe71dd4a > --- /dev/null > +++ b/arch/riscv/include/asm/kaslr.h > @@ -0,0 +1,12 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * Copyright (C) 2020 SiFive > + * Copyright (C) 2020 Zong Li <zong.li@sifive.com> > + */ > + > +#ifndef _ASM_RISCV_KASLR_H > +#define _ASM_RISCV_KASLR_H > + > +void __init kaslr_late_init(void); > + > +#endif /* _ASM_RISCV_KASLR_H */ > diff --git a/arch/riscv/kernel/kaslr.c b/arch/riscv/kernel/kaslr.c > index 59001d6fdfc3..0bd30831c455 100644 > --- a/arch/riscv/kernel/kaslr.c > +++ b/arch/riscv/kernel/kaslr.c > @@ -356,6 +356,18 @@ static __init uintptr_t get_random_offset(u64 seed, uintptr_t kernel_size) > return get_legal_offset(random, kernel_size_align); > } > > +void __init kaslr_late_init(void) > +{ > + uintptr_t kernel_size; > + > + /* Clear original kernel image. */ > + if (kaslr_offset) { > + kernel_size = (uintptr_t) _end - (uintptr_t) _start;
kernel_size = (uintptr_t) _end - (uintptr_t) _start + 1;
> + memset((void *)PAGE_OFFSET, 0, kernel_size);
I have been thinking again about our discussion regarding PAGE_OFFSET: PAGE_OFFSET actually points to the address where the kernel was loaded, not the beginning of memory, that's a bit weird.
Just saying that here, because it took me a few seconds to remember that and understand what you were doing here.
> + set_memory_nx(PAGE_OFFSET, kaslr_offset >> PAGE_SHIFT);
Again, I certainly missed something but when do you use old kernel mappings ?
> + } > +} > + > uintptr_t __init kaslr_early_init(void) > { > u64 seed; > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > index 34c6ecf2c599..08e2ce170533 100644 > --- a/arch/riscv/mm/init.c > +++ b/arch/riscv/mm/init.c > @@ -15,6 +15,7 @@ > #include <linux/set_memory.h> > #ifdef CONFIG_RELOCATABLE > #include <linux/elf.h> > +#include <asm/kaslr.h> > #endif > > #include <asm/fixmap.h> > @@ -649,6 +650,11 @@ static void __init setup_vm_final(void) > /* Move to swapper page table */ > csr_write(CSR_SATP, PFN_DOWN(__pa_symbol(swapper_pg_dir)) | SATP_MODE); > local_flush_tlb_all(); > + > +#ifdef CONFIG_RANDOMIZE_BASE > + /* Clear orignial kernel image and set the right permission. */ > + kaslr_late_init(); > +#endif > } > > void free_initmem(void) >
Alex
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