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    Subject[RFC v4][PATCH 3/9] x86 support for checkpoint/restart
    Date
    (Following Dave Hansen's refactoring of the original post)

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

    Currently only x86-32 is supported. Compiling on x86-64 will trigger
    an explicit error.

    Signed-off-by: Oren Laadan <orenl@cs.columbia.edu>
    ---
    arch/x86/mm/Makefile | 2 +
    arch/x86/mm/checkpoint.c | 194 ++++++++++++++++++++++++++++++++++++++++++++
    arch/x86/mm/restart.c | 178 ++++++++++++++++++++++++++++++++++++++++
    checkpoint/checkpoint.c | 13 +++-
    checkpoint/ckpt_arch.h | 7 ++
    checkpoint/restart.c | 13 +++-
    include/asm-x86/ckpt_hdr.h | 72 ++++++++++++++++
    include/linux/ckpt_hdr.h | 1 +
    8 files changed, 478 insertions(+), 2 deletions(-)
    create mode 100644 arch/x86/mm/checkpoint.c
    create mode 100644 arch/x86/mm/restart.c
    create mode 100644 checkpoint/ckpt_arch.h
    create mode 100644 include/asm-x86/ckpt_hdr.h

    diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
    index dfb932d..58fe072 100644
    --- a/arch/x86/mm/Makefile
    +++ b/arch/x86/mm/Makefile
    @@ -22,3 +22,5 @@ endif
    obj-$(CONFIG_ACPI_NUMA) += srat_$(BITS).o

    obj-$(CONFIG_MEMTEST) += memtest.o
    +
    +obj-$(CONFIG_CHECKPOINT_RESTART) += checkpoint.o restart.o
    diff --git a/arch/x86/mm/checkpoint.c b/arch/x86/mm/checkpoint.c
    new file mode 100644
    index 0000000..71d21e6
    --- /dev/null
    +++ b/arch/x86/mm/checkpoint.c
    @@ -0,0 +1,194 @@
    +/*
    + * Checkpoint/restart - architecture specific support for x86
    + *
    + * 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 <asm/desc.h>
    +#include <asm/i387.h>
    +
    +#include <linux/ckpt.h>
    +#include <linux/ckpt_hdr.h>
    +
    +/* dump the thread_struct of a given task */
    +int cr_write_thread(struct cr_ctx *ctx, struct task_struct *t)
    +{
    + struct cr_hdr h;
    + struct cr_hdr_thread *hh = cr_hbuf_get(ctx, sizeof(*hh));
    + struct thread_struct *thread;
    + struct desc_struct *desc;
    + int ntls = 0;
    + int n, ret;
    +
    + h.type = CR_HDR_THREAD;
    + h.len = sizeof(*hh);
    + h.parent = task_pid_vnr(t);
    +
    + thread = &t->thread;
    +
    + /* calculate no. of TLS entries that follow */
    + desc = thread->tls_array;
    + for (n = GDT_ENTRY_TLS_ENTRIES; n > 0; n--, desc++) {
    + if (desc->a || desc->b)
    + ntls++;
    + }
    +
    + hh->gdt_entry_tls_entries = GDT_ENTRY_TLS_ENTRIES;
    + hh->sizeof_tls_array = sizeof(thread->tls_array);
    + hh->ntls = ntls;
    +
    + ret = cr_write_obj(ctx, &h, hh);
    + cr_hbuf_put(ctx, sizeof(*hh));
    + if (ret < 0)
    + return ret;
    +
    + /* for simplicity dump the entire array, cherry-pick upon restart */
    + ret = cr_kwrite(ctx, thread->tls_array, sizeof(thread->tls_array));
    +
    + cr_debug("ntls %d\n", ntls);
    +
    + /* IGNORE RESTART BLOCKS FOR NOW ... */
    +
    + return ret;
    +}
    +
    +#ifdef CONFIG_X86_64
    +
    +#error "CONFIG_X86_64 unsupported yet."
    +
    +#else /* !CONFIG_X86_64 */
    +
    +void cr_write_cpu_regs(struct cr_hdr_cpu *hh, struct task_struct *t)
    +{
    + struct thread_struct *thread = &t->thread;
    + struct pt_regs *regs = task_pt_regs(t);
    +
    + hh->bp = regs->bp;
    + hh->bx = regs->bx;
    + hh->ax = regs->ax;
    + hh->cx = regs->cx;
    + hh->dx = regs->dx;
    + hh->si = regs->si;
    + hh->di = regs->di;
    + hh->orig_ax = regs->orig_ax;
    + hh->ip = regs->ip;
    + hh->cs = regs->cs;
    + hh->flags = regs->flags;
    + hh->sp = regs->sp;
    + hh->ss = regs->ss;
    +
    + hh->ds = regs->ds;
    + hh->es = regs->es;
    +
    + /* for checkpoint in process context (from within a container)
    + the GS and FS registers should be saved from the hardware;
    + otherwise they are already sabed on the thread structure */
    + if (t == current) {
    + savesegment(gs, hh->gs);
    + savesegment(fs, hh->fs);
    + } else {
    + hh->gs = thread->gs;
    + hh->fs = thread->fs;
    + }
    +
    + /*
    + * 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(hh->orig_ax < 0);
    + hh->ax = 0;
    + }
    +}
    +
    +void cr_write_cpu_debug(struct cr_hdr_cpu *hh, struct task_struct *t)
    +{
    + struct thread_struct *thread = &t->thread;
    +
    + /* debug regs */
    +
    + preempt_disable();
    +
    + /*
    + * for checkpoint in process context (from within a container),
    + * get the actual registers; otherwise get the saved values.
    + */
    +
    + if (t == current) {
    + get_debugreg(hh->debugreg0, 0);
    + get_debugreg(hh->debugreg1, 1);
    + get_debugreg(hh->debugreg2, 2);
    + get_debugreg(hh->debugreg3, 3);
    + get_debugreg(hh->debugreg6, 6);
    + get_debugreg(hh->debugreg7, 7);
    + } else {
    + hh->debugreg0 = thread->debugreg0;
    + hh->debugreg1 = thread->debugreg1;
    + hh->debugreg2 = thread->debugreg2;
    + hh->debugreg3 = thread->debugreg3;
    + hh->debugreg6 = thread->debugreg6;
    + hh->debugreg7 = thread->debugreg7;
    + }
    +
    + hh->debugreg4 = 0;
    + hh->debugreg5 = 0;
    +
    + hh->uses_debug = !!(task_thread_info(t)->flags & TIF_DEBUG);
    +
    + preempt_enable();
    +}
    +
    +void cr_write_cpu_fpu(struct cr_hdr_cpu *hh, struct task_struct *t)
    +{
    + struct thread_struct *thread = &t->thread;
    + struct thread_info *thread_info = task_thread_info(t);
    +
    + /* i387 + MMU + SSE logic */
    +
    + preempt_disable();
    +
    + hh->used_math = tsk_used_math(t) ? 1 : 0;
    + if (hh->used_math) {
    + /* normally, no need to unlazy_fpu(), since TS_USEDFPU flag
    + * have been cleared when task was conexted-switched out...
    + * except if we are in process context, in which case we do */
    + if (thread_info->status & TS_USEDFPU)
    + unlazy_fpu(current);
    +
    + hh->has_fxsr = cpu_has_fxsr;
    + memcpy(&hh->xstate, &thread->xstate, sizeof(thread->xstate));
    + }
    +
    + preempt_enable();
    +}
    +
    +#endif /* CONFIG_X86_64 */
    +
    +/* 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 h;
    + struct cr_hdr_cpu *hh = cr_hbuf_get(ctx, sizeof(*hh));
    + int ret;
    +
    + h.type = CR_HDR_CPU;
    + h.len = sizeof(*hh);
    + h.parent = task_pid_vnr(t);
    +
    + cr_write_cpu_regs(hh, t);
    + cr_write_cpu_debug(hh, t);
    + cr_write_cpu_fpu(hh, t);
    +
    + cr_debug("math %d debug %d\n", hh->used_math, hh->uses_debug);
    +
    + ret = cr_write_obj(ctx, &h, hh);
    + cr_hbuf_put(ctx, sizeof(*hh));
    + return ret;
    +}
    diff --git a/arch/x86/mm/restart.c b/arch/x86/mm/restart.c
    new file mode 100644
    index 0000000..883a163
    --- /dev/null
    +++ b/arch/x86/mm/restart.c
    @@ -0,0 +1,178 @@
    +/*
    + * Checkpoint/restart - architecture specific support for x86
    + *
    + * 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 <asm/desc.h>
    +#include <asm/i387.h>
    +
    +#include <linux/ckpt.h>
    +#include <linux/ckpt_hdr.h>
    +
    +/* read the thread_struct into the current task */
    +int cr_read_thread(struct cr_ctx *ctx)
    +{
    + struct cr_hdr_thread *hh = cr_hbuf_get(ctx, sizeof(*hh));
    + struct task_struct *t = current;
    + struct thread_struct *thread = &t->thread;
    + int parent;
    +
    + parent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_THREAD);
    + if (parent < 0)
    + return parent;
    +#if 0 /* activate when containers are used */
    + if (parent != task_pid_vnr(t))
    + return -EINVAL;
    +#endif
    + cr_debug("ntls %d\n", hh->ntls);
    +
    + if (hh->gdt_entry_tls_entries != GDT_ENTRY_TLS_ENTRIES ||
    + hh->sizeof_tls_array != sizeof(thread->tls_array) ||
    + hh->ntls < 0 || hh->ntls > GDT_ENTRY_TLS_ENTRIES)
    + return -EINVAL;
    +
    + if (hh->ntls > 0) {
    +
    + /* restore TLS by hand: why convert to struct user_desc if
    + * sys_set_thread_entry() will convert it back ? */
    +
    + struct desc_struct *desc;
    + int size, cpu, ret;
    +
    + size = sizeof(*desc) * GDT_ENTRY_TLS_ENTRIES;
    + desc = kmalloc(size, GFP_KERNEL);
    + if (!desc)
    + return -ENOMEM;
    +
    + ret = cr_kread(ctx, desc, size);
    + if (ret >= 0) {
    + /* FIX: add sanity checks (eg. that values makes
    + * sense, that we don't overwrite old values, etc */
    + cpu = get_cpu();
    + memcpy(thread->tls_array, desc, size);
    + load_TLS(thread, cpu);
    + put_cpu();
    + }
    + kfree(desc);
    + }
    +
    + return 0;
    +}
    +
    +#ifdef CONFIG_X86_64
    +
    +#error "CONFIG_X86_64 unsupported yet."
    +
    +#else /* !CONFIG_X86_64 */
    +
    +int cr_read_cpu_regs(struct cr_hdr_cpu *hh, struct task_struct *t)
    +{
    + struct thread_struct *thread = &t->thread;
    + struct pt_regs *regs = task_pt_regs(t);
    +
    + regs->bx = hh->bx;
    + regs->cx = hh->cx;
    + regs->dx = hh->dx;
    + regs->si = hh->si;
    + regs->di = hh->di;
    + regs->bp = hh->bp;
    + regs->ax = hh->ax;
    + regs->ds = hh->ds;
    + regs->es = hh->es;
    + regs->orig_ax = hh->orig_ax;
    + regs->ip = hh->ip;
    + regs->cs = hh->cs;
    + regs->flags = hh->flags;
    + regs->sp = hh->sp;
    + regs->ss = hh->ss;
    +
    + thread->gs = hh->gs;
    + thread->fs = hh->fs;
    + loadsegment(gs, hh->gs);
    + loadsegment(fs, hh->fs);
    +
    + return 0;
    +}
    +
    +int cr_read_cpu_debug(struct cr_hdr_cpu *hh, struct task_struct *t)
    +{
    + /* debug regs */
    +
    + preempt_disable();
    +
    + if (hh->uses_debug) {
    + set_debugreg(hh->debugreg0, 0);
    + set_debugreg(hh->debugreg1, 1);
    + /* ignore 4, 5 */
    + set_debugreg(hh->debugreg2, 2);
    + set_debugreg(hh->debugreg3, 3);
    + set_debugreg(hh->debugreg6, 6);
    + set_debugreg(hh->debugreg7, 7);
    + }
    +
    + preempt_enable();
    +
    + return 0;
    +}
    +
    +int cr_read_cpu_fpu(struct cr_hdr_cpu *hh, struct task_struct *t)
    +{
    + struct thread_struct *thread = &t->thread;
    +
    + /* i387 + MMU + SSE */
    +
    + preempt_disable();
    +
    + __clear_fpu(t); /* in case we used FPU in user mode */
    +
    + if (!hh->used_math)
    + clear_used_math();
    + else {
    + if (hh->has_fxsr != cpu_has_fxsr) {
    + force_sig(SIGFPE, t);
    + return -EINVAL;
    + }
    + memcpy(&thread->xstate, &hh->xstate, sizeof(thread->xstate));
    + set_used_math();
    + }
    +
    + preempt_enable();
    +
    + return 0;
    +}
    +
    +#endif /* CONFIG_X86_64 */
    +
    +/* read the cpu state and registers for the current task */
    +int cr_read_cpu(struct cr_ctx *ctx)
    +{
    + struct cr_hdr_cpu *hh = cr_hbuf_get(ctx, sizeof(*hh));
    + struct task_struct *t = current;
    + int parent, ret;
    +
    + parent = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_CPU);
    + if (parent < 0)
    + return parent;
    +#if 0 /* activate when containers are used */
    + if (parent != task_pid_vnr(t))
    + return -EINVAL;
    +#endif
    + /* FIX: sanity check for sensitive registers (eg. eflags) */
    +
    + ret = cr_read_cpu_regs(hh, t);
    + if (ret < 0)
    + goto out;
    + ret = cr_read_cpu_debug(hh, t);
    + if (ret < 0)
    + goto out;
    + ret = cr_read_cpu_fpu(hh, t);
    +
    + cr_debug("math %d debug %d\n", hh->used_math, hh->uses_debug);
    + out:
    + return ret;
    +}
    diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c
    index ad1099f..d34a691 100644
    --- a/checkpoint/checkpoint.c
    +++ b/checkpoint/checkpoint.c
    @@ -20,6 +20,8 @@
    #include <linux/ckpt.h>
    #include <linux/ckpt_hdr.h>

    +#include "ckpt_arch.h"
    +
    /**
    * cr_write_obj - write a record described by a cr_hdr
    * @ctx: checkpoint context
    @@ -159,8 +161,17 @@ static int cr_write_task(struct cr_ctx *ctx, struct task_struct *t)
    }

    ret = cr_write_task_struct(ctx, t);
    - cr_debug("ret %d\n", ret);
    + cr_debug("task_struct: ret %d\n", ret);
    + if (ret < 0)
    + goto out;
    + ret = cr_write_thread(ctx, t);
    + cr_debug("thread: ret %d\n", ret);
    + if (ret < 0)
    + goto out;
    + ret = cr_write_cpu(ctx, t);
    + cr_debug("cpu: ret %d\n", ret);

    + out:
    return ret;
    }

    diff --git a/checkpoint/ckpt_arch.h b/checkpoint/ckpt_arch.h
    new file mode 100644
    index 0000000..5bd4703
    --- /dev/null
    +++ b/checkpoint/ckpt_arch.h
    @@ -0,0 +1,7 @@
    +#include <linux/ckpt.h>
    +
    +int cr_write_thread(struct cr_ctx *ctx, struct task_struct *t);
    +int cr_write_cpu(struct cr_ctx *ctx, struct task_struct *t);
    +
    +int cr_read_thread(struct cr_ctx *ctx);
    +int cr_read_cpu(struct cr_ctx *ctx);
    diff --git a/checkpoint/restart.c b/checkpoint/restart.c
    index 171cd2d..5226994 100644
    --- a/checkpoint/restart.c
    +++ b/checkpoint/restart.c
    @@ -15,6 +15,8 @@
    #include <linux/ckpt.h>
    #include <linux/ckpt_hdr.h>

    +#include "ckpt_arch.h"
    +
    /**
    * cr_read_obj - read a whole record (cr_hdr followed by payload)
    * @ctx: checkpoint context
    @@ -164,8 +166,17 @@ static int cr_read_task(struct cr_ctx *ctx)
    int ret;

    ret = cr_read_task_struct(ctx);
    - cr_debug("ret %d\n", ret);
    + cr_debug("task_struct: ret %d\n", ret);
    + if (ret < 0)
    + goto out;
    + ret = cr_read_thread(ctx);
    + cr_debug("thread: ret %d\n", ret);
    + if (ret < 0)
    + goto out;
    + ret = cr_read_cpu(ctx);
    + cr_debug("cpu: ret %d\n", ret);

    + out:
    return ret;
    }

    diff --git a/include/asm-x86/ckpt_hdr.h b/include/asm-x86/ckpt_hdr.h
    new file mode 100644
    index 0000000..44a903c
    --- /dev/null
    +++ b/include/asm-x86/ckpt_hdr.h
    @@ -0,0 +1,72 @@
    +#ifndef __ASM_X86_CKPT_HDR_H
    +#define __ASM_X86_CKPT_HDR_H
    +/*
    + * Checkpoint/restart - architecture specific headers x86
    + *
    + * 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 <asm/processor.h>
    +
    +struct cr_hdr_thread {
    + /* NEED: restart blocks */
    +
    + __s16 gdt_entry_tls_entries;
    + __s16 sizeof_tls_array;
    + __s16 ntls; /* number of TLS entries to follow */
    +} __attribute__((aligned(8)));
    +
    +struct cr_hdr_cpu {
    + /* 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 cs;
    + __u64 flags;
    + __u64 sp;
    + __u64 ss;
    +
    + /* segment registers */
    + __u64 ds;
    + __u64 es;
    + __u64 fs;
    + __u64 gs;
    +
    + /* debug registers */
    + __u64 debugreg0;
    + __u64 debugreg1;
    + __u64 debugreg2;
    + __u64 debugreg3;
    + __u64 debugreg4;
    + __u64 debugreg5;
    + __u64 debugreg6;
    + __u64 debugreg7;
    +
    + __u16 uses_debug;
    + __u16 used_math;
    + __u16 has_fxsr;
    + __u16 _padding;
    +
    + union thread_xstate xstate; /* i387 */
    +
    +} __attribute__((aligned(8)));
    +
    +#endif /* __ASM_X86_CKPT_HDR__H */
    diff --git a/include/linux/ckpt_hdr.h b/include/linux/ckpt_hdr.h
    index dd05ecc..e66f322 100644
    --- a/include/linux/ckpt_hdr.h
    +++ b/include/linux/ckpt_hdr.h
    @@ -12,6 +12,7 @@

    #include <linux/types.h>
    #include <linux/utsname.h>
    +#include <asm/ckpt_hdr.h>

    /*
    * To maintain compatibility between 32-bit and 64-bit architecture flavors,
    --
    1.5.4.3


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