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 <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens
Martin Schwidefsky
Родитель
51eee033dc
Коммит
e76e82d772
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@ -31,6 +31,18 @@ config DEBUG_STRICT_USER_COPY_CHECKS
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If unsure, or if you run an older (pre 4.4) gcc, say N.
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config S390_PTDUMP
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bool "Export kernel pagetable layout to userspace via debugfs"
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depends on DEBUG_KERNEL
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select DEBUG_FS
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---help---
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Say Y here if you want to show the kernel pagetable layout in a
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debugfs file. This information is only useful for kernel developers
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who are working in architecture specific areas of the kernel.
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It is probably not a good idea to enable this feature in a production
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kernel.
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If in doubt, say "N"
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config DEBUG_SET_MODULE_RONX
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def_bool y
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depends on MODULES
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@ -7,3 +7,4 @@ obj-y := init.o fault.o extmem.o mmap.o vmem.o pgtable.o maccess.o \
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obj-$(CONFIG_CMM) += cmm.o
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obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
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obj-$(CONFIG_DEBUG_SET_MODULE_RONX) += pageattr.o
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obj-$(CONFIG_S390_PTDUMP) += dump_pagetables.o
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@ -0,0 +1,219 @@
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#include <linux/seq_file.h>
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#include <linux/debugfs.h>
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#include <linux/module.h>
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#include <linux/mm.h>
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#include <asm/sections.h>
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#include <asm/pgtable.h>
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static unsigned long max_addr;
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struct addr_marker {
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unsigned long start_address;
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const char *name;
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};
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enum address_markers_idx {
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IDENTITY_NR = 0,
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KERNEL_START_NR,
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KERNEL_END_NR,
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VMEMMAP_NR,
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VMALLOC_NR,
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};
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static struct addr_marker address_markers[] = {
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[IDENTITY_NR] = {0, "Identity Mapping"},
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[KERNEL_START_NR] = {(unsigned long)&_stext, "Kernel Image Start"},
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[KERNEL_END_NR] = {(unsigned long)&_end, "Kernel Image End"},
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[VMEMMAP_NR] = {0, "vmemmap Area"},
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[VMALLOC_NR] = {0, "vmalloc Area"},
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{ -1, NULL }
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};
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struct pg_state {
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int level;
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unsigned int current_prot;
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unsigned long start_address;
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unsigned long current_address;
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const struct addr_marker *marker;
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};
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static void print_prot(struct seq_file *m, unsigned int pr, int level)
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{
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static const char * const level_name[] =
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{ "ASCE", "PGD", "PUD", "PMD", "PTE" };
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seq_printf(m, "%s ", level_name[level]);
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if (pr & _PAGE_INVALID)
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seq_printf(m, "I\n");
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else
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seq_printf(m, "%s\n", pr & _PAGE_RO ? "RO" : "RW");
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}
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static void note_page(struct seq_file *m, struct pg_state *st,
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unsigned int new_prot, int level)
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{
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static const char units[] = "KMGTPE";
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int width = sizeof(unsigned long) * 2;
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const char *unit = units;
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unsigned int prot, cur;
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unsigned long delta;
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/*
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* If we have a "break" in the series, we need to flush the state
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* that we have now. "break" is either changing perms, levels or
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* address space marker.
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*/
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prot = new_prot;
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cur = st->current_prot;
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if (!st->level) {
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/* First entry */
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st->current_prot = new_prot;
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st->level = level;
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st->marker = address_markers;
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seq_printf(m, "---[ %s ]---\n", st->marker->name);
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} else if (prot != cur || level != st->level ||
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st->current_address >= st->marker[1].start_address) {
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/* Print the actual finished series */
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seq_printf(m, "0x%0*lx-0x%0*lx",
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width, st->start_address,
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width, st->current_address);
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delta = (st->current_address - st->start_address) >> 10;
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while (!(delta & 0x3ff) && unit[1]) {
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delta >>= 10;
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unit++;
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}
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seq_printf(m, "%9lu%c ", delta, *unit);
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print_prot(m, st->current_prot, st->level);
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if (st->current_address >= st->marker[1].start_address) {
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st->marker++;
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seq_printf(m, "---[ %s ]---\n", st->marker->name);
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}
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st->start_address = st->current_address;
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st->current_prot = new_prot;
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st->level = level;
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}
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}
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/*
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* The actual page table walker functions. In order to keep the implementation
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* of print_prot() short, we only check and pass _PAGE_INVALID and _PAGE_RO
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* flags to note_page() if a region, segment or page table entry is invalid or
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* read-only.
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* After all it's just a hint that the current level being walked contains an
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* invalid or read-only entry.
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*/
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static void walk_pte_level(struct seq_file *m, struct pg_state *st,
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pmd_t *pmd, unsigned long addr)
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{
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unsigned int prot;
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pte_t *pte;
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int i;
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for (i = 0; i < PTRS_PER_PTE && addr < max_addr; i++) {
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st->current_address = addr;
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pte = pte_offset_kernel(pmd, addr);
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prot = pte_val(*pte) & (_PAGE_RO | _PAGE_INVALID);
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note_page(m, st, prot, 4);
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addr += PAGE_SIZE;
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}
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}
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static void walk_pmd_level(struct seq_file *m, struct pg_state *st,
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pud_t *pud, unsigned long addr)
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{
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unsigned int prot;
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pmd_t *pmd;
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int i;
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for (i = 0; i < PTRS_PER_PMD && addr < max_addr; i++) {
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st->current_address = addr;
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pmd = pmd_offset(pud, addr);
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if (!pmd_none(*pmd)) {
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if (pmd_large(*pmd)) {
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prot = pmd_val(*pmd) & _SEGMENT_ENTRY_RO;
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note_page(m, st, prot, 3);
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} else
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walk_pte_level(m, st, pmd, addr);
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} else
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note_page(m, st, _PAGE_INVALID, 3);
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addr += PMD_SIZE;
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}
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}
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static void walk_pud_level(struct seq_file *m, struct pg_state *st,
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pgd_t *pgd, unsigned long addr)
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{
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pud_t *pud;
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int i;
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for (i = 0; i < PTRS_PER_PUD && addr < max_addr; i++) {
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st->current_address = addr;
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pud = pud_offset(pgd, addr);
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if (!pud_none(*pud))
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walk_pmd_level(m, st, pud, addr);
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else
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note_page(m, st, _PAGE_INVALID, 2);
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addr += PUD_SIZE;
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}
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}
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static void walk_pgd_level(struct seq_file *m)
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{
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unsigned long addr = 0;
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struct pg_state st;
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pgd_t *pgd;
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int i;
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memset(&st, 0, sizeof(st));
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for (i = 0; i < PTRS_PER_PGD && addr < max_addr; i++) {
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st.current_address = addr;
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pgd = pgd_offset_k(addr);
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if (!pgd_none(*pgd))
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walk_pud_level(m, &st, pgd, addr);
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else
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note_page(m, &st, _PAGE_INVALID, 1);
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addr += PGDIR_SIZE;
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}
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/* Flush out the last page */
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st.current_address = max_addr;
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note_page(m, &st, 0, 0);
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}
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static int ptdump_show(struct seq_file *m, void *v)
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{
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walk_pgd_level(m);
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return 0;
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}
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static int ptdump_open(struct inode *inode, struct file *filp)
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{
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return single_open(filp, ptdump_show, NULL);
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}
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static const struct file_operations ptdump_fops = {
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.open = ptdump_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static int pt_dump_init(void)
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{
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/*
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* Figure out the maximum virtual address being accessible with the
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* kernel ASCE. We need this to keep the page table walker functions
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* from accessing non-existent entries.
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*/
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#ifdef CONFIG_64BIT
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max_addr = (S390_lowcore.kernel_asce & _REGION_ENTRY_TYPE_MASK) >> 2;
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max_addr = 1UL << (max_addr * 11 + 31);
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#else
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max_addr = 1UL << 31;
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#endif
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address_markers[VMEMMAP_NR].start_address = (unsigned long) vmemmap;
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address_markers[VMALLOC_NR].start_address = VMALLOC_START;
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debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops);
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return 0;
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}
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device_initcall(pt_dump_init);
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