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Message-ID: <20210127164230.GA584465@sequoia>
Date: Wed, 27 Jan 2021 10:42:30 -0600
From: Tyler Hicks <tyhicks@...ux.microsoft.com>
To: Pavel Tatashin <pasha.tatashin@...een.com>
Cc: jmorris@...ei.org, sashal@...nel.org, ebiederm@...ssion.com,
kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
corbet@....net, catalin.marinas@....com, will@...nel.org,
linux-arm-kernel@...ts.infradead.org, maz@...nel.org,
james.morse@....com, vladimir.murzin@....com,
matthias.bgg@...il.com, linux-mm@...ck.org, mark.rutland@....com,
steve.capper@....com, rfontana@...hat.com, tglx@...utronix.de,
selindag@...il.com
Subject: Re: [PATCH v10 16/18] arm64: kexec: configure trans_pgd page table
for kexec
On 2021-01-25 19:21:22, Pavel Tatashin wrote:
> I forgot to make changes to arch/arm64/Kconfig. The correct patch is
> below.
>
> ---
>
> From a2bc374320d7c7efd3c40644ad3d6d59a024b301 Mon Sep 17 00:00:00 2001
> From: Pavel Tatashin <pasha.tatashin@...een.com>
> Date: Mon, 29 Jul 2019 21:24:25 -0400
> Subject: [PATCH v10 16/18] arm64: kexec: configure trans_pgd page table for
> kexec
>
> Configure a page table located in kexec-safe memory that has
> the following mappings:
>
> 1. identity mapping for text of relocation function with executable
> permission.
> 2. va mappings for all source ranges
> 3. va mappings for all destination ranges.
>
> Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
> ---
> arch/arm64/Kconfig | 2 +-
> arch/arm64/include/asm/kexec.h | 12 ++++
> arch/arm64/kernel/asm-offsets.c | 6 ++
> arch/arm64/kernel/machine_kexec.c | 91 ++++++++++++++++++++++++++++++-
> 4 files changed, 109 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index fc0ed9d6e011..440abd0c0ee1 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1134,7 +1134,7 @@ config CRASH_DUMP
>
> config TRANS_TABLE
> def_bool y
> - depends on HIBERNATION
> + depends on HIBERNATION || KEXEC_CORE
>
> config XEN_DOM0
> def_bool y
> diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
> index b96d8a6aac80..049cde429b1b 100644
> --- a/arch/arm64/include/asm/kexec.h
> +++ b/arch/arm64/include/asm/kexec.h
> @@ -105,6 +105,12 @@ extern const char arm64_kexec_el2_vectors[];
> * el2_vector If present means that relocation routine will go to EL1
> * from EL2 to do the copy, and then back to EL2 to do the jump
> * to new world.
> + * trans_ttbr0 idmap for relocation function and its argument
> + * trans_ttbr1 map for source/destination addresses.
> + * trans_t0sz t0sz for idmap page in trans_ttbr0
> + * src_addr start address for source pages.
> + * dst_addr start address for destination pages.
> + * copy_len Number of bytes that need to be copied
> */
> struct kern_reloc_arg {
> phys_addr_t head;
> @@ -114,6 +120,12 @@ struct kern_reloc_arg {
> phys_addr_t kern_arg2;
> phys_addr_t kern_arg3;
> phys_addr_t el2_vector;
> + phys_addr_t trans_ttbr0;
> + phys_addr_t trans_ttbr1;
> + unsigned long trans_t0sz;
> + unsigned long src_addr;
> + unsigned long dst_addr;
> + unsigned long copy_len;
> };
>
> #define ARCH_HAS_KIMAGE_ARCH
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index 8a9475be1b62..06278611451d 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -160,6 +160,12 @@ int main(void)
> DEFINE(KEXEC_KRELOC_KERN_ARG2, offsetof(struct kern_reloc_arg, kern_arg2));
> DEFINE(KEXEC_KRELOC_KERN_ARG3, offsetof(struct kern_reloc_arg, kern_arg3));
> DEFINE(KEXEC_KRELOC_EL2_VECTOR, offsetof(struct kern_reloc_arg, el2_vector));
> + DEFINE(KEXEC_KRELOC_TRANS_TTBR0, offsetof(struct kern_reloc_arg, trans_ttbr0));
> + DEFINE(KEXEC_KRELOC_TRANS_TTBR1, offsetof(struct kern_reloc_arg, trans_ttbr1));
> + DEFINE(KEXEC_KRELOC_TRANS_T0SZ, offsetof(struct kern_reloc_arg, trans_t0sz));
> + DEFINE(KEXEC_KRELOC_SRC_ADDR, offsetof(struct kern_reloc_arg, src_addr));
> + DEFINE(KEXEC_KRELOC_DST_ADDR, offsetof(struct kern_reloc_arg, dst_addr));
> + DEFINE(KEXEC_KRELOC_COPY_LEN, offsetof(struct kern_reloc_arg, copy_len));
> #endif
> return 0;
> }
> diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
> index 41d1e3ca13f8..dc1b7e5a54fb 100644
> --- a/arch/arm64/kernel/machine_kexec.c
> +++ b/arch/arm64/kernel/machine_kexec.c
> @@ -21,6 +21,7 @@
> #include <asm/mmu_context.h>
> #include <asm/page.h>
> #include <asm/sections.h>
> +#include <asm/trans_pgd.h>
>
> #include "cpu-reset.h"
>
> @@ -71,11 +72,91 @@ static void *kexec_page_alloc(void *arg)
> return page_address(page);
> }
>
> +/*
> + * Map source segments starting from src_va, and map destination
> + * segments starting from dst_va, and return size of copy in
> + * *copy_len argument.
> + * Relocation function essentially needs to do:
> + * memcpy(dst_va, src_va, copy_len);
> + */
> +static int map_segments(struct kimage *kimage, pgd_t *pgdp,
> + struct trans_pgd_info *info,
> + unsigned long src_va,
> + unsigned long dst_va,
> + unsigned long *copy_len)
> +{
> + unsigned long *ptr = 0;
> + unsigned long dest = 0;
> + unsigned long len = 0;
> + unsigned long entry, addr;
> + int rc;
> +
> + for (entry = kimage->head; !(entry & IND_DONE); entry = *ptr++) {
> + addr = entry & PAGE_MASK;
> +
> + switch (entry & IND_FLAGS) {
> + case IND_DESTINATION:
> + dest = addr;
> + break;
> + case IND_INDIRECTION:
> + ptr = __va(addr);
> + if (rc)
We're checking a potentially uninitialized value here. I think this
whole "if (rc) return rc;" conditional can go away.
Tyler
> + return rc;
> + break;
> + case IND_SOURCE:
> + rc = trans_pgd_map_page(info, pgdp, __va(addr),
> + src_va, PAGE_KERNEL);
> + if (rc)
> + return rc;
> + rc = trans_pgd_map_page(info, pgdp, __va(dest),
> + dst_va, PAGE_KERNEL);
> + if (rc)
> + return rc;
> + dest += PAGE_SIZE;
> + src_va += PAGE_SIZE;
> + dst_va += PAGE_SIZE;
> + len += PAGE_SIZE;
> + }
> + }
> + *copy_len = len;
> +
> + return 0;
> +}
> +
> +static int mmu_relocate_setup(struct kimage *kimage, void *reloc_code,
> + struct kern_reloc_arg *kern_reloc_arg)
> +{
> + struct trans_pgd_info info = {
> + .trans_alloc_page = kexec_page_alloc,
> + .trans_alloc_arg = kimage,
> + };
> + pgd_t *trans_pgd = kexec_page_alloc(kimage);
> + int rc;
> +
> + if (!trans_pgd)
> + return -ENOMEM;
> +
> + /* idmap relocation function */
> + rc = trans_pgd_idmap_page(&info, &kern_reloc_arg->trans_ttbr0,
> + &kern_reloc_arg->trans_t0sz, reloc_code);
> + if (rc)
> + return rc;
> +
> + kern_reloc_arg->src_addr = _PAGE_OFFSET(VA_BITS_MIN);
> + kern_reloc_arg->dst_addr = _PAGE_OFFSET(VA_BITS_MIN - 1);
> + kern_reloc_arg->trans_ttbr1 = phys_to_ttbr(__pa(trans_pgd));
> +
> + rc = map_segments(kimage, trans_pgd, &info, kern_reloc_arg->src_addr,
> + kern_reloc_arg->dst_addr, &kern_reloc_arg->copy_len);
> + return rc;
> +}
> +
> int machine_kexec_post_load(struct kimage *kimage)
> {
> void *reloc_code = page_to_virt(kimage->control_code_page);
> struct kern_reloc_arg *kern_reloc_arg = kexec_page_alloc(kimage);
> long func_offset, vector_offset, reloc_size;
> + int rc = 0;
>
> if (!kern_reloc_arg)
> return -ENOMEM;
> @@ -95,6 +176,14 @@ int machine_kexec_post_load(struct kimage *kimage)
> if (is_hyp_mode_available() && !is_kernel_in_hyp_mode())
> kern_reloc_arg->el2_vector = __pa(reloc_code) + vector_offset;
>
> + /*
> + * If relocation is not needed, we do not need to enable MMU in
> + * relocation routine, therefore do not create page tables for
> + * scenarios such as crash kernel
> + */
> + if (!(kimage->head & IND_DONE))
> + rc = mmu_relocate_setup(kimage, reloc_code, kern_reloc_arg);
> +
> kexec_image_info(kimage);
>
> /* Flush the reloc_code in preparation for its execution. */
> @@ -103,7 +192,7 @@ int machine_kexec_post_load(struct kimage *kimage)
> reloc_size);
> __flush_dcache_area(kern_reloc_arg, sizeof(struct kern_reloc_arg));
>
> - return 0;
> + return rc;
> }
>
> /**
> --
> 2.25.1
>
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