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imgact_binmisc: abstract away the list lock (NFC)

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This module handles relatively few execs (initial qemu-user-static, then
qemu-user-static handles exec'ing itself for binaries it's already running),
but all execs pay the price of at least taking the relatively expensive
sx/slock to check for a match when this module is loaded. Future work will
almost certainly swap this out for another lock, perhaps an rmslock.

The RLOCK/WLOCK phrasing was chosen based on what the callers are really
wanting, rather than using the verbiage typically appropriate for an sx.

MFC after:	1 week
This commit is contained in:
Kyle Evans 2020-11-07 05:10:46 +00:00
parent 3701068b5d
commit 2192cd125f
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=367444
1 changed files with 36 additions and 27 deletions
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63
sys/kern/imgact_binmisc.c
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@ -98,6 +98,16 @@ static int interp_list_entry_count;
static struct sx interp_list_sx; static struct sx interp_list_sx;
#define INTERP_LIST_WLOCK() sx_xlock(&interp_list_sx)
#define INTERP_LIST_RLOCK() sx_slock(&interp_list_sx)
#define INTERP_LIST_WUNLOCK() sx_xunlock(&interp_list_sx)
#define INTERP_LIST_RUNLOCK() sx_sunlock(&interp_list_sx)
#define INTERP_LIST_LOCK_INIT() sx_init(&interp_list_sx, KMOD_NAME)
#define INTERP_LIST_LOCK_DESTROY() sx_destroy(&interp_list_sx)
#define INTERP_LIST_ASSERT_LOCKED() sx_assert(&interp_list_sx, SA_LOCKED)
/* /*
* Populate the entry with the information about the interpreter. * Populate the entry with the information about the interpreter.
*/ */
@ -198,7 +208,7 @@ imgact_binmisc_find_entry(char *name)
{ {
imgact_binmisc_entry_t *ibe; imgact_binmisc_entry_t *ibe;
sx_assert(&interp_list_sx, SA_LOCKED); INTERP_LIST_ASSERT_LOCKED();
SLIST_FOREACH(ibe, &interpreter_list, link) { SLIST_FOREACH(ibe, &interpreter_list, link) {
if (strncmp(name, ibe->ibe_name, IBE_NAME_MAX) == 0) if (strncmp(name, ibe->ibe_name, IBE_NAME_MAX) == 0)
@ -256,9 +266,9 @@ imgact_binmisc_add_entry(ximgact_binmisc_entry_t *xbe)
} }
} }
sx_xlock(&interp_list_sx); INTERP_LIST_WLOCK();
if (imgact_binmisc_find_entry(xbe->xbe_name) != NULL) { if (imgact_binmisc_find_entry(xbe->xbe_name) != NULL) {
sx_xunlock(&interp_list_sx); INTERP_LIST_WUNLOCK();
return (EEXIST); return (EEXIST);
} }
@ -267,7 +277,7 @@ imgact_binmisc_add_entry(ximgact_binmisc_entry_t *xbe)
SLIST_INSERT_HEAD(&interpreter_list, ibe, link); SLIST_INSERT_HEAD(&interpreter_list, ibe, link);
interp_list_entry_count++; interp_list_entry_count++;
sx_xunlock(&interp_list_sx); INTERP_LIST_WUNLOCK();
return (0); return (0);
} }
@ -281,14 +291,14 @@ imgact_binmisc_remove_entry(char *name)
{ {
imgact_binmisc_entry_t *ibe; imgact_binmisc_entry_t *ibe;
sx_xlock(&interp_list_sx); INTERP_LIST_WLOCK();
if ((ibe = imgact_binmisc_find_entry(name)) == NULL) { if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
sx_xunlock(&interp_list_sx); INTERP_LIST_WUNLOCK();
return (ENOENT); return (ENOENT);
} }
SLIST_REMOVE(&interpreter_list, ibe, imgact_binmisc_entry, link); SLIST_REMOVE(&interpreter_list, ibe, imgact_binmisc_entry, link);
interp_list_entry_count--; interp_list_entry_count--;
sx_xunlock(&interp_list_sx); INTERP_LIST_WUNLOCK();
imgact_binmisc_destroy_entry(ibe); imgact_binmisc_destroy_entry(ibe);
@ -304,14 +314,14 @@ imgact_binmisc_disable_entry(char *name)
{ {
imgact_binmisc_entry_t *ibe; imgact_binmisc_entry_t *ibe;
sx_xlock(&interp_list_sx); INTERP_LIST_WLOCK();
if ((ibe = imgact_binmisc_find_entry(name)) == NULL) { if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
sx_xunlock(&interp_list_sx); INTERP_LIST_WUNLOCK();
return (ENOENT); return (ENOENT);
} }
ibe->ibe_flags &= ~IBF_ENABLED; ibe->ibe_flags &= ~IBF_ENABLED;
sx_xunlock(&interp_list_sx); INTERP_LIST_WUNLOCK();
return (0); return (0);
} }
@ -325,14 +335,14 @@ imgact_binmisc_enable_entry(char *name)
{ {
imgact_binmisc_entry_t *ibe; imgact_binmisc_entry_t *ibe;
sx_xlock(&interp_list_sx); INTERP_LIST_WLOCK();
if ((ibe = imgact_binmisc_find_entry(name)) == NULL) { if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
sx_xunlock(&interp_list_sx); INTERP_LIST_WUNLOCK();
return (ENOENT); return (ENOENT);
} }
ibe->ibe_flags |= IBF_ENABLED; ibe->ibe_flags |= IBF_ENABLED;
sx_xunlock(&interp_list_sx); INTERP_LIST_WUNLOCK();
return (0); return (0);
} }
@ -343,8 +353,7 @@ imgact_binmisc_populate_xbe(ximgact_binmisc_entry_t *xbe,
{ {
uint32_t i; uint32_t i;
sx_assert(&interp_list_sx, SA_LOCKED); INTERP_LIST_ASSERT_LOCKED();
memset(xbe, 0, sizeof(*xbe)); memset(xbe, 0, sizeof(*xbe));
strlcpy(xbe->xbe_name, ibe->ibe_name, IBE_NAME_MAX); strlcpy(xbe->xbe_name, ibe->ibe_name, IBE_NAME_MAX);
@ -375,14 +384,14 @@ imgact_binmisc_lookup_entry(char *name, ximgact_binmisc_entry_t *xbe)
imgact_binmisc_entry_t *ibe; imgact_binmisc_entry_t *ibe;
int error = 0; int error = 0;
sx_slock(&interp_list_sx); INTERP_LIST_RLOCK();
if ((ibe = imgact_binmisc_find_entry(name)) == NULL) { if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
sx_sunlock(&interp_list_sx); INTERP_LIST_RUNLOCK();
return (ENOENT); return (ENOENT);
} }
error = imgact_binmisc_populate_xbe(xbe, ibe); error = imgact_binmisc_populate_xbe(xbe, ibe);
sx_sunlock(&interp_list_sx); INTERP_LIST_RUNLOCK();
return (error); return (error);
} }
@ -397,7 +406,7 @@ imgact_binmisc_get_all_entries(struct sysctl_req *req)
imgact_binmisc_entry_t *ibe; imgact_binmisc_entry_t *ibe;
int error = 0, count; int error = 0, count;
sx_slock(&interp_list_sx); INTERP_LIST_RLOCK();
count = interp_list_entry_count; count = interp_list_entry_count;
xbe = malloc(sizeof(*xbe) * count, M_BINMISC, M_WAITOK|M_ZERO); xbe = malloc(sizeof(*xbe) * count, M_BINMISC, M_WAITOK|M_ZERO);
@ -407,7 +416,7 @@ imgact_binmisc_get_all_entries(struct sysctl_req *req)
if (error) if (error)
break; break;
} }
sx_sunlock(&interp_list_sx); INTERP_LIST_RUNLOCK();
if (!error) if (!error)
error = SYSCTL_OUT(req, xbe, sizeof(*xbe) * count); error = SYSCTL_OUT(req, xbe, sizeof(*xbe) * count);
@ -546,7 +555,7 @@ imgact_binmisc_find_interpreter(const char *image_header)
int i; int i;
size_t sz; size_t sz;
sx_assert(&interp_list_sx, SA_LOCKED); INTERP_LIST_ASSERT_LOCKED();
SLIST_FOREACH(ibe, &interpreter_list, link) { SLIST_FOREACH(ibe, &interpreter_list, link) {
if (!(IBF_ENABLED & ibe->ibe_flags)) if (!(IBF_ENABLED & ibe->ibe_flags))
@ -584,7 +593,7 @@ imgact_binmisc_exec(struct image_params *imgp)
sname = NULL; sname = NULL;
/* Do we have an interpreter for the given image header? */ /* Do we have an interpreter for the given image header? */
sx_slock(&interp_list_sx); INTERP_LIST_RLOCK();
if ((ibe = imgact_binmisc_find_interpreter(image_header)) == NULL) { if ((ibe = imgact_binmisc_find_interpreter(image_header)) == NULL) {
error = -1; error = -1;
goto done; goto done;
@ -702,7 +711,7 @@ imgact_binmisc_exec(struct image_params *imgp)
imgp->interpreter_name = imgp->args->begin_argv; imgp->interpreter_name = imgp->args->begin_argv;
done: done:
sx_sunlock(&interp_list_sx); INTERP_LIST_RUNLOCK();
if (sname) if (sname)
sbuf_delete(sname); sbuf_delete(sname);
return (error); return (error);
@ -712,7 +721,7 @@ static void
imgact_binmisc_init(void *arg) imgact_binmisc_init(void *arg)
{ {
sx_init(&interp_list_sx, KMOD_NAME); INTERP_LIST_LOCK_INIT();
} }
static void static void
@ -721,15 +730,15 @@ imgact_binmisc_fini(void *arg)
imgact_binmisc_entry_t *ibe, *ibe_tmp; imgact_binmisc_entry_t *ibe, *ibe_tmp;
/* Free all the interpreters. */ /* Free all the interpreters. */
sx_xlock(&interp_list_sx); INTERP_LIST_WLOCK();
SLIST_FOREACH_SAFE(ibe, &interpreter_list, link, ibe_tmp) { SLIST_FOREACH_SAFE(ibe, &interpreter_list, link, ibe_tmp) {
SLIST_REMOVE(&interpreter_list, ibe, imgact_binmisc_entry, SLIST_REMOVE(&interpreter_list, ibe, imgact_binmisc_entry,
link); link);
imgact_binmisc_destroy_entry(ibe); imgact_binmisc_destroy_entry(ibe);
} }
sx_xunlock(&interp_list_sx); INTERP_LIST_WUNLOCK();
sx_destroy(&interp_list_sx); INTERP_LIST_LOCK_DESTROY();
} }
SYSINIT(imgact_binmisc, SI_SUB_EXEC, SI_ORDER_MIDDLE, imgact_binmisc_init, SYSINIT(imgact_binmisc, SI_SUB_EXEC, SI_ORDER_MIDDLE, imgact_binmisc_init,