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riscv: Support CONFIG_RELOCATABLE on NOMMU

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Move relocate_kernel() out of the CONFIG_MMU block so it can be called
from the NOMMU version of setup_vm(). Set some offsets in kernel_map so
relocate_kernel() does not need to be modified. Relocatable NOMMU
kernels can be loaded to any physical memory address; they no longer
depend on CONFIG_PAGE_OFFSET.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Link: https://lore.kernel.org/r/20241026171441.3047904-4-samuel.holland@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Samuel Holland 2024-10-26 10:13:55 -07:00 committed by Palmer Dabbelt
parent 2c0391b29b
commit 51b766c79a
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GPG Key ID: 2E1319F35FBB1889
3 changed files with 49 additions and 39 deletions
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2
arch/riscv/Kconfig
View File

@ -1075,7 +1075,7 @@ config PARAVIRT_TIME_ACCOUNTING
config RELOCATABLE
bool "Build a relocatable kernel"
depends on MMU && 64BIT && !XIP_KERNEL
depends on 64BIT && !XIP_KERNEL
select MODULE_SECTIONS if MODULES
help
This builds a kernel as a Position Independent Executable (PIE),

4
arch/riscv/include/asm/pgtable.h
View File

@ -12,7 +12,11 @@
#include <asm/pgtable-bits.h>
#ifndef CONFIG_MMU
#ifdef CONFIG_RELOCATABLE
#define KERNEL_LINK_ADDR UL(0)
#else
#define KERNEL_LINK_ADDR _AC(CONFIG_PAGE_OFFSET, UL)
#endif
#define KERN_VIRT_SIZE (UL(-1))
#else

82
arch/riscv/mm/init.c
View File

@ -323,6 +323,44 @@ static void __init setup_bootmem(void)
hugetlb_cma_reserve(PUD_SHIFT - PAGE_SHIFT);
}
#ifdef CONFIG_RELOCATABLE
extern unsigned long __rela_dyn_start, __rela_dyn_end;
static void __init relocate_kernel(void)
{
Elf64_Rela *rela = (Elf64_Rela *)&__rela_dyn_start;
/*
* This holds the offset between the linked virtual address and the
* relocated virtual address.
*/
uintptr_t reloc_offset = kernel_map.virt_addr - KERNEL_LINK_ADDR;
/*
* This holds the offset between kernel linked virtual address and
* physical address.
*/
uintptr_t va_kernel_link_pa_offset = KERNEL_LINK_ADDR - kernel_map.phys_addr;
for ( ; rela < (Elf64_Rela *)&__rela_dyn_end; rela++) {
Elf64_Addr addr = (rela->r_offset - va_kernel_link_pa_offset);
Elf64_Addr relocated_addr = rela->r_addend;
if (rela->r_info != R_RISCV_RELATIVE)
continue;
/*
* Make sure to not relocate vdso symbols like rt_sigreturn
* which are linked from the address 0 in vmlinux since
* vdso symbol addresses are actually used as an offset from
* mm->context.vdso in VDSO_OFFSET macro.
*/
if (relocated_addr >= KERNEL_LINK_ADDR)
relocated_addr += reloc_offset;
*(Elf64_Addr *)addr = relocated_addr;
}
}
#endif /* CONFIG_RELOCATABLE */
#ifdef CONFIG_MMU
struct pt_alloc_ops pt_ops __meminitdata;
@ -893,44 +931,6 @@ retry:
#error "setup_vm() is called from head.S before relocate so it should not use absolute addressing."
#endif
#ifdef CONFIG_RELOCATABLE
extern unsigned long __rela_dyn_start, __rela_dyn_end;
static void __init relocate_kernel(void)
{
Elf64_Rela *rela = (Elf64_Rela *)&__rela_dyn_start;
/*
* This holds the offset between the linked virtual address and the
* relocated virtual address.
*/
uintptr_t reloc_offset = kernel_map.virt_addr - KERNEL_LINK_ADDR;
/*
* This holds the offset between kernel linked virtual address and
* physical address.
*/
uintptr_t va_kernel_link_pa_offset = KERNEL_LINK_ADDR - kernel_map.phys_addr;
for ( ; rela < (Elf64_Rela *)&__rela_dyn_end; rela++) {
Elf64_Addr addr = (rela->r_offset - va_kernel_link_pa_offset);
Elf64_Addr relocated_addr = rela->r_addend;
if (rela->r_info != R_RISCV_RELATIVE)
continue;
/*
* Make sure to not relocate vdso symbols like rt_sigreturn
* which are linked from the address 0 in vmlinux since
* vdso symbol addresses are actually used as an offset from
* mm->context.vdso in VDSO_OFFSET macro.
*/
if (relocated_addr >= KERNEL_LINK_ADDR)
relocated_addr += reloc_offset;
*(Elf64_Addr *)addr = relocated_addr;
}
}
#endif /* CONFIG_RELOCATABLE */
#ifdef CONFIG_XIP_KERNEL
static void __init create_kernel_page_table(pgd_t *pgdir,
__always_unused bool early)
@ -1378,6 +1378,12 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
{
dtb_early_va = (void *)dtb_pa;
dtb_early_pa = dtb_pa;
#ifdef CONFIG_RELOCATABLE
kernel_map.virt_addr = (uintptr_t)_start;
kernel_map.phys_addr = (uintptr_t)_start;
relocate_kernel();
#endif
}
static inline void setup_vm_final(void)