arm64: kernel: Add support for hibernate/suspend-to-disk

Add support for hibernate/suspend-to-disk.

Suspend borrows code from cpu_suspend() to write cpu state onto the stack,
before calling swsusp_save() to save the memory image.

Restore creates a set of temporary page tables, covering only the
linear map, copies the restore code to a 'safe' page, then uses the copy to
restore the memory image. The copied code executes in the lower half of the
address space, and once complete, restores the original kernel's page
tables. It then calls into cpu_resume(), and follows the normal
cpu_suspend() path back into the suspend code.

To restore a kernel using KASLR, the address of the page tables, and
cpu_resume() are stored in the hibernate arch-header and the el2
vectors are pivotted via the 'safe' page in low memory.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Kevin Hilman <khilman@baylibre.com> # Tested on Juno R2
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 461 insertions, 0 deletions

diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
new file mode 100644
index 000000000000..7e16fb327644
--- /dev/null
+++ b/arch/arm64/kernel/hibernate.c
@@ -0,0 +1,461 @@
+/*:
+ * Hibernate support specific for ARM64
+ *
+ * Derived from work on ARM hibernation support by:
+ *
+ * Ubuntu project, hibernation support for mach-dove
+ * Copyright (C) 2010 Nokia Corporation (Hiroshi Doyu)
+ * Copyright (C) 2010 Texas Instruments, Inc. (Teerth Reddy et al.)
+ *  https://lkml.org/lkml/2010/6/18/4
+ *  https://lists.linux-foundation.org/pipermail/linux-pm/2010-June/027422.html
+ *  https://patchwork.kernel.org/patch/96442/
+ *
+ * Copyright (C) 2006 Rafael J. Wysocki <rjw@sisk.pl>
+ *
+ * License terms: GNU General Public License (GPL) version 2
+ */
+#define pr_fmt(x) "hibernate: " x
+#include <linux/kvm_host.h>
+#include <linux/mm.h>
+#include <linux/pm.h>
+#include <linux/sched.h>
+#include <linux/suspend.h>
+#include <linux/utsname.h>
+#include <linux/version.h>
+
+#include <asm/barrier.h>
+#include <asm/cacheflush.h>
+#include <asm/irqflags.h>
+#include <asm/memory.h>
+#include <asm/mmu_context.h>
+#include <asm/pgalloc.h>
+#include <asm/pgtable.h>
+#include <asm/pgtable-hwdef.h>
+#include <asm/sections.h>
+#include <asm/suspend.h>
+#include <asm/virt.h>
+
+/*
+ * Hibernate core relies on this value being 0 on resume, and marks it
+ * __nosavedata assuming it will keep the resume kernel's '0' value. This
+ * doesn't happen with either KASLR.
+ *
+ * defined as "__visible int in_suspend __nosavedata" in
+ * kernel/power/hibernate.c
+ */
+extern int in_suspend;
+
+/* Find a symbols alias in the linear map */
+#define LMADDR(x)	phys_to_virt(virt_to_phys(x))
+
+/* Do we need to reset el2? */
+#define el2_reset_needed() (is_hyp_mode_available() && !is_kernel_in_hyp_mode())
+
+/*
+ * Start/end of the hibernate exit code, this must be copied to a 'safe'
+ * location in memory, and executed from there.
+ */
+extern char __hibernate_exit_text_start[], __hibernate_exit_text_end[];
+
+/* temporary el2 vectors in the __hibernate_exit_text section. */
+extern char hibernate_el2_vectors[];
+
+/* hyp-stub vectors, used to restore el2 during resume from hibernate. */
+extern char __hyp_stub_vectors[];
+
+/*
+ * Values that may not change over hibernate/resume. We put the build number
+ * and date in here so that we guarantee not to resume with a different
+ * kernel.
+ */
+struct arch_hibernate_hdr_invariants {
+	char		uts_version[__NEW_UTS_LEN + 1];
+};
+
+/* These values need to be know across a hibernate/restore. */
+static struct arch_hibernate_hdr {
+	struct arch_hibernate_hdr_invariants invariants;
+
+	/* These are needed to find the relocated kernel if built with kaslr */
+	phys_addr_t	ttbr1_el1;
+	void		(*reenter_kernel)(void);
+
+	/*
+	 * We need to know where the __hyp_stub_vectors are after restore to
+	 * re-configure el2.
+	 */
+	phys_addr_t	__hyp_stub_vectors;
+} resume_hdr;
+
+static inline void arch_hdr_invariants(struct arch_hibernate_hdr_invariants *i)
+{
+	memset(i, 0, sizeof(*i));
+	memcpy(i->uts_version, init_utsname()->version, sizeof(i->uts_version));
+}
+
+int pfn_is_nosave(unsigned long pfn)
+{
+	unsigned long nosave_begin_pfn = virt_to_pfn(&__nosave_begin);
+	unsigned long nosave_end_pfn = virt_to_pfn(&__nosave_end - 1);
+
+	return (pfn >= nosave_begin_pfn) && (pfn <= nosave_end_pfn);
+}
+
+void notrace save_processor_state(void)
+{
+	WARN_ON(num_online_cpus() != 1);
+}
+
+void notrace restore_processor_state(void)
+{
+}
+
+int arch_hibernation_header_save(void *addr, unsigned int max_size)
+{
+	struct arch_hibernate_hdr *hdr = addr;
+
+	if (max_size < sizeof(*hdr))
+		return -EOVERFLOW;
+
+	arch_hdr_invariants(&hdr->invariants);
+	hdr->ttbr1_el1		= virt_to_phys(swapper_pg_dir);
+	hdr->reenter_kernel	= _cpu_resume;
+
+	/* We can't use __hyp_get_vectors() because kvm may still be loaded */
+	if (el2_reset_needed())
+		hdr->__hyp_stub_vectors = virt_to_phys(__hyp_stub_vectors);
+	else
+		hdr->__hyp_stub_vectors = 0;
+
+	return 0;
+}
+EXPORT_SYMBOL(arch_hibernation_header_save);
+
+int arch_hibernation_header_restore(void *addr)
+{
+	struct arch_hibernate_hdr_invariants invariants;
+	struct arch_hibernate_hdr *hdr = addr;
+
+	arch_hdr_invariants(&invariants);
+	if (memcmp(&hdr->invariants, &invariants, sizeof(invariants))) {
+		pr_crit("Hibernate image not generated by this kernel!\n");
+		return -EINVAL;
+	}
+
+	resume_hdr = *hdr;
+
+	return 0;
+}
+EXPORT_SYMBOL(arch_hibernation_header_restore);
+
+/*
+ * Copies length bytes, starting at src_start into an new page,
+ * perform cache maintentance, then maps it at the specified address low
+ * address as executable.
+ *
+ * This is used by hibernate to copy the code it needs to execute when
+ * overwriting the kernel text. This function generates a new set of page
+ * tables, which it loads into ttbr0.
+ *
+ * Length is provided as we probably only want 4K of data, even on a 64K
+ * page system.
+ */
+static int create_safe_exec_page(void *src_start, size_t length,
+				 unsigned long dst_addr,
+				 phys_addr_t *phys_dst_addr,
+				 void *(*allocator)(gfp_t mask),
+				 gfp_t mask)
+{
+	int rc = 0;
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+	unsigned long dst = (unsigned long)allocator(mask);
+
+	if (!dst) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	memcpy((void *)dst, src_start, length);
+	flush_icache_range(dst, dst + length);
+
+	pgd = pgd_offset_raw(allocator(mask), dst_addr);
+	if (pgd_none(*pgd)) {
+		pud = allocator(mask);
+		if (!pud) {
+			rc = -ENOMEM;
+			goto out;
+		}
+		pgd_populate(&init_mm, pgd, pud);
+	}
+
+	pud = pud_offset(pgd, dst_addr);
+	if (pud_none(*pud)) {
+		pmd = allocator(mask);
+		if (!pmd) {
+			rc = -ENOMEM;
+			goto out;
+		}
+		pud_populate(&init_mm, pud, pmd);
+	}
+
+	pmd = pmd_offset(pud, dst_addr);
+	if (pmd_none(*pmd)) {
+		pte = allocator(mask);
+		if (!pte) {
+			rc = -ENOMEM;
+			goto out;
+		}
+		pmd_populate_kernel(&init_mm, pmd, pte);
+	}
+
+	pte = pte_offset_kernel(pmd, dst_addr);
+	set_pte(pte, __pte(virt_to_phys((void *)dst) |
+			 pgprot_val(PAGE_KERNEL_EXEC)));
+
+	/* Load our new page tables */
+	asm volatile("msr	ttbr0_el1, %0;"
+		     "isb;"
+		     "tlbi	vmalle1is;"
+		     "dsb	ish;"
+		     "isb" : : "r"(virt_to_phys(pgd)));
+
+	*phys_dst_addr = virt_to_phys((void *)dst);
+
+out:
+	return rc;
+}
+
+
+int swsusp_arch_suspend(void)
+{
+	int ret = 0;
+	unsigned long flags;
+	struct sleep_stack_data state;
+
+	local_dbg_save(flags);
+
+	if (__cpu_suspend_enter(&state)) {
+		ret = swsusp_save();
+	} else {
+		/* Clean kernel to PoC for secondary core startup */
+		__flush_dcache_area(LMADDR(KERNEL_START), KERNEL_END - KERNEL_START);
+
+		/*
+		 * Tell the hibernation core that we've just restored
+		 * the memory
+		 */
+		in_suspend = 0;
+
+		__cpu_suspend_exit();
+	}
+
+	local_dbg_restore(flags);
+
+	return ret;
+}
+
+static int copy_pte(pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long start,
+		    unsigned long end)
+{
+	pte_t *src_pte;
+	pte_t *dst_pte;
+	unsigned long addr = start;
+
+	dst_pte = (pte_t *)get_safe_page(GFP_ATOMIC);
+	if (!dst_pte)
+		return -ENOMEM;
+	pmd_populate_kernel(&init_mm, dst_pmd, dst_pte);
+	dst_pte = pte_offset_kernel(dst_pmd, start);
+
+	src_pte = pte_offset_kernel(src_pmd, start);
+	do {
+		if (!pte_none(*src_pte))
+			/*
+			 * Resume will overwrite areas that may be marked
+			 * read only (code, rodata). Clear the RDONLY bit from
+			 * the temporary mappings we use during restore.
+			 */
+			set_pte(dst_pte, __pte(pte_val(*src_pte) & ~PTE_RDONLY));
+	} while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
+
+	return 0;
+}
+
+static int copy_pmd(pud_t *dst_pud, pud_t *src_pud, unsigned long start,
+		    unsigned long end)
+{
+	pmd_t *src_pmd;
+	pmd_t *dst_pmd;
+	unsigned long next;
+	unsigned long addr = start;
+
+	if (pud_none(*dst_pud)) {
+		dst_pmd = (pmd_t *)get_safe_page(GFP_ATOMIC);
+		if (!dst_pmd)
+			return -ENOMEM;
+		pud_populate(&init_mm, dst_pud, dst_pmd);
+	}
+	dst_pmd = pmd_offset(dst_pud, start);
+
+	src_pmd = pmd_offset(src_pud, start);
+	do {
+		next = pmd_addr_end(addr, end);
+		if (pmd_none(*src_pmd))
+			continue;
+		if (pmd_table(*src_pmd)) {
+			if (copy_pte(dst_pmd, src_pmd, addr, next))
+				return -ENOMEM;
+		} else {
+			set_pmd(dst_pmd,
+				__pmd(pmd_val(*src_pmd) & ~PMD_SECT_RDONLY));
+		}
+	} while (dst_pmd++, src_pmd++, addr = next, addr != end);
+
+	return 0;
+}
+
+static int copy_pud(pgd_t *dst_pgd, pgd_t *src_pgd, unsigned long start,
+		    unsigned long end)
+{
+	pud_t *dst_pud;
+	pud_t *src_pud;
+	unsigned long next;
+	unsigned long addr = start;
+
+	if (pgd_none(*dst_pgd)) {
+		dst_pud = (pud_t *)get_safe_page(GFP_ATOMIC);
+		if (!dst_pud)
+			return -ENOMEM;
+		pgd_populate(&init_mm, dst_pgd, dst_pud);
+	}
+	dst_pud = pud_offset(dst_pgd, start);
+
+	src_pud = pud_offset(src_pgd, start);
+	do {
+		next = pud_addr_end(addr, end);
+		if (pud_none(*src_pud))
+			continue;
+		if (pud_table(*(src_pud))) {
+			if (copy_pmd(dst_pud, src_pud, addr, next))
+				return -ENOMEM;
+		} else {
+			set_pud(dst_pud,
+				__pud(pud_val(*src_pud) & ~PMD_SECT_RDONLY));
+		}
+	} while (dst_pud++, src_pud++, addr = next, addr != end);
+
+	return 0;
+}
+
+static int copy_page_tables(pgd_t *dst_pgd, unsigned long start,
+			    unsigned long end)
+{
+	unsigned long next;
+	unsigned long addr = start;
+	pgd_t *src_pgd = pgd_offset_k(start);
+
+	dst_pgd = pgd_offset_raw(dst_pgd, start);
+	do {
+		next = pgd_addr_end(addr, end);
+		if (pgd_none(*src_pgd))
+			continue;
+		if (copy_pud(dst_pgd, src_pgd, addr, next))
+			return -ENOMEM;
+	} while (dst_pgd++, src_pgd++, addr = next, addr != end);
+
+	return 0;
+}
+
+/*
+ * Setup then Resume from the hibernate image using swsusp_arch_suspend_exit().
+ *
+ * Memory allocated by get_safe_page() will be dealt with by the hibernate code,
+ * we don't need to free it here.
+ */
+int swsusp_arch_resume(void)
+{
+	int rc = 0;
+	void *zero_page;
+	size_t exit_size;
+	pgd_t *tmp_pg_dir;
+	void *lm_restore_pblist;
+	phys_addr_t phys_hibernate_exit;
+	void __noreturn (*hibernate_exit)(phys_addr_t, phys_addr_t, void *,
+					  void *, phys_addr_t, phys_addr_t);
+
+	/*
+	 * Locate the exit code in the bottom-but-one page, so that *NULL
+	 * still has disastrous affects.
+	 */
+	hibernate_exit = (void *)PAGE_SIZE;
+	exit_size = __hibernate_exit_text_end - __hibernate_exit_text_start;
+	/*
+	 * Copy swsusp_arch_suspend_exit() to a safe page. This will generate
+	 * a new set of ttbr0 page tables and load them.
+	 */
+	rc = create_safe_exec_page(__hibernate_exit_text_start, exit_size,
+				   (unsigned long)hibernate_exit,
+				   &phys_hibernate_exit,
+				   (void *)get_safe_page, GFP_ATOMIC);
+	if (rc) {
+		pr_err("Failed to create safe executable page for hibernate_exit code.");
+		goto out;
+	}
+
+	/*
+	 * The hibernate exit text contains a set of el2 vectors, that will
+	 * be executed at el2 with the mmu off in order to reload hyp-stub.
+	 */
+	__flush_dcache_area(hibernate_exit, exit_size);
+
+	/*
+	 * Restoring the memory image will overwrite the ttbr1 page tables.
+	 * Create a second copy of just the linear map, and use this when
+	 * restoring.
+	 */
+	tmp_pg_dir = (pgd_t *)get_safe_page(GFP_ATOMIC);
+	if (!tmp_pg_dir) {
+		pr_err("Failed to allocate memory for temporary page tables.");
+		rc = -ENOMEM;
+		goto out;
+	}
+	rc = copy_page_tables(tmp_pg_dir, PAGE_OFFSET, 0);
+	if (rc)
+		goto out;
+
+	/*
+	 * Since we only copied the linear map, we need to find restore_pblist's
+	 * linear map address.
+	 */
+	lm_restore_pblist = LMADDR(restore_pblist);
+
+	/*
+	 * KASLR will cause the el2 vectors to be in a different location in
+	 * the resumed kernel. Load hibernate's temporary copy into el2.
+	 *
+	 * We can skip this step if we booted at EL1, or are running with VHE.
+	 */
+	if (el2_reset_needed()) {
+		phys_addr_t el2_vectors = phys_hibernate_exit;  /* base */
+		el2_vectors += hibernate_el2_vectors -
+			       __hibernate_exit_text_start;     /* offset */
+
+		__hyp_set_vectors(el2_vectors);
+	}
+
+	/*
+	 * We need a zero page that is zero before & after resume in order to
+	 * to break before make on the ttbr1 page tables.
+	 */
+	zero_page = (void *)get_safe_page(GFP_ATOMIC);
+
+	hibernate_exit(virt_to_phys(tmp_pg_dir), resume_hdr.ttbr1_el1,
+		       resume_hdr.reenter_kernel, lm_restore_pblist,
+		       resume_hdr.__hyp_stub_vectors, virt_to_phys(zero_page));
+
+out:
+	return rc;
+}