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kdat: Handle pagemaps with zeroed pfns

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Recent kernels allow for user to read proc pagemap file, but zero
pfns in it. Support this mode for user dumps.

https://github.com/xemul/criu/issues/101

Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Acked-by: Andrew Vagin <avagin@virtuozzo.com>
This commit is contained in:
Pavel Emelyanov 2015-12-30 13:45:00 +03:00 committed by Pavel Emelyanov
parent 40184b9797
commit d7684252c8
5 changed files with 74 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/kerndat.h
View File

@ -16,6 +16,13 @@ extern int kerndat_get_dirty_track(void);
extern int kerndat_fdinfo_has_lock(void);
extern int kerndat_loginuid(bool only_dump);
enum pagemap_func {
PM_UNKNOWN,
PM_DISABLED, /* /proc/pid/pagemap doesn't open (user mode) */
PM_FLAGS_ONLY, /* pagemap zeroes pfn part (user mode) */
PM_FULL,
};
struct kerndat_s {
dev_t shmem_dev;
int tcp_max_rshare;
@ -27,6 +34,7 @@ struct kerndat_s {
unsigned long task_size;
bool ipv6;
bool has_loginuid;
enum pagemap_func pmap;
};
extern struct kerndat_s kdat;

54
kerndat.c
View File

@ -41,6 +41,42 @@ struct kerndat_s kdat = {
.tcp_max_rshare = 87380,
};
static int check_pagemap(void)
{
int ret, fd;
u64 pfn = 0;
fd = __open_proc(PROC_SELF, EPERM, O_RDONLY, "pagemap");
if (fd < 0) {
if (errno == EPERM) {
pr_info("Pagemap disabled");
kdat.pmap = PM_DISABLED;
return 0;
}
return -1;
}
/* Get the PFN of some present page. Stack is here, so try it :) */
ret = pread(fd, &pfn, sizeof(pfn), (((unsigned long)&ret) / page_size()) * sizeof(pfn));
if (ret != sizeof(pfn)) {
pr_perror("Can't read pagemap");
return -1;
}
close(fd);
if ((pfn & PME_PFRAME_MASK) == 0) {
pr_info("Pagemap provides flags only\n");
kdat.pmap = PM_FLAGS_ONLY;
} else {
pr_info("Pagemap is fully functional\n");
kdat.pmap = PM_FULL;
}
return 0;
}
/*
* Anonymous shared mappings are backed by hidden tmpfs
* mount. Find out its dev to distinguish such mappings
@ -322,13 +358,15 @@ static int init_zero_page_pfn()
return -1;
}
if (kdat.pmap != PM_FULL) {
pr_info("Zero page detection failed, optimization turns off.\n");
return 0;
}
ret = vaddr_to_pfn((unsigned long)addr, &kdat.zero_page_pfn);
munmap(addr, PAGE_SIZE);
if (ret == 1) {
pr_info("Zero page detection failed, optimization turns off.\n");
ret = 0;
} else if (kdat.zero_page_pfn == 0)
if (kdat.zero_page_pfn == 0)
ret = -1;
return ret;
@ -456,7 +494,9 @@ int kerndat_init(void)
{
int ret;
ret = kerndat_get_shmemdev();
ret = check_pagemap();
if (!ret)
ret = kerndat_get_shmemdev();
if (!ret)
ret = kerndat_get_dirty_track();
if (!ret)
@ -487,7 +527,9 @@ int kerndat_init_rst(void)
* not available inside namespaces.
*/
ret = tcp_read_sysctl_limits();
ret = check_pagemap();
if (!ret)
ret = tcp_read_sysctl_limits();
if (!ret)
ret = get_last_cap();
if (!ret)

11
pagemap-cache.c
View File

@ -46,13 +46,14 @@ int pmc_init(pmc_t *pmc, pid_t pid, const struct list_head *vma_head, size_t siz
if (!pmc->map)
goto err;
pmc->fd = __open_proc(pid, EPERM, O_RDONLY, "pagemap");
if (pmc->fd < 0) {
if (errno != EPERM)
goto err;
if (kdat.pmap == PM_DISABLED) {
pmc->fd = -1;
pr_warn("No pagemap for %d available, "
"switching to greedy mode\n", pid);
} else {
pmc->fd = open_proc(pid, "pagemap");
if (pmc->fd < 0)
goto err;
}
pr_debug("created for pid %d (takes %zu bytes)\n", pid, pmc->map_len);

4
util.c
View File

@ -763,9 +763,9 @@ int vaddr_to_pfn(unsigned long vaddr, u64 *pfn)
int fd, ret = -1;
off_t off;
fd = __open_proc(getpid(), EPERM, O_RDONLY, "pagemap");
fd = open_proc(getpid(), "pagemap");
if (fd < 0)
return errno == EPERM ? 1 : -1;
return -1;
off = (vaddr / page_size()) * sizeof(u64);
ret = pread(fd, pfn, sizeof(*pfn), off);

18
vdso.c
View File

@ -43,20 +43,19 @@ int parasite_fixup_vdso(struct parasite_ctl *ctl, pid_t pid,
struct vma_area *proxy_vdso_marked = NULL;
struct vma_area *proxy_vvar_marked = NULL;
struct parasite_vdso_vma_entry *args;
int fd, ret, exit_code = -1;
int fd = -1, ret, exit_code = -1;
u64 pfn = VDSO_BAD_PFN;
struct vma_area *vma;
off_t off;
args = parasite_args(ctl, struct parasite_vdso_vma_entry);
fd = __open_proc(pid, EPERM, O_RDONLY, "pagemap");
if (fd < 0) {
if (errno == EPERM) {
pr_info("Pagemap is unavailable, trying a slow way\n");
} else
if (kdat.pmap == PM_FULL) {
BUG_ON(vdso_pfn == VDSO_BAD_PFN);
fd = open_proc(pid, "pagemap");
if (fd < 0)
return -1;
} else
BUG_ON(vdso_pfn == VDSO_BAD_PFN);
pr_info("Pagemap is unavailable, trying a slow way\n");
list_for_each_entry(vma, &vma_area_list->h, list) {
if (!vma_area_is(vma, VMA_AREA_REGULAR))
@ -311,8 +310,11 @@ int vdso_init(void)
{
if (vdso_fill_self_symtable(&vdso_sym_rt))
return -1;
if (vaddr_to_pfn(vdso_sym_rt.vma_start, &vdso_pfn) != 0)
if (kdat.pmap != PM_FULL)
pr_info("VDSO detection turned off\n");
else if (vaddr_to_pfn(vdso_sym_rt.vma_start, &vdso_pfn))
return -1;
return 0;
}