Gitweb:
http://git.fedorahosted.org/git/?p=lvm2.git;a=commitdiff;h=6d21438d0c6426...
Commit: 6d21438d0c64267ac11b4825ad719c458b80059e
Parent: 31548e4e7c4e3ae3b2f04b7b32491617ec7181d0
Author: Zdenek Kabelac <zkabelac(a)redhat.com>
AuthorDate: Thu Sep 18 00:40:45 2014 +0200
Committer: Zdenek Kabelac <zkabelac(a)redhat.com>
CommitterDate: Thu Sep 18 00:48:06 2014 +0200
debug: catch mmap with -DDEBUG_MEMLOCK
---
lib/mm/memlock.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
make.tmpl.in | 4 +++
2 files changed, 72 insertions(+), 0 deletions(-)
diff --git a/lib/mm/memlock.c b/lib/mm/memlock.c
index 7d9a8f3..72575c5 100644
--- a/lib/mm/memlock.c
+++ b/lib/mm/memlock.c
@@ -316,6 +316,71 @@ static int _memlock_maps(struct cmd_context *cmd, lvmlock_t lock,
size_t *mstats
return ret;
}
+#ifdef DEBUG_MEMLOCK
+/*
+ * LVM is not supposed to use mmap while devices are suspended.
+ * This code causes a core dump if gets called."
+ */
+# ifdef __i386__
+# define ARCH_X86
+# endif /* __i386__ */
+# ifdef __x86_64__
+# ifndef ARCH_X86
+# define ARCH_X86
+# endif /* ARCH_X86 */
+# endif /* __x86_64__ */
+
+#endif /* DEBUG_MEMLOCK */
+
+#ifdef ARCH_X86
+static char _mmap_orig;
+static unsigned char *_mmap_addr;
+#endif
+
+static int _disable_mmap(void)
+{
+#ifdef ARCH_X86
+ volatile unsigned char *plt, *abs_addr;
+
+ if (!_mmap_addr) {
+ (void) mmap(NULL, -1, -1, -1, -1, -1);
+ plt = (unsigned char *)mmap;
+ if (plt[0] != 0xff || plt[1] != 0x25) {
+ log_error("Can't find jump entry for mmap remapping.");
+ _mmap_addr = NULL;
+ return 0;
+ }
+#ifdef __x86_64__
+ abs_addr = plt + 6 + *(int32_t *)(plt + 2);
+#endif /* __x86_64__ */
+#ifdef __i386__
+ abs_addr = *(void **)(plt + 2);
+#endif /* __i386__ */
+ _mmap_addr = *(void **)abs_addr;
+ if (mprotect((void *)((unsigned long)_mmap_addr & ~4095UL), 4096,
PROT_READ|PROT_WRITE|PROT_EXEC)) {
+ log_sys_error("mprotect", "");
+ _mmap_addr = NULL;
+ return 1;
+ }
+ _mmap_orig = *_mmap_addr;
+ }
+ *_mmap_addr = 0xcc;
+ log_debug("Remapped mmap jump entry %x to %x.", _mmap_orig, *_mmap_addr);
+#endif /* ARCH_X86 */
+ return 1;
+}
+
+static int _restore_mmap(void)
+{
+#ifdef ARCH_X86
+ if (!_mmap_addr)
+ return 0;
+ log_debug("Restoring mmap jump entry.");
+ *_mmap_addr = _mmap_orig;
+#endif /* ARCH_X86 */
+ return 1;
+}
+
/* Stop memory getting swapped out */
static void _lock_mem(struct cmd_context *cmd)
{
@@ -345,6 +410,8 @@ static void _lock_mem(struct cmd_context *cmd)
}
log_very_verbose("Locking memory");
+ if (!_disable_mmap())
+ stack;
if (!_memlock_maps(cmd, LVM_MLOCK, &_mstats))
stack;
@@ -366,6 +433,7 @@ static void _unlock_mem(struct cmd_context *cmd)
if (!_memlock_maps(cmd, LVM_MUNLOCK, &unlock_mstats))
stack;
+ _restore_mmap();
if (!_use_mlockall) {
if (close(_maps_fd))
log_sys_error("close", _procselfmaps);
diff --git a/make.tmpl.in b/make.tmpl.in
index 455e9c2..7a178ad 100644
--- a/make.tmpl.in
+++ b/make.tmpl.in
@@ -214,6 +214,10 @@ endif
#DEFS += -DDEBUG_ENFORCE_POOL_LOCKING
#DEFS += -DBOUNDS_CHECK
+# LVM is not supposed to use mmap while devices are suspended.
+# This code causes a core dump if gets called.
+#DEFS += -DDEBUG_MEMLOCK
+
#CFLAGS += -pg
#LDFLAGS += -pg