[PATCH 1/3] powerpc: bare minimum checkpoint/restart implementation

[Nathan Lynch <ntl@pobox.com>]

The only thing of significance here is that the checkpointed task's
pt_regs and fp state are saved and restored (see cr_write_cpu and
cr_read_cpu); the rest of the code consists of dummy implementations
of the APIs the arch needs to provide to the checkpoint/restart core.

What works:
* self and external checkpoint of simple (single thread, one open
  file) 32- and 64-bit processes on a ppc64 kernel

What doesn't work:
* restarting a 32-bit task from a 64-bit task and vice versa

Untested:
* ppc32 (but it builds)

Signed-off-by: Nathan Lynch <ntl@pobox.com>
---
 arch/powerpc/include/asm/checkpoint_hdr.h |   40 +++++
 arch/powerpc/mm/Makefile                  |    1 +
 arch/powerpc/mm/checkpoint.c              |  261 +++++++++++++++++++++++++++++
 3 files changed, 302 insertions(+), 0 deletions(-)
 create mode 100644 arch/powerpc/include/asm/checkpoint_hdr.h
 create mode 100644 arch/powerpc/mm/checkpoint.c

diff --git a/arch/powerpc/include/asm/checkpoint_hdr.h b/arch/powerpc/include/asm/checkpoint_hdr.h
new file mode 100644
index 0000000..752c53f
--- /dev/null
+++ b/arch/powerpc/include/asm/checkpoint_hdr.h
@@ -0,0 +1,40 @@
+#ifndef __ASM_PPC_CKPT_HDR_H
+#define __ASM_PPC_CKPT_HDR_H
+/*
+ *  Checkpoint/restart - architecture specific headers ppc
+ *
+ *  Copyright (C) 2008 Oren Laadan
+ *
+ *  This file is subject to the terms and conditions of the GNU General Public
+ *  License.  See the file COPYING in the main directory of the Linux
+ *  distribution for more details.
+ */
+
+#include <linux/types.h>
+#include <asm/ptrace.h>
+#include <asm/mmu.h>
+#include <asm/processor.h>
+
+struct cr_hdr_head_arch {
+	__u32 unimplemented;
+};
+
+struct cr_hdr_thread {
+	__u32 unimplemented;
+};
+
+struct cr_hdr_cpu {
+	struct pt_regs pt_regs;
+	/* relevant fields from thread_struct */
+	double fpr[32][TS_FPRWIDTH];
+	unsigned int fpscr;
+	int fpexc_mode;
+	/* unsigned int align_ctl; this is never updated? */
+	unsigned long dabr;
+};
+
+struct cr_hdr_mm_context {
+	__u32 unimplemented;
+};
+
+#endif /* __ASM_PPC_CKPT_HDR__H */
diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile
index e7392b4..8a523a0 100644
--- a/arch/powerpc/mm/Makefile
+++ b/arch/powerpc/mm/Makefile
@@ -24,3 +24,4 @@ obj-$(CONFIG_NEED_MULTIPLE_NODES) += numa.o
 obj-$(CONFIG_PPC_MM_SLICES)	+= slice.o
 obj-$(CONFIG_HUGETLB_PAGE)	+= hugetlbpage.o
 obj-$(CONFIG_PPC_SUBPAGE_PROT)	+= subpage-prot.o
+obj-$(CONFIG_CHECKPOINT_RESTART) += checkpoint.o
diff --git a/arch/powerpc/mm/checkpoint.c b/arch/powerpc/mm/checkpoint.c
new file mode 100644
index 0000000..8cdff24
--- /dev/null
+++ b/arch/powerpc/mm/checkpoint.c
@@ -0,0 +1,261 @@
+/*
+ *  Checkpoint/restart - architecture specific support for powerpc.
+ *  Based on x86 implementation.
+ *
+ *  Copyright (C) 2008 Oren Laadan
+ *  Copyright 2009 IBM Corp.
+ *
+ *  This file is subject to the terms and conditions of the GNU General Public
+ *  License.  See the file COPYING in the main directory of the Linux
+ *  distribution for more details.
+ */
+
+#define DEBUG 1 /* for pr_debug */
+
+#include <linux/checkpoint.h>
+#include <linux/checkpoint_hdr.h>
+#include <linux/kernel.h>
+#include <asm/processor.h>
+
+static void cr_hdr_init(struct cr_hdr *hdr, __s16 type, __s16 len, __u32 parent)
+{
+	hdr->type = type;
+	hdr->len = len;
+	hdr->parent = parent;
+}
+
+/* dump the thread_struct of a given task */
+int cr_write_thread(struct cr_ctx *ctx, struct task_struct *t)
+{
+	struct cr_hdr_thread *thread_hdr;
+	struct cr_hdr cr_hdr;
+	u32 parent;
+	int ret;
+
+	thread_hdr = cr_hbuf_get(ctx, sizeof(*thread_hdr));
+	if (!thread_hdr)
+		return -ENOMEM;
+
+	parent = task_pid_vnr(t);
+
+	cr_hdr_init(&cr_hdr, CR_HDR_THREAD, sizeof(*thread_hdr), parent);
+
+	thread_hdr->unimplemented = 0xdeadbeef;
+
+	ret = cr_write_obj(ctx, &cr_hdr, thread_hdr);
+	cr_hbuf_put(ctx, sizeof(*thread_hdr));
+
+	return ret;
+}
+
+/* dump the cpu state and registers of a given task */
+int cr_write_cpu(struct cr_ctx *ctx, struct task_struct *t)
+{
+	struct cr_hdr_cpu *cpu_hdr;
+	struct pt_regs *pt_regs;
+	struct cr_hdr cr_hdr;
+	u32 parent;
+	int ret;
+
+	cpu_hdr = cr_hbuf_get(ctx, sizeof(*cpu_hdr));
+	if (!cpu_hdr)
+		return -ENOMEM;
+
+	parent = task_pid_vnr(t);
+
+	cr_hdr_init(&cr_hdr, CR_HDR_CPU, sizeof(*cpu_hdr), parent);
+
+	/* pt_regs: GPRs, MSR, etc */
+	pt_regs = task_pt_regs(t);
+	cpu_hdr->pt_regs = *pt_regs;
+
+	/* FP state */
+	memcpy(cpu_hdr->fpr, t->thread.fpr, sizeof(cpu_hdr->fpr));
+	cpu_hdr->fpscr = t->thread.fpscr.val;
+	cpu_hdr->fpexc_mode = t->thread.fpexc_mode;
+
+	/* Handle DABR for now, dbcr[01] later */
+	cpu_hdr->dabr = t->thread.dabr;
+
+	/* ToDo: Altivec/VSX/SPE state */
+
+	ret = cr_write_obj(ctx, &cr_hdr, cpu_hdr);
+	cr_hbuf_put(ctx, sizeof(*cpu_hdr));
+
+	return ret;
+}
+
+int cr_write_head_arch(struct cr_ctx *ctx)
+{
+	struct cr_hdr_head_arch *arch_hdr;
+	struct cr_hdr cr_hdr;
+	int ret;
+
+	arch_hdr = cr_hbuf_get(ctx, sizeof(*arch_hdr));
+	if (!arch_hdr)
+		return -ENOMEM;
+
+	cr_hdr_init(&cr_hdr, CR_HDR_HEAD_ARCH, sizeof(*arch_hdr), 0);
+
+	arch_hdr->unimplemented = 0xdeadbeef;
+
+	ret = cr_write_obj(ctx, &cr_hdr, arch_hdr);
+	cr_hbuf_put(ctx, sizeof(*arch_hdr));
+
+	return ret;
+}
+
+/* dump the mm->context state */
+int cr_write_mm_context(struct cr_ctx *ctx, struct mm_struct *mm, int parent)
+{
+	struct cr_hdr_mm_context *mm_hdr;
+	struct cr_hdr cr_hdr;
+	size_t size;
+	int ret;
+
+	size = sizeof(*mm_hdr);
+
+	mm_hdr = cr_hbuf_get(ctx, size);
+	if (!mm_hdr)
+		return -ENOMEM;
+
+	cr_hdr_init(&cr_hdr, CR_HDR_MM_CONTEXT, size, parent);
+
+	mm_hdr->unimplemented = 0xdeadbeef;
+
+	ret = cr_write_obj(ctx, &cr_hdr, mm_hdr);
+	cr_hbuf_put(ctx, size);
+
+	return ret;
+}
+
+/* restart APIs */
+
+/* read the thread_struct into the current task */
+int cr_read_thread(struct cr_ctx *ctx)
+{
+	struct cr_hdr_thread *thread_hdr;
+	int ret;
+
+	thread_hdr = cr_hbuf_get(ctx, sizeof(*thread_hdr));
+	if (!thread_hdr)
+		return -ENOMEM;
+
+	ret = cr_read_obj_type(ctx, thread_hdr, sizeof(*thread_hdr),
+				  CR_HDR_THREAD);
+	if (ret < 0)
+		goto out;
+
+	ret = 0;
+
+	if (thread_hdr->unimplemented != 0xdeadbeef) {
+		pr_debug("%s: unexpected thread_hdr contents: 0x%lx\n",
+			 __func__, (unsigned long)thread_hdr->unimplemented);
+		ret = -EINVAL;
+	}
+out:
+	cr_hbuf_put(ctx, sizeof(*thread_hdr));
+	return ret;
+}
+
+/* Based on the MSR value from a checkpoint image, produce an MSR
+ * value that is appropriate for the restored task.  Right now we only
+ * check for MSR_SF (64-bit) for PPC64.
+ */
+static unsigned long sanitize_msr(unsigned long msr_ckpt)
+{
+#ifdef CONFIG_PPC32
+	return MSR_USER;
+#else
+	if (msr_ckpt & MSR_SF)
+		return MSR_USER64;
+	return MSR_USER32;
+#endif
+}
+
+int cr_read_cpu(struct cr_ctx *ctx)
+{
+	struct cr_hdr_cpu *cpu_hdr;
+	struct pt_regs *regs;
+	int ret;
+
+	cpu_hdr = cr_hbuf_get(ctx, sizeof(*cpu_hdr));
+	if (!cpu_hdr)
+		return -ENOMEM;
+
+	ret = cr_read_obj_type(ctx, cpu_hdr, sizeof(*cpu_hdr),
+				  CR_HDR_CPU);
+	if (ret < 0)
+		goto out;
+
+	ret = 0;
+
+	regs = task_pt_regs(current);
+	*regs = cpu_hdr->pt_regs;
+
+	regs->msr = sanitize_msr(regs->msr);
+
+	/* FP state */
+	memcpy(current->thread.fpr, cpu_hdr->fpr, sizeof(current->thread.fpr));
+	current->thread.fpscr.val = cpu_hdr->fpscr;
+	current->thread.fpexc_mode = cpu_hdr->fpexc_mode;
+
+	/* debug registers */
+	current->thread.dabr = cpu_hdr->dabr;
+out:
+	cr_hbuf_put(ctx, sizeof(*cpu_hdr));
+	return ret;
+}
+
+int cr_read_head_arch(struct cr_ctx *ctx)
+{
+	struct cr_hdr_head_arch *arch_hdr;
+	int ret;
+
+	arch_hdr = cr_hbuf_get(ctx, sizeof(*arch_hdr));
+	if (!arch_hdr)
+		return -ENOMEM;
+
+	ret = cr_read_obj_type(ctx, arch_hdr, sizeof(*arch_hdr),
+				  CR_HDR_HEAD_ARCH);
+	if (ret < 0)
+		goto out;
+
+	ret = 0;
+
+	if (arch_hdr->unimplemented != 0xdeadbeef) {
+		pr_debug("%s: unexpected arch_hdr contents: 0x%lx\n",
+			 __func__, (unsigned long)arch_hdr->unimplemented);
+		ret = -EINVAL;
+	}
+out:
+	cr_hbuf_put(ctx, sizeof(*arch_hdr));
+	return ret;
+}
+
+int cr_read_mm_context(struct cr_ctx *ctx, struct mm_struct *mm, int rparent)
+{
+	struct cr_hdr_mm_context *mm_hdr;
+	int ret;
+
+	mm_hdr = cr_hbuf_get(ctx, sizeof(*mm_hdr));
+	if (!mm_hdr)
+		return -ENOMEM;
+
+	ret = cr_read_obj_type(ctx, mm_hdr, sizeof(*mm_hdr),
+				  CR_HDR_MM_CONTEXT);
+	if (ret != rparent)
+		goto out;
+
+	ret = 0;
+
+	if (mm_hdr->unimplemented != 0xdeadbeef) {
+		pr_debug("%s: unexpected mm_hdr contents: 0x%lx\n",
+			 __func__, (unsigned long)mm_hdr->unimplemented);
+		ret = -EINVAL;
+	}
+
+out:
+	cr_hbuf_put(ctx, sizeof(*mm_hdr));
+	return ret;
+}
-- 
1.5.5