[RFC v2][PATCH 3/9] x86 support for checkpoint/restart

Oren Laadan
2008-08-21T03:07:46Z

(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>
---
checkpoint/Makefile | 1 +
checkpoint/checkpoint.c | 9 ++-
checkpoint/ckpt_arch.h | 7 ++
checkpoint/ckpt_x86.c | 190 +++++++++++++++++++++++++++++++++++++++++++++++
checkpoint/restart.c | 11 ++-
checkpoint/rstr_x86.c | 176 +++++++++++++++++++++++++++++++++++++++++++
include/asm-x86/ckpt.h | 72 ++++++++++++++++++
7 files changed, 463 insertions(+), 3 deletions(-)
create mode 100644 checkpoint/ckpt_arch.h
create mode 100644 checkpoint/ckpt_x86.c
create mode 100644 checkpoint/rstr_x86.c
create mode 100644 include/asm-x86/ckpt.h

diff --git a/checkpoint/Makefile b/checkpoint/Makefile
index d129878..29dbb2d 100644
--- a/checkpoint/Makefile
+++ b/checkpoint/Makefile
@@ -1 +1,2 @@
obj-y += sys.o checkpoint.o restart.o
+obj-$(CONFIG_X86) += ckpt_x86.o rstr_x86.o
diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c
index 25343f5..949ed58 100644
--- a/checkpoint/checkpoint.c
+++ b/checkpoint/checkpoint.c
@@ -20,6 +20,7 @@

#include "ckpt.h"
#include "ckpt_hdr.h"
+#include "ckpt_arch.h"

/**
* cr_fill_fname - return pathname of a given file
@@ -166,7 +167,13 @@ 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)
+ ret = cr_write_thread(ctx, t);
+ cr_debug("thread: ret %d\n", ret);
+ if (!ret)
+ ret = cr_write_cpu(ctx, t);
+ cr_debug("cpu: ret %d\n", ret);

return ret;
}
diff --git a/checkpoint/ckpt_arch.h b/checkpoint/ckpt_arch.h
new file mode 100644
index 0000000..b7cc8c9
--- /dev/null
+++ b/checkpoint/ckpt_arch.h
@@ -0,0 +1,7 @@
+#include "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/ckpt_x86.c b/checkpoint/ckpt_x86.c
new file mode 100644
index 0000000..ad6c8e8
--- /dev/null
+++ b/checkpoint/ckpt_x86.c
@@ -0,0 +1,190 @@
+/*
+ * 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/ckpt.h>
+#include <asm/desc.h>
+#include <asm/i387.h>
+
+#include "ckpt.h"
+#include "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 = ctx->hbuf;
+ struct thread_struct *thread;
+ struct desc_struct *desc;
+ int ntls = 0;
+ int n, ret;
+
+ h.type = CR_HDR_THREAD;
+ h.len = sizeof(*hh);
+ h.ptag = 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;
+
+ if ((ret = cr_write_obj(ctx, &h, hh)) < 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 = ctx->hbuf;
+
+ h.type = CR_HDR_CPU;
+ h.len = sizeof(*hh);
+ h.ptag = 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);
+
+ return cr_write_obj(ctx, &h, hh);
+}
diff --git a/checkpoint/restart.c b/checkpoint/restart.c
index be7d08c..a85f48b 100644
--- a/checkpoint/restart.c
+++ b/checkpoint/restart.c
@@ -21,6 +21,7 @@

#include "ckpt.h"
#include "ckpt_hdr.h"
+#include "ckpt_arch.h"

/**
* cr_hbuf_get - reserve space on the hbuf
@@ -63,7 +64,7 @@ int cr_read_obj(struct cr_ctx *ctx, struct cr_hdr *h, void *buf, int n)
if (ret < 0)
return ret;

- cr_debug("type %d len %d id %d (%d)\n", h->type, h->len, h->ptag, n);
+ cr_debug("type %d len %d ptag %d (%d)\n", h->type, h->len, h->ptag, n);

if (h->len < 0 || h->len > n)
return -EINVAL;
@@ -180,7 +181,13 @@ 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)
+ ret = cr_read_thread(ctx);
+ cr_debug("thread: ret %d\n", ret);
+ if (!ret)
+ ret = cr_read_cpu(ctx);
+ cr_debug("cpu: ret %d\n", ret);

return ret;
}
diff --git a/checkpoint/rstr_x86.c b/checkpoint/rstr_x86.c
new file mode 100644
index 0000000..a24a7de
--- /dev/null
+++ b/checkpoint/rstr_x86.c
@@ -0,0 +1,176 @@
+/*
+ * 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/ckpt.h>
+#include <asm/desc.h>
+#include <asm/i387.h>
+
+#include "ckpt.h"
+#include "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 ret;
+
+ ret = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_THREAD);
+ if (ret < 0)
+ return ret;
+#if 0 /* activate when containers are used */
+ if (ret != 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 *buf = ctx->tbuf;
+ int size = sizeof(*buf) * GDT_ENTRY_TLS_ENTRIES;
+ int cpu;
+
+ BUG_ON(size > CR_TBUF_TOTAL);
+
+ ret = cr_kread(ctx, buf, size);
+ if (ret < 0)
+ return ret;
+
+ /* FIX: add sanity checks (eg. that values makes sense, that
+ * that we don't overwrite old values, etc */
+
+ cpu = get_cpu();
+ memcpy(thread->tls_array, buf, size);
+ load_TLS(thread, cpu);
+ put_cpu();
+ }
+
+ 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 ret;
+
+ ret = cr_read_obj_type(ctx, hh, sizeof(*hh), CR_HDR_CPU);
+ if (ret < 0)
+ return ret;
+#if 0 /* activate when containers are used */
+ if (ret != task_pid_vnr(t))
+ return -EINVAL;
+#endif
+ /* FIX: sanity check for sensitive registers (eg. eflags) */
+
+ ret = cr_read_cpu_regs(hh, t);
+ if (!ret)
+ ret = cr_read_cpu_debug(hh, t);
+ if (!ret)
+ ret = cr_read_cpu_fpu(hh, t);
+
+ cr_debug("math %d debug %d\n", hh->used_math, hh->uses_debug);
+
+ return ret;
+}
diff --git a/include/asm-x86/ckpt.h b/include/asm-x86/ckpt.h
new file mode 100644
index 0000000..cd74657
--- /dev/null
+++ b/include/asm-x86/ckpt.h
@@ -0,0 +1,72 @@
+#ifndef __ASM_X86_CKPT_H
+#define __ASM_X86_CKPT_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_H */
--
1.5.4.3