Module Name: src
Committed By: riastradh
Date: Thu Jun 3 09:22:47 UTC 2021
Modified Files:
src/sys/kern: kern_ksyms.c
Log Message:
ksyms(4): Allow multiple concurrent opens of /dev/ksyms.
First one takes a snapshot; others all agree with the snapshot.
Previously this code path was just broken (could fail horribly if
modules were unloaded after one of the opens is closed), so I just
blocked it off in an earlier commit, but that broke crash(8). So
let's continue allowing multiple opens seeing the same snapshot, but
without the horrible bugs.
To generate a diff of this commit:
cvs rdiff -u -r1.96 -r1.97 src/sys/kern/kern_ksyms.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/kern_ksyms.c
diff -u src/sys/kern/kern_ksyms.c:1.96 src/sys/kern/kern_ksyms.c:1.97
--- src/sys/kern/kern_ksyms.c:1.96 Thu Jun 3 01:00:24 2021
+++ src/sys/kern/kern_ksyms.c Thu Jun 3 09:22:47 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_ksyms.c,v 1.96 2021/06/03 01:00:24 riastradh Exp $ */
+/* $NetBSD: kern_ksyms.c,v 1.97 2021/06/03 09:22:47 riastradh Exp $ */
/*-
* Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -73,7 +73,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_ksyms.c,v 1.96 2021/06/03 01:00:24 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_ksyms.c,v 1.97 2021/06/03 09:22:47 riastradh Exp $");
#if defined(_KERNEL) && defined(_KERNEL_OPT)
#include "opt_copy_symtab.h"
@@ -112,7 +112,7 @@ static uint32_t *ksyms_nmap = NULL;
#endif
static int ksyms_maxlen;
-static bool ksyms_isopen;
+static uint64_t ksyms_opencnt;
static struct ksyms_symtab *ksyms_last_snapshot;
static bool ksyms_initted;
static bool ksyms_loaded;
@@ -791,7 +791,7 @@ ksyms_modunload(const char *name)
continue;
st->sd_gone = true;
ksyms_sizes_calc();
- if (!ksyms_isopen) {
+ if (ksyms_opencnt == 0) {
/*
* Ensure ddb never witnesses an inconsistent
* state of the queue, unless memory is so
@@ -1004,14 +1004,12 @@ ksymsopen(dev_t dev, int oflags, int dev
return ENXIO;
/*
- * Create a "snapshot" of the kernel symbol table. Setting
- * ksyms_isopen will prevent symbol tables from being freed.
+ * Create a "snapshot" of the kernel symbol table. Bumping
+ * ksyms_opencnt will prevent symbol tables from being freed.
*/
mutex_enter(&ksyms_lock);
- if (ksyms_isopen) {
- mutex_exit(&ksyms_lock);
- return EBUSY;
- }
+ if (ksyms_opencnt++)
+ goto out;
ksyms_hdr.kh_shdr[SYMTAB].sh_size = ksyms_symsz;
ksyms_hdr.kh_shdr[SYMTAB].sh_info = ksyms_symsz / sizeof(Elf_Sym);
ksyms_hdr.kh_shdr[STRTAB].sh_offset = ksyms_symsz +
@@ -1020,9 +1018,8 @@ ksymsopen(dev_t dev, int oflags, int dev
ksyms_hdr.kh_shdr[SHCTF].sh_offset = ksyms_strsz +
ksyms_hdr.kh_shdr[STRTAB].sh_offset;
ksyms_hdr.kh_shdr[SHCTF].sh_size = ksyms_ctfsz;
- ksyms_isopen = true;
ksyms_last_snapshot = TAILQ_LAST(&ksyms_symtabs, ksyms_symtab_queue);
- mutex_exit(&ksyms_lock);
+out: mutex_exit(&ksyms_lock);
return 0;
}
@@ -1036,7 +1033,8 @@ ksymsclose(dev_t dev, int oflags, int de
/* Discard references to symbol tables. */
mutex_enter(&ksyms_lock);
- ksyms_isopen = false;
+ if (--ksyms_opencnt)
+ goto out;
ksyms_last_snapshot = NULL;
TAILQ_FOREACH_SAFE(st, &ksyms_symtabs, sd_queue, next) {
if (st->sd_gone) {
@@ -1053,7 +1051,7 @@ ksymsclose(dev_t dev, int oflags, int de
}
if (!TAILQ_EMPTY(&to_free))
ksyms_sizes_calc();
- mutex_exit(&ksyms_lock);
+out: mutex_exit(&ksyms_lock);
TAILQ_FOREACH_SAFE(st, &to_free, sd_queue, next) {
kmem_free(st->sd_nmap, st->sd_nmapsize * sizeof(uint32_t));
