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Count number of threads that enter and leave dynamically registered

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syscalls. On the dynamic syscall deregistration, wait until all
threads leave the syscall code. This somewhat increases the safety
of the loadable modules unloading.

Reviewed by:	jhb
Tested by:	pho
MFC after:	1 month
This commit is contained in:
Konstantin Belousov 2010-06-28 18:06:46 +00:00
parent dc2db34f42
commit 153ac44cf6
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=209579
6 changed files with 101 additions and 29 deletions
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20
sys/compat/freebsd32/syscalls.master
View file

@ -386,16 +386,16 @@
;
; The following are reserved for loadable syscalls
;
210 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
211 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
212 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
213 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
214 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
215 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
216 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
217 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
218 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
219 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
210 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
211 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
212 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
213 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
214 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
215 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
216 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
217 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
218 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
219 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
;
; The following were introduced with NetBSD/4.4Lite-2

56
sys/kern/kern_syscalls.c
View file

@ -28,12 +28,15 @@
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/module.h>
#include <sys/sx.h>
#include <sys/syscall.h>
#include <sys/sysent.h>
#include <sys/sysproto.h>
#include <sys/systm.h>
#include <machine/atomic.h>
/*
* Acts like "nosys" but can be identified in sysent for dynamic call
@ -55,6 +58,51 @@ lkmressys(struct thread *td, struct nosys_args *args)
return (nosys(td, args));
}
static void
syscall_thread_drain(struct sysent *se)
{
u_int32_t cnt, oldcnt;
do {
oldcnt = se->sy_thrcnt;
KASSERT((oldcnt & SY_THR_STATIC) == 0,
("drain on static syscall"));
cnt = oldcnt | SY_THR_DRAINING;
} while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
while (atomic_cmpset_32(&se->sy_thrcnt, SY_THR_DRAINING,
SY_THR_ABSENT) == 0)
pause("scdrn", hz/2);
}
int
syscall_thread_enter(struct thread *td, struct sysent *se)
{
u_int32_t cnt, oldcnt;
do {
oldcnt = se->sy_thrcnt;
if ((oldcnt & SY_THR_STATIC) != 0)
return (0);
if ((oldcnt & (SY_THR_DRAINING | SY_THR_ABSENT)) != 0)
return (ENOSYS);
cnt = oldcnt + SY_THR_INCR;
} while (atomic_cmpset_acq_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
return (0);
}
void
syscall_thread_exit(struct thread *td, struct sysent *se)
{
u_int32_t cnt, oldcnt;
do {
oldcnt = se->sy_thrcnt;
if ((oldcnt & SY_THR_STATIC) != 0)
return;
cnt = oldcnt - SY_THR_INCR;
} while (atomic_cmpset_rel_32(&se->sy_thrcnt, oldcnt, cnt) == 0);
}
int
syscall_register(int *offset, struct sysent *new_sysent,
struct sysent *old_sysent)
@ -74,8 +122,12 @@ syscall_register(int *offset, struct sysent *new_sysent,
sysent[*offset].sy_call != (sy_call_t *)lkmressys)
return (EEXIST);
KASSERT(sysent[*offset].sy_thrcnt == SY_THR_ABSENT,
("dynamic syscall is not protected"));
*old_sysent = sysent[*offset];
new_sysent->sy_thrcnt = SY_THR_ABSENT;
sysent[*offset] = *new_sysent;
atomic_store_rel_32(&sysent[*offset].sy_thrcnt, 0);
return (0);
}
@ -83,8 +135,10 @@ int
syscall_deregister(int *offset, struct sysent *old_sysent)
{
if (*offset)
if (*offset) {
syscall_thread_drain(&sysent[*offset]);
sysent[*offset] = *old_sysent;
}
return (0);
}

18
sys/kern/makesyscalls.sh
View file

@ -253,6 +253,10 @@ s/\$//g
f=4 # toss number, type, audit event
argc= 0;
argssize = "0"
thr_flag = "SY_THR_STATIC"
if (flag("NOTSTATIC")) {
thr_flag = "SY_THR_ABSENT"
}
if ($NF != "}") {
funcalias=$(NF-2)
argalias=$(NF-1)
@ -401,10 +405,10 @@ s/\$//g
printf("\t{ %s, (sy_call_t *)", argssize) > sysent
column = 8 + 2 + length(argssize) + 15
if (flag("NOSTD")) {
printf("%s },", "lkmressys, AUE_NULL, NULL, 0, 0, 0") > sysent
printf("%s },", "lkmressys, AUE_NULL, NULL, 0, 0, 0, SY_THR_ABSENT") > sysent
column = column + length("lkmressys") + length("AUE_NULL") + 3
} else {
printf("%s, %s, NULL, 0, 0, %s },", funcname, auditev, flags) > sysent
printf("%s, %s, NULL, 0, 0, %s, %s },", funcname, auditev, flags, thr_flag) > sysent
column = column + length(funcname) + length(auditev) + length(flags) + 3
}
align_sysent_comment(column)
@ -472,13 +476,13 @@ s/\$//g
prefix, funcname, auditev) > sysaue
}
if (flag("NOSTD")) {
printf("\t{ %s, (sy_call_t *)%s, %s, NULL, 0, 0, 0 },",
printf("\t{ %s, (sy_call_t *)%s, %s, NULL, 0, 0, 0, SY_THR_ABSENT },",
"0", "lkmressys", "AUE_NULL") > sysent
align_sysent_comment(8 + 2 + length("0") + 15 + \
length("lkmressys") + length("AUE_NULL") + 3)
} else {
printf("\t{ %s(%s,%s), %s, NULL, 0, 0, %s },",
wrap, argssize, funcname, auditev, flags) > sysent
printf("\t{ %s(%s,%s), %s, NULL, 0, 0, %s, %s },",
wrap, argssize, funcname, auditev, flags, thr_flag) > sysent
align_sysent_comment(8 + 9 + length(argssize) + 1 + \
length(funcname) + length(auditev) + \
length(flags) + 4)
@ -498,7 +502,7 @@ s/\$//g
next
}
type("OBSOL") {
printf("\t{ 0, (sy_call_t *)nosys, AUE_NULL, NULL, 0, 0, 0 },") > sysent
printf("\t{ 0, (sy_call_t *)nosys, AUE_NULL, NULL, 0, 0, 0, SY_THR_ABSENT },") > sysent
align_sysent_comment(34)
printf("/* %d = obsolete %s */\n", syscall, comment) > sysent
printf("\t\"obs_%s\",\t\t\t/* %d = obsolete %s */\n",
@ -509,7 +513,7 @@ s/\$//g
next
}
type("UNIMPL") {
printf("\t{ 0, (sy_call_t *)nosys, AUE_NULL, NULL, 0, 0, 0 },\t\t\t/* %d = %s */\n",
printf("\t{ 0, (sy_call_t *)nosys, AUE_NULL, NULL, 0, 0, 0, SY_THR_ABSENT },\t\t\t/* %d = %s */\n",
syscall, comment) > sysent
printf("\t\"#%d\",\t\t\t/* %d = %s */\n",
syscall, syscall, comment) > sysnames

4
sys/kern/subr_trap.c
View file

@ -298,6 +298,9 @@ syscallenter(struct thread *td, struct syscall_args *sa)
if (error != 0)
goto retval;
}
error = syscall_thread_enter(td, sa->callp);
if (error != 0)
goto retval;
#ifdef KDTRACE_HOOKS
/*
@ -327,6 +330,7 @@ syscallenter(struct thread *td, struct syscall_args *sa)
(*systrace_probe_func)(sa->callp->sy_return, sa->code,
sa->callp, sa->args);
#endif
syscall_thread_exit(td, sa->callp);
CTR4(KTR_SYSC, "syscall: p=%p error=%d return %#lx %#lx",
p, error, td->td_retval[0], td->td_retval[1]);
}

22
sys/kern/syscalls.master
View file

@ -40,7 +40,7 @@
; NOPROTO same as STD except do not create structure or
; function prototype in sys/sysproto.h. Does add a
; definition to syscall.h besides adding a sysent.
; NONSTATIC syscall is loadable
;
; Please copy any additions and changes to the following compatability tables:
; sys/compat/freebsd32/syscalls.master
@ -403,16 +403,16 @@
;
; The following are reserved for loadable syscalls
;
210 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
211 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
212 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
213 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
214 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
215 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
216 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
217 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
218 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
219 AUE_NULL NODEF lkmnosys lkmnosys nosys_args int
210 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
211 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
212 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
213 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
214 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
215 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
216 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
217 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
218 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
219 AUE_NULL NODEF|NOTSTATIC lkmnosys lkmnosys nosys_args int
;
; The following were introduced with NetBSD/4.4Lite-2

10
sys/sys/sysent.h
View file

@ -61,8 +61,15 @@ struct sysent { /* system call table */
u_int32_t sy_entry; /* DTrace entry ID for systrace. */
u_int32_t sy_return; /* DTrace return ID for systrace. */
u_int32_t sy_flags; /* General flags for system calls. */
u_int32_t sy_thrcnt;
};
#define SY_THR_FLAGMASK 0x7
#define SY_THR_STATIC 0x1
#define SY_THR_DRAINING 0x2
#define SY_THR_ABSENT 0x4
#define SY_THR_INCR 0x8
struct image_params;
struct __sigset;
struct syscall_args;
@ -211,6 +218,9 @@ struct nosys_args;
int lkmnosys(struct thread *, struct nosys_args *);
int lkmressys(struct thread *, struct nosys_args *);
int syscall_thread_enter(struct thread *td, struct sysent *se);
void syscall_thread_exit(struct thread *td, struct sysent *se);
#endif /* _KERNEL */
#endif /* !_SYS_SYSENT_H_ */