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debug: catch mmap with -DDEBUG_MEMLOCK

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This commit is contained in:
Zdenek Kabelac 2014-09-18 00:40:45 +02:00
parent 31548e4e7c
commit 6d21438d0c
2 changed files with 72 additions and 0 deletions
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68
lib/mm/memlock.c
View File

@ -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);

4
make.tmpl.in
View File

@ -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