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From:   Alexandre Ghiti <alex@ghiti.fr>
To:     Jonathan Corbet <corbet@lwn.net>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Arnd Bergmann <arnd@arndb.de>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>, linux-doc@vger.kernel.org,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        kasan-dev@googlegroups.com, linux-arch@vger.kernel.org,
        linux-mm@kvack.org
Cc:     Alexandre Ghiti <alex@ghiti.fr>
Subject: [PATCH] riscv: Fix 32b kernel caused by 64b kernel mapping moving outside linear mapping
Date:   Sat, 17 Apr 2021 13:21:59 -0400
Message-Id: <20210417172159.32085-1-alex@ghiti.fr>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Fix multiple leftovers when moving the kernel mapping outside the linear
mapping for 64b kernel that left the 32b kernel unusable.

Fixes: 4b67f48da707 ("riscv: Move kernel mapping outside of linear mapping")
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
---
 arch/riscv/include/asm/page.h    |  9 +++++++++
 arch/riscv/include/asm/pgtable.h | 16 ++++++++++++----
 arch/riscv/mm/init.c             | 25 ++++++++++++++++++++++++-
 3 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
index 22cfb2be60dc..f64b61296c0c 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -90,15 +90,20 @@ typedef struct page *pgtable_t;
 
 #ifdef CONFIG_MMU
 extern unsigned long va_pa_offset;
+#ifdef CONFIG_64BIT
 extern unsigned long va_kernel_pa_offset;
+#endif
 extern unsigned long pfn_base;
 #define ARCH_PFN_OFFSET		(pfn_base)
 #else
 #define va_pa_offset		0
+#ifdef CONFIG_64BIT
 #define va_kernel_pa_offset	0
+#endif
 #define ARCH_PFN_OFFSET		(PAGE_OFFSET >> PAGE_SHIFT)
 #endif /* CONFIG_MMU */
 
+#ifdef CONFIG_64BIT
 extern unsigned long kernel_virt_addr;
 
 #define linear_mapping_pa_to_va(x)	((void *)((unsigned long)(x) + va_pa_offset))
@@ -112,6 +117,10 @@ extern unsigned long kernel_virt_addr;
 	(_x < kernel_virt_addr) ?						\
 		linear_mapping_va_to_pa(_x) : kernel_mapping_va_to_pa(_x);	\
 	})
+#else
+#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)
+#endif
 
 #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 80e63a93e903..5afda75cc2c3 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -16,19 +16,27 @@
 #else
 
 #define ADDRESS_SPACE_END	(UL(-1))
-/*
- * Leave 2GB for kernel and BPF at the end of the address space
- */
+
+#ifdef CONFIG_64BIT
+/* Leave 2GB for kernel and BPF at the end of the address space */
 #define KERNEL_LINK_ADDR	(ADDRESS_SPACE_END - SZ_2G + 1)
+#else
+#define KERNEL_LINK_ADDR	PAGE_OFFSET
+#endif
 
 #define VMALLOC_SIZE     (KERN_VIRT_SIZE >> 1)
 #define VMALLOC_END      (PAGE_OFFSET - 1)
 #define VMALLOC_START    (PAGE_OFFSET - VMALLOC_SIZE)
 
-/* KASLR should leave at least 128MB for BPF after the kernel */
 #define BPF_JIT_REGION_SIZE	(SZ_128M)
+#ifdef CONFIG_64BIT
+/* KASLR should leave at least 128MB for BPF after the kernel */
 #define BPF_JIT_REGION_START	PFN_ALIGN((unsigned long)&_end)
 #define BPF_JIT_REGION_END	(BPF_JIT_REGION_START + BPF_JIT_REGION_SIZE)
+#else
+#define BPF_JIT_REGION_START	(PAGE_OFFSET - BPF_JIT_REGION_SIZE)
+#define BPF_JIT_REGION_END	(VMALLOC_END)
+#endif
 
 /* Modules always live before the kernel */
 #ifdef CONFIG_64BIT
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 093f3a96ecfc..dc9b988e0778 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -91,8 +91,10 @@ static void print_vm_layout(void)
 		  (unsigned long)VMALLOC_END);
 	print_mlm("lowmem", (unsigned long)PAGE_OFFSET,
 		  (unsigned long)high_memory);
+#ifdef CONFIG_64BIT
 	print_mlm("kernel", (unsigned long)KERNEL_LINK_ADDR,
 		  (unsigned long)ADDRESS_SPACE_END);
+#endif
 }
 #else
 static void print_vm_layout(void) { }
@@ -165,9 +167,11 @@ static struct pt_alloc_ops pt_ops;
 /* Offset between linear mapping virtual address and kernel load address */
 unsigned long va_pa_offset;
 EXPORT_SYMBOL(va_pa_offset);
+#ifdef CONFIG_64BIT
 /* Offset between kernel mapping virtual address and kernel load address */
 unsigned long va_kernel_pa_offset;
 EXPORT_SYMBOL(va_kernel_pa_offset);
+#endif
 unsigned long pfn_base;
 EXPORT_SYMBOL(pfn_base);
 
@@ -410,7 +414,9 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 	load_sz = (uintptr_t)(&_end) - load_pa;
 
 	va_pa_offset = PAGE_OFFSET - load_pa;
+#ifdef CONFIG_64BIT
 	va_kernel_pa_offset = kernel_virt_addr - load_pa;
+#endif
 
 	pfn_base = PFN_DOWN(load_pa);
 
@@ -469,12 +475,16 @@ 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 */
+#ifdef CONFIG_64BIT
 	/*
 	 * __va can't be used since it would return a linear mapping address
 	 * whereas dtb_early_va will be used before setup_vm_final installs
 	 * the linear mapping.
 	 */
 	dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
+#else
+	dtb_early_va = __va(dtb_pa);
+#endif /* CONFIG_64BIT */
 #endif /* CONFIG_BUILTIN_DTB */
 #else
 #ifndef CONFIG_BUILTIN_DTB
@@ -486,7 +496,11 @@ 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 */
+#ifdef CONFIG_64BIT
 	dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
+#else
+	dtb_early_va = __va(dtb_pa);
+#endif /* CONFIG_64BIT */
 #endif /* CONFIG_BUILTIN_DTB */
 #endif
 	dtb_early_pa = dtb_pa;
@@ -571,12 +585,21 @@ 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);
+					   map_size,
+#ifdef CONFIG_64BIT
+					   PAGE_KERNEL
+#else
+					   PAGE_KERNEL_EXEC
+#endif
+					);
+
 		}
 	}
 
+#ifdef CONFIG_64BIT
 	/* Map the kernel */
 	create_kernel_page_table(swapper_pg_dir, PMD_SIZE);
+#endif
 
 	/* Clear fixmap PTE and PMD mappings */
 	clear_fixmap(FIX_PTE);
-- 
2.20.1