[PATCH v4 0/4] vmalloc kernel mapping and relocatable kernel

[PATCH v4 0/4] vmalloc kernel mapping and relocatable kernel

[Alexandre Ghiti]

This patchset originally implemented relocatable kernel support but now          
also moves the kernel mapping into the vmalloc zone.                             
                                                                                 
The first patch explains why we need to move the kernel into vmalloc             
zone (instead of memcpying it around). That patch should ease KASLR              
implementation a lot.                                                            
                                                                                 
The second patch allows to build relocatable kernels but is not selected         
by default.                                                                      
                                                                                 
The third and fourth patches take advantage of an already existing powerpc       
script that checks relocations at compile-time, and uses it for riscv.           
                                                                                 
Changes in v4:                                                                   
  * Fix BPF region that overlapped with kernel's as suggested by Zong            
  * Fix end of module region that could be larger than 2GB as suggested by Zong  
  * Fix the size of the vm area reserved for the kernel as we could lose         
    PMD_SIZE if the size was already aligned on PMD_SIZE                         
  * Split compile time relocations check patch into 2 patches as suggested by Anup
  * Applied Reviewed-by from Zong and Anup                                       
                                                                                 
Changes in v3:                                                                   
  * Move kernel mapping to vmalloc                                               
                                                                                 
Changes in v2:                                                                   
  * Make RELOCATABLE depend on MMU as suggested by Anup                          
  * Rename kernel_load_addr into kernel_virt_addr as suggested by Anup           
  * Use __pa_symbol instead of __pa, as suggested by Zong                        
  * Rebased on top of v5.6-rc3                                                   
  * Tested with sv48 patchset                                                    
  * Add Reviewed/Tested-by from Zong and Anup

Alexandre Ghiti (4):
  riscv: Move kernel mapping to vmalloc zone
  riscv: Introduce CONFIG_RELOCATABLE
  powerpc: Move script to check relocations at compile time in scripts/
  riscv: Check relocations at compile time

 arch/powerpc/tools/relocs_check.sh |  18 +----
 arch/riscv/Kconfig                 |  12 +++
 arch/riscv/Makefile                |   5 +-
 arch/riscv/Makefile.postlink       |  36 +++++++++
 arch/riscv/boot/loader.lds.S       |   3 +-
 arch/riscv/include/asm/page.h      |  10 ++-
 arch/riscv/include/asm/pgtable.h   |  38 ++++++---
 arch/riscv/kernel/head.S           |   3 +-
 arch/riscv/kernel/module.c         |   4 +-
 arch/riscv/kernel/vmlinux.lds.S    |   9 ++-
 arch/riscv/mm/Makefile             |   4 +
 arch/riscv/mm/init.c               | 121 +++++++++++++++++++++++++----
 arch/riscv/mm/physaddr.c           |   2 +-
 arch/riscv/tools/relocs_check.sh   |  26 +++++++
 scripts/relocs_check.sh            |  20 +++++
 15 files changed, 259 insertions(+), 52 deletions(-)
 create mode 100644 arch/riscv/Makefile.postlink
 create mode 100755 arch/riscv/tools/relocs_check.sh
 create mode 100755 scripts/relocs_check.sh

-- 
2.20.1

[PATCH v4 1/4] riscv: Move kernel mapping to vmalloc zone

[Alexandre Ghiti]

This is a preparatory patch for relocatable kernel.

The kernel used to be linked at PAGE_OFFSET address and used to be loaded
physically at the beginning of the main memory. Therefore, we could use
the linear mapping for the kernel mapping.

But the relocated kernel base address will be different from PAGE_OFFSET
and since in the linear mapping, two different virtual addresses cannot
point to the same physical address, the kernel mapping needs to lie outside
the linear mapping.

In addition, because modules and BPF must be close to the kernel (inside
+-2GB window), the kernel is placed at the end of the vmalloc zone minus
2GB, which leaves room for modules and BPF. The kernel could not be
placed at the beginning of the vmalloc zone since other vmalloc
allocations from the kernel could get all the +-2GB window around the
kernel which would prevent new modules and BPF programs to be loaded.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
---
 arch/riscv/boot/loader.lds.S     |  3 +-
 arch/riscv/include/asm/page.h    | 10 +++++-
 arch/riscv/include/asm/pgtable.h | 38 ++++++++++++++-------
 arch/riscv/kernel/head.S         |  3 +-
 arch/riscv/kernel/module.c       |  4 +--
 arch/riscv/kernel/vmlinux.lds.S  |  3 +-
 arch/riscv/mm/init.c             | 58 +++++++++++++++++++++++++-------
 arch/riscv/mm/physaddr.c         |  2 +-
 8 files changed, 88 insertions(+), 33 deletions(-)

diff --git a/arch/riscv/boot/loader.lds.S b/arch/riscv/boot/loader.lds.S
index 47a5003c2e28..62d94696a19c 100644
--- a/arch/riscv/boot/loader.lds.S
+++ b/arch/riscv/boot/loader.lds.S
@@ -1,13 +1,14 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 
 #include <asm/page.h>
+#include <asm/pgtable.h>
 
 OUTPUT_ARCH(riscv)
 ENTRY(_start)
 
 SECTIONS
 {
-	. = PAGE_OFFSET;
+	. = KERNEL_LINK_ADDR;
 
 	.payload : {
 		*(.payload)
diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
index 2d50f76efe48..48bb09b6a9b7 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -90,18 +90,26 @@ typedef struct page *pgtable_t;
 
 #ifdef CONFIG_MMU
 extern unsigned long va_pa_offset;
+extern unsigned long va_kernel_pa_offset;
 extern unsigned long pfn_base;
 #define ARCH_PFN_OFFSET		(pfn_base)
 #else
 #define va_pa_offset		0
+#define va_kernel_pa_offset	0
 #define ARCH_PFN_OFFSET		(PAGE_OFFSET >> PAGE_SHIFT)
 #endif /* CONFIG_MMU */
 
 extern unsigned long max_low_pfn;
 extern unsigned long min_low_pfn;
+extern unsigned long kernel_virt_addr;
 
 #define __pa_to_va_nodebug(x)	((void *)((unsigned long) (x) + va_pa_offset))
-#define __va_to_pa_nodebug(x)	((unsigned long)(x) - va_pa_offset)
+#define linear_mapping_va_to_pa(x)	((unsigned long)(x) - va_pa_offset)
+#define kernel_mapping_va_to_pa(x)	\
+	((unsigned long)(x) - va_kernel_pa_offset)
+#define __va_to_pa_nodebug(x)		\
+	(((x) >= PAGE_OFFSET) ?		\
+		linear_mapping_va_to_pa(x) : kernel_mapping_va_to_pa(x))
 
 #ifdef CONFIG_DEBUG_VIRTUAL
 extern phys_addr_t __virt_to_phys(unsigned long x);
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 35b60035b6b0..94ef3b49dfb6 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -11,23 +11,29 @@
 
 #include <asm/pgtable-bits.h>
 
-#ifndef __ASSEMBLY__
-
-/* Page Upper Directory not used in RISC-V */
-#include <asm-generic/pgtable-nopud.h>
-#include <asm/page.h>
-#include <asm/tlbflush.h>
-#include <linux/mm_types.h>
-
-#ifdef CONFIG_MMU
+#ifndef CONFIG_MMU
+#define KERNEL_VIRT_ADDR	PAGE_OFFSET
+#define KERNEL_LINK_ADDR	PAGE_OFFSET
+#else
+/*
+ * Leave 2GB for modules and BPF that must lie within a 2GB range around
+ * the kernel.
+ */
+#define KERNEL_VIRT_ADDR	(VMALLOC_END - SZ_2G + 1)
+#define KERNEL_LINK_ADDR	KERNEL_VIRT_ADDR
 
 #define VMALLOC_SIZE     (KERN_VIRT_SIZE >> 1)
 #define VMALLOC_END      (PAGE_OFFSET - 1)
 #define VMALLOC_START    (PAGE_OFFSET - VMALLOC_SIZE)
 
 #define BPF_JIT_REGION_SIZE	(SZ_128M)
-#define BPF_JIT_REGION_START	(PAGE_OFFSET - BPF_JIT_REGION_SIZE)
-#define BPF_JIT_REGION_END	(VMALLOC_END)
+#define BPF_JIT_REGION_START	PFN_ALIGN((unsigned long)&_end)
+#define BPF_JIT_REGION_END	(BPF_JIT_REGION_START + BPF_JIT_REGION_SIZE)
+
+#ifdef CONFIG_64BIT
+#define VMALLOC_MODULE_START	BPF_JIT_REGION_END
+#define VMALLOC_MODULE_END	(((unsigned long)&_start & PAGE_MASK) + SZ_2G)
+#endif
 
 /*
  * Roughly size the vmemmap space to be large enough to fit enough
@@ -57,9 +63,16 @@
 #define FIXADDR_SIZE     PGDIR_SIZE
 #endif
 #define FIXADDR_START    (FIXADDR_TOP - FIXADDR_SIZE)
-
 #endif
 
+#ifndef __ASSEMBLY__
+
+/* Page Upper Directory not used in RISC-V */
+#include <asm-generic/pgtable-nopud.h>
+#include <asm/page.h>
+#include <asm/tlbflush.h>
+#include <linux/mm_types.h>
+
 #ifdef CONFIG_64BIT
 #include <asm/pgtable-64.h>
 #else
@@ -483,6 +496,7 @@ static inline void __kernel_map_pages(struct page *page, int numpages, int enabl
 
 #define kern_addr_valid(addr)   (1) /* FIXME */
 
+extern char _start[];
 extern void *dtb_early_va;
 void setup_bootmem(void);
 void paging_init(void);
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 98a406474e7d..8f5bb7731327 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -49,7 +49,8 @@ ENTRY(_start)
 #ifdef CONFIG_MMU
 relocate:
 	/* Relocate return address */
-	li a1, PAGE_OFFSET
+	la a1, kernel_virt_addr
+	REG_L a1, 0(a1)
 	la a2, _start
 	sub a1, a1, a2
 	add ra, ra, a1
diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
index 8bbe5dbe1341..1a8fbe05accf 100644
--- a/arch/riscv/kernel/module.c
+++ b/arch/riscv/kernel/module.c
@@ -392,12 +392,10 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 }
 
 #if defined(CONFIG_MMU) && defined(CONFIG_64BIT)
-#define VMALLOC_MODULE_START \
-	 max(PFN_ALIGN((unsigned long)&_end - SZ_2G), VMALLOC_START)
 void *module_alloc(unsigned long size)
 {
 	return __vmalloc_node_range(size, 1, VMALLOC_MODULE_START,
-				    VMALLOC_END, GFP_KERNEL,
+				    VMALLOC_MODULE_END, GFP_KERNEL,
 				    PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
 				    __builtin_return_address(0));
 }
diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
index 0339b6bbe11a..a9abde62909f 100644
--- a/arch/riscv/kernel/vmlinux.lds.S
+++ b/arch/riscv/kernel/vmlinux.lds.S
@@ -4,7 +4,8 @@
  * Copyright (C) 2017 SiFive
  */
 
-#define LOAD_OFFSET PAGE_OFFSET
+#include <asm/pgtable.h>
+#define LOAD_OFFSET KERNEL_LINK_ADDR
 #include <asm/vmlinux.lds.h>
 #include <asm/page.h>
 #include <asm/cache.h>
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 736de6c8739f..37be2eb45e58 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -22,6 +22,9 @@
 
 #include "../kernel/head.h"
 
+unsigned long kernel_virt_addr = KERNEL_VIRT_ADDR;
+EXPORT_SYMBOL(kernel_virt_addr);
+
 unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
 							__page_aligned_bss;
 EXPORT_SYMBOL(empty_zero_page);
@@ -178,8 +181,12 @@ void __init setup_bootmem(void)
 }
 
 #ifdef CONFIG_MMU
+/* Offset between linear mapping virtual address and kernel load address */
 unsigned long va_pa_offset;
 EXPORT_SYMBOL(va_pa_offset);
+/* Offset between kernel mapping virtual address and kernel load address */
+unsigned long va_kernel_pa_offset;
+EXPORT_SYMBOL(va_kernel_pa_offset);
 unsigned long pfn_base;
 EXPORT_SYMBOL(pfn_base);
 
@@ -271,7 +278,7 @@ static phys_addr_t __init alloc_pmd(uintptr_t va)
 	if (mmu_enabled)
 		return memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE);
 
-	pmd_num = (va - PAGE_OFFSET) >> PGDIR_SHIFT;
+	pmd_num = (va - kernel_virt_addr) >> PGDIR_SHIFT;
 	BUG_ON(pmd_num >= NUM_EARLY_PMDS);
 	return (uintptr_t)&early_pmd[pmd_num * PTRS_PER_PMD];
 }
@@ -372,14 +379,30 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
 #error "setup_vm() is called from head.S before relocate so it should not use absolute addressing."
 #endif
 
+static uintptr_t load_pa, load_sz;
+
+void create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
+{
+	uintptr_t va, end_va;
+
+	end_va = kernel_virt_addr + load_sz;
+	for (va = kernel_virt_addr; va < end_va; va += map_size)
+		create_pgd_mapping(pgdir, va,
+				   load_pa + (va - kernel_virt_addr),
+				   map_size, PAGE_KERNEL_EXEC);
+}
+
 asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 {
 	uintptr_t va, end_va;
-	uintptr_t load_pa = (uintptr_t)(&_start);
-	uintptr_t load_sz = (uintptr_t)(&_end) - load_pa;
 	uintptr_t map_size = best_map_size(load_pa, MAX_EARLY_MAPPING_SIZE);
 
+	load_pa = (uintptr_t)(&_start);
+	load_sz = (uintptr_t)(&_end) - load_pa;
+
 	va_pa_offset = PAGE_OFFSET - load_pa;
+	va_kernel_pa_offset = kernel_virt_addr - load_pa;
+
 	pfn_base = PFN_DOWN(load_pa);
 
 	/*
@@ -402,26 +425,22 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 	create_pmd_mapping(fixmap_pmd, FIXADDR_START,
 			   (uintptr_t)fixmap_pte, PMD_SIZE, PAGE_TABLE);
 	/* Setup trampoline PGD and PMD */
-	create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET,
+	create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
 			   (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
-	create_pmd_mapping(trampoline_pmd, PAGE_OFFSET,
+	create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
 			   load_pa, PMD_SIZE, PAGE_KERNEL_EXEC);
 #else
 	/* Setup trampoline PGD */
-	create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET,
+	create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
 			   load_pa, PGDIR_SIZE, PAGE_KERNEL_EXEC);
 #endif
 
 	/*
-	 * Setup early PGD covering entire kernel which will allows
+	 * Setup early PGD covering entire kernel which will allow
 	 * us to reach paging_init(). We map all memory banks later
 	 * in setup_vm_final() below.
 	 */
-	end_va = PAGE_OFFSET + load_sz;
-	for (va = PAGE_OFFSET; va < end_va; va += map_size)
-		create_pgd_mapping(early_pg_dir, va,
-				   load_pa + (va - PAGE_OFFSET),
-				   map_size, PAGE_KERNEL_EXEC);
+	create_kernel_page_table(early_pg_dir, map_size);
 
 	/* Create fixed mapping for early FDT parsing */
 	end_va = __fix_to_virt(FIX_FDT) + FIX_FDT_SIZE;
@@ -441,6 +460,7 @@ static void __init setup_vm_final(void)
 	uintptr_t va, map_size;
 	phys_addr_t pa, start, end;
 	struct memblock_region *reg;
+	static struct vm_struct vm_kernel = { 0 };
 
 	/* Set mmu_enabled flag */
 	mmu_enabled = true;
@@ -467,10 +487,22 @@ static void __init setup_vm_final(void)
 		for (pa = start; pa < end; pa += map_size) {
 			va = (uintptr_t)__va(pa);
 			create_pgd_mapping(swapper_pg_dir, va, pa,
-					   map_size, PAGE_KERNEL_EXEC);
+					   map_size, PAGE_KERNEL);
 		}
 	}
 
+	/* Map the kernel */
+	create_kernel_page_table(swapper_pg_dir, PMD_SIZE);
+
+	/* Reserve the vmalloc area occupied by the kernel */
+	vm_kernel.addr = (void *)kernel_virt_addr;
+	vm_kernel.phys_addr = load_pa;
+	vm_kernel.size = (load_sz + PMD_SIZE - 1) & ~(PMD_SIZE - 1);
+	vm_kernel.flags = VM_MAP | VM_NO_GUARD;
+	vm_kernel.caller = __builtin_return_address(0);
+
+	vm_area_add_early(&vm_kernel);
+
 	/* Clear fixmap PTE and PMD mappings */
 	clear_fixmap(FIX_PTE);
 	clear_fixmap(FIX_PMD);
diff --git a/arch/riscv/mm/physaddr.c b/arch/riscv/mm/physaddr.c
index e8e4dcd39fed..35703d5ef5fd 100644
--- a/arch/riscv/mm/physaddr.c
+++ b/arch/riscv/mm/physaddr.c
@@ -23,7 +23,7 @@ EXPORT_SYMBOL(__virt_to_phys);
 
 phys_addr_t __phys_addr_symbol(unsigned long x)
 {
-	unsigned long kernel_start = (unsigned long)PAGE_OFFSET;
+	unsigned long kernel_start = (unsigned long)kernel_virt_addr;
 	unsigned long kernel_end = (unsigned long)_end;
 
 	/*
-- 
2.20.1

[PATCH v4 2/4] riscv: Introduce CONFIG_RELOCATABLE

[Alexandre Ghiti]

This config allows to compile the kernel as PIE and to relocate it at
any virtual address at runtime: this paves the way to KASLR and to 4-level
page table folding at runtime. Runtime relocation is possible since
relocation metadata are embedded into the kernel.

Note that relocating at runtime introduces an overhead even if the
kernel is loaded at the same address it was linked at and that the compiler
options are those used in arm64 which uses the same RELA relocation
format.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
---
 arch/riscv/Kconfig              | 12 +++++++
 arch/riscv/Makefile             |  5 ++-
 arch/riscv/kernel/vmlinux.lds.S |  6 ++--
 arch/riscv/mm/Makefile          |  4 +++
 arch/riscv/mm/init.c            | 63 +++++++++++++++++++++++++++++++++
 5 files changed, 87 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index a31e1a41913a..93127d5913fe 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -170,6 +170,18 @@ config PGTABLE_LEVELS
 	default 3 if 64BIT
 	default 2
 
+config RELOCATABLE
+	bool
+	depends on MMU
+	help
+          This builds a kernel as a Position Independent Executable (PIE),
+          which retains all relocation metadata required to relocate the
+          kernel binary at runtime to a different virtual address than the
+          address it was linked at.
+          Since RISCV uses the RELA relocation format, this requires a
+          relocation pass at runtime even if the kernel is loaded at the
+          same address it was linked at.
+
 source "arch/riscv/Kconfig.socs"
 
 menu "Platform type"
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index fb6e37db836d..1406416ea743 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -9,7 +9,10 @@
 #
 
 OBJCOPYFLAGS    := -O binary
-LDFLAGS_vmlinux :=
+ifeq ($(CONFIG_RELOCATABLE),y)
+LDFLAGS_vmlinux := -shared -Bsymbolic -z notext -z norelro
+KBUILD_CFLAGS += -fPIE
+endif
 ifeq ($(CONFIG_DYNAMIC_FTRACE),y)
 	LDFLAGS_vmlinux := --no-relax
 endif
diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
index a9abde62909f..e8ffba8c2044 100644
--- a/arch/riscv/kernel/vmlinux.lds.S
+++ b/arch/riscv/kernel/vmlinux.lds.S
@@ -85,8 +85,10 @@ SECTIONS
 
 	BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0)
 
-	.rel.dyn : {
-		*(.rel.dyn*)
+	.rela.dyn : ALIGN(8) {
+		__rela_dyn_start = .;
+		*(.rela .rela*)
+		__rela_dyn_end = .;
 	}
 
 	_end = .;
diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
index 363ef01c30b1..dc5cdaa80bc1 100644
--- a/arch/riscv/mm/Makefile
+++ b/arch/riscv/mm/Makefile
@@ -1,6 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
 CFLAGS_init.o := -mcmodel=medany
+ifdef CONFIG_RELOCATABLE
+CFLAGS_init.o += -fno-pie
+endif
+
 ifdef CONFIG_FTRACE
 CFLAGS_REMOVE_init.o = -pg
 endif
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 37be2eb45e58..e63ea5b6b6cf 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -13,6 +13,9 @@
 #include <linux/of_fdt.h>
 #include <linux/libfdt.h>
 #include <linux/set_memory.h>
+#ifdef CONFIG_RELOCATABLE
+#include <linux/elf.h>
+#endif
 
 #include <asm/fixmap.h>
 #include <asm/tlbflush.h>
@@ -379,6 +382,53 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
 #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;
+
+#ifdef CONFIG_64BIT
+#define Elf_Rela Elf64_Rela
+#define Elf_Addr Elf64_Addr
+#else
+#define Elf_Rela Elf32_Rela
+#define Elf_Addr Elf32_Addr
+#endif
+
+void __init relocate_kernel(uintptr_t load_pa)
+{
+	Elf_Rela *rela = (Elf_Rela *)&__rela_dyn_start;
+	/*
+	 * This holds the offset between the linked virtual address and the
+	 * relocated virtual address.
+	 */
+	uintptr_t reloc_offset = kernel_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 - load_pa;
+
+	for ( ; rela < (Elf_Rela *)&__rela_dyn_end; rela++) {
+		Elf_Addr addr = (rela->r_offset - va_kernel_link_pa_offset);
+		Elf_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;
+
+		*(Elf_Addr *)addr = relocated_addr;
+	}
+}
+
+#endif
+
 static uintptr_t load_pa, load_sz;
 
 void create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
@@ -405,6 +455,19 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 
 	pfn_base = PFN_DOWN(load_pa);
 
+#ifdef CONFIG_RELOCATABLE
+#ifdef CONFIG_64BIT
+	/*
+	 * Early page table uses only one PGDIR, which makes it possible
+	 * to map PGDIR_SIZE aligned on PGDIR_SIZE: if the relocation offset
+	 * makes the kernel cross over a PGDIR_SIZE boundary, raise a bug
+	 * since a part of the kernel would not get mapped.
+	 * This cannot happen on rv32 as we use the entire page directory level.
+	 */
+	BUG_ON(PGDIR_SIZE - (kernel_virt_addr & (PGDIR_SIZE - 1)) < load_sz);
+#endif
+	relocate_kernel(load_pa);
+#endif
 	/*
 	 * Enforce boot alignment requirements of RV32 and
 	 * RV64 by only allowing PMD or PGD mappings.
-- 
2.20.1

[PATCH v4 3/4] powerpc: Move script to check relocations at compile time in scripts/

[Alexandre Ghiti]

Relocating kernel at runtime is done very early in the boot process, so
it is not convenient to check for relocations there and react in case a
relocation was not expected.

Powerpc architecture has a script that allows to check at compile time
for such unexpected relocations: extract the common logic to scripts/
so that other architectures can take advantage of it.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Anup Patel <anup@brainfault.org>
---
 arch/powerpc/tools/relocs_check.sh | 18 ++----------------
 scripts/relocs_check.sh            | 20 ++++++++++++++++++++
 2 files changed, 22 insertions(+), 16 deletions(-)
 create mode 100755 scripts/relocs_check.sh

diff --git a/arch/powerpc/tools/relocs_check.sh b/arch/powerpc/tools/relocs_check.sh
index 014e00e74d2b..e367895941ae 100755
--- a/arch/powerpc/tools/relocs_check.sh
+++ b/arch/powerpc/tools/relocs_check.sh
@@ -15,21 +15,8 @@ if [ $# -lt 3 ]; then
 	exit 1
 fi
 
-# Have Kbuild supply the path to objdump and nm so we handle cross compilation.
-objdump="$1"
-nm="$2"
-vmlinux="$3"
-
-# Remove from the bad relocations those that match an undefined weak symbol
-# which will result in an absolute relocation to 0.
-# Weak unresolved symbols are of that form in nm output:
-# "                  w _binary__btf_vmlinux_bin_end"
-undef_weak_symbols=$($nm "$vmlinux" | awk '$1 ~ /w/ { print $2 }')
-
 bad_relocs=$(
-$objdump -R "$vmlinux" |
-	# Only look at relocation lines.
-	grep -E '\<R_' |
+${srctree}/scripts/relocs_check.sh "$@" |
 	# These relocations are okay
 	# On PPC64:
 	#	R_PPC64_RELATIVE, R_PPC64_NONE
@@ -43,8 +30,7 @@ R_PPC_ADDR16_LO
 R_PPC_ADDR16_HI
 R_PPC_ADDR16_HA
 R_PPC_RELATIVE
-R_PPC_NONE' |
-	([ "$undef_weak_symbols" ] && grep -F -w -v "$undef_weak_symbols" || cat)
+R_PPC_NONE'
 )
 
 if [ -z "$bad_relocs" ]; then
diff --git a/scripts/relocs_check.sh b/scripts/relocs_check.sh
new file mode 100755
index 000000000000..137c660499f3
--- /dev/null
+++ b/scripts/relocs_check.sh
@@ -0,0 +1,20 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# Get a list of all the relocations, remove from it the relocations
+# that are known to be legitimate and return this list to arch specific
+# script that will look for suspicious relocations.
+
+objdump="$1"
+nm="$2"
+vmlinux="$3"
+
+# Remove from the possible bad relocations those that match an undefined
+# weak symbol which will result in an absolute relocation to 0.
+# Weak unresolved symbols are of that form in nm output:
+# "                  w _binary__btf_vmlinux_bin_end"
+undef_weak_symbols=$($nm "$vmlinux" | awk '$1 ~ /w/ { print $2 }')
+
+$objdump -R "$vmlinux" |
+	grep -E '\<R_' |
+	([ "$undef_weak_symbols" ] && grep -F -w -v "$undef_weak_symbols" || cat)
-- 
2.20.1

[PATCH v4 4/4] riscv: Check relocations at compile time

[Alexandre Ghiti]

Relocating kernel at runtime is done very early in the boot process, so
it is not convenient to check for relocations there and react in case a
relocation was not expected.

There exists a script in scripts/ that extracts the relocations from
vmlinux that is then used at postlink to check the relocations.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Reviewed-by: Anup Patel <anup@brainfault.org>
---
 arch/riscv/Makefile.postlink     | 36 ++++++++++++++++++++++++++++++++
 arch/riscv/tools/relocs_check.sh | 26 +++++++++++++++++++++++
 2 files changed, 62 insertions(+)
 create mode 100644 arch/riscv/Makefile.postlink
 create mode 100755 arch/riscv/tools/relocs_check.sh

diff --git a/arch/riscv/Makefile.postlink b/arch/riscv/Makefile.postlink
new file mode 100644
index 000000000000..bf2b2bca1845
--- /dev/null
+++ b/arch/riscv/Makefile.postlink
@@ -0,0 +1,36 @@
+# SPDX-License-Identifier: GPL-2.0
+# ===========================================================================
+# Post-link riscv pass
+# ===========================================================================
+#
+# Check that vmlinux relocations look sane
+
+PHONY := __archpost
+__archpost:
+
+-include include/config/auto.conf
+include scripts/Kbuild.include
+
+quiet_cmd_relocs_check = CHKREL  $@
+cmd_relocs_check = 							\
+	$(CONFIG_SHELL) $(srctree)/arch/riscv/tools/relocs_check.sh "$(OBJDUMP)" "$(NM)" "$@"
+
+# `@true` prevents complaint when there is nothing to be done
+
+vmlinux: FORCE
+	@true
+ifdef CONFIG_RELOCATABLE
+	$(call if_changed,relocs_check)
+endif
+
+%.ko: FORCE
+	@true
+
+clean:
+	@true
+
+PHONY += FORCE clean
+
+FORCE:
+
+.PHONY: $(PHONY)
diff --git a/arch/riscv/tools/relocs_check.sh b/arch/riscv/tools/relocs_check.sh
new file mode 100755
index 000000000000..baeb2e7b2290
--- /dev/null
+++ b/arch/riscv/tools/relocs_check.sh
@@ -0,0 +1,26 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-or-later
+# Based on powerpc relocs_check.sh
+
+# This script checks the relocations of a vmlinux for "suspicious"
+# relocations.
+
+if [ $# -lt 3 ]; then
+        echo "$0 [path to objdump] [path to nm] [path to vmlinux]" 1>&2
+        exit 1
+fi
+
+bad_relocs=$(
+${srctree}/scripts/relocs_check.sh "$@" |
+	# These relocations are okay
+	#	R_RISCV_RELATIVE
+	grep -F -w -v 'R_RISCV_RELATIVE'
+)
+
+if [ -z "$bad_relocs" ]; then
+	exit 0
+fi
+
+num_bad=$(echo "$bad_relocs" | wc -l)
+echo "WARNING: $num_bad bad relocations"
+echo "$bad_relocs"
-- 
2.20.1

Re: [PATCH v4 1/4] riscv: Move kernel mapping to vmalloc zone

[kernel test robot]

[-- Attachment #1: Type: text/plain, Size: 2412 bytes --]

Hi Alexandre,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on powerpc/next]
[also build test WARNING on linus/master v5.7 next-20200603]
[cannot apply to mpe/next atish-riscv-linux/topo_v3]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Alexandre-Ghiti/vmalloc-kernel-mapping-and-relocatable-kernel/20200603-160652
base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: riscv-randconfig-r013-20200603 (attached as .config)
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 16437992cac249f6fe1efd392d20e3469b47e39e)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install riscv cross compiling tool for clang build
        # apt-get install binutils-riscv64-linux-gnu
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=riscv 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>, old ones prefixed by <<):

>> arch/riscv/mm/init.c:383:6: warning: no previous prototype for function 'create_kernel_page_table' [-Wmissing-prototypes]
void create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
^
arch/riscv/mm/init.c:383:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
void create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
^
static
1 warning generated.

vim +/create_kernel_page_table +383 arch/riscv/mm/init.c

   382	
 > 383	void create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
   384	{
   385		uintptr_t va, end_va;
   386	
   387		end_va = kernel_virt_addr + load_sz;
   388		for (va = kernel_virt_addr; va < end_va; va += map_size)
   389			create_pgd_mapping(pgdir, va,
   390					   load_pa + (va - kernel_virt_addr),
   391					   map_size, PAGE_KERNEL_EXEC);
   392	}
   393	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 26433 bytes --]

Re: [PATCH v4 1/4] riscv: Move kernel mapping to vmalloc zone

[Zong Li]

On Wed, Jun 3, 2020 at 4:01 PM Alexandre Ghiti <alex@ghiti.fr> wrote:
>
> This is a preparatory patch for relocatable kernel.
>
> The kernel used to be linked at PAGE_OFFSET address and used to be loaded
> physically at the beginning of the main memory. Therefore, we could use
> the linear mapping for the kernel mapping.
>
> But the relocated kernel base address will be different from PAGE_OFFSET
> and since in the linear mapping, two different virtual addresses cannot
> point to the same physical address, the kernel mapping needs to lie outside
> the linear mapping.
>
> In addition, because modules and BPF must be close to the kernel (inside
> +-2GB window), the kernel is placed at the end of the vmalloc zone minus
> 2GB, which leaves room for modules and BPF. The kernel could not be
> placed at the beginning of the vmalloc zone since other vmalloc
> allocations from the kernel could get all the +-2GB window around the
> kernel which would prevent new modules and BPF programs to be loaded.
>
> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
> ---
>  arch/riscv/boot/loader.lds.S     |  3 +-
>  arch/riscv/include/asm/page.h    | 10 +++++-
>  arch/riscv/include/asm/pgtable.h | 38 ++++++++++++++-------
>  arch/riscv/kernel/head.S         |  3 +-
>  arch/riscv/kernel/module.c       |  4 +--
>  arch/riscv/kernel/vmlinux.lds.S  |  3 +-
>  arch/riscv/mm/init.c             | 58 +++++++++++++++++++++++++-------
>  arch/riscv/mm/physaddr.c         |  2 +-
>  8 files changed, 88 insertions(+), 33 deletions(-)
>
> diff --git a/arch/riscv/boot/loader.lds.S b/arch/riscv/boot/loader.lds.S
> index 47a5003c2e28..62d94696a19c 100644
> --- a/arch/riscv/boot/loader.lds.S
> +++ b/arch/riscv/boot/loader.lds.S
> @@ -1,13 +1,14 @@
>  /* SPDX-License-Identifier: GPL-2.0 */
>
>  #include <asm/page.h>
> +#include <asm/pgtable.h>
>
>  OUTPUT_ARCH(riscv)
>  ENTRY(_start)
>
>  SECTIONS
>  {
> -       . = PAGE_OFFSET;
> +       . = KERNEL_LINK_ADDR;
>
>         .payload : {
>                 *(.payload)
> diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
> index 2d50f76efe48..48bb09b6a9b7 100644
> --- a/arch/riscv/include/asm/page.h
> +++ b/arch/riscv/include/asm/page.h
> @@ -90,18 +90,26 @@ typedef struct page *pgtable_t;
>
>  #ifdef CONFIG_MMU
>  extern unsigned long va_pa_offset;
> +extern unsigned long va_kernel_pa_offset;
>  extern unsigned long pfn_base;
>  #define ARCH_PFN_OFFSET                (pfn_base)
>  #else
>  #define va_pa_offset           0
> +#define va_kernel_pa_offset    0
>  #define ARCH_PFN_OFFSET                (PAGE_OFFSET >> PAGE_SHIFT)
>  #endif /* CONFIG_MMU */
>
>  extern unsigned long max_low_pfn;
>  extern unsigned long min_low_pfn;
> +extern unsigned long kernel_virt_addr;
>
>  #define __pa_to_va_nodebug(x)  ((void *)((unsigned long) (x) + va_pa_offset))
> -#define __va_to_pa_nodebug(x)  ((unsigned long)(x) - va_pa_offset)
> +#define linear_mapping_va_to_pa(x)     ((unsigned long)(x) - va_pa_offset)
> +#define kernel_mapping_va_to_pa(x)     \
> +       ((unsigned long)(x) - va_kernel_pa_offset)
> +#define __va_to_pa_nodebug(x)          \
> +       (((x) >= PAGE_OFFSET) ?         \
> +               linear_mapping_va_to_pa(x) : kernel_mapping_va_to_pa(x))
>
>  #ifdef CONFIG_DEBUG_VIRTUAL
>  extern phys_addr_t __virt_to_phys(unsigned long x);
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index 35b60035b6b0..94ef3b49dfb6 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -11,23 +11,29 @@
>
>  #include <asm/pgtable-bits.h>
>
> -#ifndef __ASSEMBLY__
> -
> -/* Page Upper Directory not used in RISC-V */
> -#include <asm-generic/pgtable-nopud.h>
> -#include <asm/page.h>
> -#include <asm/tlbflush.h>
> -#include <linux/mm_types.h>
> -
> -#ifdef CONFIG_MMU
> +#ifndef CONFIG_MMU
> +#define KERNEL_VIRT_ADDR       PAGE_OFFSET
> +#define KERNEL_LINK_ADDR       PAGE_OFFSET
> +#else
> +/*
> + * Leave 2GB for modules and BPF that must lie within a 2GB range around
> + * the kernel.
> + */
> +#define KERNEL_VIRT_ADDR       (VMALLOC_END - SZ_2G + 1)
> +#define KERNEL_LINK_ADDR       KERNEL_VIRT_ADDR
>
>  #define VMALLOC_SIZE     (KERN_VIRT_SIZE >> 1)
>  #define VMALLOC_END      (PAGE_OFFSET - 1)
>  #define VMALLOC_START    (PAGE_OFFSET - VMALLOC_SIZE)
>
>  #define BPF_JIT_REGION_SIZE    (SZ_128M)
> -#define BPF_JIT_REGION_START   (PAGE_OFFSET - BPF_JIT_REGION_SIZE)
> -#define BPF_JIT_REGION_END     (VMALLOC_END)
> +#define BPF_JIT_REGION_START   PFN_ALIGN((unsigned long)&_end)
> +#define BPF_JIT_REGION_END     (BPF_JIT_REGION_START + BPF_JIT_REGION_SIZE)
> +
> +#ifdef CONFIG_64BIT
> +#define VMALLOC_MODULE_START   BPF_JIT_REGION_END
> +#define VMALLOC_MODULE_END     (((unsigned long)&_start & PAGE_MASK) + SZ_2G)
> +#endif
>
>  /*
>   * Roughly size the vmemmap space to be large enough to fit enough
> @@ -57,9 +63,16 @@
>  #define FIXADDR_SIZE     PGDIR_SIZE
>  #endif
>  #define FIXADDR_START    (FIXADDR_TOP - FIXADDR_SIZE)
> -
>  #endif
>
> +#ifndef __ASSEMBLY__
> +
> +/* Page Upper Directory not used in RISC-V */
> +#include <asm-generic/pgtable-nopud.h>
> +#include <asm/page.h>
> +#include <asm/tlbflush.h>
> +#include <linux/mm_types.h>
> +
>  #ifdef CONFIG_64BIT
>  #include <asm/pgtable-64.h>
>  #else
> @@ -483,6 +496,7 @@ static inline void __kernel_map_pages(struct page *page, int numpages, int enabl
>
>  #define kern_addr_valid(addr)   (1) /* FIXME */
>
> +extern char _start[];
>  extern void *dtb_early_va;
>  void setup_bootmem(void);
>  void paging_init(void);
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index 98a406474e7d..8f5bb7731327 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -49,7 +49,8 @@ ENTRY(_start)
>  #ifdef CONFIG_MMU
>  relocate:
>         /* Relocate return address */
> -       li a1, PAGE_OFFSET
> +       la a1, kernel_virt_addr
> +       REG_L a1, 0(a1)
>         la a2, _start
>         sub a1, a1, a2
>         add ra, ra, a1
> diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
> index 8bbe5dbe1341..1a8fbe05accf 100644
> --- a/arch/riscv/kernel/module.c
> +++ b/arch/riscv/kernel/module.c
> @@ -392,12 +392,10 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
>  }
>
>  #if defined(CONFIG_MMU) && defined(CONFIG_64BIT)
> -#define VMALLOC_MODULE_START \
> -        max(PFN_ALIGN((unsigned long)&_end - SZ_2G), VMALLOC_START)
>  void *module_alloc(unsigned long size)
>  {
>         return __vmalloc_node_range(size, 1, VMALLOC_MODULE_START,
> -                                   VMALLOC_END, GFP_KERNEL,
> +                                   VMALLOC_MODULE_END, GFP_KERNEL,
>                                     PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
>                                     __builtin_return_address(0));
>  }
> diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
> index 0339b6bbe11a..a9abde62909f 100644
> --- a/arch/riscv/kernel/vmlinux.lds.S
> +++ b/arch/riscv/kernel/vmlinux.lds.S
> @@ -4,7 +4,8 @@
>   * Copyright (C) 2017 SiFive
>   */
>
> -#define LOAD_OFFSET PAGE_OFFSET
> +#include <asm/pgtable.h>
> +#define LOAD_OFFSET KERNEL_LINK_ADDR
>  #include <asm/vmlinux.lds.h>
>  #include <asm/page.h>
>  #include <asm/cache.h>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 736de6c8739f..37be2eb45e58 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -22,6 +22,9 @@
>
>  #include "../kernel/head.h"
>
> +unsigned long kernel_virt_addr = KERNEL_VIRT_ADDR;
> +EXPORT_SYMBOL(kernel_virt_addr);
> +
>  unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
>                                                         __page_aligned_bss;
>  EXPORT_SYMBOL(empty_zero_page);
> @@ -178,8 +181,12 @@ void __init setup_bootmem(void)
>  }
>
>  #ifdef CONFIG_MMU
> +/* Offset between linear mapping virtual address and kernel load address */
>  unsigned long va_pa_offset;
>  EXPORT_SYMBOL(va_pa_offset);
> +/* Offset between kernel mapping virtual address and kernel load address */
> +unsigned long va_kernel_pa_offset;
> +EXPORT_SYMBOL(va_kernel_pa_offset);
>  unsigned long pfn_base;
>  EXPORT_SYMBOL(pfn_base);
>
> @@ -271,7 +278,7 @@ static phys_addr_t __init alloc_pmd(uintptr_t va)
>         if (mmu_enabled)
>                 return memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE);
>
> -       pmd_num = (va - PAGE_OFFSET) >> PGDIR_SHIFT;
> +       pmd_num = (va - kernel_virt_addr) >> PGDIR_SHIFT;
>         BUG_ON(pmd_num >= NUM_EARLY_PMDS);
>         return (uintptr_t)&early_pmd[pmd_num * PTRS_PER_PMD];
>  }
> @@ -372,14 +379,30 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
>  #error "setup_vm() is called from head.S before relocate so it should not use absolute addressing."
>  #endif
>
> +static uintptr_t load_pa, load_sz;
> +
> +void create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)

It could be static if this function is only used in this file, as
kbuild test reported.
Apart from this, it looks good to me.
Reviewed-by: Zong Li <zong.li@sifive.com>

> +{
> +       uintptr_t va, end_va;
> +
> +       end_va = kernel_virt_addr + load_sz;
> +       for (va = kernel_virt_addr; va < end_va; va += map_size)
> +               create_pgd_mapping(pgdir, va,
> +                                  load_pa + (va - kernel_virt_addr),
> +                                  map_size, PAGE_KERNEL_EXEC);
> +}
> +
>  asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>  {
>         uintptr_t va, end_va;
> -       uintptr_t load_pa = (uintptr_t)(&_start);
> -       uintptr_t load_sz = (uintptr_t)(&_end) - load_pa;
>         uintptr_t map_size = best_map_size(load_pa, MAX_EARLY_MAPPING_SIZE);
>
> +       load_pa = (uintptr_t)(&_start);
> +       load_sz = (uintptr_t)(&_end) - load_pa;
> +
>         va_pa_offset = PAGE_OFFSET - load_pa;
> +       va_kernel_pa_offset = kernel_virt_addr - load_pa;
> +
>         pfn_base = PFN_DOWN(load_pa);
>
>         /*
> @@ -402,26 +425,22 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>         create_pmd_mapping(fixmap_pmd, FIXADDR_START,
>                            (uintptr_t)fixmap_pte, PMD_SIZE, PAGE_TABLE);
>         /* Setup trampoline PGD and PMD */
> -       create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET,
> +       create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>                            (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
> -       create_pmd_mapping(trampoline_pmd, PAGE_OFFSET,
> +       create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
>                            load_pa, PMD_SIZE, PAGE_KERNEL_EXEC);
>  #else
>         /* Setup trampoline PGD */
> -       create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET,
> +       create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>                            load_pa, PGDIR_SIZE, PAGE_KERNEL_EXEC);
>  #endif
>
>         /*
> -        * Setup early PGD covering entire kernel which will allows
> +        * Setup early PGD covering entire kernel which will allow
>          * us to reach paging_init(). We map all memory banks later
>          * in setup_vm_final() below.
>          */
> -       end_va = PAGE_OFFSET + load_sz;
> -       for (va = PAGE_OFFSET; va < end_va; va += map_size)
> -               create_pgd_mapping(early_pg_dir, va,
> -                                  load_pa + (va - PAGE_OFFSET),
> -                                  map_size, PAGE_KERNEL_EXEC);
> +       create_kernel_page_table(early_pg_dir, map_size);
>
>         /* Create fixed mapping for early FDT parsing */
>         end_va = __fix_to_virt(FIX_FDT) + FIX_FDT_SIZE;
> @@ -441,6 +460,7 @@ static void __init setup_vm_final(void)
>         uintptr_t va, map_size;
>         phys_addr_t pa, start, end;
>         struct memblock_region *reg;
> +       static struct vm_struct vm_kernel = { 0 };
>
>         /* Set mmu_enabled flag */
>         mmu_enabled = true;
> @@ -467,10 +487,22 @@ static void __init setup_vm_final(void)
>                 for (pa = start; pa < end; pa += map_size) {
>                         va = (uintptr_t)__va(pa);
>                         create_pgd_mapping(swapper_pg_dir, va, pa,
> -                                          map_size, PAGE_KERNEL_EXEC);
> +                                          map_size, PAGE_KERNEL);
>                 }
>         }
>
> +       /* Map the kernel */
> +       create_kernel_page_table(swapper_pg_dir, PMD_SIZE);
> +
> +       /* Reserve the vmalloc area occupied by the kernel */
> +       vm_kernel.addr = (void *)kernel_virt_addr;
> +       vm_kernel.phys_addr = load_pa;
> +       vm_kernel.size = (load_sz + PMD_SIZE - 1) & ~(PMD_SIZE - 1);
> +       vm_kernel.flags = VM_MAP | VM_NO_GUARD;
> +       vm_kernel.caller = __builtin_return_address(0);
> +
> +       vm_area_add_early(&vm_kernel);
> +
>         /* Clear fixmap PTE and PMD mappings */
>         clear_fixmap(FIX_PTE);
>         clear_fixmap(FIX_PMD);
> diff --git a/arch/riscv/mm/physaddr.c b/arch/riscv/mm/physaddr.c
> index e8e4dcd39fed..35703d5ef5fd 100644
> --- a/arch/riscv/mm/physaddr.c
> +++ b/arch/riscv/mm/physaddr.c
> @@ -23,7 +23,7 @@ EXPORT_SYMBOL(__virt_to_phys);
>
>  phys_addr_t __phys_addr_symbol(unsigned long x)
>  {
> -       unsigned long kernel_start = (unsigned long)PAGE_OFFSET;
> +       unsigned long kernel_start = (unsigned long)kernel_virt_addr;
>         unsigned long kernel_end = (unsigned long)_end;
>
>         /*
> --
> 2.20.1
>

Re: [PATCH v4 1/4] riscv: Move kernel mapping to vmalloc zone

[Alex Ghiti]

Hi Zong,

Le 6/3/20 à 10:52 PM, Zong Li a écrit :
> On Wed, Jun 3, 2020 at 4:01 PM Alexandre Ghiti <alex@ghiti.fr> wrote:
>> This is a preparatory patch for relocatable kernel.
>>
>> The kernel used to be linked at PAGE_OFFSET address and used to be loaded
>> physically at the beginning of the main memory. Therefore, we could use
>> the linear mapping for the kernel mapping.
>>
>> But the relocated kernel base address will be different from PAGE_OFFSET
>> and since in the linear mapping, two different virtual addresses cannot
>> point to the same physical address, the kernel mapping needs to lie outside
>> the linear mapping.
>>
>> In addition, because modules and BPF must be close to the kernel (inside
>> +-2GB window), the kernel is placed at the end of the vmalloc zone minus
>> 2GB, which leaves room for modules and BPF. The kernel could not be
>> placed at the beginning of the vmalloc zone since other vmalloc
>> allocations from the kernel could get all the +-2GB window around the
>> kernel which would prevent new modules and BPF programs to be loaded.
>>
>> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
>> ---
>>   arch/riscv/boot/loader.lds.S     |  3 +-
>>   arch/riscv/include/asm/page.h    | 10 +++++-
>>   arch/riscv/include/asm/pgtable.h | 38 ++++++++++++++-------
>>   arch/riscv/kernel/head.S         |  3 +-
>>   arch/riscv/kernel/module.c       |  4 +--
>>   arch/riscv/kernel/vmlinux.lds.S  |  3 +-
>>   arch/riscv/mm/init.c             | 58 +++++++++++++++++++++++++-------
>>   arch/riscv/mm/physaddr.c         |  2 +-
>>   8 files changed, 88 insertions(+), 33 deletions(-)
>>
>> diff --git a/arch/riscv/boot/loader.lds.S b/arch/riscv/boot/loader.lds.S
>> index 47a5003c2e28..62d94696a19c 100644
>> --- a/arch/riscv/boot/loader.lds.S
>> +++ b/arch/riscv/boot/loader.lds.S
>> @@ -1,13 +1,14 @@
>>   /* SPDX-License-Identifier: GPL-2.0 */
>>
>>   #include <asm/page.h>
>> +#include <asm/pgtable.h>
>>
>>   OUTPUT_ARCH(riscv)
>>   ENTRY(_start)
>>
>>   SECTIONS
>>   {
>> -       . = PAGE_OFFSET;
>> +       . = KERNEL_LINK_ADDR;
>>
>>          .payload : {
>>                  *(.payload)
>> diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
>> index 2d50f76efe48..48bb09b6a9b7 100644
>> --- a/arch/riscv/include/asm/page.h
>> +++ b/arch/riscv/include/asm/page.h
>> @@ -90,18 +90,26 @@ typedef struct page *pgtable_t;
>>
>>   #ifdef CONFIG_MMU
>>   extern unsigned long va_pa_offset;
>> +extern unsigned long va_kernel_pa_offset;
>>   extern unsigned long pfn_base;
>>   #define ARCH_PFN_OFFSET                (pfn_base)
>>   #else
>>   #define va_pa_offset           0
>> +#define va_kernel_pa_offset    0
>>   #define ARCH_PFN_OFFSET                (PAGE_OFFSET >> PAGE_SHIFT)
>>   #endif /* CONFIG_MMU */
>>
>>   extern unsigned long max_low_pfn;
>>   extern unsigned long min_low_pfn;
>> +extern unsigned long kernel_virt_addr;
>>
>>   #define __pa_to_va_nodebug(x)  ((void *)((unsigned long) (x) + va_pa_offset))
>> -#define __va_to_pa_nodebug(x)  ((unsigned long)(x) - va_pa_offset)
>> +#define linear_mapping_va_to_pa(x)     ((unsigned long)(x) - va_pa_offset)
>> +#define kernel_mapping_va_to_pa(x)     \
>> +       ((unsigned long)(x) - va_kernel_pa_offset)
>> +#define __va_to_pa_nodebug(x)          \
>> +       (((x) >= PAGE_OFFSET) ?         \
>> +               linear_mapping_va_to_pa(x) : kernel_mapping_va_to_pa(x))
>>
>>   #ifdef CONFIG_DEBUG_VIRTUAL
>>   extern phys_addr_t __virt_to_phys(unsigned long x);
>> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
>> index 35b60035b6b0..94ef3b49dfb6 100644
>> --- a/arch/riscv/include/asm/pgtable.h
>> +++ b/arch/riscv/include/asm/pgtable.h
>> @@ -11,23 +11,29 @@
>>
>>   #include <asm/pgtable-bits.h>
>>
>> -#ifndef __ASSEMBLY__
>> -
>> -/* Page Upper Directory not used in RISC-V */
>> -#include <asm-generic/pgtable-nopud.h>
>> -#include <asm/page.h>
>> -#include <asm/tlbflush.h>
>> -#include <linux/mm_types.h>
>> -
>> -#ifdef CONFIG_MMU
>> +#ifndef CONFIG_MMU
>> +#define KERNEL_VIRT_ADDR       PAGE_OFFSET
>> +#define KERNEL_LINK_ADDR       PAGE_OFFSET
>> +#else
>> +/*
>> + * Leave 2GB for modules and BPF that must lie within a 2GB range around
>> + * the kernel.
>> + */
>> +#define KERNEL_VIRT_ADDR       (VMALLOC_END - SZ_2G + 1)
>> +#define KERNEL_LINK_ADDR       KERNEL_VIRT_ADDR
>>
>>   #define VMALLOC_SIZE     (KERN_VIRT_SIZE >> 1)
>>   #define VMALLOC_END      (PAGE_OFFSET - 1)
>>   #define VMALLOC_START    (PAGE_OFFSET - VMALLOC_SIZE)
>>
>>   #define BPF_JIT_REGION_SIZE    (SZ_128M)
>> -#define BPF_JIT_REGION_START   (PAGE_OFFSET - BPF_JIT_REGION_SIZE)
>> -#define BPF_JIT_REGION_END     (VMALLOC_END)
>> +#define BPF_JIT_REGION_START   PFN_ALIGN((unsigned long)&_end)
>> +#define BPF_JIT_REGION_END     (BPF_JIT_REGION_START + BPF_JIT_REGION_SIZE)
>> +
>> +#ifdef CONFIG_64BIT
>> +#define VMALLOC_MODULE_START   BPF_JIT_REGION_END
>> +#define VMALLOC_MODULE_END     (((unsigned long)&_start & PAGE_MASK) + SZ_2G)
>> +#endif
>>
>>   /*
>>    * Roughly size the vmemmap space to be large enough to fit enough
>> @@ -57,9 +63,16 @@
>>   #define FIXADDR_SIZE     PGDIR_SIZE
>>   #endif
>>   #define FIXADDR_START    (FIXADDR_TOP - FIXADDR_SIZE)
>> -
>>   #endif
>>
>> +#ifndef __ASSEMBLY__
>> +
>> +/* Page Upper Directory not used in RISC-V */
>> +#include <asm-generic/pgtable-nopud.h>
>> +#include <asm/page.h>
>> +#include <asm/tlbflush.h>
>> +#include <linux/mm_types.h>
>> +
>>   #ifdef CONFIG_64BIT
>>   #include <asm/pgtable-64.h>
>>   #else
>> @@ -483,6 +496,7 @@ static inline void __kernel_map_pages(struct page *page, int numpages, int enabl
>>
>>   #define kern_addr_valid(addr)   (1) /* FIXME */
>>
>> +extern char _start[];
>>   extern void *dtb_early_va;
>>   void setup_bootmem(void);
>>   void paging_init(void);
>> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
>> index 98a406474e7d..8f5bb7731327 100644
>> --- a/arch/riscv/kernel/head.S
>> +++ b/arch/riscv/kernel/head.S
>> @@ -49,7 +49,8 @@ ENTRY(_start)
>>   #ifdef CONFIG_MMU
>>   relocate:
>>          /* Relocate return address */
>> -       li a1, PAGE_OFFSET
>> +       la a1, kernel_virt_addr
>> +       REG_L a1, 0(a1)
>>          la a2, _start
>>          sub a1, a1, a2
>>          add ra, ra, a1
>> diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
>> index 8bbe5dbe1341..1a8fbe05accf 100644
>> --- a/arch/riscv/kernel/module.c
>> +++ b/arch/riscv/kernel/module.c
>> @@ -392,12 +392,10 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
>>   }
>>
>>   #if defined(CONFIG_MMU) && defined(CONFIG_64BIT)
>> -#define VMALLOC_MODULE_START \
>> -        max(PFN_ALIGN((unsigned long)&_end - SZ_2G), VMALLOC_START)
>>   void *module_alloc(unsigned long size)
>>   {
>>          return __vmalloc_node_range(size, 1, VMALLOC_MODULE_START,
>> -                                   VMALLOC_END, GFP_KERNEL,
>> +                                   VMALLOC_MODULE_END, GFP_KERNEL,
>>                                      PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
>>                                      __builtin_return_address(0));
>>   }
>> diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
>> index 0339b6bbe11a..a9abde62909f 100644
>> --- a/arch/riscv/kernel/vmlinux.lds.S
>> +++ b/arch/riscv/kernel/vmlinux.lds.S
>> @@ -4,7 +4,8 @@
>>    * Copyright (C) 2017 SiFive
>>    */
>>
>> -#define LOAD_OFFSET PAGE_OFFSET
>> +#include <asm/pgtable.h>
>> +#define LOAD_OFFSET KERNEL_LINK_ADDR
>>   #include <asm/vmlinux.lds.h>
>>   #include <asm/page.h>
>>   #include <asm/cache.h>
>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>> index 736de6c8739f..37be2eb45e58 100644
>> --- a/arch/riscv/mm/init.c
>> +++ b/arch/riscv/mm/init.c
>> @@ -22,6 +22,9 @@
>>
>>   #include "../kernel/head.h"
>>
>> +unsigned long kernel_virt_addr = KERNEL_VIRT_ADDR;
>> +EXPORT_SYMBOL(kernel_virt_addr);
>> +
>>   unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
>>                                                          __page_aligned_bss;
>>   EXPORT_SYMBOL(empty_zero_page);
>> @@ -178,8 +181,12 @@ void __init setup_bootmem(void)
>>   }
>>
>>   #ifdef CONFIG_MMU
>> +/* Offset between linear mapping virtual address and kernel load address */
>>   unsigned long va_pa_offset;
>>   EXPORT_SYMBOL(va_pa_offset);
>> +/* Offset between kernel mapping virtual address and kernel load address */
>> +unsigned long va_kernel_pa_offset;
>> +EXPORT_SYMBOL(va_kernel_pa_offset);
>>   unsigned long pfn_base;
>>   EXPORT_SYMBOL(pfn_base);
>>
>> @@ -271,7 +278,7 @@ static phys_addr_t __init alloc_pmd(uintptr_t va)
>>          if (mmu_enabled)
>>                  return memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE);
>>
>> -       pmd_num = (va - PAGE_OFFSET) >> PGDIR_SHIFT;
>> +       pmd_num = (va - kernel_virt_addr) >> PGDIR_SHIFT;
>>          BUG_ON(pmd_num >= NUM_EARLY_PMDS);
>>          return (uintptr_t)&early_pmd[pmd_num * PTRS_PER_PMD];
>>   }
>> @@ -372,14 +379,30 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
>>   #error "setup_vm() is called from head.S before relocate so it should not use absolute addressing."
>>   #endif
>>
>> +static uintptr_t load_pa, load_sz;
>> +
>> +void create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
> It could be static if this function is only used in this file, as
> kbuild test reported.
> Apart from this, it looks good to me.
> Reviewed-by: Zong Li <zong.li@sifive.com>


Thanks, that was the missing Reviewed-by of this series :) I send a v5 
right now.

Looking forward to seeing your KASLR patchset on top of that.

Alex


>
>> +{
>> +       uintptr_t va, end_va;
>> +
>> +       end_va = kernel_virt_addr + load_sz;
>> +       for (va = kernel_virt_addr; va < end_va; va += map_size)
>> +               create_pgd_mapping(pgdir, va,
>> +                                  load_pa + (va - kernel_virt_addr),
>> +                                  map_size, PAGE_KERNEL_EXEC);
>> +}
>> +
>>   asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>   {
>>          uintptr_t va, end_va;
>> -       uintptr_t load_pa = (uintptr_t)(&_start);
>> -       uintptr_t load_sz = (uintptr_t)(&_end) - load_pa;
>>          uintptr_t map_size = best_map_size(load_pa, MAX_EARLY_MAPPING_SIZE);
>>
>> +       load_pa = (uintptr_t)(&_start);
>> +       load_sz = (uintptr_t)(&_end) - load_pa;
>> +
>>          va_pa_offset = PAGE_OFFSET - load_pa;
>> +       va_kernel_pa_offset = kernel_virt_addr - load_pa;
>> +
>>          pfn_base = PFN_DOWN(load_pa);
>>
>>          /*
>> @@ -402,26 +425,22 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>          create_pmd_mapping(fixmap_pmd, FIXADDR_START,
>>                             (uintptr_t)fixmap_pte, PMD_SIZE, PAGE_TABLE);
>>          /* Setup trampoline PGD and PMD */
>> -       create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET,
>> +       create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>>                             (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
>> -       create_pmd_mapping(trampoline_pmd, PAGE_OFFSET,
>> +       create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
>>                             load_pa, PMD_SIZE, PAGE_KERNEL_EXEC);
>>   #else
>>          /* Setup trampoline PGD */
>> -       create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET,
>> +       create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>>                             load_pa, PGDIR_SIZE, PAGE_KERNEL_EXEC);
>>   #endif
>>
>>          /*
>> -        * Setup early PGD covering entire kernel which will allows
>> +        * Setup early PGD covering entire kernel which will allow
>>           * us to reach paging_init(). We map all memory banks later
>>           * in setup_vm_final() below.
>>           */
>> -       end_va = PAGE_OFFSET + load_sz;
>> -       for (va = PAGE_OFFSET; va < end_va; va += map_size)
>> -               create_pgd_mapping(early_pg_dir, va,
>> -                                  load_pa + (va - PAGE_OFFSET),
>> -                                  map_size, PAGE_KERNEL_EXEC);
>> +       create_kernel_page_table(early_pg_dir, map_size);
>>
>>          /* Create fixed mapping for early FDT parsing */
>>          end_va = __fix_to_virt(FIX_FDT) + FIX_FDT_SIZE;
>> @@ -441,6 +460,7 @@ static void __init setup_vm_final(void)
>>          uintptr_t va, map_size;
>>          phys_addr_t pa, start, end;
>>          struct memblock_region *reg;
>> +       static struct vm_struct vm_kernel = { 0 };
>>
>>          /* Set mmu_enabled flag */
>>          mmu_enabled = true;
>> @@ -467,10 +487,22 @@ static void __init setup_vm_final(void)
>>                  for (pa = start; pa < end; pa += map_size) {
>>                          va = (uintptr_t)__va(pa);
>>                          create_pgd_mapping(swapper_pg_dir, va, pa,
>> -                                          map_size, PAGE_KERNEL_EXEC);
>> +                                          map_size, PAGE_KERNEL);
>>                  }
>>          }
>>
>> +       /* Map the kernel */
>> +       create_kernel_page_table(swapper_pg_dir, PMD_SIZE);
>> +
>> +       /* Reserve the vmalloc area occupied by the kernel */
>> +       vm_kernel.addr = (void *)kernel_virt_addr;
>> +       vm_kernel.phys_addr = load_pa;
>> +       vm_kernel.size = (load_sz + PMD_SIZE - 1) & ~(PMD_SIZE - 1);
>> +       vm_kernel.flags = VM_MAP | VM_NO_GUARD;
>> +       vm_kernel.caller = __builtin_return_address(0);
>> +
>> +       vm_area_add_early(&vm_kernel);
>> +
>>          /* Clear fixmap PTE and PMD mappings */
>>          clear_fixmap(FIX_PTE);
>>          clear_fixmap(FIX_PMD);
>> diff --git a/arch/riscv/mm/physaddr.c b/arch/riscv/mm/physaddr.c
>> index e8e4dcd39fed..35703d5ef5fd 100644
>> --- a/arch/riscv/mm/physaddr.c
>> +++ b/arch/riscv/mm/physaddr.c
>> @@ -23,7 +23,7 @@ EXPORT_SYMBOL(__virt_to_phys);
>>
>>   phys_addr_t __phys_addr_symbol(unsigned long x)
>>   {
>> -       unsigned long kernel_start = (unsigned long)PAGE_OFFSET;
>> +       unsigned long kernel_start = (unsigned long)kernel_virt_addr;
>>          unsigned long kernel_end = (unsigned long)_end;
>>
>>          /*
>> --
>> 2.20.1
>>