Re: [RFC v5][PATCH 3/8] x86 support for checkpoint/restart

[Serge E. Hallyn]

Quoting Oren Laadan (orenl@xxxxxxxxxxxxxxx):
> (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@xxxxxxxxxxxxxxx>

Acked-by: Serge Hallyn <serue@xxxxxxxxxx>

> ---
>  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
> 
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