RISC-V Fixes for 5.10-rc3

* An SPDX comment style fix.
 * A fix to ignore memory that is unusable.
 * A fix to avoid setting a kernel text offset for the !MMU kernels, where
   skipping the first page of memory is both unnecessary and costly.
 * A fix to avoid passing the flag bits in satp to pfn_to_virt().
 * A fix to __put_kernel_nofault, where we had the arguments to
   __put_user_nocheck reversed.
 * A workaround for a bug in the FU540 to avoid triggering PMP issues during
   early boot.
 * A change to how we pull symbols out of the vDSO.  The old mechanism was
   removed from binutils-2.35 (and has been backported to Debian's 2.34).
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Merge tag 'riscv-for-linus-5.10-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

Pull RISC-V fixes from Palmer Dabbelt:

 - SPDX comment style fix

 - ignore memory that is unusable

 - avoid setting a kernel text offset for the !MMU kernels, where
   skipping the first page of memory is both unnecessary and costly

 - avoid passing the flag bits in satp to pfn_to_virt()

 - fix __put_kernel_nofault, where we had the arguments to
   __put_user_nocheck reversed

 - workaround for a bug in the FU540 to avoid triggering PMP issues
   during early boot

 - change to how we pull symbols out of the vDSO. The old mechanism was
   removed from binutils-2.35 (and has been backported to Debian's 2.34)

* tag 'riscv-for-linus-5.10-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  RISC-V: Fix the VDSO symbol generaton for binutils-2.35+
  RISC-V: Use non-PGD mappings for early DTB access
  riscv: uaccess: fix __put_kernel_nofault()
  riscv: fix pfn_to_virt err in do_page_fault().
  riscv: Set text_offset correctly for M-Mode
  RISC-V: Remove any memblock representing unusable memory area
  risc-v: kernel: ftrace: Fixes improper SPDX comment style

arch/riscv/include/asm/uaccess.h

@@ -476,7 +476,7 @@ do {									\
 do {									\
 	long __kr_err;							\
 									\
-	__put_user_nocheck(*((type *)(dst)), (type *)(src), __kr_err);	\
+	__put_user_nocheck(*((type *)(src)), (type *)(dst), __kr_err);	\
 	if (unlikely(__kr_err))						\
 		goto err_label;						\
 } while (0)

arch/riscv/kernel/ftrace.c

@@ -1,4 +1,4 @@
-/* SPDX-License-Identifier: GPL-2.0 */
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2013 Linaro Limited
  * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>

arch/riscv/kernel/head.S

@@ -35,12 +35,17 @@ ENTRY(_start)
 	.word 0
 #endif
 	.balign 8
+#ifdef CONFIG_RISCV_M_MODE
+	/* Image load offset (0MB) from start of RAM for M-mode */
+	.dword 0
+#else
 #if __riscv_xlen == 64
 	/* Image load offset(2MB) from start of RAM */
 	.dword 0x200000
 #else
 	/* Image load offset(4MB) from start of RAM */
 	.dword 0x400000
+#endif
 #endif
 	/* Effective size of kernel image */
 	.dword _end - _start

arch/riscv/kernel/vdso/.gitignore

@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0-only
 vdso.lds
 *.tmp
+vdso-syms.S

arch/riscv/kernel/vdso/Makefile

@@ -43,19 +43,14 @@ $(obj)/vdso.o: $(obj)/vdso.so
 SYSCFLAGS_vdso.so.dbg = $(c_flags)
 $(obj)/vdso.so.dbg: $(src)/vdso.lds $(obj-vdso) FORCE
 	$(call if_changed,vdsold)
+SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \
+	-Wl,--build-id -Wl,--hash-style=both
 
 # We also create a special relocatable object that should mirror the symbol
 # table and layout of the linked DSO. With ld --just-symbols we can then
 # refer to these symbols in the kernel code rather than hand-coded addresses.
-
-SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \
-	-Wl,--build-id=sha1 -Wl,--hash-style=both
-$(obj)/vdso-dummy.o: $(src)/vdso.lds $(obj)/rt_sigreturn.o FORCE
-	$(call if_changed,vdsold)
-
-LDFLAGS_vdso-syms.o := -r --just-symbols
-$(obj)/vdso-syms.o: $(obj)/vdso-dummy.o FORCE
-	$(call if_changed,ld)
+$(obj)/vdso-syms.S: $(obj)/vdso.so FORCE
+	$(call if_changed,so2s)
 
 # strip rule for the .so file
 $(obj)/%.so: OBJCOPYFLAGS := -S
@@ -73,6 +68,11 @@ quiet_cmd_vdsold = VDSOLD  $@
                            $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \
                    rm $@.tmp
 
+# Extracts symbol offsets from the VDSO, converting them into an assembly file
+# that contains the same symbols at the same offsets.
+quiet_cmd_so2s = SO2S    $@
+      cmd_so2s = $(NM) -D $< | $(srctree)/$(src)/so2s.sh > $@
+
 # install commands for the unstripped file
 quiet_cmd_vdso_install = INSTALL $@
       cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@

arch/riscv/kernel/vdso/so2s.sh

@@ -0,0 +1,6 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0+
+# Copyright 2020 Palmer Dabbelt <palmerdabbelt@google.com>
+
+sed 's!\([0-9a-f]*\) T \([a-z0-9_]*\)\(@@LINUX_4.15\)*!.global \2\n.set \2,0x\1!' \
+| grep '^\.'

arch/riscv/mm/fault.c

@@ -86,6 +86,7 @@ static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long a
 	pmd_t *pmd, *pmd_k;
 	pte_t *pte_k;
 	int index;
+	unsigned long pfn;
 
 	/* User mode accesses just cause a SIGSEGV */
 	if (user_mode(regs))
@@ -100,7 +101,8 @@ static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long a
 	 * of a task switch.
 	 */
 	index = pgd_index(addr);
-	pgd = (pgd_t *)pfn_to_virt(csr_read(CSR_SATP)) + index;
+	pfn = csr_read(CSR_SATP) & SATP_PPN;
+	pgd = (pgd_t *)pfn_to_virt(pfn) + index;
 	pgd_k = init_mm.pgd + index;
 
 	if (!pgd_present(*pgd_k)) {

arch/riscv/mm/init.c

@@ -154,9 +154,8 @@ disable:
 
 void __init setup_bootmem(void)
 {
-	phys_addr_t mem_size = 0;
-	phys_addr_t total_mem = 0;
-	phys_addr_t mem_start, start, end = 0;
+	phys_addr_t mem_start = 0;
+	phys_addr_t start, end = 0;
 	phys_addr_t vmlinux_end = __pa_symbol(&_end);
 	phys_addr_t vmlinux_start = __pa_symbol(&_start);
 	u64 i;
@@ -164,21 +163,18 @@ void __init setup_bootmem(void)
 	/* Find the memory region containing the kernel */
 	for_each_mem_range(i, &start, &end) {
 		phys_addr_t size = end - start;
-		if (!total_mem)
+		if (!mem_start)
 			mem_start = start;
 		if (start <= vmlinux_start && vmlinux_end <= end)
 			BUG_ON(size == 0);
-		total_mem = total_mem + size;
 	}
 
 	/*
-	 * Remove memblock from the end of usable area to the
-	 * end of region
+	 * The maximal physical memory size is -PAGE_OFFSET.
+	 * Make sure that any memory beyond mem_start + (-PAGE_OFFSET) is removed
+	 * as it is unusable by kernel.
 	 */
-	mem_size = min(total_mem, (phys_addr_t)-PAGE_OFFSET);
-	if (mem_start + mem_size < end)
-		memblock_remove(mem_start + mem_size,
-				end - mem_start - mem_size);
+	memblock_enforce_memory_limit(mem_start - PAGE_OFFSET);
 
 	/* Reserve from the start of the kernel to the end of the kernel */
 	memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);
@@ -297,6 +293,7 @@ pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
 #define NUM_EARLY_PMDS		(1UL + MAX_EARLY_MAPPING_SIZE / PGDIR_SIZE)
 #endif
 pmd_t early_pmd[PTRS_PER_PMD * NUM_EARLY_PMDS] __initdata __aligned(PAGE_SIZE);
+pmd_t early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
 
 static pmd_t *__init get_pmd_virt_early(phys_addr_t pa)
 {
@@ -494,6 +491,18 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 				   load_pa + (va - PAGE_OFFSET),
 				   map_size, PAGE_KERNEL_EXEC);
 
+#ifndef __PAGETABLE_PMD_FOLDED
+	/* Setup early PMD for DTB */
+	create_pgd_mapping(early_pg_dir, DTB_EARLY_BASE_VA,
+			   (uintptr_t)early_dtb_pmd, PGDIR_SIZE, PAGE_TABLE);
+	/* Create two consecutive PMD mappings for FDT early scan */
+	pa = dtb_pa & ~(PMD_SIZE - 1);
+	create_pmd_mapping(early_dtb_pmd, DTB_EARLY_BASE_VA,
+			   pa, PMD_SIZE, PAGE_KERNEL);
+	create_pmd_mapping(early_dtb_pmd, DTB_EARLY_BASE_VA + PMD_SIZE,
+			   pa + PMD_SIZE, PMD_SIZE, PAGE_KERNEL);
+	dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PMD_SIZE - 1));
+#else
 	/* Create two consecutive PGD mappings for FDT early scan */
 	pa = dtb_pa & ~(PGDIR_SIZE - 1);
 	create_pgd_mapping(early_pg_dir, DTB_EARLY_BASE_VA,
@@ -501,6 +510,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 	create_pgd_mapping(early_pg_dir, DTB_EARLY_BASE_VA + PGDIR_SIZE,
 			   pa + PGDIR_SIZE, PGDIR_SIZE, PAGE_KERNEL);
 	dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PGDIR_SIZE - 1));
+#endif
 	dtb_early_pa = dtb_pa;
 
 	/*