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vdso/kdat: Add test for preserving "[vdso]" hint after mremap()

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If it does preserve, we can omit checking pagemap for dumpee or
filling symtable in parasite.

Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>
This commit is contained in:
Dmitry Safonov 2017-07-17 15:40:01 +03:00 • committed by Andrei Vagin
parent b8f3fca489
commit ff28da9504
4 changed files with 81 additions and 0 deletions
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1
criu/include/kerndat.h
View file

@ -56,6 +56,7 @@ struct kerndat_s {
unsigned long uffd_features;
bool has_thp_disable;
bool can_map_vdso;
bool vdso_hint_reliable;
#ifdef CONFIG_VDSO
struct vdso_symtable vdso_sym;
#ifdef CONFIG_COMPAT

2
criu/include/vdso.h
View file

@ -16,6 +16,7 @@ extern struct vdso_maps vdso_maps_compat;
extern int vdso_init_dump(void);
extern int vdso_init_restore(void);
extern int kerndat_vdso_fill_symtable(void);
extern int kerndat_vdso_preserves_hint(void);
extern int parasite_fixup_vdso(struct parasite_ctl *ctl, pid_t pid,
struct vm_area_list *vma_area_list);
@ -30,6 +31,7 @@ extern void compat_vdso_helper(struct vdso_maps *native, int pipe_fd,
#define vdso_init_dump() (0)
#define vdso_init_restore() (0)
#define kerndat_vdso_fill_symtable() (0)
#define kerndat_vdso_preserves_hint() (0)
#define parasite_fixup_vdso(ctl, pid, vma_area_list) (0)
#endif /* CONFIG_VDSO */

3
criu/kerndat.c
View file

@ -870,6 +870,9 @@ int kerndat_init(void)
/* Needs kdat.compat_cr filled before */
if (!ret)
ret = kerndat_vdso_fill_symtable();
/* Depends on kerndat_vdso_fill_symtable() */
if (!ret)
ret = kerndat_vdso_preserves_hint();
kerndat_lsm();
kerndat_mmap_min_addr();

75
criu/vdso.c
View file

@ -621,3 +621,78 @@ int kerndat_vdso_fill_symtable(void)
return 0;
}
/*
* On x86 pre-v3.16 kernels can lose "[vdso]" hint
* in /proc/.../maps file after mremap()'ing vdso vma.
* Depends on kerndat_vdso_fill_symtable() - assuming that
* vdso_maps and vdso_maps_compat are filled.
*/
int kerndat_vdso_preserves_hint(void)
{
struct vdso_maps vdso_maps_after;
int status, ret = -1;
pid_t child;
kdat.vdso_hint_reliable = 0;
if (vdso_maps.vdso_start == VDSO_BAD_ADDR)
return 0;
child = fork();
if (child < 0) {
pr_perror("fork() failed");
return -1;
}
if (child == 0) {
unsigned long vdso_addr = vdso_maps.vdso_start;
unsigned long vdso_size = vdso_maps.sym.vdso_size;
void *new_addr;
new_addr = mmap(0, vdso_size, PROT_NONE,
MAP_ANON | MAP_PRIVATE, -1, 0);
if (new_addr == MAP_FAILED)
exit(1);
child = getpid();
new_addr = (void *)syscall(SYS_mremap, vdso_addr, vdso_size,
vdso_size, MREMAP_MAYMOVE | MREMAP_FIXED, new_addr);
if (new_addr == MAP_FAILED)
syscall(SYS_exit, 2);
syscall(SYS_kill, child, SIGSTOP);
syscall(SYS_exit, 3);
}
waitpid(child, &status, WUNTRACED);
if (WIFEXITED(status)) {
int ret = WEXITSTATUS(status);
pr_err("Child unexpectedly exited with %d\n", ret);
goto out;
} else if (WIFSIGNALED(status)) {
int sig = WTERMSIG(status);
pr_err("Child unexpectedly signaled with %d: %s\n",
sig, strsignal(sig));
goto out;
} else if (!WIFSTOPPED(status) || WSTOPSIG(status) != SIGSTOP) {
pr_err("Child is unstoppable or was stopped by other means\n");
goto out_kill;
}
if (vdso_parse_maps(child, &vdso_maps_after)) {
pr_err("Failed parsing maps for child helper\n");
goto out_kill;
}
if (vdso_maps_after.vdso_start != VDSO_BAD_ADDR)
kdat.vdso_hint_reliable = 1;
ret = 0;
out_kill:
kill(child, SIGKILL);
waitpid(child, &status, 0);
out:
return ret;
}