[CRIU] [PATCH] kerndat: Separate per-arch kerndat
Andrei Vagin
avagin at virtuozzo.com
Mon Feb 19 20:49:47 MSK 2018
Applied, thanks!
On Thu, Feb 15, 2018 at 09:08:04PM +0000, Dmitry Safonov wrote:
> x86's kerndat section in crtools.c has grown too much.
> Let's make it more readable and *looking at cleared include-list*,
> it'll better parallelize build.
>
> Maybe we should turn __weak function into 0-defines.
> Or clean 0-defines with ifdefs in generic file.
> I have no strong opinion on that.
>
> Signed-off-by: Dmitry Safonov <dima at arista.com>
> ---
> criu/arch/aarch64/include/asm/kerndat.h | 7 +
> criu/arch/aarch64/include/asm/restorer.h | 2 -
> criu/arch/arm/include/asm/kerndat.h | 7 +
> criu/arch/arm/include/asm/restorer.h | 2 -
> criu/arch/ppc64/include/asm/kerndat.h | 7 +
> criu/arch/ppc64/include/asm/restorer.h | 2 -
> criu/arch/s390/include/asm/kerndat.h | 7 +
> criu/arch/s390/include/asm/restorer.h | 2 -
> criu/arch/x86/Makefile | 1 +
> criu/arch/x86/crtools.c | 269 +------------------------------
> criu/arch/x86/include/asm/kerndat.h | 8 +
> criu/arch/x86/include/asm/restorer.h | 5 -
> criu/arch/x86/kerndat.c | 249 ++++++++++++++++++++++++++++
> criu/include/kerndat.h | 1 +
> 14 files changed, 295 insertions(+), 274 deletions(-)
> create mode 100644 criu/arch/aarch64/include/asm/kerndat.h
> create mode 100644 criu/arch/arm/include/asm/kerndat.h
> create mode 100644 criu/arch/ppc64/include/asm/kerndat.h
> create mode 100644 criu/arch/s390/include/asm/kerndat.h
> create mode 100644 criu/arch/x86/include/asm/kerndat.h
> create mode 100644 criu/arch/x86/kerndat.c
>
> diff --git a/criu/arch/aarch64/include/asm/kerndat.h b/criu/arch/aarch64/include/asm/kerndat.h
> new file mode 100644
> index 000000000000..60956b573db9
> --- /dev/null
> +++ b/criu/arch/aarch64/include/asm/kerndat.h
> @@ -0,0 +1,7 @@
> +#ifndef __CR_ASM_KERNDAT_H__
> +#define __CR_ASM_KERNDAT_H__
> +
> +#define kdat_compatible_cr() 0
> +#define kdat_can_map_vdso() 0
> +
> +#endif /* __CR_ASM_KERNDAT_H__ */
> diff --git a/criu/arch/aarch64/include/asm/restorer.h b/criu/arch/aarch64/include/asm/restorer.h
> index bef85f3a3210..f502cdcaf67c 100644
> --- a/criu/arch/aarch64/include/asm/restorer.h
> +++ b/criu/arch/aarch64/include/asm/restorer.h
> @@ -52,8 +52,6 @@
> : "sp", "x0", "memory")
>
>
> -#define kdat_compatible_cr() 0
> -#define kdat_can_map_vdso() 0
> #define arch_map_vdso(map, compat) -1
>
> int restore_gpregs(struct rt_sigframe *f, UserAarch64RegsEntry *r);
> diff --git a/criu/arch/arm/include/asm/kerndat.h b/criu/arch/arm/include/asm/kerndat.h
> new file mode 100644
> index 000000000000..60956b573db9
> --- /dev/null
> +++ b/criu/arch/arm/include/asm/kerndat.h
> @@ -0,0 +1,7 @@
> +#ifndef __CR_ASM_KERNDAT_H__
> +#define __CR_ASM_KERNDAT_H__
> +
> +#define kdat_compatible_cr() 0
> +#define kdat_can_map_vdso() 0
> +
> +#endif /* __CR_ASM_KERNDAT_H__ */
> diff --git a/criu/arch/arm/include/asm/restorer.h b/criu/arch/arm/include/asm/restorer.h
> index d9208185f731..217d920e846e 100644
> --- a/criu/arch/arm/include/asm/restorer.h
> +++ b/criu/arch/arm/include/asm/restorer.h
> @@ -53,8 +53,6 @@
> : "memory")
>
>
> -#define kdat_compatible_cr() 0
> -#define kdat_can_map_vdso() 0
> #define arch_map_vdso(map, compat) -1
>
> int restore_gpregs(struct rt_sigframe *f, UserArmRegsEntry *r);
> diff --git a/criu/arch/ppc64/include/asm/kerndat.h b/criu/arch/ppc64/include/asm/kerndat.h
> new file mode 100644
> index 000000000000..60956b573db9
> --- /dev/null
> +++ b/criu/arch/ppc64/include/asm/kerndat.h
> @@ -0,0 +1,7 @@
> +#ifndef __CR_ASM_KERNDAT_H__
> +#define __CR_ASM_KERNDAT_H__
> +
> +#define kdat_compatible_cr() 0
> +#define kdat_can_map_vdso() 0
> +
> +#endif /* __CR_ASM_KERNDAT_H__ */
> diff --git a/criu/arch/ppc64/include/asm/restorer.h b/criu/arch/ppc64/include/asm/restorer.h
> index 3fffa833c157..d48d833d6b6c 100644
> --- a/criu/arch/ppc64/include/asm/restorer.h
> +++ b/criu/arch/ppc64/include/asm/restorer.h
> @@ -48,8 +48,6 @@
> "r"(&thread_args[i]) /* %6 */ \
> : "memory","0","3","4","5","6","7","14","15")
>
> -#define kdat_compatible_cr() 0
> -#define kdat_can_map_vdso() 0
> #define arch_map_vdso(map, compat) -1
>
> int restore_gpregs(struct rt_sigframe *f, UserPpc64RegsEntry *r);
> diff --git a/criu/arch/s390/include/asm/kerndat.h b/criu/arch/s390/include/asm/kerndat.h
> new file mode 100644
> index 000000000000..60956b573db9
> --- /dev/null
> +++ b/criu/arch/s390/include/asm/kerndat.h
> @@ -0,0 +1,7 @@
> +#ifndef __CR_ASM_KERNDAT_H__
> +#define __CR_ASM_KERNDAT_H__
> +
> +#define kdat_compatible_cr() 0
> +#define kdat_can_map_vdso() 0
> +
> +#endif /* __CR_ASM_KERNDAT_H__ */
> diff --git a/criu/arch/s390/include/asm/restorer.h b/criu/arch/s390/include/asm/restorer.h
> index 63e09986339b..cfdefcab9bab 100644
> --- a/criu/arch/s390/include/asm/restorer.h
> +++ b/criu/arch/s390/include/asm/restorer.h
> @@ -39,8 +39,6 @@
> "d"(&thread_args[i]) \
> : "0", "1", "2", "3", "4", "5", "6", "cc", "memory")
>
> -#define kdat_compatible_cr() 0
> -#define kdat_can_map_vdso() 0
> #define arch_map_vdso(map, compat) -1
>
> int restore_gpregs(struct rt_sigframe *f, UserS390RegsEntry *r);
> diff --git a/criu/arch/x86/Makefile b/criu/arch/x86/Makefile
> index 669dc073a5be..75fa782c8279 100644
> --- a/criu/arch/x86/Makefile
> +++ b/criu/arch/x86/Makefile
> @@ -11,6 +11,7 @@ ldflags-y += -r -z noexecstack
>
> obj-y += cpu.o
> obj-y += crtools.o
> +obj-y += kerndat.o
> obj-y += sigframe.o
> ifeq ($(CONFIG_COMPAT),y)
> obj-y += sigaction_compat.o
> diff --git a/criu/arch/x86/crtools.c b/criu/arch/x86/crtools.c
> index e13b39b90076..0b5a0acd6779 100644
> --- a/criu/arch/x86/crtools.c
> +++ b/criu/arch/x86/crtools.c
> @@ -1,267 +1,14 @@
> -#include <signal.h>
> -#include <stdlib.h>
> -#include <string.h>
> -#include <unistd.h>
> -#include <elf.h>
> -#include <sched.h>
> -#include <sys/mman.h>
> -#include <sys/syscall.h>
> -#include <sys/auxv.h>
> -#include <sys/wait.h>
> -#include <sys/ptrace.h>
> -
> -#include "types.h"
> -#include "log.h"
> -#include "asm/compat.h"
> -#include "asm/parasite-syscall.h"
> -#include "asm/restorer.h"
> -#include <compel/asm/fpu.h>
> -#include "asm/dump.h"
> -
> -#include "cr_options.h"
> -#include "common/compiler.h"
> -#include "restorer.h"
> -#include "parasite-syscall.h"
> -#include "util.h"
> +#include "compel/asm/fpu.h"
> +#include "compel/compel.h"
> +#include "compel/plugins/std/syscall-codes.h"
> #include "cpu.h"
> -#include <compel/plugins/std/syscall-codes.h>
> -#include "kerndat.h"
> -#include <compel/compel.h>
> -
> -#include "protobuf.h"
> +#include "cr_options.h"
> #include "images/core.pb-c.h"
> -#include "images/creds.pb-c.h"
> -
> -/* XXX: Move all kerndat features to per-arch kerndat .c */
> -int kdat_can_map_vdso(void)
> -{
> - pid_t child;
> - int stat;
> -
> - /*
> - * Running under fork so if vdso_64 is disabled - don't create
> - * it for criu accidentally.
> - */
> - child = fork();
> - if (child < 0) {
> - pr_perror("%s(): failed to fork()", __func__);
> - return -1;
> - }
> -
> - if (child == 0) {
> - int ret;
> -
> - ret = syscall(SYS_arch_prctl, ARCH_MAP_VDSO_32, 0);
> - if (ret == 0)
> - exit(1);
> - /*
> - * Mapping vDSO while have not unmap it yet:
> - * this is restricted by API if ARCH_MAP_VDSO_* is supported.
> - */
> - if (ret == -1 && errno == EEXIST)
> - exit(1);
> - exit(0);
> - }
> -
> - if (waitpid(child, &stat, 0) != child) {
> - pr_err("Failed to wait for arch_prctl() test\n");
> - kill(child, SIGKILL);
> - return -1;
> - }
> -
> - if (!WIFEXITED(stat))
> - return -1;
> -
> - return WEXITSTATUS(stat);
> -
> -}
> -
> -#ifdef CONFIG_COMPAT
> -void *mmap_ia32(void *addr, size_t len, int prot,
> - int flags, int fildes, off_t off)
> -{
> - struct syscall_args32 s;
> -
> - s.nr = __NR32_mmap2;
> - s.arg0 = (uint32_t)(uintptr_t)addr;
> - s.arg1 = (uint32_t)len;
> - s.arg2 = prot;
> - s.arg3 = flags;
> - s.arg4 = fildes;
> - s.arg5 = (uint32_t)off;
> -
> - do_full_int80(&s);
> -
> - return (void *)(uintptr_t)s.nr;
> -}
> -
> -/*
> - * The idea of the test:
> - * From kernel's top-down allocator we assume here that
> - * 1. A = mmap(0, ...); munmap(A);
> - * 2. B = mmap(0, ...);
> - * results in A == B.
> - * ...but if we have 32-bit mmap() bug, then A will have only lower
> - * 4 bytes of 64-bit address allocated with mmap().
> - * That means, that the next mmap() will return B != A
> - * (as munmap(A) hasn't really unmapped A mapping).
> - *
> - * As mapping with lower 4 bytes of A may really exist, we run
> - * this test under fork().
> - *
> - * Another approach to test bug's presence would be to parse
> - * /proc/self/maps before and after 32-bit mmap(), but that would
> - * be soo slow.
> - */
> -static void mmap_bug_test(void)
> -{
> - void *map1, *map2;
> - int err;
> -
> - map1 = mmap_ia32(0, PAGE_SIZE, PROT_NONE, MAP_ANON|MAP_PRIVATE, -1, 0);
> - /* 32-bit error, not sign-extended - can't use IS_ERR_VALUE() here */
> - err = (uintptr_t)map1 % PAGE_SIZE;
> - if (err) {
> - pr_err("ia32 mmap() failed: %d\n", err);
> - exit(1);
> - }
> -
> - if (munmap(map1, PAGE_SIZE)) {
> - pr_err("Failed to unmap() 32-bit mapping: %m\n");
> - exit(1);
> - }
> -
> - map2 = mmap_ia32(0, PAGE_SIZE, PROT_NONE, MAP_ANON|MAP_PRIVATE, -1, 0);
> - err = (uintptr_t)map2 % PAGE_SIZE;
> - if (err) {
> - pr_err("ia32 mmap() failed: %d\n", err);
> - exit(1);
> - }
> -
> - if (map1 != map2)
> - exit(1);
> - exit(0);
> -}
> -
> -/*
> - * Pre v4.12 kernels have a bug: for a process started as 64-bit
> - * 32-bit mmap() may return 8 byte pointer.
> - * Which is fatal for us: after 32-bit C/R a task will map 64-bit
> - * addresses, cut upper 4 bytes and try to use lower 4 bytes.
> - * This is a check if the bug was fixed in the kernel.
> - */
> -static int has_32bit_mmap_bug(void)
> -{
> - pid_t child = fork();
> - int stat;
> -
> - if (child < 0) {
> - pr_perror("%s(): failed to fork()", __func__);
> - return -1;
> - }
> -
> - if (child == 0)
> - mmap_bug_test();
> -
> - if (waitpid(child, &stat, 0) != child) {
> - pr_err("Failed to wait for mmap test\n");
> - kill(child, SIGKILL);
> - return -1;
> - }
> -
> - if (!WIFEXITED(stat) || WEXITSTATUS(stat) != 0)
> - return 1;
> - return 0;
> -}
> -
> -int kdat_compatible_cr(void)
> -{
> - if (!kdat.can_map_vdso)
> - return 0;
> -
> - if (has_32bit_mmap_bug())
> - return 0;
> -
> - return 1;
> -}
> -#else /* !CONFIG_COMPAT */
> -int kdat_compatible_cr(void)
> -{
> - return 0;
> -}
> -#endif
> -
> -static int kdat_x86_has_ptrace_fpu_xsave_bug_child(void *arg)
> -{
> - ptrace(PTRACE_TRACEME, 0, 0, 0);
> - kill(getpid(), SIGSTOP);
> - pr_err("Continue after SIGSTOP.. Urr what?\n");
> - _exit(1);
> -}
> -
> -/*
> - * Pre v4.14 kernels have a bug on Skylake CPUs:
> - * copyout_from_xsaves() creates fpu state for
> - * ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov)
> - * without MXCSR and MXCSR_FLAGS if there is SSE/YMM state, but no FP state.
> - * That is xfeatures had either/both XFEATURE_MASK_{SSE,YMM} set, but not
> - * XFEATURE_MASK_FP.
> - * But we *really* need to C/R MXCSR & MXCSR_FLAGS if SSE/YMM active,
> - * as mxcsr store part of the state.
> - */
> -int kdat_x86_has_ptrace_fpu_xsave_bug(void)
> -{
> - user_fpregs_struct_t xsave = { };
> - struct iovec iov;
> - char stack[PAGE_SIZE];
> - int flags = CLONE_VM | CLONE_FILES | CLONE_UNTRACED | SIGCHLD;
> - int ret = -1;
> - pid_t child;
> - int stat;
> -
> - /* OSXSAVE can't be changed during boot. */
> - if (!compel_cpu_has_feature(X86_FEATURE_OSXSAVE))
> - return 0;
> -
> - child = clone(kdat_x86_has_ptrace_fpu_xsave_bug_child,
> - stack + ARRAY_SIZE(stack), flags, 0);
> - if (child < 0) {
> - pr_perror("%s(): failed to clone()", __func__);
> - return -1;
> - }
> -
> - if (waitpid(child, &stat, WUNTRACED) != child) {
> - /*
> - * waitpid() may end with ECHILD if SIGCHLD == SIG_IGN,
> - * and the child has stopped already.
> - */
> - pr_perror("Failed to wait for %s() test\n", __func__);
> - goto out_kill;
> - }
> -
> - if (!WIFSTOPPED(stat)) {
> - pr_err("Born child is unstoppable! (might be dead)\n");
> - goto out_kill;
> - }
> -
> - iov.iov_base = &xsave;
> - iov.iov_len = sizeof(xsave);
> -
> - if (ptrace(PTRACE_GETREGSET, child, (unsigned)NT_X86_XSTATE, &iov) < 0) {
> - pr_perror("Can't obtain FPU registers for %d", child);
> - goto out_kill;
> - }
> - /*
> - * MXCSR should be never 0x0: e.g., it should contain either:
> - * R+/R-/RZ/RN to determine rounding model.
> - */
> - ret = !xsave.i387.mxcsr;
> +#include "log.h"
> +#include "protobuf.h"
> +#include "types.h"
>
> -out_kill:
> - kill(child, SIGKILL);
> - waitpid(child, &stat, 0);
> - return ret;
> -}
> +#include "asm/compat.h"
>
> int save_task_regs(void *x, user_regs_struct_t *regs, user_fpregs_struct_t *fpregs)
> {
> diff --git a/criu/arch/x86/include/asm/kerndat.h b/criu/arch/x86/include/asm/kerndat.h
> new file mode 100644
> index 000000000000..903bc80f7c44
> --- /dev/null
> +++ b/criu/arch/x86/include/asm/kerndat.h
> @@ -0,0 +1,8 @@
> +#ifndef __CR_ASM_KERNDAT_H__
> +#define __CR_ASM_KERNDAT_H__
> +
> +extern int kdat_compatible_cr(void);
> +extern int kdat_can_map_vdso(void);
> +extern int kdat_x86_has_ptrace_fpu_xsave_bug(void);
> +
> +#endif /* __CR_ASM_KERNDAT_H__ */
> diff --git a/criu/arch/x86/include/asm/restorer.h b/criu/arch/x86/include/asm/restorer.h
> index 179f1942f9f8..15867aa1260c 100644
> --- a/criu/arch/x86/include/asm/restorer.h
> +++ b/criu/arch/x86/include/asm/restorer.h
> @@ -80,11 +80,6 @@ static inline int set_compat_robust_list(uint32_t head_ptr, uint32_t len)
> # define ARCH_MAP_VDSO_64 0x2003
> #endif
>
> -/* XXX: Introduce per-arch kerndat header */
> -extern int kdat_compatible_cr(void);
> -extern int kdat_can_map_vdso(void);
> -extern int kdat_x86_has_ptrace_fpu_xsave_bug(void);
> -
> static inline void
> __setup_sas_compat(struct ucontext_ia32* uc, ThreadSasEntry *sas)
> {
> diff --git a/criu/arch/x86/kerndat.c b/criu/arch/x86/kerndat.c
> new file mode 100644
> index 000000000000..a67017d3456e
> --- /dev/null
> +++ b/criu/arch/x86/kerndat.c
> @@ -0,0 +1,249 @@
> +#include <elf.h>
> +#include <sched.h>
> +#include <signal.h>
> +#include <stdlib.h>
> +#include <sys/wait.h>
> +#include <sys/ptrace.h>
> +#include <sys/types.h>
> +#include <sys/uio.h>
> +#include <unistd.h>
> +
> +#include "compel/asm/fpu.h"
> +#include "compel/plugins/std/syscall-codes.h"
> +#include "cpu.h"
> +#include "kerndat.h"
> +#include "log.h"
> +#include "types.h"
> +
> +#include "asm/compat.h"
> +#include "asm/dump.h"
> +
> +int kdat_can_map_vdso(void)
> +{
> + pid_t child;
> + int stat;
> +
> + /*
> + * Running under fork so if vdso_64 is disabled - don't create
> + * it for criu accidentally.
> + */
> + child = fork();
> + if (child < 0) {
> + pr_perror("%s(): failed to fork()", __func__);
> + return -1;
> + }
> +
> + if (child == 0) {
> + int ret;
> +
> + ret = syscall(SYS_arch_prctl, ARCH_MAP_VDSO_32, 0);
> + if (ret == 0)
> + exit(1);
> + /*
> + * Mapping vDSO while have not unmap it yet:
> + * this is restricted by API if ARCH_MAP_VDSO_* is supported.
> + */
> + if (ret == -1 && errno == EEXIST)
> + exit(1);
> + exit(0);
> + }
> +
> + if (waitpid(child, &stat, 0) != child) {
> + pr_err("Failed to wait for arch_prctl() test\n");
> + kill(child, SIGKILL);
> + return -1;
> + }
> +
> + if (!WIFEXITED(stat))
> + return -1;
> +
> + return WEXITSTATUS(stat);
> +
> +}
> +
> +#ifdef CONFIG_COMPAT
> +void *mmap_ia32(void *addr, size_t len, int prot,
> + int flags, int fildes, off_t off)
> +{
> + struct syscall_args32 s;
> +
> + s.nr = __NR32_mmap2;
> + s.arg0 = (uint32_t)(uintptr_t)addr;
> + s.arg1 = (uint32_t)len;
> + s.arg2 = prot;
> + s.arg3 = flags;
> + s.arg4 = fildes;
> + s.arg5 = (uint32_t)off;
> +
> + do_full_int80(&s);
> +
> + return (void *)(uintptr_t)s.nr;
> +}
> +
> +/*
> + * The idea of the test:
> + * From kernel's top-down allocator we assume here that
> + * 1. A = mmap(0, ...); munmap(A);
> + * 2. B = mmap(0, ...);
> + * results in A == B.
> + * ...but if we have 32-bit mmap() bug, then A will have only lower
> + * 4 bytes of 64-bit address allocated with mmap().
> + * That means, that the next mmap() will return B != A
> + * (as munmap(A) hasn't really unmapped A mapping).
> + *
> + * As mapping with lower 4 bytes of A may really exist, we run
> + * this test under fork().
> + *
> + * Another approach to test bug's presence would be to parse
> + * /proc/self/maps before and after 32-bit mmap(), but that would
> + * be soo slow.
> + */
> +static void mmap_bug_test(void)
> +{
> + void *map1, *map2;
> + int err;
> +
> + map1 = mmap_ia32(0, PAGE_SIZE, PROT_NONE, MAP_ANON|MAP_PRIVATE, -1, 0);
> + /* 32-bit error, not sign-extended - can't use IS_ERR_VALUE() here */
> + err = (uintptr_t)map1 % PAGE_SIZE;
> + if (err) {
> + pr_err("ia32 mmap() failed: %d\n", err);
> + exit(1);
> + }
> +
> + if (munmap(map1, PAGE_SIZE)) {
> + pr_err("Failed to unmap() 32-bit mapping: %m\n");
> + exit(1);
> + }
> +
> + map2 = mmap_ia32(0, PAGE_SIZE, PROT_NONE, MAP_ANON|MAP_PRIVATE, -1, 0);
> + err = (uintptr_t)map2 % PAGE_SIZE;
> + if (err) {
> + pr_err("ia32 mmap() failed: %d\n", err);
> + exit(1);
> + }
> +
> + if (map1 != map2)
> + exit(1);
> + exit(0);
> +}
> +
> +/*
> + * Pre v4.12 kernels have a bug: for a process started as 64-bit
> + * 32-bit mmap() may return 8 byte pointer.
> + * Which is fatal for us: after 32-bit C/R a task will map 64-bit
> + * addresses, cut upper 4 bytes and try to use lower 4 bytes.
> + * This is a check if the bug was fixed in the kernel.
> + */
> +static int has_32bit_mmap_bug(void)
> +{
> + pid_t child = fork();
> + int stat;
> +
> + if (child < 0) {
> + pr_perror("%s(): failed to fork()", __func__);
> + return -1;
> + }
> +
> + if (child == 0)
> + mmap_bug_test();
> +
> + if (waitpid(child, &stat, 0) != child) {
> + pr_err("Failed to wait for mmap test\n");
> + kill(child, SIGKILL);
> + return -1;
> + }
> +
> + if (!WIFEXITED(stat) || WEXITSTATUS(stat) != 0)
> + return 1;
> + return 0;
> +}
> +
> +int kdat_compatible_cr(void)
> +{
> + if (!kdat.can_map_vdso)
> + return 0;
> +
> + if (has_32bit_mmap_bug())
> + return 0;
> +
> + return 1;
> +}
> +#else /* !CONFIG_COMPAT */
> +int kdat_compatible_cr(void)
> +{
> + return 0;
> +}
> +#endif
> +
> +static int kdat_x86_has_ptrace_fpu_xsave_bug_child(void *arg)
> +{
> + ptrace(PTRACE_TRACEME, 0, 0, 0);
> + kill(getpid(), SIGSTOP);
> + pr_err("Continue after SIGSTOP.. Urr what?\n");
> + _exit(1);
> +}
> +
> +/*
> + * Pre v4.14 kernels have a bug on Skylake CPUs:
> + * copyout_from_xsaves() creates fpu state for
> + * ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov)
> + * without MXCSR and MXCSR_FLAGS if there is SSE/YMM state, but no FP state.
> + * That is xfeatures had either/both XFEATURE_MASK_{SSE,YMM} set, but not
> + * XFEATURE_MASK_FP.
> + * But we *really* need to C/R MXCSR & MXCSR_FLAGS if SSE/YMM active,
> + * as mxcsr store part of the state.
> + */
> +int kdat_x86_has_ptrace_fpu_xsave_bug(void)
> +{
> + user_fpregs_struct_t xsave = { };
> + struct iovec iov;
> + char stack[PAGE_SIZE];
> + int flags = CLONE_VM | CLONE_FILES | CLONE_UNTRACED | SIGCHLD;
> + int ret = -1;
> + pid_t child;
> + int stat;
> +
> + /* OSXSAVE can't be changed during boot. */
> + if (!compel_cpu_has_feature(X86_FEATURE_OSXSAVE))
> + return 0;
> +
> + child = clone(kdat_x86_has_ptrace_fpu_xsave_bug_child,
> + stack + ARRAY_SIZE(stack), flags, 0);
> + if (child < 0) {
> + pr_perror("%s(): failed to clone()", __func__);
> + return -1;
> + }
> +
> + if (waitpid(child, &stat, WUNTRACED) != child) {
> + /*
> + * waitpid() may end with ECHILD if SIGCHLD == SIG_IGN,
> + * and the child has stopped already.
> + */
> + pr_perror("Failed to wait for %s() test\n", __func__);
> + goto out_kill;
> + }
> +
> + if (!WIFSTOPPED(stat)) {
> + pr_err("Born child is unstoppable! (might be dead)\n");
> + goto out_kill;
> + }
> +
> + iov.iov_base = &xsave;
> + iov.iov_len = sizeof(xsave);
> +
> + if (ptrace(PTRACE_GETREGSET, child, (unsigned)NT_X86_XSTATE, &iov) < 0) {
> + pr_perror("Can't obtain FPU registers for %d", child);
> + goto out_kill;
> + }
> + /*
> + * MXCSR should be never 0x0: e.g., it should contain either:
> + * R+/R-/RZ/RN to determine rounding model.
> + */
> + ret = !xsave.i387.mxcsr;
> +
> +out_kill:
> + kill(child, SIGKILL);
> + waitpid(child, &stat, 0);
> + return ret;
> +}
> diff --git a/criu/include/kerndat.h b/criu/include/kerndat.h
> index 9e7af14a39e5..d26d7630bbd2 100644
> --- a/criu/include/kerndat.h
> +++ b/criu/include/kerndat.h
> @@ -4,6 +4,7 @@
> #include <stdbool.h>
> #include "int.h"
> #include "common/config.h"
> +#include "asm/kerndat.h"
> #ifdef CONFIG_VDSO
> #include "util-vdso.h"
> #endif
> --
> 2.13.6
>
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