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probe-file.c
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probe-file.c
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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* probe-file.c : operate ftrace k/uprobe events files
*
* Written by Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
*/
#include <errno.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>
#include <linux/zalloc.h>
#include "namespaces.h"
#include "event.h"
#include "strlist.h"
#include "strfilter.h"
#include "debug.h"
#include "build-id.h"
#include "dso.h"
#include "color.h"
#include "symbol.h"
#include "strbuf.h"
#include <api/fs/tracing_path.h>
#include <api/fs/fs.h>
#include "probe-event.h"
#include "probe-file.h"
#include "session.h"
#include "perf_regs.h"
#include "string2.h"
/* 4096 - 2 ('\n' + '\0') */
#define MAX_CMDLEN 4094
static bool print_common_warning(int err, bool readwrite)
{
if (err == -EACCES)
pr_warning("No permission to %s tracefs.\nPlease %s\n",
readwrite ? "write" : "read",
readwrite ? "run this command again with sudo." :
"try 'sudo mount -o remount,mode=755 /sys/kernel/tracing/'");
else
return false;
return true;
}
static bool print_configure_probe_event(int kerr, int uerr)
{
const char *config, *file;
if (kerr == -ENOENT && uerr == -ENOENT) {
file = "{k,u}probe_events";
config = "CONFIG_KPROBE_EVENTS=y and CONFIG_UPROBE_EVENTS=y";
} else if (kerr == -ENOENT) {
file = "kprobe_events";
config = "CONFIG_KPROBE_EVENTS=y";
} else if (uerr == -ENOENT) {
file = "uprobe_events";
config = "CONFIG_UPROBE_EVENTS=y";
} else
return false;
if (!debugfs__configured() && !tracefs__configured())
pr_warning("Debugfs or tracefs is not mounted\n"
"Please try 'sudo mount -t tracefs nodev /sys/kernel/tracing/'\n");
else
pr_warning("%s/%s does not exist.\nPlease rebuild kernel with %s.\n",
tracing_path_mount(), file, config);
return true;
}
static void print_open_warning(int err, bool uprobe, bool readwrite)
{
char sbuf[STRERR_BUFSIZE];
if (print_common_warning(err, readwrite))
return;
if (print_configure_probe_event(uprobe ? 0 : err, uprobe ? err : 0))
return;
pr_warning("Failed to open %s/%cprobe_events: %s\n",
tracing_path_mount(), uprobe ? 'u' : 'k',
str_error_r(-err, sbuf, sizeof(sbuf)));
}
static void print_both_open_warning(int kerr, int uerr, bool readwrite)
{
char sbuf[STRERR_BUFSIZE];
if (kerr == uerr && print_common_warning(kerr, readwrite))
return;
if (print_configure_probe_event(kerr, uerr))
return;
if (kerr < 0)
pr_warning("Failed to open %s/kprobe_events: %s.\n",
tracing_path_mount(),
str_error_r(-kerr, sbuf, sizeof(sbuf)));
if (uerr < 0)
pr_warning("Failed to open %s/uprobe_events: %s.\n",
tracing_path_mount(),
str_error_r(-uerr, sbuf, sizeof(sbuf)));
}
int open_trace_file(const char *trace_file, bool readwrite)
{
char buf[PATH_MAX];
int ret;
ret = e_snprintf(buf, PATH_MAX, "%s/%s", tracing_path_mount(), trace_file);
if (ret >= 0) {
pr_debug("Opening %s write=%d\n", buf, readwrite);
if (readwrite && !probe_event_dry_run)
ret = open(buf, O_RDWR | O_APPEND, 0);
else
ret = open(buf, O_RDONLY, 0);
if (ret < 0)
ret = -errno;
}
return ret;
}
static int open_kprobe_events(bool readwrite)
{
return open_trace_file("kprobe_events", readwrite);
}
static int open_uprobe_events(bool readwrite)
{
return open_trace_file("uprobe_events", readwrite);
}
int probe_file__open(int flag)
{
int fd;
if (flag & PF_FL_UPROBE)
fd = open_uprobe_events(flag & PF_FL_RW);
else
fd = open_kprobe_events(flag & PF_FL_RW);
if (fd < 0)
print_open_warning(fd, flag & PF_FL_UPROBE, flag & PF_FL_RW);
return fd;
}
int probe_file__open_both(int *kfd, int *ufd, int flag)
{
if (!kfd || !ufd)
return -EINVAL;
*kfd = open_kprobe_events(flag & PF_FL_RW);
*ufd = open_uprobe_events(flag & PF_FL_RW);
if (*kfd < 0 && *ufd < 0) {
print_both_open_warning(*kfd, *ufd, flag & PF_FL_RW);
return *kfd;
}
return 0;
}
/* Get raw string list of current kprobe_events or uprobe_events */
struct strlist *probe_file__get_rawlist(int fd)
{
int ret, idx, fddup;
FILE *fp;
char buf[MAX_CMDLEN];
char *p;
struct strlist *sl;
if (fd < 0)
return NULL;
sl = strlist__new(NULL, NULL);
if (sl == NULL)
return NULL;
fddup = dup(fd);
if (fddup < 0)
goto out_free_sl;
fp = fdopen(fddup, "r");
if (!fp)
goto out_close_fddup;
while (!feof(fp)) {
p = fgets(buf, MAX_CMDLEN, fp);
if (!p)
break;
idx = strlen(p) - 1;
if (p[idx] == '\n')
p[idx] = '\0';
ret = strlist__add(sl, buf);
if (ret < 0) {
pr_debug("strlist__add failed (%d)\n", ret);
goto out_close_fp;
}
}
fclose(fp);
return sl;
out_close_fp:
fclose(fp);
goto out_free_sl;
out_close_fddup:
close(fddup);
out_free_sl:
strlist__delete(sl);
return NULL;
}
static struct strlist *__probe_file__get_namelist(int fd, bool include_group)
{
char buf[128];
struct strlist *sl, *rawlist;
struct str_node *ent;
struct probe_trace_event tev;
int ret = 0;
memset(&tev, 0, sizeof(tev));
rawlist = probe_file__get_rawlist(fd);
if (!rawlist)
return NULL;
sl = strlist__new(NULL, NULL);
strlist__for_each_entry(ent, rawlist) {
ret = parse_probe_trace_command(ent->s, &tev);
if (ret < 0)
break;
if (include_group) {
ret = e_snprintf(buf, 128, "%s:%s", tev.group,
tev.event);
if (ret >= 0)
ret = strlist__add(sl, buf);
} else
ret = strlist__add(sl, tev.event);
clear_probe_trace_event(&tev);
/* Skip if there is same name multi-probe event in the list */
if (ret == -EEXIST)
ret = 0;
if (ret < 0)
break;
}
strlist__delete(rawlist);
if (ret < 0) {
strlist__delete(sl);
return NULL;
}
return sl;
}
/* Get current perf-probe event names */
struct strlist *probe_file__get_namelist(int fd)
{
return __probe_file__get_namelist(fd, false);
}
int probe_file__add_event(int fd, struct probe_trace_event *tev)
{
int ret = 0;
char *buf = synthesize_probe_trace_command(tev);
char sbuf[STRERR_BUFSIZE];
if (!buf) {
pr_debug("Failed to synthesize probe trace event.\n");
return -EINVAL;
}
pr_debug("Writing event: %s\n", buf);
if (!probe_event_dry_run) {
if (write(fd, buf, strlen(buf)) < (int)strlen(buf)) {
ret = -errno;
pr_warning("Failed to write event: %s\n",
str_error_r(errno, sbuf, sizeof(sbuf)));
}
}
free(buf);
return ret;
}
static int __del_trace_probe_event(int fd, struct str_node *ent)
{
char *p;
char buf[128];
int ret;
/* Convert from perf-probe event to trace-probe event */
ret = e_snprintf(buf, 128, "-:%s", ent->s);
if (ret < 0)
goto error;
p = strchr(buf + 2, ':');
if (!p) {
pr_debug("Internal error: %s should have ':' but not.\n",
ent->s);
ret = -ENOTSUP;
goto error;
}
*p = '/';
pr_debug("Writing event: %s\n", buf);
ret = write(fd, buf, strlen(buf));
if (ret < 0) {
ret = -errno;
goto error;
}
return 0;
error:
pr_warning("Failed to delete event: %s\n",
str_error_r(-ret, buf, sizeof(buf)));
return ret;
}
int probe_file__get_events(int fd, struct strfilter *filter,
struct strlist *plist)
{
struct strlist *namelist;
struct str_node *ent;
const char *p;
int ret = -ENOENT;
if (!plist)
return -EINVAL;
namelist = __probe_file__get_namelist(fd, true);
if (!namelist)
return -ENOENT;
strlist__for_each_entry(ent, namelist) {
p = strchr(ent->s, ':');
if ((p && strfilter__compare(filter, p + 1)) ||
strfilter__compare(filter, ent->s)) {
ret = strlist__add(plist, ent->s);
if (ret == -ENOMEM) {
pr_err("strlist__add failed with -ENOMEM\n");
goto out;
}
ret = 0;
}
}
out:
strlist__delete(namelist);
return ret;
}
int probe_file__del_strlist(int fd, struct strlist *namelist)
{
int ret = 0;
struct str_node *ent;
strlist__for_each_entry(ent, namelist) {
ret = __del_trace_probe_event(fd, ent);
if (ret < 0)
break;
}
return ret;
}
int probe_file__del_events(int fd, struct strfilter *filter)
{
struct strlist *namelist;
int ret;
namelist = strlist__new(NULL, NULL);
if (!namelist)
return -ENOMEM;
ret = probe_file__get_events(fd, filter, namelist);
if (ret < 0)
goto out;
ret = probe_file__del_strlist(fd, namelist);
out:
strlist__delete(namelist);
return ret;
}
/* Caller must ensure to remove this entry from list */
static void probe_cache_entry__delete(struct probe_cache_entry *entry)
{
if (entry) {
BUG_ON(!list_empty(&entry->node));
strlist__delete(entry->tevlist);
clear_perf_probe_event(&entry->pev);
zfree(&entry->spev);
free(entry);
}
}
static struct probe_cache_entry *
probe_cache_entry__new(struct perf_probe_event *pev)
{
struct probe_cache_entry *entry = zalloc(sizeof(*entry));
if (entry) {
INIT_LIST_HEAD(&entry->node);
entry->tevlist = strlist__new(NULL, NULL);
if (!entry->tevlist)
zfree(&entry);
else if (pev) {
entry->spev = synthesize_perf_probe_command(pev);
if (!entry->spev ||
perf_probe_event__copy(&entry->pev, pev) < 0) {
probe_cache_entry__delete(entry);
return NULL;
}
}
}
return entry;
}
int probe_cache_entry__get_event(struct probe_cache_entry *entry,
struct probe_trace_event **tevs)
{
struct probe_trace_event *tev;
struct str_node *node;
int ret, i;
ret = strlist__nr_entries(entry->tevlist);
if (ret > probe_conf.max_probes)
return -E2BIG;
*tevs = zalloc(ret * sizeof(*tev));
if (!*tevs)
return -ENOMEM;
i = 0;
strlist__for_each_entry(node, entry->tevlist) {
tev = &(*tevs)[i++];
ret = parse_probe_trace_command(node->s, tev);
if (ret < 0)
break;
}
return i;
}
/* For the kernel probe caches, pass target = NULL or DSO__NAME_KALLSYMS */
static int probe_cache__open(struct probe_cache *pcache, const char *target,
struct nsinfo *nsi)
{
char cpath[PATH_MAX];
char sbuildid[SBUILD_ID_SIZE];
char *dir_name = NULL;
bool is_kallsyms = false;
int ret, fd;
struct nscookie nsc;
if (target && build_id_cache__cached(target)) {
/* This is a cached buildid */
strlcpy(sbuildid, target, SBUILD_ID_SIZE);
dir_name = build_id_cache__linkname(sbuildid, NULL, 0);
goto found;
}
if (!target || !strcmp(target, DSO__NAME_KALLSYMS)) {
target = DSO__NAME_KALLSYMS;
is_kallsyms = true;
ret = sysfs__sprintf_build_id("/", sbuildid);
} else {
nsinfo__mountns_enter(nsi, &nsc);
ret = filename__sprintf_build_id(target, sbuildid);
nsinfo__mountns_exit(&nsc);
}
if (ret < 0) {
pr_debug("Failed to get build-id from %s.\n", target);
return ret;
}
/* If we have no buildid cache, make it */
if (!build_id_cache__cached(sbuildid)) {
ret = build_id_cache__add_s(sbuildid, target, nsi,
is_kallsyms, NULL);
if (ret < 0) {
pr_debug("Failed to add build-id cache: %s\n", target);
return ret;
}
}
dir_name = build_id_cache__cachedir(sbuildid, target, nsi, is_kallsyms,
false);
found:
if (!dir_name) {
pr_debug("Failed to get cache from %s\n", target);
return -ENOMEM;
}
snprintf(cpath, PATH_MAX, "%s/probes", dir_name);
fd = open(cpath, O_CREAT | O_RDWR, 0644);
if (fd < 0)
pr_debug("Failed to open cache(%d): %s\n", fd, cpath);
free(dir_name);
pcache->fd = fd;
return fd;
}
static int probe_cache__load(struct probe_cache *pcache)
{
struct probe_cache_entry *entry = NULL;
char buf[MAX_CMDLEN], *p;
int ret = 0, fddup;
FILE *fp;
fddup = dup(pcache->fd);
if (fddup < 0)
return -errno;
fp = fdopen(fddup, "r");
if (!fp) {
close(fddup);
return -EINVAL;
}
while (!feof(fp)) {
if (!fgets(buf, MAX_CMDLEN, fp))
break;
p = strchr(buf, '\n');
if (p)
*p = '\0';
/* #perf_probe_event or %sdt_event */
if (buf[0] == '#' || buf[0] == '%') {
entry = probe_cache_entry__new(NULL);
if (!entry) {
ret = -ENOMEM;
goto out;
}
if (buf[0] == '%')
entry->sdt = true;
entry->spev = strdup(buf + 1);
if (entry->spev)
ret = parse_perf_probe_command(buf + 1,
&entry->pev);
else
ret = -ENOMEM;
if (ret < 0) {
probe_cache_entry__delete(entry);
goto out;
}
list_add_tail(&entry->node, &pcache->entries);
} else { /* trace_probe_event */
if (!entry) {
ret = -EINVAL;
goto out;
}
ret = strlist__add(entry->tevlist, buf);
if (ret == -ENOMEM) {
pr_err("strlist__add failed with -ENOMEM\n");
goto out;
}
}
}
out:
fclose(fp);
return ret;
}
static struct probe_cache *probe_cache__alloc(void)
{
struct probe_cache *pcache = zalloc(sizeof(*pcache));
if (pcache) {
INIT_LIST_HEAD(&pcache->entries);
pcache->fd = -EINVAL;
}
return pcache;
}
void probe_cache__purge(struct probe_cache *pcache)
{
struct probe_cache_entry *entry, *n;
list_for_each_entry_safe(entry, n, &pcache->entries, node) {
list_del_init(&entry->node);
probe_cache_entry__delete(entry);
}
}
void probe_cache__delete(struct probe_cache *pcache)
{
if (!pcache)
return;
probe_cache__purge(pcache);
if (pcache->fd > 0)
close(pcache->fd);
free(pcache);
}
struct probe_cache *probe_cache__new(const char *target, struct nsinfo *nsi)
{
struct probe_cache *pcache = probe_cache__alloc();
int ret;
if (!pcache)
return NULL;
ret = probe_cache__open(pcache, target, nsi);
if (ret < 0) {
pr_debug("Cache open error: %d\n", ret);
goto out_err;
}
ret = probe_cache__load(pcache);
if (ret < 0) {
pr_debug("Cache read error: %d\n", ret);
goto out_err;
}
return pcache;
out_err:
probe_cache__delete(pcache);
return NULL;
}
static bool streql(const char *a, const char *b)
{
if (a == b)
return true;
if (!a || !b)
return false;
return !strcmp(a, b);
}
struct probe_cache_entry *
probe_cache__find(struct probe_cache *pcache, struct perf_probe_event *pev)
{
struct probe_cache_entry *entry = NULL;
char *cmd = synthesize_perf_probe_command(pev);
if (!cmd)
return NULL;
for_each_probe_cache_entry(entry, pcache) {
if (pev->sdt) {
if (entry->pev.event &&
streql(entry->pev.event, pev->event) &&
(!pev->group ||
streql(entry->pev.group, pev->group)))
goto found;
continue;
}
/* Hit if same event name or same command-string */
if ((pev->event &&
(streql(entry->pev.group, pev->group) &&
streql(entry->pev.event, pev->event))) ||
(!strcmp(entry->spev, cmd)))
goto found;
}
entry = NULL;
found:
free(cmd);
return entry;
}
struct probe_cache_entry *
probe_cache__find_by_name(struct probe_cache *pcache,
const char *group, const char *event)
{
struct probe_cache_entry *entry = NULL;
for_each_probe_cache_entry(entry, pcache) {
/* Hit if same event name or same command-string */
if (streql(entry->pev.group, group) &&
streql(entry->pev.event, event))
goto found;
}
entry = NULL;
found:
return entry;
}
int probe_cache__add_entry(struct probe_cache *pcache,
struct perf_probe_event *pev,
struct probe_trace_event *tevs, int ntevs)
{
struct probe_cache_entry *entry = NULL;
char *command;
int i, ret = 0;
if (!pcache || !pev || !tevs || ntevs <= 0) {
ret = -EINVAL;
goto out_err;
}
/* Remove old cache entry */
entry = probe_cache__find(pcache, pev);
if (entry) {
list_del_init(&entry->node);
probe_cache_entry__delete(entry);
}
ret = -ENOMEM;
entry = probe_cache_entry__new(pev);
if (!entry)
goto out_err;
for (i = 0; i < ntevs; i++) {
if (!tevs[i].point.symbol)
continue;
command = synthesize_probe_trace_command(&tevs[i]);
if (!command)
goto out_err;
ret = strlist__add(entry->tevlist, command);
if (ret == -ENOMEM) {
pr_err("strlist__add failed with -ENOMEM\n");
goto out_err;
}
free(command);
}
list_add_tail(&entry->node, &pcache->entries);
pr_debug("Added probe cache: %d\n", ntevs);
return 0;
out_err:
pr_debug("Failed to add probe caches\n");
probe_cache_entry__delete(entry);
return ret;
}
#ifdef HAVE_GELF_GETNOTE_SUPPORT
static unsigned long long sdt_note__get_addr(struct sdt_note *note)
{
return note->bit32 ?
(unsigned long long)note->addr.a32[SDT_NOTE_IDX_LOC] :
(unsigned long long)note->addr.a64[SDT_NOTE_IDX_LOC];
}
static unsigned long long sdt_note__get_ref_ctr_offset(struct sdt_note *note)
{
return note->bit32 ?
(unsigned long long)note->addr.a32[SDT_NOTE_IDX_REFCTR] :
(unsigned long long)note->addr.a64[SDT_NOTE_IDX_REFCTR];
}
static const char * const type_to_suffix[] = {
":s64", "", "", "", ":s32", "", ":s16", ":s8",
"", ":u8", ":u16", "", ":u32", "", "", "", ":u64"
};
/*
* Isolate the string number and convert it into a decimal value;
* this will be an index to get suffix of the uprobe name (defining
* the type)
*/
static int sdt_arg_parse_size(char *n_ptr, const char **suffix)
{
long type_idx;
type_idx = strtol(n_ptr, NULL, 10);
if (type_idx < -8 || type_idx > 8) {
pr_debug4("Failed to get a valid sdt type\n");
return -1;
}
*suffix = type_to_suffix[type_idx + 8];
return 0;
}
static int synthesize_sdt_probe_arg(struct strbuf *buf, int i, const char *arg)
{
char *op, *desc = strdup(arg), *new_op = NULL;
const char *suffix = "";
int ret = -1;
if (desc == NULL) {
pr_debug4("Allocation error\n");
return ret;
}
/*
* Argument is in N@OP format. N is size of the argument and OP is
* the actual assembly operand. N can be omitted; in that case
* argument is just OP(without @).
*/
op = strchr(desc, '@');
if (op) {
op[0] = '\0';
op++;
if (sdt_arg_parse_size(desc, &suffix))
goto error;
} else {
op = desc;
}
ret = arch_sdt_arg_parse_op(op, &new_op);
if (ret < 0)
goto error;
if (ret == SDT_ARG_VALID) {
ret = strbuf_addf(buf, " arg%d=%s%s", i + 1, new_op, suffix);
if (ret < 0)
goto error;
}
ret = 0;
error:
free(desc);
free(new_op);
return ret;
}
static char *synthesize_sdt_probe_command(struct sdt_note *note,
const char *pathname,
const char *sdtgrp)
{
struct strbuf buf;
char *ret = NULL;
int i, args_count, err;
unsigned long long ref_ctr_offset;
char *arg;
int arg_idx = 0;
if (strbuf_init(&buf, 32) < 0)
return NULL;
err = strbuf_addf(&buf, "p:%s/%s %s:0x%llx",
sdtgrp, note->name, pathname,
sdt_note__get_addr(note));
ref_ctr_offset = sdt_note__get_ref_ctr_offset(note);
if (ref_ctr_offset && err >= 0)
err = strbuf_addf(&buf, "(0x%llx)", ref_ctr_offset);
if (err < 0)
goto error;
if (!note->args)
goto out;
if (note->args) {
char **args = argv_split(note->args, &args_count);
if (args == NULL)
goto error;
for (i = 0; i < args_count; ) {
/*
* FIXUP: Arm64 ELF section '.note.stapsdt' uses string
* format "-4@[sp, NUM]" if a probe is to access data in
* the stack, e.g. below is an example for the SDT
* Arguments:
*
* Arguments: -4@[sp, 12] -4@[sp, 8] -4@[sp, 4]
*
* Since the string introduces an extra space character
* in the middle of square brackets, the argument is
* divided into two items. Fixup for this case, if an
* item contains sub string "[sp,", need to concatenate
* the two items.
*/
if (strstr(args[i], "[sp,") && (i+1) < args_count) {
err = asprintf(&arg, "%s %s", args[i], args[i+1]);
i += 2;
} else {
err = asprintf(&arg, "%s", args[i]);
i += 1;
}
/* Failed to allocate memory */
if (err < 0) {
argv_free(args);
goto error;
}
if (synthesize_sdt_probe_arg(&buf, arg_idx, arg) < 0) {
free(arg);
argv_free(args);
goto error;
}
free(arg);
arg_idx++;
}
argv_free(args);
}
out:
ret = strbuf_detach(&buf, NULL);
error:
strbuf_release(&buf);
return ret;
}
int probe_cache__scan_sdt(struct probe_cache *pcache, const char *pathname)
{
struct probe_cache_entry *entry = NULL;
struct list_head sdtlist;
struct sdt_note *note;
char *buf;
char sdtgrp[64];
int ret;
INIT_LIST_HEAD(&sdtlist);
ret = get_sdt_note_list(&sdtlist, pathname);
if (ret < 0) {
pr_debug4("Failed to get sdt note: %d\n", ret);
return ret;
}
list_for_each_entry(note, &sdtlist, note_list) {
ret = snprintf(sdtgrp, 64, "sdt_%s", note->provider);
if (ret < 0)
break;
/* Try to find same-name entry */
entry = probe_cache__find_by_name(pcache, sdtgrp, note->name);
if (!entry) {
entry = probe_cache_entry__new(NULL);
if (!entry) {
ret = -ENOMEM;
break;
}
entry->sdt = true;
ret = asprintf(&entry->spev, "%s:%s=%s", sdtgrp,
note->name, note->name);
if (ret < 0)
break;
entry->pev.event = strdup(note->name);
entry->pev.group = strdup(sdtgrp);
list_add_tail(&entry->node, &pcache->entries);
}
buf = synthesize_sdt_probe_command(note, pathname, sdtgrp);
if (!buf) {
ret = -ENOMEM;
break;
}
ret = strlist__add(entry->tevlist, buf);
free(buf);
entry = NULL;
if (ret == -ENOMEM) {
pr_err("strlist__add failed with -ENOMEM\n");
break;
}
}
if (entry) {
list_del_init(&entry->node);
probe_cache_entry__delete(entry);
}
cleanup_sdt_note_list(&sdtlist);
return ret;
}
#endif
static int probe_cache_entry__write(struct probe_cache_entry *entry, int fd)
{
struct str_node *snode;
struct stat st;
struct iovec iov[3];
const char *prefix = entry->sdt ? "%" : "#";
int ret;
/* Save stat for rollback */
ret = fstat(fd, &st);
if (ret < 0)
return ret;
pr_debug("Writing cache: %s%s\n", prefix, entry->spev);
iov[0].iov_base = (void *)prefix; iov[0].iov_len = 1;
iov[1].iov_base = entry->spev; iov[1].iov_len = strlen(entry->spev);
iov[2].iov_base = (void *)"\n"; iov[2].iov_len = 1;
ret = writev(fd, iov, 3);
if (ret < (int)iov[1].iov_len + 2)
goto rollback;
strlist__for_each_entry(snode, entry->tevlist) {
iov[0].iov_base = (void *)snode->s;
iov[0].iov_len = strlen(snode->s);
iov[1].iov_base = (void *)"\n"; iov[1].iov_len = 1;
ret = writev(fd, iov, 2);
if (ret < (int)iov[0].iov_len + 1)
goto rollback;
}
return 0;
rollback:
/* Rollback to avoid cache file corruption */
if (ret > 0)