[PATCH v18 21/80] c/r: x86_32 support for checkpoint/restart

Oren Laadan
2009-09-24T00:41:45Z

Add logic to save and restore architecture specific state, including
thread-specific state, CPU registers and FPU state.

In addition, architecture capabilities are saved in an architecure
specific extension of the header (ckpt_hdr_head_arch); Currently this
includes only FPU capabilities.

Currently only x86-32 is supported.

Changelog[v17]:
- Fix compilation for architectures that don't support checkpoint
- Validate cpu registers and TLS descriptors on restart
- Validate debug registers on restart
- Export asm/checkpoint_hdr.h to userspace
Changelog[v16]:
- All objects are preceded by ckpt_hdr (TLS and xstate_buf)
- Add architecture identifier to main header
Changelog[v14]:
- Use new interface ckpt_hdr_get/put()
- Embed struct ckpt_hdr in struct ckpt_hdr...
- Remove preempt_disable/enable() around init_fpu() and fix leak
- Revert change to pr_debug(), back to ckpt_debug()
- Move code related to task_struct to checkpoint/process.c
Changelog[v12]:
- A couple of missed calls to ckpt_hbuf_put()
- Replace obsolete ckpt_debug() with pr_debug()
Changelog[v9]:
- Add arch-specific header that details architecture capabilities;
split FPU restore to send capabilities only once.
- Test for zero TLS entries in ckpt_write_thread()
- Fix asm/checkpoint_hdr.h so it can be included from user-space
Changelog[v7]:
- Fix save/restore state of FPU
Changelog[v5]:
- Remove preempt_disable() when restoring debug registers
Changelog[v4]:
- Fix header structure alignment
Changelog[v2]:
- Pad header structures to 64 bits to ensure compatibility
- Follow Dave Hansen's refactoring of the original post

Signed-off-by: Oren Laadan <orenl@cs.columbia.edu>
---
arch/x86/include/asm/Kbuild | 1 +
arch/x86/include/asm/checkpoint_hdr.h | 121 ++++++++
arch/x86/include/asm/ptrace.h | 5 +
arch/x86/kernel/ptrace.c | 8 +-
arch/x86/mm/Makefile | 2 +
arch/x86/mm/checkpoint.c | 531 +++++++++++++++++++++++++++++++++
checkpoint/checkpoint.c | 7 +-
checkpoint/process.c | 19 ++-
checkpoint/restart.c | 6 +
include/linux/checkpoint.h | 9 +
include/linux/checkpoint_hdr.h | 16 +-
11 files changed, 718 insertions(+), 7 deletions(-)
create mode 100644 arch/x86/include/asm/checkpoint_hdr.h
create mode 100644 arch/x86/mm/checkpoint.c

diff --git a/arch/x86/include/asm/Kbuild b/arch/x86/include/asm/Kbuild
index 4a8e80c..f76cb6e 100644
--- a/arch/x86/include/asm/Kbuild
+++ b/arch/x86/include/asm/Kbuild
@@ -2,6 +2,7 @@ include include/asm-generic/Kbuild.asm

header-y += boot.h
header-y += bootparam.h
+header-y += checkpoint_hdr.h
header-y += debugreg.h
header-y += ldt.h
header-y += msr-index.h
diff --git a/arch/x86/include/asm/checkpoint_hdr.h b/arch/x86/include/asm/checkpoint_hdr.h
new file mode 100644
index 0000000..f4d1e14
--- /dev/null
+++ b/arch/x86/include/asm/checkpoint_hdr.h
@@ -0,0 +1,121 @@
+#ifndef __ASM_X86_CKPT_HDR_H
+#define __ASM_X86_CKPT_HDR_H
+/*
+ * Checkpoint/restart - architecture specific headers x86
+ *
+ * Copyright (C) 2008-2009 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.
+ */
+
+#ifndef _CHECKPOINT_CKPT_HDR_H_
+#error asm/checkpoint_hdr.h included directly
+#endif
+
+#include <linux/types.h>
+
+/*
+ * To maintain compatibility between 32-bit and 64-bit architecture flavors,
+ * keep data 64-bit aligned: use padding for structure members, and use
+ * __attribute__((aligned (8))) for the entire structure.
+ *
+ * Quoting Arnd Bergmann:
+ * "This structure has an odd multiple of 32-bit members, which means
+ * that if you put it into a larger structure that also contains 64-bit
+ * members, the larger structure may get different alignment on x86-32
+ * and x86-64, which you might want to avoid. I can't tell if this is
+ * an actual problem here. ... In this case, I'm pretty sure that
+ * sizeof(ckpt_hdr_task) on x86-32 is different from x86-64, since it
+ * will be 32-bit aligned on x86-32."
+ */
+
+/* i387 structure seen from kernel/userspace */
+#ifdef __KERNEL__
+#include <asm/processor.h>
+#else
+#include <sys/user.h>
+#endif
+
+#ifdef CONFIG_X86_32
+#define CKPT_ARCH_ID CKPT_ARCH_X86_32
+#endif
+
+/* arch dependent header types */
+enum {
+ CKPT_HDR_CPU_FPU = 201,
+};
+
+struct ckpt_hdr_header_arch {
+ struct ckpt_hdr h;
+ /* FIXME: add HAVE_HWFP */
+ __u16 has_fxsr;
+ __u16 has_xsave;
+ __u16 xstate_size;
+ __u16 _pading;
+} __attribute__((aligned(8)));
+
+struct ckpt_hdr_thread {
+ struct ckpt_hdr h;
+ __u32 thread_info_flags;
+ __u16 gdt_entry_tls_entries;
+ __u16 sizeof_tls_array;
+} __attribute__((aligned(8)));
+
+/* designed to work for both x86_32 and x86_64 */
+struct ckpt_hdr_cpu {
+ struct ckpt_hdr h;
+ /* see struct pt_regs (x86_64) */
+ __u64 r15;
+ __u64 r14;
+ __u64 r13;
+ __u64 r12;
+ __u64 bp;
+ __u64 bx;
+ __u64 r11;
+ __u64 r10;
+ __u64 r9;
+ __u64 r8;
+ __u64 ax;
+ __u64 cx;
+ __u64 dx;
+ __u64 si;
+ __u64 di;
+ __u64 orig_ax;
+ __u64 ip;
+ __u64 sp;
+
+ __u64 flags;
+
+ /* segment registers */
+ __u64 fs;
+ __u64 gs;
+
+ __u16 fsindex;
+ __u16 gsindex;
+ __u16 cs;
+ __u16 ss;
+ __u16 ds;
+ __u16 es;
+
+ __u32 used_math;
+
+ /* debug registers */
+ __u64 debugreg0;
+ __u64 debugreg1;
+ __u64 debugreg2;
+ __u64 debugreg3;
+ __u64 debugreg6;
+ __u64 debugreg7;
+
+ /* thread_xstate contents follow (if used_math) */
+} __attribute__((aligned(8)));
+
+#define CKPT_X86_SEG_NULL 0
+#define CKPT_X86_SEG_USER32_CS 1
+#define CKPT_X86_SEG_USER32_DS 2
+#define CKPT_X86_SEG_TLS 0x4000 /* 0100 0000 0000 00xx */
+#define CKPT_X86_SEG_LDT 0x8000 /* 100x xxxx xxxx xxxx */
+
+#endif /* __ASM_X86_CKPT_HDR__H */
diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index 0f0d908..66b507b 100644
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -242,6 +242,11 @@ extern void ptrace_bts_untrace(struct task_struct *tsk);
#define arch_ptrace_untrace(tsk) ptrace_bts_untrace(tsk)
#endif /* CONFIG_X86_PTRACE_BTS */

+extern int ptrace_check_debugreg(int _32bit,
+ unsigned long dr0, unsigned long dr1,
+ unsigned long dr2, unsigned long dr3,
+ unsigned long dr6, unsigned long dr7);
+
#endif /* __KERNEL__ */

#endif /* !__ASSEMBLY__ */
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 9b4cacf..3b434bd 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -466,10 +466,10 @@ static unsigned long ptrace_get_debugreg(struct task_struct *child, int n)
return 0;
}

-static int ptrace_check_debugreg(int _32bit,
- unsigned long dr0, unsigned long dr1,
- unsigned long dr2, unsigned long dr3,
- unsigned long dr6, unsigned long dr7)
+int ptrace_check_debugreg(int _32bit,
+ unsigned long dr0, unsigned long dr1,
+ unsigned long dr2, unsigned long dr3,
+ unsigned long dr6, unsigned long dr7)
{
/* Breakpoint type: 00: --x, 01: -w-, 10: undefined, 11: rw- */
unsigned int rw[4];
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index eefdeee..ddd5abb 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -21,3 +21,5 @@ obj-$(CONFIG_K8_NUMA) += k8topology_64.o
obj-$(CONFIG_ACPI_NUMA) += srat_$(BITS).o

obj-$(CONFIG_MEMTEST) += memtest.o
+
+obj-$(CONFIG_CHECKPOINT) += checkpoint.o
diff --git a/arch/x86/mm/checkpoint.c b/arch/x86/mm/checkpoint.c
new file mode 100644
index 0000000..023039f
--- /dev/null
+++ b/arch/x86/mm/checkpoint.c
@@ -0,0 +1,531 @@
+/*
+ * Checkpoint/restart - architecture specific support for x86
+ *
+ * Copyright (C) 2008-2009 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.
+ */
+
+/* default debug level for output */
+#define CKPT_DFLAG CKPT_DSYS
+
+#include <asm/desc.h>
+#include <asm/i387.h>
+
+#include <linux/checkpoint.h>
+#include <linux/checkpoint_hdr.h>
+
+/*
+ * helpers to encode/decode/validate registers/segments/eflags
+ */
+
+static int check_eflags(__u32 eflags)
+{
+#define X86_EFLAGS_CKPT_MASK \
+ (X86_EFLAGS_CF | X86_EFLAGS_PF | X86_EFLAGS_AF | X86_EFLAGS_ZF | \
+ X86_EFLAGS_SF | X86_EFLAGS_TF | X86_EFLAGS_DF | X86_EFLAGS_OF | \
+ X86_EFLAGS_NT | X86_EFLAGS_AC | X86_EFLAGS_ID)
+
+ if ((eflags & ~X86_EFLAGS_CKPT_MASK) != (X86_EFLAGS_IF | 0x2))
+ return 0;
+ return 1;
+}
+
+static int check_tls(struct desc_struct *desc)
+{
+ if (!desc->a && !desc->b)
+ return 1;
+ if (desc->l != 0 || desc->s != 1 || desc->dpl != 3)
+ return 0;
+ return 1;
+}
+
+static int check_segment(__u16 seg)
+{
+ int ret = 0;
+
+ switch (seg) {
+ case CKPT_X86_SEG_NULL:
+ case CKPT_X86_SEG_USER32_CS:
+ case CKPT_X86_SEG_USER32_DS:
+ return 1;
+ }
+ if (seg & CKPT_X86_SEG_TLS) {
+ seg &= ~CKPT_X86_SEG_TLS;
+ if (seg <= GDT_ENTRY_TLS_MAX - GDT_ENTRY_TLS_MIN)
+ ret = 1;
+ } else if (seg & CKPT_X86_SEG_LDT) {
+ seg &= ~CKPT_X86_SEG_LDT;
+ if (seg <= 0x1fff)
+ ret = 1;
+ }
+ return ret;
+}
+
+static __u16 encode_segment(unsigned short seg)
+{
+ if (seg == 0)
+ return CKPT_X86_SEG_NULL;
+ BUG_ON((seg & 3) != 3);
+
+ if (seg == __USER_CS)
+ return CKPT_X86_SEG_USER32_CS;
+ if (seg == __USER_DS)
+ return CKPT_X86_SEG_USER32_DS;
+
+ if (seg & 4)
+ return CKPT_X86_SEG_LDT | (seg >> 3);
+
+ seg >>= 3;
+ if (GDT_ENTRY_TLS_MIN <= seg && seg <= GDT_ENTRY_TLS_MAX)
+ return CKPT_X86_SEG_TLS | (seg - GDT_ENTRY_TLS_MIN);
+
+ printk(KERN_ERR "c/r: (decode) bad segment %#hx\n", seg);
+ BUG();
+}
+
+static unsigned short decode_segment(__u16 seg)
+{
+ if (seg == CKPT_X86_SEG_NULL)
+ return 0;
+ if (seg == CKPT_X86_SEG_USER32_CS)
+ return __USER_CS;
+ if (seg == CKPT_X86_SEG_USER32_DS)
+ return __USER_DS;
+
+ if (seg & CKPT_X86_SEG_TLS) {
+ seg &= ~CKPT_X86_SEG_TLS;
+ return ((GDT_ENTRY_TLS_MIN + seg) << 3) | 3;
+ }
+ if (seg & CKPT_X86_SEG_LDT) {
+ seg &= ~CKPT_X86_SEG_LDT;
+ return (seg << 3) | 7;
+ }
+ BUG();
+}
+
+#define CKPT_X86_TIF_UNSUPPORTED (_TIF_SECCOMP | _TIF_IO_BITMAP)
+
+/**************************************************************************
+ * Checkpoint
+ */
+
+static int may_checkpoint_thread(struct ckpt_ctx *ctx, struct task_struct *t)
+{
+ if (t->thread.vm86_info) {
+ ckpt_write_err(ctx, "TE", "task in VM86 mode", -EBUSY);
+ return -EBUSY;
+ }
+ if (task_thread_info(t)->flags & CKPT_X86_TIF_UNSUPPORTED) {
+ ckpt_write_err(ctx, "TE", "bad thread info flags %#lx", -EBUSY);
+ return -EBUSY;
+ }
+ return 0;
+}
+
+/* dump the thread_struct of a given task */
+int checkpoint_thread(struct ckpt_ctx *ctx, struct task_struct *t)
+{
+ struct ckpt_hdr_thread *h;
+ int tls_size;
+ int ret;
+
+ ret = may_checkpoint_thread(ctx, t);
+ if (ret < 0)
+ return ret;
+
+ tls_size = sizeof(t->thread.tls_array);
+
+ h = ckpt_hdr_get_type(ctx, sizeof(*h) + tls_size, CKPT_HDR_THREAD);
+ if (!h)
+ return -ENOMEM;
+
+ h->thread_info_flags =
+ task_thread_info(t)->flags & ~CKPT_X86_TIF_UNSUPPORTED;
+ h->gdt_entry_tls_entries = GDT_ENTRY_TLS_ENTRIES;
+ h->sizeof_tls_array = tls_size;
+
+ /* For simplicity dump the entire array */
+ memcpy(h + 1, t->thread.tls_array, tls_size);
+
+ ret = ckpt_write_obj(ctx, &h->h);
+ ckpt_hdr_put(ctx, h);
+ return ret;
+}
+
+#ifdef CONFIG_X86_32
+
+static void save_cpu_regs(struct ckpt_hdr_cpu *h, struct task_struct *t)
+{
+ struct thread_struct *thread = &t->thread;
+ struct pt_regs *regs = task_pt_regs(t);
+ unsigned long _gs;
+
+ h->bp = regs->bp;
+ h->bx = regs->bx;
+ h->ax = regs->ax;
+ h->cx = regs->cx;
+ h->dx = regs->dx;
+ h->si = regs->si;
+ h->di = regs->di;
+ h->orig_ax = regs->orig_ax;
+ h->ip = regs->ip;
+
+ h->flags = regs->flags;
+ h->sp = regs->sp;
+
+ h->cs = encode_segment(regs->cs);
+ h->ss = encode_segment(regs->ss);
+ h->ds = encode_segment(regs->ds);
+ h->es = encode_segment(regs->es);
+
+ /*
+ * for checkpoint in process context (from within a container)
+ * the GS segment register should be saved from the hardware;
+ * otherwise it is already saved on the thread structure
+ */
+ if (t == current)
+ _gs = get_user_gs(regs);
+ else
+ _gs = thread->gs;
+
+ h->fsindex = encode_segment(regs->fs);
+ h->gsindex = encode_segment(_gs);
+
+ /*
+ * for checkpoint in process context (from within a container),
+ * the actual syscall is taking place at this very moment; so
+ * we (optimistically) subtitute the future return value (0) of
+ * this syscall into the orig_eax, so that upon restart it will
+ * succeed (or it will endlessly retry checkpoint...)
+ */
+ if (t == current) {
+ BUG_ON(h->orig_ax < 0);
+ h->ax = 0;
+ }
+}
+
+static void save_cpu_debug(struct ckpt_hdr_cpu *h, struct task_struct *t)
+{
+ struct thread_struct *thread = &t->thread;
+
+ /* debug regs */
+
+ /*
+ * for checkpoint in process context (from within a container),
+ * get the actual registers; otherwise get the saved values.
+ */
+
+ if (t == current) {
+ get_debugreg(h->debugreg0, 0);
+ get_debugreg(h->debugreg1, 1);
+ get_debugreg(h->debugreg2, 2);
+ get_debugreg(h->debugreg3, 3);
+ get_debugreg(h->debugreg6, 6);
+ get_debugreg(h->debugreg7, 7);
+ } else {
+ h->debugreg0 = thread->debugreg0;
+ h->debugreg1 = thread->debugreg1;
+ h->debugreg2 = thread->debugreg2;
+ h->debugreg3 = thread->debugreg3;
+ h->debugreg6 = thread->debugreg6;
+ h->debugreg7 = thread->debugreg7;
+ }
+}
+
+static void save_cpu_fpu(struct ckpt_hdr_cpu *h, struct task_struct *t)
+{
+ h->used_math = tsk_used_math(t) ? 1 : 0;
+}
+
+static int checkpoint_cpu_fpu(struct ckpt_ctx *ctx, struct task_struct *t)
+{
+ struct ckpt_hdr *h;
+ int ret;
+
+ h = ckpt_hdr_get_type(ctx, xstate_size + sizeof(*h),
+ CKPT_HDR_CPU_FPU);
+ if (!h)
+ return -ENOMEM;
+
+ /* i387 + MMU + SSE logic */
+ preempt_disable(); /* needed it (t == current) */
+
+ /*
+ * normally, no need to unlazy_fpu(), since TS_USEDFPU flag
+ * was cleared when task was context-switched out...
+ * except if we are in process context, in which case we do
+ */
+ if (t == current && (task_thread_info(t)->status & TS_USEDFPU))
+ unlazy_fpu(current);
+
+ /*
+ * For simplicity dump the entire structure.
+ * FIX: need to be deliberate about what registers we are
+ * dumping for traceability and compatibility.
+ */
+ memcpy(h + 1, t->thread.xstate, xstate_size);
+ preempt_enable(); /* needed if (t == current) */
+
+ ret = ckpt_write_obj(ctx, h);
+ ckpt_hdr_put(ctx, h);
+
+ return ret;
+}
+
+#endif /* CONFIG_X86_32 */
+
+/* dump the cpu state and registers of a given task */
+int checkpoint_cpu(struct ckpt_ctx *ctx, struct task_struct *t)
+{
+ struct ckpt_hdr_cpu *h;
+ int ret;
+
+ h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_CPU);
+ if (!h)
+ return -ENOMEM;
+
+ save_cpu_regs(h, t);
+ save_cpu_debug(h, t);
+ save_cpu_fpu(h, t);
+
+ ckpt_debug("math %d debug %d\n", h->used_math, !!h->debugreg7);
+
+ ret = ckpt_write_obj(ctx, &h->h);
+ if (ret < 0)
+ goto out;
+
+ if (h->used_math)
+ ret = checkpoint_cpu_fpu(ctx, t);
+ out:
+ ckpt_hdr_put(ctx, h);
+ return ret;
+}
+
+int checkpoint_write_header_arch(struct ckpt_ctx *ctx)
+{
+ struct ckpt_hdr_header_arch *h;
+ int ret;
+
+ h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_HEADER_ARCH);
+ if (!h)
+ return -ENOMEM;
+
+ /* FPU capabilities */
+ h->has_fxsr = cpu_has_fxsr;
+ h->has_xsave = cpu_has_xsave;
+ h->xstate_size = xstate_size;
+
+ ret = ckpt_write_obj(ctx, &h->h);
+ ckpt_hdr_put(ctx, h);
+
+ return ret;
+}
+
+/**************************************************************************
+ * Restart
+ */
+
+/* read the thread_struct into the current task */
+int restore_thread(struct ckpt_ctx *ctx)
+{
+ struct ckpt_hdr_thread *h;
+ struct thread_struct *thread = &current->thread;
+ struct desc_struct *desc;
+ int tls_size;
+ int i, cpu, ret;
+
+ tls_size = sizeof(thread->tls_array);
+
+ h = ckpt_read_obj_type(ctx, sizeof(*h) + tls_size, CKPT_HDR_THREAD);
+ if (IS_ERR(h))
+ return PTR_ERR(h);
+
+ ret = -EINVAL;
+ if (h->thread_info_flags & CKPT_X86_TIF_UNSUPPORTED)
+ goto out;
+ if (h->gdt_entry_tls_entries != GDT_ENTRY_TLS_ENTRIES)
+ goto out;
+ if (h->sizeof_tls_array != tls_size)
+ goto out;
+
+ /*
+ * restore TLS by hand: why convert to struct user_desc if
+ * sys_set_thread_entry() will convert it back ?
+ */
+ desc = (struct desc_struct *) (h + 1);
+
+ for (i = 0; i < GDT_ENTRY_TLS_ENTRIES; i++) {
+ if (!check_tls(&desc[i]))
+ goto out;
+ }
+
+ cpu = get_cpu();
+ memcpy(thread->tls_array, desc, tls_size);
+ load_TLS(thread, cpu);
+ put_cpu();
+
+ /* TODO: restore TIF flags as necessary (e.g. TIF_NOTSC) */
+
+ ret = 0;
+ out:
+ ckpt_hdr_put(ctx, h);
+ return ret;
+}
+
+#ifdef CONFIG_X86_32
+
+static int load_cpu_regs(struct ckpt_hdr_cpu *h, struct task_struct *t)
+{
+ struct thread_struct *thread = &t->thread;
+ struct pt_regs *regs = task_pt_regs(t);
+
+ if (!check_eflags(h->flags))
+ return -EINVAL;
+ if (h->cs == CKPT_X86_SEG_NULL)
+ return -EINVAL;
+ if (!check_segment(h->cs) || !check_segment(h->ds) ||
+ !check_segment(h->es) || !check_segment(h->ss) ||
+ !check_segment(h->fsindex) || !check_segment(h->gsindex))
+ return -EINVAL;
+
+ regs->bp = h->bp;
+ regs->bx = h->bx;
+ regs->ax = h->ax;
+ regs->cx = h->cx;
+ regs->dx = h->dx;
+ regs->si = h->si;
+ regs->di = h->di;
+ regs->orig_ax = h->orig_ax;
+ regs->ip = h->ip;
+
+ regs->flags = h->flags;
+ regs->sp = h->sp;
+
+ regs->ds = decode_segment(h->ds);
+ regs->es = decode_segment(h->es);
+ regs->cs = decode_segment(h->cs);
+ regs->ss = decode_segment(h->ss);
+
+ regs->fs = decode_segment(h->fsindex);
+ regs->gs = decode_segment(h->gsindex);
+
+ thread->gs = regs->gs;
+ lazy_load_gs(regs->gs);
+
+ return 0;
+}
+
+static int load_cpu_debug(struct ckpt_hdr_cpu *h, struct task_struct *t)
+{
+ int ret;
+
+ ret = ptrace_check_debugreg(1, h->debugreg0, h->debugreg1, h->debugreg2,
+ h->debugreg3, h->debugreg6, h->debugreg7);
+ if (ret < 0)
+ return ret;
+
+ set_debugreg(h->debugreg0, 0);
+ set_debugreg(h->debugreg1, 1);
+ /* ignore 4, 5 */
+ set_debugreg(h->debugreg2, 2);
+ set_debugreg(h->debugreg3, 3);
+ set_debugreg(h->debugreg6, 6);
+ set_debugreg(h->debugreg7, 7);
+
+ if (h->debugreg7)
+ set_tsk_thread_flag(t, TIF_DEBUG);
+ else
+ clear_tsk_thread_flag(t, TIF_DEBUG);
+
+ return 0;
+}
+
+static int load_cpu_fpu(struct ckpt_hdr_cpu *h, struct task_struct *t)
+{
+ preempt_disable();
+
+ __clear_fpu(t); /* in case we used FPU in user mode */
+
+ if (!h->used_math)
+ clear_used_math();
+
+ preempt_enable();
+ return 0;
+}
+
+static int restore_cpu_fpu(struct ckpt_ctx *ctx, struct task_struct *t)
+{
+ struct ckpt_hdr *h;
+ int ret;
+
+ /* init_fpu() eventually also calls set_used_math() */
+ ret = init_fpu(current);
+ if (ret < 0)
+ return ret;
+
+ h = ckpt_read_obj_type(ctx, xstate_size + sizeof(*h),
+ CKPT_HDR_CPU_FPU);
+ if (IS_ERR(h))
+ return PTR_ERR(h);
+
+ memcpy(t->thread.xstate, h + 1, xstate_size);
+
+ ckpt_hdr_put(ctx, h);
+ return ret;
+}
+
+#endif /* CONFIG_X86_32 */
+
+/* read the cpu state and registers for the current task */
+int restore_cpu(struct ckpt_ctx *ctx)
+{
+ struct ckpt_hdr_cpu *h;
+ struct task_struct *t = current;
+ int ret;
+
+ h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_CPU);
+ if (IS_ERR(h))
+ return PTR_ERR(h);
+
+ ckpt_debug("math %d debug %d\n", h->used_math, !!h->debugreg7);
+
+ ret = load_cpu_regs(h, t);
+ if (ret < 0)
+ goto out;
+ ret = load_cpu_debug(h, t);
+ if (ret < 0)
+ goto out;
+ ret = load_cpu_fpu(h, t);
+ if (ret < 0)
+ goto out;
+
+ if (h->used_math)
+ ret = restore_cpu_fpu(ctx, t);
+ out:
+ ckpt_hdr_put(ctx, h);
+ return ret;
+}
+
+int restore_read_header_arch(struct ckpt_ctx *ctx)
+{
+ struct ckpt_hdr_header_arch *h;
+ int ret = 0;
+
+ h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_HEADER_ARCH);
+ if (IS_ERR(h))
+ return PTR_ERR(h);
+
+ /* FIX: verify compatibility of architecture features */
+
+ /* verify FPU capabilities */
+ if (h->has_fxsr != cpu_has_fxsr ||
+ h->has_xsave != cpu_has_xsave ||
+ h->xstate_size != xstate_size)
+ ret = -EINVAL;
+
+ ckpt_hdr_put(ctx, h);
+ return ret;
+}
diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c
index 57eb7d8..e228151 100644
--- a/checkpoint/checkpoint.c
+++ b/checkpoint/checkpoint.c
@@ -300,6 +300,8 @@ static int checkpoint_write_header(struct ckpt_ctx *ctx)
do_gettimeofday(&ktv);
uts = utsname();

+ h->arch_id = cpu_to_le16(CKPT_ARCH_ID); /* see asm/checkpoitn.h */
+
h->magic = CHECKPOINT_MAGIC_HEAD;
h->major = (LINUX_VERSION_CODE >> 16) & 0xff;
h->minor = (LINUX_VERSION_CODE >> 8) & 0xff;
@@ -327,7 +329,10 @@ static int checkpoint_write_header(struct ckpt_ctx *ctx)
ret = ckpt_write_buffer(ctx, uts->machine, sizeof(uts->machine));
up:
up_read(&uts_sem);
- return ret;
+ if (ret < 0)
+ return ret;
+
+ return checkpoint_write_header_arch(ctx);
}

/* write the checkpoint trailer */
diff --git a/checkpoint/process.c b/checkpoint/process.c
index d221c2a..1d1170c 100644
--- a/checkpoint/process.c
+++ b/checkpoint/process.c
@@ -57,6 +57,15 @@ int checkpoint_task(struct ckpt_ctx *ctx, struct task_struct *t)
ret = checkpoint_task_struct(ctx, t);
ckpt_debug("task %d\n", ret);

+ if (ret < 0)
+ goto out;
+ ret = checkpoint_thread(ctx, t);
+ ckpt_debug("thread %d\n", ret);
+ if (ret < 0)
+ goto out;
+ ret = checkpoint_cpu(ctx, t);
+ ckpt_debug("cpu %d\n", ret);
+ out:
ctx->tsk = NULL;
return ret;
}
@@ -97,6 +106,14 @@ int restore_task(struct ckpt_ctx *ctx)

ret = restore_task_struct(ctx);
ckpt_debug("task %d\n", ret);
-
+ if (ret < 0)
+ goto out;
+ ret = restore_thread(ctx);
+ ckpt_debug("thread %d\n", ret);
+ if (ret < 0)
+ goto out;
+ ret = restore_cpu(ctx);
+ ckpt_debug("cpu %d\n", ret);
+ out:
return ret;
}
diff --git a/checkpoint/restart.c b/checkpoint/restart.c
index 9f08f4d..afe51c2 100644
--- a/checkpoint/restart.c
+++ b/checkpoint/restart.c
@@ -354,6 +354,8 @@ static int restore_read_header(struct ckpt_ctx *ctx)
return PTR_ERR(h);

ret = -EINVAL;
+ if (le16_to_cpu(h->arch_id) != CKPT_ARCH_ID)
+ goto out;
if (h->magic != CHECKPOINT_MAGIC_HEAD ||
h->rev != CHECKPOINT_VERSION ||
h->major != ((LINUX_VERSION_CODE >> 16) & 0xff) ||
@@ -382,6 +384,10 @@ static int restore_read_header(struct ckpt_ctx *ctx)
if (ret < 0)
goto out;
ret = _ckpt_read_buffer(ctx, uts->machine, sizeof(uts->machine));
+ if (ret < 0)
+ goto out;
+
+ ret = restore_read_header_arch(ctx);
out:
kfree(uts);
ckpt_hdr_put(ctx, h);
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index be0ba4b..aa8ce11 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -61,6 +61,15 @@ extern long do_restart(struct ckpt_ctx *ctx, pid_t pid);
extern int checkpoint_task(struct ckpt_ctx *ctx, struct task_struct *t);
extern int restore_task(struct ckpt_ctx *ctx);

+/* arch hooks */
+extern int checkpoint_write_header_arch(struct ckpt_ctx *ctx);
+extern int checkpoint_thread(struct ckpt_ctx *ctx, struct task_struct *t);
+extern int checkpoint_cpu(struct ckpt_ctx *ctx, struct task_struct *t);
+
+extern int restore_read_header_arch(struct ckpt_ctx *ctx);
+extern int restore_thread(struct ckpt_ctx *ctx);
+extern int restore_cpu(struct ckpt_ctx *ctx);
+
static inline int ckpt_validate_errno(int errno)
{
return (errno >= 0) && (errno < MAX_ERRNO);
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index 22dadbd..92d082e 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -40,19 +40,33 @@ struct ckpt_hdr {
__u32 len;
} __attribute__((aligned(8)));

+
+#include <asm/checkpoint_hdr.h>
+
+
/* header types */
enum {
CKPT_HDR_HEADER = 1,
+ CKPT_HDR_HEADER_ARCH,
CKPT_HDR_BUFFER,
CKPT_HDR_STRING,

CKPT_HDR_TASK = 101,
+ CKPT_HDR_THREAD,
+ CKPT_HDR_CPU,
+
+ /* 201-299: reserved for arch-dependent */

CKPT_HDR_TAIL = 9001,

CKPT_HDR_ERROR = 9999,
};

+/* architecture */
+enum {
+ CKPT_ARCH_X86_32 = 1,
+};
+
/* kernel constants */
struct ckpt_const {
/* task */
@@ -68,7 +82,7 @@ struct ckpt_hdr_header {
struct ckpt_hdr h;
__u64 magic;

- __u16 _padding;
+ __u16 arch_id;

__u16 major;
__u16 minor;
--
1.6.0.4