From: Heiko Carstens Date: Thu, 4 Oct 2012 12:46:12 +0000 (+0200) Subject: s390/mm: add page table dumper X-Git-Tag: v3.7-rc1~62^2~9 X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=e76e82d772522b05ed93228478d2a4460754b6a4 s390/mm: add page table dumper This is more or less the same as the x86 page table dumper which was merged four years ago: 926e5392 "x86: add code to dump the (kernel) page tables for visual inspection by kernel developers". We add a file at /sys/kernel/debug/kernel_page_tables for debugging purposes so it's quite easy to see the kernel page table layout and possible odd mappings: ---[ Identity Mapping ]--- 0x0000000000000000-0x0000000000100000 1M PTE RW ---[ Kernel Image Start ]--- 0x0000000000100000-0x0000000000800000 7M PMD RO 0x0000000000800000-0x00000000008a9000 676K PTE RO 0x00000000008a9000-0x0000000000900000 348K PTE RW 0x0000000000900000-0x0000000001500000 12M PMD RW ---[ Kernel Image End ]--- 0x0000000001500000-0x0000000280000000 10219M PMD RW 0x0000000280000000-0x000003d280000000 3904G PUD I ---[ vmemmap Area ]--- 0x000003d280000000-0x000003d288c00000 140M PTE RW 0x000003d288c00000-0x000003d300000000 1908M PMD I 0x000003d300000000-0x000003e000000000 52G PUD I ---[ vmalloc Area ]--- 0x000003e000000000-0x000003e000009000 36K PTE RW 0x000003e000009000-0x000003e0000ee000 916K PTE I 0x000003e0000ee000-0x000003e000146000 352K PTE RW 0x000003e000146000-0x000003e000200000 744K PTE I 0x000003e000200000-0x000003e080000000 2046M PMD I 0x000003e080000000-0x0000040000000000 126G PUD I This usually makes only sense for kernel developers. The output with CONFIG_DEBUG_PAGEALLOC is not very helpful, because of the huge number of mapped out pages, however I decided for the time being to not add a !DEBUG_PAGEALLOC dependency. Maybe it's helpful for somebody even with that option. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky --- diff --git a/arch/s390/Kconfig.debug b/arch/s390/Kconfig.debug index d76cef3fef37..fc32a2df4974 100644 --- a/arch/s390/Kconfig.debug +++ b/arch/s390/Kconfig.debug @@ -31,6 +31,18 @@ config DEBUG_STRICT_USER_COPY_CHECKS If unsure, or if you run an older (pre 4.4) gcc, say N. +config S390_PTDUMP + bool "Export kernel pagetable layout to userspace via debugfs" + depends on DEBUG_KERNEL + select DEBUG_FS + ---help--- + Say Y here if you want to show the kernel pagetable layout in a + debugfs file. This information is only useful for kernel developers + who are working in architecture specific areas of the kernel. + It is probably not a good idea to enable this feature in a production + kernel. + If in doubt, say "N" + config DEBUG_SET_MODULE_RONX def_bool y depends on MODULES diff --git a/arch/s390/mm/Makefile b/arch/s390/mm/Makefile index 0f5536b0c1a1..1bea6d1f55ab 100644 --- a/arch/s390/mm/Makefile +++ b/arch/s390/mm/Makefile @@ -7,3 +7,4 @@ obj-y := init.o fault.o extmem.o mmap.o vmem.o pgtable.o maccess.o \ obj-$(CONFIG_CMM) += cmm.o obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o obj-$(CONFIG_DEBUG_SET_MODULE_RONX) += pageattr.o +obj-$(CONFIG_S390_PTDUMP) += dump_pagetables.o diff --git a/arch/s390/mm/dump_pagetables.c b/arch/s390/mm/dump_pagetables.c new file mode 100644 index 000000000000..cd1c62d160ed --- /dev/null +++ b/arch/s390/mm/dump_pagetables.c @@ -0,0 +1,219 @@ +#include +#include +#include +#include +#include +#include + +static unsigned long max_addr; + +struct addr_marker { + unsigned long start_address; + const char *name; +}; + +enum address_markers_idx { + IDENTITY_NR = 0, + KERNEL_START_NR, + KERNEL_END_NR, + VMEMMAP_NR, + VMALLOC_NR, +}; + +static struct addr_marker address_markers[] = { + [IDENTITY_NR] = {0, "Identity Mapping"}, + [KERNEL_START_NR] = {(unsigned long)&_stext, "Kernel Image Start"}, + [KERNEL_END_NR] = {(unsigned long)&_end, "Kernel Image End"}, + [VMEMMAP_NR] = {0, "vmemmap Area"}, + [VMALLOC_NR] = {0, "vmalloc Area"}, + { -1, NULL } +}; + +struct pg_state { + int level; + unsigned int current_prot; + unsigned long start_address; + unsigned long current_address; + const struct addr_marker *marker; +}; + +static void print_prot(struct seq_file *m, unsigned int pr, int level) +{ + static const char * const level_name[] = + { "ASCE", "PGD", "PUD", "PMD", "PTE" }; + + seq_printf(m, "%s ", level_name[level]); + if (pr & _PAGE_INVALID) + seq_printf(m, "I\n"); + else + seq_printf(m, "%s\n", pr & _PAGE_RO ? "RO" : "RW"); +} + +static void note_page(struct seq_file *m, struct pg_state *st, + unsigned int new_prot, int level) +{ + static const char units[] = "KMGTPE"; + int width = sizeof(unsigned long) * 2; + const char *unit = units; + unsigned int prot, cur; + unsigned long delta; + + /* + * If we have a "break" in the series, we need to flush the state + * that we have now. "break" is either changing perms, levels or + * address space marker. + */ + prot = new_prot; + cur = st->current_prot; + + if (!st->level) { + /* First entry */ + st->current_prot = new_prot; + st->level = level; + st->marker = address_markers; + seq_printf(m, "---[ %s ]---\n", st->marker->name); + } else if (prot != cur || level != st->level || + st->current_address >= st->marker[1].start_address) { + /* Print the actual finished series */ + seq_printf(m, "0x%0*lx-0x%0*lx", + width, st->start_address, + width, st->current_address); + delta = (st->current_address - st->start_address) >> 10; + while (!(delta & 0x3ff) && unit[1]) { + delta >>= 10; + unit++; + } + seq_printf(m, "%9lu%c ", delta, *unit); + print_prot(m, st->current_prot, st->level); + if (st->current_address >= st->marker[1].start_address) { + st->marker++; + seq_printf(m, "---[ %s ]---\n", st->marker->name); + } + st->start_address = st->current_address; + st->current_prot = new_prot; + st->level = level; + } +} + +/* + * The actual page table walker functions. In order to keep the implementation + * of print_prot() short, we only check and pass _PAGE_INVALID and _PAGE_RO + * flags to note_page() if a region, segment or page table entry is invalid or + * read-only. + * After all it's just a hint that the current level being walked contains an + * invalid or read-only entry. + */ +static void walk_pte_level(struct seq_file *m, struct pg_state *st, + pmd_t *pmd, unsigned long addr) +{ + unsigned int prot; + pte_t *pte; + int i; + + for (i = 0; i < PTRS_PER_PTE && addr < max_addr; i++) { + st->current_address = addr; + pte = pte_offset_kernel(pmd, addr); + prot = pte_val(*pte) & (_PAGE_RO | _PAGE_INVALID); + note_page(m, st, prot, 4); + addr += PAGE_SIZE; + } +} + +static void walk_pmd_level(struct seq_file *m, struct pg_state *st, + pud_t *pud, unsigned long addr) +{ + unsigned int prot; + pmd_t *pmd; + int i; + + for (i = 0; i < PTRS_PER_PMD && addr < max_addr; i++) { + st->current_address = addr; + pmd = pmd_offset(pud, addr); + if (!pmd_none(*pmd)) { + if (pmd_large(*pmd)) { + prot = pmd_val(*pmd) & _SEGMENT_ENTRY_RO; + note_page(m, st, prot, 3); + } else + walk_pte_level(m, st, pmd, addr); + } else + note_page(m, st, _PAGE_INVALID, 3); + addr += PMD_SIZE; + } +} + +static void walk_pud_level(struct seq_file *m, struct pg_state *st, + pgd_t *pgd, unsigned long addr) +{ + pud_t *pud; + int i; + + for (i = 0; i < PTRS_PER_PUD && addr < max_addr; i++) { + st->current_address = addr; + pud = pud_offset(pgd, addr); + if (!pud_none(*pud)) + walk_pmd_level(m, st, pud, addr); + else + note_page(m, st, _PAGE_INVALID, 2); + addr += PUD_SIZE; + } +} + +static void walk_pgd_level(struct seq_file *m) +{ + unsigned long addr = 0; + struct pg_state st; + pgd_t *pgd; + int i; + + memset(&st, 0, sizeof(st)); + for (i = 0; i < PTRS_PER_PGD && addr < max_addr; i++) { + st.current_address = addr; + pgd = pgd_offset_k(addr); + if (!pgd_none(*pgd)) + walk_pud_level(m, &st, pgd, addr); + else + note_page(m, &st, _PAGE_INVALID, 1); + addr += PGDIR_SIZE; + } + /* Flush out the last page */ + st.current_address = max_addr; + note_page(m, &st, 0, 0); +} + +static int ptdump_show(struct seq_file *m, void *v) +{ + walk_pgd_level(m); + return 0; +} + +static int ptdump_open(struct inode *inode, struct file *filp) +{ + return single_open(filp, ptdump_show, NULL); +} + +static const struct file_operations ptdump_fops = { + .open = ptdump_open, + .read = seq_read, + .llseek = seq_lseek, + .release = single_release, +}; + +static int pt_dump_init(void) +{ + /* + * Figure out the maximum virtual address being accessible with the + * kernel ASCE. We need this to keep the page table walker functions + * from accessing non-existent entries. + */ +#ifdef CONFIG_64BIT + max_addr = (S390_lowcore.kernel_asce & _REGION_ENTRY_TYPE_MASK) >> 2; + max_addr = 1UL << (max_addr * 11 + 31); +#else + max_addr = 1UL << 31; +#endif + address_markers[VMEMMAP_NR].start_address = (unsigned long) vmemmap; + address_markers[VMALLOC_NR].start_address = VMALLOC_START; + debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops); + return 0; +} +device_initcall(pt_dump_init);