Re: [PATCH V2 RESEND] mm: Define default value for FIRST_USER_ADDRESS

From: Palmer Dabbelt
Date: Sun May 23 2021 - 18:33:22 EST

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On Sun, 09 May 2021 20:02:05 PDT (-0700), anshuman.khandual@xxxxxxx wrote:

Currently most platforms define FIRST_USER_ADDRESS as 0UL duplication the
same code all over. Instead just define a generic default value (i.e 0UL)
for FIRST_USER_ADDRESS and let the platforms override when required. This
makes it much cleaner with reduced code.

The default FIRST_USER_ADDRESS here would be skipped in <linux/pgtable.h>
when the given platform overrides its value via <asm/pgtable.h>.

Cc: Richard Henderson <rth@xxxxxxxxxxx>
Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Guo Ren <guoren@xxxxxxxxxx>
Cc: Brian Cain <bcain@xxxxxxxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: Michal Simek <monstr@xxxxxxxxx>
Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
Cc: Ley Foon Tan <ley.foon.tan@xxxxxxxxx>
Cc: Jonas Bonn <jonas@xxxxxxxxxxxx>
Cc: Stefan Kristiansson <stefan.kristiansson@xxxxxxxxxxxxx>
Cc: Stafford Horne <shorne@xxxxxxxxx>
Cc: "James E.J. Bottomley" <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Jeff Dike <jdike@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Chris Zankel <chris@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-arch@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Acked-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> #m68k
Acked-by: Guo Ren <guoren@xxxxxxxxxx> #csky
Acked-by: Stafford Horne <shorne@xxxxxxxxx> #openrisc
Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx> #arm64
Acked-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
This applies on v5.13-rc1 and has been boot tested on arm64 platform.
But has been cross compiled on multiple other platforms.

Changes in V2:

- Dropped ARCH_HAS_FIRST_USER_ADDRESS construct

Changes in V1:

https://patchwork.kernel.org/project/linux-mm/patch/1618368899-20311-1-git-send-email-anshuman.khandual@xxxxxxx/

arch/alpha/include/asm/pgtable.h | 1 -
arch/arc/include/asm/pgtable.h | 6 ------
arch/arm64/include/asm/pgtable.h | 2 --
arch/csky/include/asm/pgtable.h | 1 -
arch/hexagon/include/asm/pgtable.h | 3 ---
arch/ia64/include/asm/pgtable.h | 1 -
arch/m68k/include/asm/pgtable_mm.h | 1 -
arch/microblaze/include/asm/pgtable.h | 2 --
arch/mips/include/asm/pgtable-32.h | 1 -
arch/mips/include/asm/pgtable-64.h | 1 -
arch/nios2/include/asm/pgtable.h | 2 --
arch/openrisc/include/asm/pgtable.h | 1 -
arch/parisc/include/asm/pgtable.h | 2 --
arch/powerpc/include/asm/book3s/pgtable.h | 1 -
arch/powerpc/include/asm/nohash/32/pgtable.h | 1 -
arch/powerpc/include/asm/nohash/64/pgtable.h | 2 --
arch/riscv/include/asm/pgtable.h | 2 --
arch/s390/include/asm/pgtable.h | 2 --
arch/sh/include/asm/pgtable.h | 2 --
arch/sparc/include/asm/pgtable_32.h | 1 -
arch/sparc/include/asm/pgtable_64.h | 3 ---
arch/um/include/asm/pgtable-2level.h | 1 -
arch/um/include/asm/pgtable-3level.h | 1 -
arch/x86/include/asm/pgtable_types.h | 2 --
arch/xtensa/include/asm/pgtable.h | 1 -
include/linux/pgtable.h | 9 +++++++++
26 files changed, 9 insertions(+), 43 deletions(-)

diff --git a/arch/alpha/include/asm/pgtable.h b/arch/alpha/include/asm/pgtable.h
index 8d856c62e22a..1a2fb0dc905b 100644
--- a/arch/alpha/include/asm/pgtable.h
+++ b/arch/alpha/include/asm/pgtable.h
@@ -46,7 +46,6 @@ struct vm_area_struct;
#define PTRS_PER_PMD (1UL << (PAGE_SHIFT-3))
#define PTRS_PER_PGD (1UL << (PAGE_SHIFT-3))
#define USER_PTRS_PER_PGD (TASK_SIZE / PGDIR_SIZE)
-#define FIRST_USER_ADDRESS 0UL

/* Number of pointers that fit on a page: this will go away. */
#define PTRS_PER_PAGE (1UL << (PAGE_SHIFT-3))
diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h
index 163641726a2b..a9fabfb70664 100644
--- a/arch/arc/include/asm/pgtable.h
+++ b/arch/arc/include/asm/pgtable.h
@@ -228,12 +228,6 @@
*/
#define USER_PTRS_PER_PGD (TASK_SIZE / PGDIR_SIZE)

-/*
- * No special requirements for lowest virtual address we permit any user space
- * mapping to be mapped at.
- */
-#define FIRST_USER_ADDRESS 0UL
-

/****************************************************************
* Bucket load of VM Helpers
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 0b10204e72fc..25f5c04b43ce 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -26,8 +26,6 @@

#define vmemmap ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT))

-#define FIRST_USER_ADDRESS 0UL
-
#ifndef __ASSEMBLY__

#include <asm/cmpxchg.h>
diff --git a/arch/csky/include/asm/pgtable.h b/arch/csky/include/asm/pgtable.h
index 0d60367b6bfa..151607ed5158 100644
--- a/arch/csky/include/asm/pgtable.h
+++ b/arch/csky/include/asm/pgtable.h
@@ -14,7 +14,6 @@
#define PGDIR_MASK (~(PGDIR_SIZE-1))

#define USER_PTRS_PER_PGD (PAGE_OFFSET/PGDIR_SIZE)
-#define FIRST_USER_ADDRESS 0UL

/*
* C-SKY is two-level paging structure:
diff --git a/arch/hexagon/include/asm/pgtable.h b/arch/hexagon/include/asm/pgtable.h
index dbb22b80b8c4..e4979508cddf 100644
--- a/arch/hexagon/include/asm/pgtable.h
+++ b/arch/hexagon/include/asm/pgtable.h
@@ -155,9 +155,6 @@ extern unsigned long _dflt_cache_att;

extern pgd_t swapper_pg_dir[PTRS_PER_PGD]; /* located in head.S */

-/* Seems to be zero even in architectures where the zero page is firewalled? */
-#define FIRST_USER_ADDRESS 0UL
-
/* HUGETLB not working currently */
#ifdef CONFIG_HUGETLB_PAGE
#define pte_mkhuge(pte) __pte((pte_val(pte) & ~0x3) | HVM_HUGEPAGE_SIZE)
diff --git a/arch/ia64/include/asm/pgtable.h b/arch/ia64/include/asm/pgtable.h
index d765fd948fae..3f5dbbd8b9d8 100644
--- a/arch/ia64/include/asm/pgtable.h
+++ b/arch/ia64/include/asm/pgtable.h
@@ -128,7 +128,6 @@
#define PTRS_PER_PGD_SHIFT PTRS_PER_PTD_SHIFT
#define PTRS_PER_PGD (1UL << PTRS_PER_PGD_SHIFT)
#define USER_PTRS_PER_PGD (5*PTRS_PER_PGD/8) /* regions 0-4 are user regions */
-#define FIRST_USER_ADDRESS 0UL

/*
* All the normal masks have the "page accessed" bits on, as any time
diff --git a/arch/m68k/include/asm/pgtable_mm.h b/arch/m68k/include/asm/pgtable_mm.h
index aca22c2c1ee2..143ba7de9bda 100644
--- a/arch/m68k/include/asm/pgtable_mm.h
+++ b/arch/m68k/include/asm/pgtable_mm.h
@@ -72,7 +72,6 @@
#define PTRS_PER_PGD 128
#endif
#define USER_PTRS_PER_PGD (TASK_SIZE/PGDIR_SIZE)
-#define FIRST_USER_ADDRESS 0UL

/* Virtual address region for use by kernel_map() */
#ifdef CONFIG_SUN3
diff --git a/arch/microblaze/include/asm/pgtable.h b/arch/microblaze/include/asm/pgtable.h
index 9ae8d2c17dd5..71cd547655d9 100644
--- a/arch/microblaze/include/asm/pgtable.h
+++ b/arch/microblaze/include/asm/pgtable.h
@@ -25,8 +25,6 @@ extern int mem_init_done;
#include <asm/mmu.h>
#include <asm/page.h>

-#define FIRST_USER_ADDRESS 0UL
-
extern unsigned long va_to_phys(unsigned long address);
extern pte_t *va_to_pte(unsigned long address);

diff --git a/arch/mips/include/asm/pgtable-32.h b/arch/mips/include/asm/pgtable-32.h
index 6c0532d7b211..95df9c293d8d 100644
--- a/arch/mips/include/asm/pgtable-32.h
+++ b/arch/mips/include/asm/pgtable-32.h
@@ -93,7 +93,6 @@ extern int add_temporary_entry(unsigned long entrylo0, unsigned long entrylo1,
#endif

#define USER_PTRS_PER_PGD (0x80000000UL/PGDIR_SIZE)
-#define FIRST_USER_ADDRESS 0UL

#define VMALLOC_START MAP_BASE

diff --git a/arch/mips/include/asm/pgtable-64.h b/arch/mips/include/asm/pgtable-64.h
index 1e7d6ce9d8d6..046465906c82 100644
--- a/arch/mips/include/asm/pgtable-64.h
+++ b/arch/mips/include/asm/pgtable-64.h
@@ -137,7 +137,6 @@
#define PTRS_PER_PTE ((PAGE_SIZE << PTE_ORDER) / sizeof(pte_t))

#define USER_PTRS_PER_PGD ((TASK_SIZE64 / PGDIR_SIZE)?(TASK_SIZE64 / PGDIR_SIZE):1)
-#define FIRST_USER_ADDRESS 0UL

/*
* TLB refill handlers also map the vmalloc area into xuseg. Avoid
diff --git a/arch/nios2/include/asm/pgtable.h b/arch/nios2/include/asm/pgtable.h
index 2600d76c310c..4a995fa628ee 100644
--- a/arch/nios2/include/asm/pgtable.h
+++ b/arch/nios2/include/asm/pgtable.h
@@ -24,8 +24,6 @@
#include <asm/pgtable-bits.h>
#include <asm-generic/pgtable-nopmd.h>

-#define FIRST_USER_ADDRESS 0UL
-
#define VMALLOC_START CONFIG_NIOS2_KERNEL_MMU_REGION_BASE
#define VMALLOC_END (CONFIG_NIOS2_KERNEL_REGION_BASE - 1)

diff --git a/arch/openrisc/include/asm/pgtable.h b/arch/openrisc/include/asm/pgtable.h
index 9425bedab4fc..4ac591c9ca33 100644
--- a/arch/openrisc/include/asm/pgtable.h
+++ b/arch/openrisc/include/asm/pgtable.h
@@ -73,7 +73,6 @@ extern void paging_init(void);
*/

#define USER_PTRS_PER_PGD (TASK_SIZE/PGDIR_SIZE)
-#define FIRST_USER_ADDRESS 0UL

/*
* Kernels own virtual memory area.
diff --git a/arch/parisc/include/asm/pgtable.h b/arch/parisc/include/asm/pgtable.h
index 39017210dbf0..7f33c29764cc 100644
--- a/arch/parisc/include/asm/pgtable.h
+++ b/arch/parisc/include/asm/pgtable.h
@@ -171,8 +171,6 @@ static inline void purge_tlb_entries(struct mm_struct *mm, unsigned long addr)
* pgd entries used up by user/kernel:
*/

-#define FIRST_USER_ADDRESS 0UL
-
/* NB: The tlb miss handlers make certain assumptions about the order */
/* of the following bits, so be careful (One example, bits 25-31 */
/* are moved together in one instruction). */
diff --git a/arch/powerpc/include/asm/book3s/pgtable.h b/arch/powerpc/include/asm/book3s/pgtable.h
index 0e1263455d73..ad130e15a126 100644
--- a/arch/powerpc/include/asm/book3s/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/pgtable.h
@@ -8,7 +8,6 @@
#include <asm/book3s/32/pgtable.h>
#endif

-#define FIRST_USER_ADDRESS 0UL
#ifndef __ASSEMBLY__
/* Insert a PTE, top-level function is out of line. It uses an inline
* low level function in the respective pgtable-* files
diff --git a/arch/powerpc/include/asm/nohash/32/pgtable.h b/arch/powerpc/include/asm/nohash/32/pgtable.h
index 96522f7f0618..f06ae00f2a65 100644
--- a/arch/powerpc/include/asm/nohash/32/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/32/pgtable.h
@@ -54,7 +54,6 @@ extern int icache_44x_need_flush;
#define PGD_MASKED_BITS 0

#define USER_PTRS_PER_PGD (TASK_SIZE / PGDIR_SIZE)
-#define FIRST_USER_ADDRESS 0UL

#define pte_ERROR(e) \
pr_err("%s:%d: bad pte %llx.\n", __FILE__, __LINE__, \
diff --git a/arch/powerpc/include/asm/nohash/64/pgtable.h b/arch/powerpc/include/asm/nohash/64/pgtable.h
index 57cd3892bfe0..53fbfdfac93d 100644
--- a/arch/powerpc/include/asm/nohash/64/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/64/pgtable.h
@@ -12,8 +12,6 @@
#include <asm/barrier.h>
#include <asm/asm-const.h>

-#define FIRST_USER_ADDRESS 0UL
-
/*
* Size of EA range mapped by our pagetables.
*/
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 9469f464e71a..286870765b49 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -537,8 +537,6 @@ void setup_bootmem(void);
void paging_init(void);
void misc_mem_init(void);

-#define FIRST_USER_ADDRESS 0
-
/*
* ZERO_PAGE is a global shared page that is always zero,
* used for zero-mapped memory areas, etc.

Acked-by: Palmer Dabbelt <palmerdabbelt@xxxxxxxxxx> # RISC-V

diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 29c7ecd5ad1d..4ee49bb98f34 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -65,8 +65,6 @@ extern unsigned long zero_page_mask;

/* TODO: s390 cannot support io_remap_pfn_range... */

-#define FIRST_USER_ADDRESS 0UL
-
#define pte_ERROR(e) \
printk("%s:%d: bad pte %p.\n", __FILE__, __LINE__, (void *) pte_val(e))
#define pmd_ERROR(e) \
diff --git a/arch/sh/include/asm/pgtable.h b/arch/sh/include/asm/pgtable.h
index 27751e9470df..d7ddb1ec86a0 100644
--- a/arch/sh/include/asm/pgtable.h
+++ b/arch/sh/include/asm/pgtable.h
@@ -59,8 +59,6 @@ static inline unsigned long long neff_sign_extend(unsigned long val)
/* Entries per level */
#define PTRS_PER_PTE (PAGE_SIZE / (1 << PTE_MAGNITUDE))

-#define FIRST_USER_ADDRESS 0UL
-
#define PHYS_ADDR_MASK29 0x1fffffff
#define PHYS_ADDR_MASK32 0xffffffff

diff --git a/arch/sparc/include/asm/pgtable_32.h b/arch/sparc/include/asm/pgtable_32.h
index a5cf79c149fe..0888bda245f5 100644
--- a/arch/sparc/include/asm/pgtable_32.h
+++ b/arch/sparc/include/asm/pgtable_32.h
@@ -48,7 +48,6 @@ unsigned long __init bootmem_init(unsigned long *pages_avail);
#define PTRS_PER_PMD 64
#define PTRS_PER_PGD 256
#define USER_PTRS_PER_PGD PAGE_OFFSET / PGDIR_SIZE
-#define FIRST_USER_ADDRESS 0UL
#define PTE_SIZE (PTRS_PER_PTE*4)

#define PAGE_NONE SRMMU_PAGE_NONE
diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index 550d3904de65..57460b7ada7b 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -95,9 +95,6 @@ bool kern_addr_valid(unsigned long addr);
#define PTRS_PER_PUD (1UL << PUD_BITS)
#define PTRS_PER_PGD (1UL << PGDIR_BITS)

-/* Kernel has a separate 44bit address space. */
-#define FIRST_USER_ADDRESS 0UL
-
#define pmd_ERROR(e) \
pr_err("%s:%d: bad pmd %p(%016lx) seen at (%pS)\n", \
__FILE__, __LINE__, &(e), pmd_val(e), __builtin_return_address(0))
diff --git a/arch/um/include/asm/pgtable-2level.h b/arch/um/include/asm/pgtable-2level.h
index 32106d31e4ab..8256ecc5b919 100644
--- a/arch/um/include/asm/pgtable-2level.h
+++ b/arch/um/include/asm/pgtable-2level.h
@@ -23,7 +23,6 @@
#define PTRS_PER_PTE 1024
#define USER_PTRS_PER_PGD ((TASK_SIZE + (PGDIR_SIZE - 1)) / PGDIR_SIZE)
#define PTRS_PER_PGD 1024
-#define FIRST_USER_ADDRESS 0UL

#define pte_ERROR(e) \
printk("%s:%d: bad pte %p(%08lx).\n", __FILE__, __LINE__, &(e), \
diff --git a/arch/um/include/asm/pgtable-3level.h b/arch/um/include/asm/pgtable-3level.h
index 7e6a4180db9d..9289a86643a9 100644
--- a/arch/um/include/asm/pgtable-3level.h
+++ b/arch/um/include/asm/pgtable-3level.h
@@ -41,7 +41,6 @@
#endif

#define USER_PTRS_PER_PGD ((TASK_SIZE + (PGDIR_SIZE - 1)) / PGDIR_SIZE)
-#define FIRST_USER_ADDRESS 0UL

#define pte_ERROR(e) \
printk("%s:%d: bad pte %p(%016lx).\n", __FILE__, __LINE__, &(e), \
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index f24d7ef8fffa..40497a9020c6 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -7,8 +7,6 @@

#include <asm/page_types.h>

-#define FIRST_USER_ADDRESS 0UL
-
#define _PAGE_BIT_PRESENT 0 /* is present */
#define _PAGE_BIT_RW 1 /* writeable */
#define _PAGE_BIT_USER 2 /* userspace addressable */
diff --git a/arch/xtensa/include/asm/pgtable.h b/arch/xtensa/include/asm/pgtable.h
index d7fc45c920c2..bd5aeb795567 100644
--- a/arch/xtensa/include/asm/pgtable.h
+++ b/arch/xtensa/include/asm/pgtable.h
@@ -59,7 +59,6 @@
#define PTRS_PER_PGD 1024
#define PGD_ORDER 0
#define USER_PTRS_PER_PGD (TASK_SIZE/PGDIR_SIZE)
-#define FIRST_USER_ADDRESS 0UL
#define FIRST_USER_PGD_NR (FIRST_USER_ADDRESS >> PGDIR_SHIFT)

#ifdef CONFIG_MMU
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 46b13780c2c8..1bed8b82e59d 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -28,6 +28,15 @@
#define USER_PGTABLES_CEILING 0UL
#endif

+/*
+ * This defines the first usable user address. Platforms
+ * can override its value with custom FIRST_USER_ADDRESS
+ * defined in their respective <asm/pgtable.h>.
+ */
+#ifndef FIRST_USER_ADDRESS
+#define FIRST_USER_ADDRESS 0UL
+#endif
+
/*
* A page table page can be thought of an array like this: pXd_t[PTRS_PER_PxD]
*

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Previous message: Sander Vanheule: "Re: [PATCH v2 2/7] gpio: regmap: Add configurable dir/value order"
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