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library: improve and/or standardize 'errno' management

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With older library logic having been modified to avoid
using those potentially deadly alloc.h routines, while
improving 'errno' handling, we're ready to standardize
and enhance newlib's approach to any potential errors.

In so doing, we'll establish the following objectives:

. . . . . . . . . . . . . functions returning an 'int'
. an error will be indicated by a negative number that
is always the inverse of some well known errno.h value

. . . . . . . . . . . functions returning an 'address'
. any error will be indicated by a NULL return pointer
with the actual reason found in the formal errno value

And, when errno is manipulated directly we will strive
to do so whenever possible within those routines which
have been declared with PROCPS_EXPORT. In other words,
in the user callable functions defined in source last.

[ But, that won't always be possible. In particular, ]
[ all the 'read_failed' functions will sometimes set ]
[ 'errno' so that they can serve callers returning a ]
[ NULL or an int without duplicating a lot of logic. ]

[ Also, that includes one subordinate function which ]
[ was called by 'read_failed' in the <slabinfo> API. ]

------------------------------------------------------
Along the way, several additional miscellaneous issues
were addressed. They're listed here now for posterity.

. the '-1' return value passed outside the library was
eliminated since it would erroneously equate to -EPERM

. the stacks_fetch functions in <diskstats> and <stat>
weren't checked for their possible minus return values

. hash create was not checked in <meminfo> or <vmstat>

. fixed 'new' function faulty parm check in <slabinfo>

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner
2017-11-18 00:00:00 -05:00
committed by Craig Small
parent 7453f8719b
commit 06be33b43e
6 changed files with 262 additions and 203 deletions
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45
proc/vmstat.c
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@ -811,14 +811,14 @@ static inline int vmstat_items_check_failed (
*/
if (numitems < 1
|| (void *)items < (void *)(unsigned long)(2 * VMSTAT_logical_end))
return -1;
return 1;
for (i = 0; i < numitems; i++) {
// a vmstat_item is currently unsigned, but we'll protect our future
if (items[i] < 0)
return -1;
return 1;
if (items[i] >= VMSTAT_logical_end)
return -1;
return 1;
}
return 0;
@ -829,13 +829,14 @@ static int vmstat_make_hash_failed (
struct vmstat_info *info)
{
#define htVAL(f) e.key = STRINGIFY(f); e.data = &info->hist.new. f; \
if (!hsearch_r(e, ENTER, &ep, &info->hashtab)) return -errno;
if (!hsearch_r(e, ENTER, &ep, &info->hashtab)) return 1;
ENTRY e, *ep;
size_t n;
n = sizeof(struct vmstat_data) / sizeof(unsigned long);
// we'll follow the hsearch recommendation of an extra 25%
hcreate_r(n + (n / 4), &info->hashtab);
if (!hcreate_r(n + (n / 4), &info->hashtab))
return 1;
htVAL(allocstall)
htVAL(balloon_deflate)
@ -985,21 +986,23 @@ static int vmstat_read_failed (
if (-1 == info->vmstat_fd
&& (info->vmstat_fd = open(VMSTAT_FILE, O_RDONLY)) == -1)
return -errno;
return 1;
if (lseek(info->vmstat_fd, 0L, SEEK_SET) == -1)
return -errno;
return 1;
for (;;) {
if ((size = read(info->vmstat_fd, buf, sizeof(buf)-1)) < 0) {
if (errno == EINTR || errno == EAGAIN)
continue;
return -errno;
return 1;
}
break;
}
if (size == 0)
return -1;
if (size == 0) {
errno = EIO;
return 1;
}
buf[size] = '\0';
head = buf;
@ -1112,7 +1115,6 @@ PROCPS_EXPORT int procps_vmstat_new (
struct vmstat_info **info)
{
struct vmstat_info *p;
int rc;
if (info == NULL || *info != NULL)
return -EINVAL;
@ -1122,18 +1124,18 @@ PROCPS_EXPORT int procps_vmstat_new (
p->refcount = 1;
p->vmstat_fd = -1;
if ((rc = vmstat_make_hash_failed(p))) {
if (vmstat_make_hash_failed(p)) {
free(p);
return rc;
return -errno;
}
/* do a priming read here for the following potential benefits: |
1) ensure there will be no problems with subsequent access |
2) make delta results potentially useful, even if 1st time |
3) elimnate need for history distortions 1st time 'switch' | */
if ((rc = vmstat_read_failed(p))) {
if (vmstat_read_failed(p)) {
procps_vmstat_unref(&p);
return rc;
return -errno;
}
*info = p;
@ -1161,6 +1163,8 @@ PROCPS_EXPORT int procps_vmstat_unref (
(*info)->refcount--;
if ((*info)->refcount < 1) {
int errno_sav = errno;
if ((*info)->extents)
vmstat_extents_free_all((*info));
if ((*info)->items)
@ -1169,6 +1173,8 @@ PROCPS_EXPORT int procps_vmstat_unref (
free(*info);
*info = NULL;
errno = errno_sav;
return 0;
}
return (*info)->refcount;
@ -1184,10 +1190,12 @@ PROCPS_EXPORT struct vmstat_result *procps_vmstat_get (
static time_t sav_secs;
time_t cur_secs;
errno = EINVAL;
if (info == NULL)
return NULL;
if (item < 0 || item >= VMSTAT_logical_end)
return NULL;
errno = 0;
/* we will NOT read the vmstat file with every call - rather, we'll offer
a granularity of 1 second between reads ... */
@ -1199,9 +1207,8 @@ PROCPS_EXPORT struct vmstat_result *procps_vmstat_get (
}
info->get_this.item = item;
// with 'get', we must NOT honor the usual 'noop' guarantee
// if (item > VMSTAT_noop)
info->get_this.result.ul_int = 0;
// with 'get', we must NOT honor the usual 'noop' guarantee
info->get_this.result.ul_int = 0;
Item_table[item].setsfunc(&info->get_this, &info->hist);
return &info->get_this;
@ -1220,10 +1227,12 @@ PROCPS_EXPORT struct vmstat_stack *procps_vmstat_select (
enum vmstat_item *items,
int numitems)
{
errno = EINVAL;
if (info == NULL || items == NULL)
return NULL;
if (vmstat_items_check_failed(numitems, items))
return NULL;
errno = 0;
/* is this the first time or have things changed since we were last called?
if so, gotta' redo all of our stacks stuff ... */