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Message-ID: <20210929124513.GD21631@willie-the-truck>
Date: Wed, 29 Sep 2021 13:45:13 +0100
From: Will Deacon <will@...nel.org>
To: Pasha 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,
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, tyhicks@...ux.microsoft.com,
kernelfans@...il.com, akpm@...ux-foundation.org,
madvenka@...ux.microsoft.com
Subject: Re: [PATCH v17 10/15] arm64: kexec: use ld script for relocation
function
On Thu, Sep 16, 2021 at 07:13:20PM -0400, Pasha Tatashin wrote:
> Currently, relocation code declares start and end variables
> which are used to compute its size.
>
> The better way to do this is to use ld script incited, and put relocation
> function in its own section.
"incited"? I don't understand ...
>
> Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
> ---
> arch/arm64/include/asm/sections.h | 1 +
> arch/arm64/kernel/machine_kexec.c | 16 ++++++----------
> arch/arm64/kernel/relocate_kernel.S | 15 ++-------------
> arch/arm64/kernel/vmlinux.lds.S | 19 +++++++++++++++++++
> 4 files changed, 28 insertions(+), 23 deletions(-)
>
> diff --git a/arch/arm64/include/asm/sections.h b/arch/arm64/include/asm/sections.h
> index e4ad9db53af1..152cb35bf9df 100644
> --- a/arch/arm64/include/asm/sections.h
> +++ b/arch/arm64/include/asm/sections.h
> @@ -21,5 +21,6 @@ extern char __exittext_begin[], __exittext_end[];
> extern char __irqentry_text_start[], __irqentry_text_end[];
> extern char __mmuoff_data_start[], __mmuoff_data_end[];
> extern char __entry_tramp_text_start[], __entry_tramp_text_end[];
> +extern char __relocate_new_kernel_start[], __relocate_new_kernel_end[];
>
> #endif /* __ASM_SECTIONS_H */
> diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
> index cf5d6f22a041..83da6045cd45 100644
> --- a/arch/arm64/kernel/machine_kexec.c
> +++ b/arch/arm64/kernel/machine_kexec.c
> @@ -21,14 +21,11 @@
> #include <asm/mmu.h>
> #include <asm/mmu_context.h>
> #include <asm/page.h>
> +#include <asm/sections.h>
> #include <asm/trans_pgd.h>
>
> #include "cpu-reset.h"
>
> -/* Global variables for the arm64_relocate_new_kernel routine. */
> -extern const unsigned char arm64_relocate_new_kernel[];
> -extern const unsigned long arm64_relocate_new_kernel_size;
> -
> /**
> * kexec_image_info - For debugging output.
> */
> @@ -163,6 +160,7 @@ static void *kexec_page_alloc(void *arg)
> int machine_kexec_post_load(struct kimage *kimage)
> {
> void *reloc_code = page_to_virt(kimage->control_code_page);
> + long reloc_size;
> struct trans_pgd_info info = {
> .trans_alloc_page = kexec_page_alloc,
> .trans_alloc_arg = kimage,
> @@ -183,17 +181,15 @@ int machine_kexec_post_load(struct kimage *kimage)
> return rc;
> }
>
> - memcpy(reloc_code, arm64_relocate_new_kernel,
> - arm64_relocate_new_kernel_size);
> + reloc_size = __relocate_new_kernel_end - __relocate_new_kernel_start;
> + memcpy(reloc_code, __relocate_new_kernel_start, reloc_size);
> kimage->arch.kern_reloc = __pa(reloc_code);
>
> /* Flush the reloc_code in preparation for its execution. */
> dcache_clean_inval_poc((unsigned long)reloc_code,
> - (unsigned long)reloc_code +
> - arm64_relocate_new_kernel_size);
> + (unsigned long)reloc_code + reloc_size);
Extra whitespace.
> icache_inval_pou((uintptr_t)reloc_code,
> - (uintptr_t)reloc_code +
> - arm64_relocate_new_kernel_size);
> + (uintptr_t)reloc_code + reloc_size);
> kexec_list_flush(kimage);
> kexec_image_info(kimage);
>
> diff --git a/arch/arm64/kernel/relocate_kernel.S b/arch/arm64/kernel/relocate_kernel.S
> index b4fb97312a80..9d2400855ee4 100644
> --- a/arch/arm64/kernel/relocate_kernel.S
> +++ b/arch/arm64/kernel/relocate_kernel.S
> @@ -15,6 +15,7 @@
> #include <asm/sysreg.h>
> #include <asm/virt.h>
>
> +.pushsection ".kexec_relocate.text", "ax"
Just use .section if you're putting the entire file in there?
> /*
> * arm64_relocate_new_kernel - Put a 2nd stage image in place and boot it.
> *
> @@ -77,16 +78,4 @@ SYM_CODE_START(arm64_relocate_new_kernel)
> mov x3, xzr
> br x4 /* Jumps from el1 */
> SYM_CODE_END(arm64_relocate_new_kernel)
> -
> -.align 3 /* To keep the 64-bit values below naturally aligned. */
> -
> -.Lcopy_end:
> -.org KEXEC_CONTROL_PAGE_SIZE
> -
> -/*
> - * arm64_relocate_new_kernel_size - Number of bytes to copy to the
> - * control_code_page.
> - */
> -.globl arm64_relocate_new_kernel_size
> -arm64_relocate_new_kernel_size:
> - .quad .Lcopy_end - arm64_relocate_new_kernel
> +.popsection
> diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
> index f6b1a88245db..ab457b609e69 100644
> --- a/arch/arm64/kernel/vmlinux.lds.S
> +++ b/arch/arm64/kernel/vmlinux.lds.S
> @@ -63,6 +63,7 @@
> #include <asm-generic/vmlinux.lds.h>
> #include <asm/cache.h>
> #include <asm/kernel-pgtable.h>
> +#include <asm/kexec.h>
> #include <asm/memory.h>
> #include <asm/page.h>
>
> @@ -100,6 +101,16 @@ jiffies = jiffies_64;
> #define HIBERNATE_TEXT
> #endif
>
> +#ifdef CONFIG_KEXEC_CORE
> +#define KEXEC_TEXT \
> + . = ALIGN(SZ_4K); \
> + __relocate_new_kernel_start = .; \
> + *(.kexec_relocate.text) \
> + __relocate_new_kernel_end = .;
> +#else
> +#define KEXEC_TEXT
> +#endif
> +
> #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
> #define TRAMP_TEXT \
> . = ALIGN(PAGE_SIZE); \
> @@ -160,6 +171,7 @@ SECTIONS
> HYPERVISOR_TEXT
> IDMAP_TEXT
> HIBERNATE_TEXT
> + KEXEC_TEXT
> TRAMP_TEXT
> *(.fixup)
> *(.gnu.warning)
> @@ -348,3 +360,10 @@ ASSERT(swapper_pg_dir - reserved_pg_dir == RESERVED_SWAPPER_OFFSET,
> ASSERT(swapper_pg_dir - tramp_pg_dir == TRAMP_SWAPPER_OFFSET,
> "TRAMP_SWAPPER_OFFSET is wrong!")
> #endif
> +
> +#ifdef CONFIG_KEXEC_CORE
> +/* kexec relocation code should fit into one KEXEC_CONTROL_PAGE_SIZE */
> +ASSERT(__relocate_new_kernel_end - (__relocate_new_kernel_start & ~(SZ_4K - 1))
> + <= SZ_4K, "kexec relocation code is too big or misaligned")
> +ASSERT(KEXEC_CONTROL_PAGE_SIZE >= SZ_4K, "KEXEC_CONTROL_PAGE_SIZE is brokern")
Typo: "brokern",
Will
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