diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index a750c1425c3a64e8a1f2d138b8bc4d9fd2224b8e..1bcda7cb2e0405a9d5fda7d8805f9f92ba7d665c 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -188,6 +188,9 @@ config ARCH_HAS_ILOG2_U64
config ARCH_HAS_BANDGAP
bool
+config FIX_EARLYCON_MEM
+ def_bool y if MMU
+
config GENERIC_HWEIGHT
bool
default y
diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
index 0415eae1df27419755c5cff78170ea3f6d029535..58cfe9f1a687e6e1c8794f5ff5f37c6b4fcd7cb9 100644
--- a/arch/arm/include/asm/fixmap.h
+++ b/arch/arm/include/asm/fixmap.h
@@ -6,9 +6,13 @@
#define FIXADDR_TOP (FIXADDR_END - PAGE_SIZE)
#include <asm/kmap_types.h>
+#include <asm/pgtable.h>
enum fixed_addresses {
- FIX_KMAP_BEGIN,
+ FIX_EARLYCON_MEM_BASE,
+ __end_of_permanent_fixed_addresses,
+
+ FIX_KMAP_BEGIN = __end_of_permanent_fixed_addresses,
FIX_KMAP_END = FIX_KMAP_BEGIN + (KM_TYPE_NR * NR_CPUS) - 1,
/* Support writing RO kernel text via kprobes, jump labels, etc. */
@@ -18,7 +22,16 @@ enum fixed_addresses {
__end_of_fixed_addresses
};
+#define FIXMAP_PAGE_COMMON (L_PTE_YOUNG | L_PTE_PRESENT | L_PTE_XN | L_PTE_DIRTY)
+
+#define FIXMAP_PAGE_NORMAL (FIXMAP_PAGE_COMMON | L_PTE_MT_WRITEBACK)
+
+/* Used by set_fixmap_(io|nocache), both meant for mapping a device */
+#define FIXMAP_PAGE_IO (FIXMAP_PAGE_COMMON | L_PTE_MT_DEV_SHARED | L_PTE_SHARED)
+#define FIXMAP_PAGE_NOCACHE FIXMAP_PAGE_IO
+
void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot);
+void __init early_fixmap_init(void);
#include <asm-generic/fixmap.h>
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 6bbec60420527b2cea13e281c01d5286f92c0083..e2ecee6b70ca487f8f38407381bb77155bb3b786 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -37,6 +37,7 @@
#include <asm/cpu.h>
#include <asm/cputype.h>
#include <asm/elf.h>
+#include <asm/fixmap.h>
#include <asm/procinfo.h>
#include <asm/psci.h>
#include <asm/sections.h>
@@ -954,6 +955,9 @@ void __init setup_arch(char **cmdline_p)
strlcpy(cmd_line, boot_command_line, COMMAND_LINE_SIZE);
*cmdline_p = cmd_line;
+ if (IS_ENABLED(CONFIG_FIX_EARLYCON_MEM))
+ early_fixmap_init();
+
parse_early_param();
#ifdef CONFIG_MMU
diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
index ee8dfa793989785488a306a9edd8b7899f3f1f3b..9df5f09585ca49bc48c209f8588a395ca5f8d449 100644
--- a/arch/arm/mm/highmem.c
+++ b/arch/arm/mm/highmem.c
@@ -79,7 +79,7 @@ void *kmap_atomic(struct page *page)
type = kmap_atomic_idx_push();
- idx = type + KM_TYPE_NR * smp_processor_id();
+ idx = FIX_KMAP_BEGIN + type + KM_TYPE_NR * smp_processor_id();
vaddr = __fix_to_virt(idx);
#ifdef CONFIG_DEBUG_HIGHMEM
/*
@@ -106,7 +106,7 @@ void __kunmap_atomic(void *kvaddr)
if (kvaddr >= (void *)FIXADDR_START) {
type = kmap_atomic_idx();
- idx = type + KM_TYPE_NR * smp_processor_id();
+ idx = FIX_KMAP_BEGIN + type + KM_TYPE_NR * smp_processor_id();
if (cache_is_vivt())
__cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
@@ -138,7 +138,7 @@ void *kmap_atomic_pfn(unsigned long pfn)
return page_address(page);
type = kmap_atomic_idx_push();
- idx = type + KM_TYPE_NR * smp_processor_id();
+ idx = FIX_KMAP_BEGIN + type + KM_TYPE_NR * smp_processor_id();
vaddr = __fix_to_virt(idx);
#ifdef CONFIG_DEBUG_HIGHMEM
BUG_ON(!pte_none(get_fixmap_pte(vaddr)));
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 6ca7d9aa896f4e14804e1096407b16e9b1020456..fb9e817d08bb800e9234b1d04bbc0c560114f829 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -357,6 +357,47 @@ const struct mem_type *get_mem_type(unsigned int type)
}
EXPORT_SYMBOL(get_mem_type);
+static pte_t *(*pte_offset_fixmap)(pmd_t *dir, unsigned long addr);
+
+static pte_t bm_pte[PTRS_PER_PTE + PTE_HWTABLE_PTRS]
+ __aligned(PTE_HWTABLE_OFF + PTE_HWTABLE_SIZE) __initdata;
+
+static pte_t * __init pte_offset_early_fixmap(pmd_t *dir, unsigned long addr)
+{
+ return &bm_pte[pte_index(addr)];
+}
+
+static pte_t *pte_offset_late_fixmap(pmd_t *dir, unsigned long addr)
+{
+ return pte_offset_kernel(dir, addr);
+}
+
+static inline pmd_t * __init fixmap_pmd(unsigned long addr)
+{
+ pgd_t *pgd = pgd_offset_k(addr);
+ pud_t *pud = pud_offset(pgd, addr);
+ pmd_t *pmd = pmd_offset(pud, addr);
+
+ return pmd;
+}
+
+void __init early_fixmap_init(void)
+{
+ pmd_t *pmd;
+
+ /*
+ * The early fixmap range spans multiple pmds, for which
+ * we are not prepared:
+ */
+ BUILD_BUG_ON((__fix_to_virt(__end_of_permanent_fixed_addresses) >> PMD_SHIFT)
+ != FIXADDR_TOP >> PMD_SHIFT);
+
+ pmd = fixmap_pmd(FIXADDR_TOP);
+ pmd_populate_kernel(&init_mm, pmd, bm_pte);
+
+ pte_offset_fixmap = pte_offset_early_fixmap;
+}
+
/*
* To avoid TLB flush broadcasts, this uses local_flush_tlb_kernel_range().
* As a result, this can only be called with preemption disabled, as under
@@ -365,7 +406,7 @@ EXPORT_SYMBOL(get_mem_type);
void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
{
unsigned long vaddr = __fix_to_virt(idx);
- pte_t *pte = pte_offset_kernel(pmd_off_k(vaddr), vaddr);
+ pte_t *pte = pte_offset_fixmap(pmd_off_k(vaddr), vaddr);
/* Make sure fixmap region does not exceed available allocation. */
BUILD_BUG_ON(FIXADDR_START + (__end_of_fixed_addresses * PAGE_SIZE) >
@@ -855,7 +896,7 @@ static void __init create_mapping(struct map_desc *md)
}
if ((md->type == MT_DEVICE || md->type == MT_ROM) &&
- md->virtual >= PAGE_OFFSET &&
+ md->virtual >= PAGE_OFFSET && md->virtual < FIXADDR_START &&
(md->virtual < VMALLOC_START || md->virtual >= VMALLOC_END)) {
pr_warn("BUG: mapping for 0x%08llx at 0x%08lx out of vmalloc space\n",
(long long)__pfn_to_phys((u64)md->pfn), md->virtual);
@@ -1213,10 +1254,10 @@ void __init arm_mm_memblock_reserve(void)
/*
* Set up the device mappings. Since we clear out the page tables for all
- * mappings above VMALLOC_START, we will remove any debug device mappings.
- * This means you have to be careful how you debug this function, or any
- * called function. This means you can't use any function or debugging
- * method which may touch any device, otherwise the kernel _will_ crash.
+ * mappings above VMALLOC_START, except early fixmap, we might remove debug
+ * device mappings. This means earlycon can be used to debug this function
+ * Any other function or debugging method which may touch any device _will_
+ * crash the kernel.
*/
static void __init devicemaps_init(const struct machine_desc *mdesc)
{
@@ -1231,7 +1272,10 @@ static void __init devicemaps_init(const struct machine_desc *mdesc)
early_trap_init(vectors);
- for (addr = VMALLOC_START; addr; addr += PMD_SIZE)
+ /*
+ * Clear page table except top pmd used by early fixmaps
+ */
+ for (addr = VMALLOC_START; addr < (FIXADDR_TOP & PMD_MASK); addr += PMD_SIZE)
pmd_clear(pmd_off_k(addr));
/*
@@ -1483,6 +1527,35 @@ void __init early_paging_init(const struct machine_desc *mdesc)
#endif
+static void __init early_fixmap_shutdown(void)
+{
+ int i;
+ unsigned long va = fix_to_virt(__end_of_permanent_fixed_addresses - 1);
+
+ pte_offset_fixmap = pte_offset_late_fixmap;
+ pmd_clear(fixmap_pmd(va));
+ local_flush_tlb_kernel_page(va);
+
+ for (i = 0; i < __end_of_permanent_fixed_addresses; i++) {
+ pte_t *pte;
+ struct map_desc map;
+
+ map.virtual = fix_to_virt(i);
+ pte = pte_offset_early_fixmap(pmd_off_k(map.virtual), map.virtual);
+
+ /* Only i/o device mappings are supported ATM */
+ if (pte_none(*pte) ||
+ (pte_val(*pte) & L_PTE_MT_MASK) != L_PTE_MT_DEV_SHARED)
+ continue;
+
+ map.pfn = pte_pfn(*pte);
+ map.type = MT_DEVICE;
+ map.length = PAGE_SIZE;
+
+ create_mapping(&map);
+ }
+}
+
/*
* paging_init() sets up the page tables, initialises the zone memory
* maps, and sets up the zero page, bad page and bad page tables.
@@ -1495,6 +1568,7 @@ void __init paging_init(const struct machine_desc *mdesc)
prepare_page_table();
map_lowmem();
dma_contiguous_remap();
+ early_fixmap_shutdown();
devicemaps_init(mdesc);
kmap_init();
tcm_init();