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    SubjectRe: [RFC v5][PATCH 3/8] x86 support for checkpoint/restart
    Quoting Oren Laadan (orenl@cs.columbia.edu):
    > (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>

    Acked-by: Serge Hallyn <serue@us.ibm.com>

    > ---
    > arch/x86/mm/Makefile | 2 +
    > arch/x86/mm/checkpoint.c | 198 ++++++++++++++++++++++++++++++++++++++
    > arch/x86/mm/restart.c | 177 ++++++++++++++++++++++++++++++++++
    > checkpoint/checkpoint.c | 13 +++-
    > checkpoint/checkpoint_arch.h | 7 ++
    > checkpoint/restart.c | 13 +++-
    > include/asm-x86/checkpoint_hdr.h | 72 ++++++++++++++
    > include/linux/checkpoint_hdr.h | 1 +
    > 8 files changed, 481 insertions(+), 2 deletions(-)
    > create mode 100644 arch/x86/mm/checkpoint.c
    > create mode 100644 arch/x86/mm/restart.c
    > create mode 100644 checkpoint/checkpoint_arch.h
    > create mode 100644 include/asm-x86/checkpoint_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..eb60003
    > --- /dev/null
    > +++ b/arch/x86/mm/checkpoint.c
    > @@ -0,0 +1,198 @@
    > +/*
    > + * 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/checkpoint.h>
    > +#include <linux/checkpoint_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..0178080
    > --- /dev/null
    > +++ b/arch/x86/mm/restart.c
    > @@ -0,0 +1,177 @@
    > +/*
    > + * 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/checkpoint.h>
    > +#include <linux/checkpoint_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) {
    > + struct desc_struct *desc;
    > + int size, cpu, ret;
    > +
    > + /*
    > + * restore TLS by hand: why convert to struct user_desc if
    > + * sys_set_thread_entry() will convert it back ?
    > + */
    > +
    > + 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 */
    > +
    > + 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);
    > + }
    > +
    > + 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 e5e188f..6ca26d0 100644
    > --- a/checkpoint/checkpoint.c
    > +++ b/checkpoint/checkpoint.c
    > @@ -20,6 +20,8 @@
    > #include <linux/checkpoint.h>
    > #include <linux/checkpoint_hdr.h>
    >
    > +#include "checkpoint_arch.h"
    > +
    > /**
    > * cr_write_obj - write a record described by a cr_hdr
    > * @ctx: checkpoint context
    > @@ -145,8 +147,17 @@ 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/checkpoint_arch.h b/checkpoint/checkpoint_arch.h
    > new file mode 100644
    > index 0000000..bf2d21e
    > --- /dev/null
    > +++ b/checkpoint/checkpoint_arch.h
    > @@ -0,0 +1,7 @@
    > +#include <linux/checkpoint.h>
    > +
    > +extern int cr_write_thread(struct cr_ctx *ctx, struct task_struct *t);
    > +extern int cr_write_cpu(struct cr_ctx *ctx, struct task_struct *t);
    > +
    > +extern int cr_read_thread(struct cr_ctx *ctx);
    > +extern int cr_read_cpu(struct cr_ctx *ctx);
    > diff --git a/checkpoint/restart.c b/checkpoint/restart.c
    > index ef6bc37..0484de0 100644
    > --- a/checkpoint/restart.c
    > +++ b/checkpoint/restart.c
    > @@ -15,6 +15,8 @@
    > #include <linux/checkpoint.h>
    > #include <linux/checkpoint_hdr.h>
    >
    > +#include "checkpoint_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/checkpoint_hdr.h b/include/asm-x86/checkpoint_hdr.h
    > new file mode 100644
    > index 0000000..44a903c
    > --- /dev/null
    > +++ b/include/asm-x86/checkpoint_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/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
    > index 79e4df2..03ec72e 100644
    > --- a/include/linux/checkpoint_hdr.h
    > +++ b/include/linux/checkpoint_hdr.h
    > @@ -12,6 +12,7 @@
    >
    > #include <linux/types.h>
    > #include <linux/utsname.h>
    > +#include <asm/checkpoint_hdr.h>
    >
    > /*
    > * To maintain compatibility between 32-bit and 64-bit architecture flavors,
    > --
    > 1.5.4.3
    >
    > _______________________________________________
    > Containers mailing list
    > Containers@lists.linux-foundation.org
    > https://lists.linux-foundation.org/mailman/listinfo/containers


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