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Message-ID: <82a05081-5662-c787-44e4-d480774ce31c@ghiti.fr>
Date: Sun, 21 Mar 2021 11:10:55 -0400
From: Alex Ghiti <alex@...ti.fr>
To: Vitaly Wool <vitaly.wool@...sulko.com>,
linux-riscv@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org, Bin Meng <bin.meng@...driver.com>,
Anup Patel <anup@...infault.org>,
Alistair Francis <alistair.francis@....com>,
Palmer Dabbelt <palmerdabbelt@...gle.com>,
Nicolas Pitre <nico@...xnic.net>
Subject: Re: [PATCH v5] RISC-V: enable XIP
Hi Vitaly,
Le 3/10/21 à 4:22 AM, Vitaly Wool a écrit :
> Introduce XIP (eXecute In Place) support for RISC-V platforms.
> It allows code to be executed directly from non-volatile storage
> directly addressable by the CPU, such as QSPI NOR flash which can
> be found on many RISC-V platforms. This makes way for significant
> optimization of RAM footprint. The XIP kernel is not compressed
> since it has to run directly from flash, so it will occupy more
> space on the non-volatile storage to The physical flash address
There seems to be missing something here.
> used to link the kernel object files and for storing it has to
> be known at compile time and is represented by a Kconfig option.
>
> XIP on RISC-V will currently only work on MMU-enabled kernels.
>
> Signed-off-by: Vitaly Wool <vitaly.wool@...sulko.com>
This fails to boot on current for-next with the following panic.
This is because dtb_early_va points to an address that is not mapped in
swapper_pg_dir: using __va(dtb_early_pa) instead works fine.
And as this likely needs another version, I'm going to add my comments
below.
[ 0.000000] OF: fdt: Ignoring memory range 0x80000000 - 0x80200000
[ 0.000000] Machine model: riscv-virtio,qemu
[ 0.000000] earlycon: sbi0 at I/O port 0x0 (options '')
[ 0.000000] printk: bootconsole [sbi0] enabled
[ 0.000000] efi: UEFI not found.
[ 0.000000] Unable to handle kernel paging request at virtual address
0000000040000001
[ 0.000000] Oops [#1]
[ 0.000000] Modules linked in:
[ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.12.0-rc2 #155
[ 0.000000] Hardware name: riscv-virtio,qemu (DT)
[ 0.000000] epc : fdt_check_header+0x0/0x1fc
[ 0.000000] ra : early_init_dt_verify+0x16/0x6e
[ 0.000000] epc : ffffffe0002b955e ra : ffffffe00082100c sp :
ffffffe001203f10
[ 0.000000] gp : ffffffe0012e40b8 tp : ffffffe00120bd80 t0 :
ffffffe23fdf7000
[ 0.000000] t1 : 0000000000000000 t2 : 0000000000000000 s0 :
ffffffe001203f30
[ 0.000000] s1 : 0000000040000000 a0 : 0000000040000000 a1 :
00000002bfffffff
[ 0.000000] a2 : ffffffe23fdf6f00 a3 : 0000000000000001 a4 :
0000000000000018
[ 0.000000] a5 : ffffffe000a0b5e8 a6 : ffffffe23fdf6ef0 a7 :
0000000000000018
[ 0.000000] s2 : 0000000080000200 s3 : 0000000000000fff s4 :
ffffffe000a0a958
[ 0.000000] s5 : 0000000000000005 s6 : 0000000000000140 s7 :
ffffffe23fdf6ec0
[ 0.000000] s8 : 0000000081000200 s9 : 0000000080000200 s10:
ffffffe000a01000
[ 0.000000] s11: 0000000000000fff t3 : ffffffffbfff7000 t4 :
ffffffffffffffff
[ 0.000000] t5 : 0000000080e00000 t6 : 0000000080202000
[ 0.000000] status: 0000000000000100 badaddr: 0000000040000001 cause:
000000000000000d
[ 0.000000] Call Trace:
[ 0.000000] [<ffffffe0002b955e>] fdt_check_header+0x0/0x1fc
[ 0.000000] [<ffffffe000802af2>] setup_arch+0x3a6/0x412
[ 0.000000] [<ffffffe0008006ea>] start_kernel+0x7e/0x580
[ 0.000000] random: get_random_bytes called from
print_oops_end_marker+0x22/0x44 with crng_init=0
[ 0.000000] ---[ end trace 0000000000000000 ]---
[ 0.000000] Kernel panic - not syncing: Fatal exception
[ 0.000000] ---[ end Kernel panic - not syncing: Fatal exception ]---
>
> ---
> Changes in v2:
> - dedicated macro for XIP address fixup when MMU is not enabled yet
> o both for 32-bit and 64-bit RISC-V
> - SP is explicitly set to a safe place in RAM before __copy_data call
> - removed redundant alignment requirements in vmlinux-xip.lds.S
> - changed long -> uintptr_t typecast in __XIP_FIXUP macro.
> Changes in v3:
> - rebased against latest for-next
> - XIP address fixup macro now takes an argument
> - SMP related fixes
> Changes in v4:
> - rebased against the current for-next
> - less #ifdef's in C/ASM code
> - dedicated XIP_FIXUP_OFFSET assembler macro in head.S
> - C-specific definitions moved into #ifndef __ASSEMBLY__
> - Fixed multi-core boot
> Changes in v5:
> - fixed build error for non-XIP kernels
>
> arch/riscv/Kconfig | 44 +++++++++-
> arch/riscv/Makefile | 8 +-
> arch/riscv/boot/Makefile | 13 +++
> arch/riscv/include/asm/pgtable.h | 65 ++++++++++++--
> arch/riscv/kernel/cpu_ops_sbi.c | 12 ++-
> arch/riscv/kernel/head.S | 59 ++++++++++++-
> arch/riscv/kernel/head.h | 3 +
> arch/riscv/kernel/setup.c | 8 +-
> arch/riscv/kernel/vmlinux-xip.lds.S | 132 ++++++++++++++++++++++++++++
> arch/riscv/kernel/vmlinux.lds.S | 6 ++
> arch/riscv/mm/init.c | 100 +++++++++++++++++++--
> 11 files changed, 432 insertions(+), 18 deletions(-)
> create mode 100644 arch/riscv/kernel/vmlinux-xip.lds.S
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 85d626b8ce5e..59fb945a900e 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -438,7 +438,7 @@ config EFI_STUB
>
> config EFI
> bool "UEFI runtime support"
> - depends on OF
> + depends on OF && !XIP_KERNEL
> select LIBFDT
> select UCS2_STRING
> select EFI_PARAMS_FROM_FDT
> @@ -462,11 +462,51 @@ config STACKPROTECTOR_PER_TASK
> def_bool y
> depends on STACKPROTECTOR && CC_HAVE_STACKPROTECTOR_TLS
>
> +config XIP_KERNEL
> + bool "Kernel Execute-In-Place from ROM"
> + depends on MMU
> + help
> + Execute-In-Place allows the kernel to run from non-volatile storage
> + directly addressable by the CPU, such as NOR flash. This saves RAM
> + space since the text section of the kernel is not loaded from flash
> + to RAM. Read-write sections, such as the data section and stack,
> + are still copied to RAM. The XIP kernel is not compressed since
> + it has to run directly from flash, so it will take more space to
> + store it. The flash address used to link the kernel object files,
> + and for storing it, is configuration dependent. Therefore, if you
> + say Y here, you must know the proper physical address where to
> + store the kernel image depending on your own flash memory usage.
> +
> + Also note that the make target becomes "make xipImage" rather than
> + "make zImage" or "make Image". The final kernel binary to put in
> + ROM memory will be arch/riscv/boot/xipImage.
> +
> + If unsure, say N.
> +
> +config XIP_PHYS_ADDR
> + hex "XIP Kernel Physical Location"
> + depends on XIP_KERNEL
> + default "0x21000000"
> + help
> + This is the physical address in your flash memory the kernel will
> + be linked for and stored to. This address is dependent on your
> + own flash usage.
> +
> +config XIP_PHYS_RAM_BASE
> + hex "Platform Physical RAM address"
> + depends on XIP_KERNEL
> + default "0x80000000"
> + help
> + This is the physical address of RAM in the system. It has to be
> + explicitly specified to run early relocations of read-write data
> + from flash to RAM.
This is not XIP specific and this is something I considered to add in
order to map the linear mapping with hugepages, maybe simply rename this
without XIP_ prefix.
> +
> endmenu
>
> config BUILTIN_DTB
> - def_bool n
> + bool
> depends on OF
> + default y if XIP_KERNEL
>
> menu "Power management options"
>
> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> index 1368d943f1f3..8fcbec03974d 100644
> --- a/arch/riscv/Makefile
> +++ b/arch/riscv/Makefile
> @@ -82,7 +82,11 @@ CHECKFLAGS += -D__riscv -D__riscv_xlen=$(BITS)
>
> # Default target when executing plain make
> boot := arch/riscv/boot
> +ifeq ($(CONFIG_XIP_KERNEL),y)
> +KBUILD_IMAGE := $(boot)/xipImage
> +else
> KBUILD_IMAGE := $(boot)/Image.gz
> +endif
>
> head-y := arch/riscv/kernel/head.o
>
> @@ -95,12 +99,14 @@ PHONY += vdso_install
> vdso_install:
> $(Q)$(MAKE) $(build)=arch/riscv/kernel/vdso $@
>
> +ifneq ($(CONFIG_XIP_KERNEL),y)
> ifeq ($(CONFIG_RISCV_M_MODE)$(CONFIG_SOC_CANAAN),yy)
> KBUILD_IMAGE := $(boot)/loader.bin
> else
> KBUILD_IMAGE := $(boot)/Image.gz
> endif
> -BOOT_TARGETS := Image Image.gz loader loader.bin
> +endif
> +BOOT_TARGETS := Image Image.gz loader loader.bin xipImage
>
> all: $(notdir $(KBUILD_IMAGE))
>
> diff --git a/arch/riscv/boot/Makefile b/arch/riscv/boot/Makefile
> index 03404c84f971..6bf299f70c27 100644
> --- a/arch/riscv/boot/Makefile
> +++ b/arch/riscv/boot/Makefile
> @@ -17,8 +17,21 @@
> KCOV_INSTRUMENT := n
>
> OBJCOPYFLAGS_Image :=-O binary -R .note -R .note.gnu.build-id -R .comment -S
> +OBJCOPYFLAGS_xipImage :=-O binary -R .note -R .note.gnu.build-id -R .comment -S
>
> targets := Image Image.* loader loader.o loader.lds loader.bin
> +targets := Image Image.* loader loader.o loader.lds loader.bin xipImage
> +
> +ifeq ($(CONFIG_XIP_KERNEL),y)
> +
> +quiet_cmd_mkxip = $(quiet_cmd_objcopy)
> +cmd_mkxip = $(cmd_objcopy)
> +
> +$(obj)/xipImage: vmlinux FORCE
> + $(call if_changed,mkxip)
> + @$(kecho) ' Physical Address of xipImage: $(CONFIG_XIP_PHYS_ADDR)'
> +
> +endif
>
> $(obj)/Image: vmlinux FORCE
> $(call if_changed,objcopy)
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index ebf817c1bdf4..4c2e6902f2b8 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -11,6 +11,33 @@
>
> #include <asm/pgtable-bits.h>
>
> +#ifdef CONFIG_MMU
> +
> +#define VMALLOC_START (PAGE_OFFSET - VMALLOC_SIZE)
> +
> +#ifdef CONFIG_XIP_KERNEL
> +#define VMALLOC_SIZE ((KERN_VIRT_SIZE >> 1) - SZ_16M)
> +#define VMALLOC_END (PAGE_OFFSET - SZ_16M - 1)
> +
> +#define XIP_OFFSET SZ_8M
> +#define XIP_MASK (SZ_8M - 1)
> +#define XIP_VIRT_ADDR(physaddr) \
> + (PAGE_OFFSET - XIP_OFFSET + ((physaddr) & XIP_MASK))
> +
> +#else
> +
> +#define VMALLOC_SIZE (KERN_VIRT_SIZE >> 1)
> +#define VMALLOC_END (PAGE_OFFSET - 1)
> +
> +#endif /* CONFIG_XIP_KERNEL */
> +
> +#else
> +
> +#ifdef CONFIG_XIP_KERNEL
> +#define XIP_VIRT_ADDR(physaddr) (physaddr)
> +#endif /* CONFIG_XIP_KERNEL */
> +#endif /* CONFIG_MMU */
> +
> #ifndef __ASSEMBLY__
>
> /* Page Upper Directory not used in RISC-V */
> @@ -21,9 +48,25 @@
>
> #ifdef CONFIG_MMU
>
> -#define VMALLOC_SIZE (KERN_VIRT_SIZE >> 1)
> -#define VMALLOC_END (PAGE_OFFSET - 1)
> -#define VMALLOC_START (PAGE_OFFSET - VMALLOC_SIZE)
> +#ifdef CONFIG_XIP_KERNEL
> +/*
> + * Since we use sections to map it, this macro replaces the physical address
> + * with its virtual address while keeping offset from the base section.
It seems the comment should be the other way around: "this macro
replaces the *virtual* address...etc".
> + */
> +#define XIP_PHYS_ADDR(va) \
> + ((uintptr_t)(va) - PAGE_OFFSET + XIP_OFFSET + CONFIG_XIP_PHYS_ADDR)
> +
> +#define XIP_VIRT_ADDR_START XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR)
> +#define __PHRAM_BASE CONFIG_XIP_PHYS_RAM_BASE
I don't think that it is necessary to define this intermediate
__PHRAM_BASE.
> +
> +#define XIP_FIXUP(addr) \
> + (((uintptr_t)(addr) >= CONFIG_XIP_PHYS_ADDR && \
> + (uintptr_t)(addr) <= CONFIG_XIP_PHYS_ADDR + SZ_16M) ? \
That should be < CONFIG_XIP_PHYS_ADDR + SZ_16M, not <=.
> + (uintptr_t)(addr) - CONFIG_XIP_PHYS_ADDR + __PHRAM_BASE - XIP_OFFSET : \
> + (uintptr_t)(addr))
There are possible side-effects in this macro definition, consider using
a temporary variable for addr.
> +#else
> +#define XIP_FIXUP(addr) (addr)
> +#endif /* CONFIG_XIP_KERNEL */
>
> #define BPF_JIT_REGION_SIZE (SZ_128M)
> #define BPF_JIT_REGION_START (PAGE_OFFSET - BPF_JIT_REGION_SIZE)
> @@ -484,8 +527,20 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
>
> #define kern_addr_valid(addr) (1) /* FIXME */
>
> -extern void *dtb_early_va;
> -extern uintptr_t dtb_early_pa;
> +extern void *_dtb_early_va;
> +extern uintptr_t _dtb_early_pa;
> +#if defined(CONFIG_XIP_KERNEL) && defined(CONFIG_MMU)
CONFIG_XIP_KERNEL already depends on CONFIG_MMU. And maybe we could
handle XIP_KERNEL and !XIP_KERNEL in XIP_FIXUP to avoid those ifdefs ?
> +
> +#define dtb_early_va (*(void **)XIP_FIXUP(&_dtb_early_va))
> +#define dtb_early_pa (*(uintptr_t *)XIP_FIXUP(&_dtb_early_pa))
> +
> +#else
> +
> +#define dtb_early_va _dtb_early_va
> +#define dtb_early_pa _dtb_early_pa
> +
> +#endif /* CONFIG_XIP_KERNEL */
> +
> void setup_bootmem(void);
> void paging_init(void);
> void misc_mem_init(void);
> diff --git a/arch/riscv/kernel/cpu_ops_sbi.c b/arch/riscv/kernel/cpu_ops_sbi.c
> index 685fae72b7f5..7d368bc656ff 100644
> --- a/arch/riscv/kernel/cpu_ops_sbi.c
> +++ b/arch/riscv/kernel/cpu_ops_sbi.c
> @@ -53,10 +53,20 @@ static int sbi_hsm_hart_get_status(unsigned long hartid)
> }
> #endif
>
> +static inline unsigned long get_secondary_start_phys(void)
> +{
> +#ifdef CONFIG_XIP_KERNEL
> + return XIP_PHYS_ADDR(secondary_start_sbi);
> +#else
> + return __pa_symbol(secondary_start_sbi);
> +#endif
> +}
> +
> +
There are 2 newlines here.
> static int sbi_cpu_start(unsigned int cpuid, struct task_struct *tidle)
> {
> int rc;
> - unsigned long boot_addr = __pa_symbol(secondary_start_sbi);
> + unsigned long boot_addr = get_secondary_start_phys();
> int hartid = cpuid_to_hartid_map(cpuid);
>
> cpu_update_secondary_bootdata(cpuid, tidle);
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index f5a9bad86e58..17ecf6095209 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -9,11 +9,33 @@
> #include <linux/linkage.h>
> #include <asm/thread_info.h>
> #include <asm/page.h>
> +#include <asm/pgtable.h>
> #include <asm/csr.h>
> #include <asm/hwcap.h>
> #include <asm/image.h>
> #include "efi-header.S"
>
> +#ifdef CONFIG_XIP_KERNEL
> +.macro XIP_FIXUP_OFFSET reg
> +#ifdef CONFIG_64BIT
> + ld t0, _xip_fixup
> +#else
> + lw t0, _xip_fixup
> +#endif
Use REG_L here.
> + add \reg, \reg, t0
> +.endm
> +
> +_xip_fixup:
> +#ifdef CONFIG_64BIT
> + .dword CONFIG_XIP_PHYS_RAM_BASE - CONFIG_XIP_PHYS_ADDR - XIP_OFFSET
> +#else
> + .word CONFIG_XIP_PHYS_RAM_BASE - CONFIG_XIP_PHYS_ADDR - XIP_OFFSET
> +#endif
> +#else
> +.macro XIP_FIXUP_OFFSET reg
> +.endm
> +#endif /* CONFIG_XIP_KERNEL */
> +
> __HEAD
> ENTRY(_start)
> /*
> @@ -69,7 +91,11 @@ pe_head_start:
> #ifdef CONFIG_MMU
> relocate:
> /* Relocate return address */
> +#ifdef CONFIG_XIP_KERNEL
> + li a1, XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR)
> +#else
> li a1, PAGE_OFFSET
> +#endif
> la a2, _start
> sub a1, a1, a2
> add ra, ra, a1
> @@ -91,6 +117,7 @@ relocate:
> * to ensure the new translations are in use.
> */
> la a0, trampoline_pg_dir
> + XIP_FIXUP_OFFSET a0
For all those pairs of la aX...; XIP_FIXUP_OFFSET aX...; maybe introduce
a macro that does both ?
> srl a0, a0, PAGE_SHIFT
> or a0, a0, a1
> sfence.vma
> @@ -144,7 +171,9 @@ secondary_start_sbi:
>
> slli a3, a0, LGREG
> la a4, __cpu_up_stack_pointer
> + XIP_FIXUP_OFFSET a4
> la a5, __cpu_up_task_pointer
> + XIP_FIXUP_OFFSET a5
> add a4, a3, a4
> add a5, a3, a5
> REG_L sp, (a4)
> @@ -156,6 +185,7 @@ secondary_start_common:
> #ifdef CONFIG_MMU
> /* Enable virtual memory and relocate to virtual address */
> la a0, swapper_pg_dir
> + XIP_FIXUP_OFFSET a0
> call relocate
> #endif
> call setup_trap_vector
> @@ -236,12 +266,33 @@ pmp_done:
> .Lgood_cores:
> #endif
>
> +#ifndef CONFIG_XIP_KERNEL
> /* Pick one hart to run the main boot sequence */
> la a3, hart_lottery
> li a2, 1
> amoadd.w a3, a2, (a3)
> bnez a3, .Lsecondary_start
>
> +#else
> + /* hart_lottery in flash contains a magic number */
> + la a3, hart_lottery
> + mv a2, a3
> + XIP_FIXUP_OFFSET a2
> + lw t1, (a3)
> + amoswap.w t0, t1, (a2)
> + /* first time here if hart_lottery in RAM is not set */
> + beq t0, t1, .Lsecondary_start
> +
> + la sp, _end + THREAD_SIZE
> + XIP_FIXUP_OFFSET sp
> + mv s0, a0
> + call __copy_data
> +
> + /* Restore a0 copy */
> + mv a0, s0
> +#endif
> +
> +#ifndef CONFIG_XIP_KERNEL
> /* Clear BSS for flat non-ELF images */
> la a3, __bss_start
> la a4, __bss_stop
> @@ -251,15 +302,18 @@ clear_bss:
> add a3, a3, RISCV_SZPTR
> blt a3, a4, clear_bss
> clear_bss_done:
> -
> +#endif
> /* Save hart ID and DTB physical address */
> mv s0, a0
> mv s1, a1
> +
> la a2, boot_cpu_hartid
> + XIP_FIXUP_OFFSET a2
> REG_S a0, (a2)
>
> /* Initialize page tables and relocate to virtual addresses */
> la sp, init_thread_union + THREAD_SIZE
> + XIP_FIXUP_OFFSET sp
> #ifdef CONFIG_BUILTIN_DTB
> la a0, __dtb_start
> #else
> @@ -268,6 +322,7 @@ clear_bss_done:
> call setup_vm
> #ifdef CONFIG_MMU
> la a0, early_pg_dir
> + XIP_FIXUP_OFFSET a0
> call relocate
> #endif /* CONFIG_MMU */
>
> @@ -292,7 +347,9 @@ clear_bss_done:
>
> slli a3, a0, LGREG
> la a1, __cpu_up_stack_pointer
> + XIP_FIXUP_OFFSET a1
> la a2, __cpu_up_task_pointer
> + XIP_FIXUP_OFFSET a2
> add a1, a3, a1
> add a2, a3, a2
>
> diff --git a/arch/riscv/kernel/head.h b/arch/riscv/kernel/head.h
> index b48dda3d04f6..aabbc3ac3e48 100644
> --- a/arch/riscv/kernel/head.h
> +++ b/arch/riscv/kernel/head.h
> @@ -12,6 +12,9 @@ extern atomic_t hart_lottery;
>
> asmlinkage void do_page_fault(struct pt_regs *regs);
> asmlinkage void __init setup_vm(uintptr_t dtb_pa);
> +#ifdef CONFIG_XIP_KERNEL
> +asmlinkage void __init __copy_data(void);
> +#endif
>
> extern void *__cpu_up_stack_pointer[];
> extern void *__cpu_up_task_pointer[];
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index e85bacff1b50..29956c41a9cc 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -50,7 +50,11 @@ struct screen_info screen_info __section(".data") = {
> * This is used before the kernel initializes the BSS so it can't be in the
> * BSS.
> */
> -atomic_t hart_lottery __section(".sdata");
> +atomic_t hart_lottery __section(".sdata")
> +#ifdef CONFIG_XIP_KERNEL
> += ATOMIC_INIT(0xC001BEEF)
> +#endif
> +;
> unsigned long boot_cpu_hartid;
> static DEFINE_PER_CPU(struct cpu, cpu_devices);
>
> @@ -254,7 +258,7 @@ void __init setup_arch(char **cmdline_p)
> #if IS_ENABLED(CONFIG_BUILTIN_DTB)
> unflatten_and_copy_device_tree();
> #else
> - if (early_init_dt_verify(__va(dtb_early_pa)))
> + if (early_init_dt_verify(dtb_early_va))
> unflatten_device_tree();
> else
> pr_err("No DTB found in kernel mappings\n");
> diff --git a/arch/riscv/kernel/vmlinux-xip.lds.S b/arch/riscv/kernel/vmlinux-xip.lds.S
> new file mode 100644
> index 000000000000..9f0f08c34cd3
> --- /dev/null
> +++ b/arch/riscv/kernel/vmlinux-xip.lds.S
> @@ -0,0 +1,132 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2012 Regents of the University of California
> + * Copyright (C) 2017 SiFive
> + * Copyright (C) 2020 Vitaly Wool, Konsulko AB
> + */
> +
> +#define LOAD_OFFSET XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR)
> +/* No __ro_after_init data in the .rodata section - which will always be ro */
> +#define RO_AFTER_INIT_DATA
> +
> +#include <asm/vmlinux.lds.h>
> +#include <asm/page.h>
> +#include <asm/pgtable.h>
> +#include <asm/cache.h>
> +#include <asm/thread_info.h>
> +
> +OUTPUT_ARCH(riscv)
> +ENTRY(_start)
> +
> +jiffies = jiffies_64;
> +
> +SECTIONS
> +{
> + /* Beginning of code and text segment */
> + . = XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR);
> + _xiprom = .;
> + _start = .;
> + HEAD_TEXT_SECTION
> + INIT_TEXT_SECTION(PAGE_SIZE)
> + /* we have to discard exit text and such at runtime, not link time */
> + .exit.text :
> + {
> + EXIT_TEXT
> + }
> +
> + .text : {
> + _text = .;
> + _stext = .;
> + TEXT_TEXT
> + SCHED_TEXT
> + CPUIDLE_TEXT
> + LOCK_TEXT
> + KPROBES_TEXT
> + ENTRY_TEXT
> + IRQENTRY_TEXT
> + SOFTIRQENTRY_TEXT
> + *(.fixup)
> + _etext = .;
> + }
> + RO_DATA(L1_CACHE_BYTES)
> + .srodata : {
> + *(.srodata*)
> + }
> + .init.rodata : {
> + INIT_SETUP(16)
> + INIT_CALLS
> + CON_INITCALL
> + INIT_RAM_FS
> + }
> + _exiprom = .; /* End of XIP ROM area */
> +
> +
> +/*
> + * From this point, stuff is considered writable and will be copied to RAM
> + */
> + __data_loc = ALIGN(16); /* location in file */
> + . = PAGE_OFFSET; /* location in memory */
> +
> + _sdata = .; /* Start of data section */
> + _data = .;
> + RW_DATA(L1_CACHE_BYTES, PAGE_SIZE, THREAD_SIZE)
> + _edata = .;
> + __start_ro_after_init = .;
> + .data.ro_after_init : AT(ADDR(.data.ro_after_init) - LOAD_OFFSET) {
> + *(.data..ro_after_init)
> + }
> + __end_ro_after_init = .;
> +
> + . = ALIGN(PAGE_SIZE);
> + __init_begin = .;
> + .init.data : {
> + INIT_DATA
> + }
> + .exit.data : {
> + EXIT_DATA
> + }
> + . = ALIGN(8);
> + __soc_early_init_table : {
> + __soc_early_init_table_start = .;
> + KEEP(*(__soc_early_init_table))
> + __soc_early_init_table_end = .;
> + }
> + __soc_builtin_dtb_table : {
> + __soc_builtin_dtb_table_start = .;
> + KEEP(*(__soc_builtin_dtb_table))
> + __soc_builtin_dtb_table_end = .;
> + }
> + PERCPU_SECTION(L1_CACHE_BYTES)
> +
> + . = ALIGN(PAGE_SIZE);
> + __init_end = .;
> +
> + .sdata : {
> + __global_pointer$ = . + 0x800;
> + *(.sdata*)
> + *(.sbss*)
> + }
> +
> + BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0)
> + EXCEPTION_TABLE(0x10)
> +
> + .rel.dyn : AT(ADDR(.rel.dyn) - LOAD_OFFSET) {
> + *(.rel.dyn*)
> + }
> +
> + /*
> + * End of copied data. We need a dummy section to get its LMA.
> + * Also located before final ALIGN() as trailing padding is not stored
> + * in the resulting binary file and useless to copy.
> + */
> + .data.endmark : AT(ADDR(.data.endmark) - LOAD_OFFSET) { }
> + _edata_loc = LOADADDR(.data.endmark);
> +
> + . = ALIGN(PAGE_SIZE);
> + _end = .;
> +
> + STABS_DEBUG
> + DWARF_DEBUG
> +
> + DISCARDS
> +}
> diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
> index de03cb22d0e9..6745ec325930 100644
> --- a/arch/riscv/kernel/vmlinux.lds.S
> +++ b/arch/riscv/kernel/vmlinux.lds.S
> @@ -4,7 +4,12 @@
> * Copyright (C) 2017 SiFive
> */
>
> +#ifdef CONFIG_XIP_KERNEL
> +#include "vmlinux-xip.lds.S"
> +#else
> +
> #define LOAD_OFFSET PAGE_OFFSET
> +
> #include <asm/vmlinux.lds.h>
> #include <asm/page.h>
> #include <asm/cache.h>
> @@ -132,3 +137,4 @@ SECTIONS
>
> DISCARDS
> }
> +#endif /* CONFIG_XIP_KERNEL */
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 067583ab1bd7..b5ac455cb159 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -31,8 +31,8 @@ EXPORT_SYMBOL(empty_zero_page);
>
> extern char _start[];
> #define DTB_EARLY_BASE_VA PGDIR_SIZE
> -void *dtb_early_va __initdata;
> -uintptr_t dtb_early_pa __initdata;
> +void *_dtb_early_va __initdata;
> +uintptr_t _dtb_early_pa __initdata;
>
> struct pt_alloc_ops {
> pte_t *(*get_pte_virt)(phys_addr_t pa);
> @@ -88,6 +88,10 @@ static void print_vm_layout(void)
> (unsigned long)VMALLOC_END);
> print_mlm("lowmem", (unsigned long)PAGE_OFFSET,
> (unsigned long)high_memory);
> +#ifdef CONFIG_XIP_KERNEL
> + print_mlm("xip", (unsigned long)XIP_VIRT_ADDR_START,
> + (unsigned long)XIP_VIRT_ADDR_START + SZ_16M);
> +#endif /* CONFIG_XIP_KERNEL */
> }
> #else
> static void print_vm_layout(void) { }
> @@ -113,6 +117,10 @@ void __init setup_bootmem(void)
> phys_addr_t dram_end = memblock_end_of_DRAM();
> phys_addr_t max_mapped_addr = __pa(~(ulong)0);
>
> +#ifdef CONFIG_XIP_KERNEL
> + vmlinux_start = __pa_symbol(&_sdata);
> +#endif
Nit: I would use IS_ENABLED(CONFIG_XIP_KERNEL) to avoid double
assignment in case CONFIG_XIP_KERNEL is set.
> +
> /* The maximal physical memory size is -PAGE_OFFSET. */
> memblock_enforce_memory_limit(-PAGE_OFFSET);
>
> @@ -148,11 +156,27 @@ void __init setup_bootmem(void)
> memblock_allow_resize();
> }
>
> +#ifdef CONFIG_XIP_KERNEL
> +
> +extern char _xiprom[], _exiprom[];
> +extern char _sdata[], _edata[];
> +
> +#endif /* CONFIG_XIP_KERNEL */
> +
> #ifdef CONFIG_MMU
> -static struct pt_alloc_ops pt_ops;
> +static struct pt_alloc_ops _pt_ops;
> +
> +#ifdef CONFIG_XIP_KERNEL
> +#define pt_ops (*(struct pt_alloc_ops *)XIP_FIXUP(&_pt_ops))
> +#else
> +#define pt_ops _pt_ops
> +#endif
>
> unsigned long va_pa_offset;
> EXPORT_SYMBOL(va_pa_offset);
> +#ifdef CONFIG_XIP_KERNEL
> +#define va_pa_offset (*((unsigned long *)XIP_FIXUP(&va_pa_offset)))
> +#endif
> unsigned long pfn_base;
> EXPORT_SYMBOL(pfn_base);
>
> @@ -162,6 +186,12 @@ pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
>
> pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
>
> +#ifdef CONFIG_XIP_KERNEL
> +#define trampoline_pg_dir ((pgd_t *)XIP_FIXUP(trampoline_pg_dir))
> +#define fixmap_pte ((pte_t *)XIP_FIXUP(fixmap_pte))
> +#define early_pg_dir ((pgd_t *)XIP_FIXUP(early_pg_dir))
> +#endif /* CONFIG_XIP_KERNEL */
> +
> void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
> {
> unsigned long addr = __fix_to_virt(idx);
> @@ -237,6 +267,15 @@ pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
> pmd_t early_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
> pmd_t early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
>
> +#ifdef CONFIG_XIP_KERNEL
> +pmd_t xip_pmd[PTRS_PER_PMD] __page_aligned_bss;
> +
> +#define trampoline_pmd ((pmd_t *)XIP_FIXUP(trampoline_pmd))
> +#define fixmap_pmd ((pmd_t *)XIP_FIXUP(fixmap_pmd))
> +#define xip_pmd ((pmd_t *)XIP_FIXUP(xip_pmd))
> +#define early_pmd ((pmd_t *)XIP_FIXUP(early_pmd))
> +#endif /* CONFIG_XIP_KERNEL */
> +
> static pmd_t *__init get_pmd_virt_early(phys_addr_t pa)
> {
> /* Before MMU is enabled */
> @@ -353,6 +392,19 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
> return PMD_SIZE;
> }
>
> +#ifdef CONFIG_XIP_KERNEL
> +/* called from head.S with MMU off */
> +asmlinkage void __init __copy_data(void)
> +{
> + void *from = (void *)(&_sdata);
> + void *end = (void *)(&_end);
> + void *to = (void *)CONFIG_XIP_PHYS_RAM_BASE;
> + size_t sz = (size_t)(end - from);
> +
> + memcpy(to, from, sz);
> +}
> +#endif
> +
> /*
> * setup_vm() is called from head.S with MMU-off.
> *
> @@ -373,7 +425,8 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
>
> asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> {
> - uintptr_t va, pa, end_va;
> + uintptr_t va, end_va;
> + uintptr_t __maybe_unused pa;
> uintptr_t load_pa = (uintptr_t)(&_start);
> uintptr_t load_sz = (uintptr_t)(&_end) - load_pa;
> uintptr_t map_size;
> @@ -381,6 +434,13 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> pmd_t fix_bmap_spmd, fix_bmap_epmd;
> #endif
>
> +#ifdef CONFIG_XIP_KERNEL
> + uintptr_t xiprom = (uintptr_t)CONFIG_XIP_PHYS_ADDR;
> + uintptr_t xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
> +
> + load_pa = (uintptr_t)CONFIG_XIP_PHYS_RAM_BASE;
> + load_sz = (uintptr_t)(&_end) - (uintptr_t)(&_sdata);
> +#endif
> va_pa_offset = PAGE_OFFSET - load_pa;
> pfn_base = PFN_DOWN(load_pa);
>
> @@ -419,6 +479,21 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> load_pa, PGDIR_SIZE, PAGE_KERNEL_EXEC);
> #endif
>
> +#ifdef CONFIG_XIP_KERNEL
> + create_pgd_mapping(trampoline_pg_dir, XIP_VIRT_ADDR_START,
> + (uintptr_t)xip_pmd, PGDIR_SIZE, PAGE_TABLE);
> + for (va = XIP_VIRT_ADDR_START;
> + va < XIP_VIRT_ADDR_START + xiprom_sz;
> + va += PMD_SIZE) {
> + create_pmd_mapping(xip_pmd, va,
> + xiprom + (va - XIP_VIRT_ADDR_START),
> + PMD_SIZE, PAGE_KERNEL_EXEC);
> + }
> +
> + create_pgd_mapping(early_pg_dir, XIP_VIRT_ADDR_START,
> + (uintptr_t)xip_pmd, PGDIR_SIZE, PAGE_TABLE);
> +#endif
> +
> /*
> * Setup early PGD covering entire kernel which will allows
> * us to reach paging_init(). We map all memory banks later
> @@ -443,7 +518,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> pa + PMD_SIZE, PMD_SIZE, PAGE_KERNEL);
> dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PMD_SIZE - 1));
> #else /* CONFIG_BUILTIN_DTB */
> - dtb_early_va = __va(dtb_pa);
> + dtb_early_va = __va(XIP_FIXUP(dtb_pa));
> #endif /* CONFIG_BUILTIN_DTB */
> #else
> #ifndef CONFIG_BUILTIN_DTB
> @@ -455,7 +530,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> pa + PGDIR_SIZE, PGDIR_SIZE, PAGE_KERNEL);
> dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PGDIR_SIZE - 1));
> #else /* CONFIG_BUILTIN_DTB */
> - dtb_early_va = __va(dtb_pa);
> + dtb_early_va = __va(XIP_FIXUP(dtb_pa));
> #endif /* CONFIG_BUILTIN_DTB */
> #endif
> dtb_early_pa = dtb_pa;
> @@ -496,6 +571,9 @@ static void __init setup_vm_final(void)
> uintptr_t va, map_size;
> phys_addr_t pa, start, end;
> u64 i;
> +#ifdef CONFIG_XIP_KERNEL
> + uintptr_t xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
> +#endif
>
> /**
> * MMU is enabled at this point. But page table setup is not complete yet.
> @@ -527,6 +605,16 @@ static void __init setup_vm_final(void)
> map_size, PAGE_KERNEL_EXEC);
> }
> }
> +#ifdef CONFIG_XIP_KERNEL
> + map_size = best_map_size(CONFIG_XIP_PHYS_ADDR, xiprom_sz);
> + for (va = XIP_VIRT_ADDR_START;
> + va < XIP_VIRT_ADDR_START + xiprom_sz;
> + va += map_size)
> + create_pgd_mapping(swapper_pg_dir, va,
> + CONFIG_XIP_PHYS_ADDR + (va - XIP_VIRT_ADDR_START),
> + map_size, PAGE_KERNEL_EXEC);
> +
> +#endif
>
> /* Clear fixmap PTE and PMD mappings */
> clear_fixmap(FIX_PTE);
>
And I'm not sure I understand which variables are required to be fixup,
can you explain it a bit more please ?
And finally, how can we try XIP_KERNEL on qemu ?
Sorry about the late review,
Thanks,
Alex
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