Add musl.dl.debug.dlclose param for debugging use-after-dlclose issues

If musl.dl.debug.dlclose is enabled, the sections of dlclosed library will not be unmapped.
Instead the mmap area will be set to PROT_NONE. If the program run into the dlclosed library
the crash log would contain the library info rather than a unmapped pc.
The param can be set by following cmdline:
param set musl.dl.debug.dlclose enable

Issue: I69Y3Z
Test: backtrace_local_test
Signed-off-by: NMapleStory <zengzhi5@huawei.com>

porting/linux/user/ldso/dynlink.c

@@ -1199,12 +1199,21 @@ static void unmap_library(struct dso *dso)
 		for (i=0; i<dso->loadmap->nsegs; i++) {
 			if (!dso->loadmap->segs[i].p_memsz)
 				continue;
-			munmap((void *)dso->loadmap->segs[i].addr,
-				dso->loadmap->segs[i].p_memsz);
+			if (!is_dlclose_debug_enable()) {
+				munmap((void *)dso->loadmap->segs[i].addr,
+					dso->loadmap->segs[i].p_memsz);
+			} else {
+				(void)mprotect((void *)dso->loadmap->segs[i].addr,
+					dso->loadmap->segs[i].p_memsz, PROT_NONE);
+			}
 		}
 		internal_free(dso->loadmap);
 	} else if (dso->map && dso->map_len) {
-		munmap(dso->map, dso->map_len);
+		if (!is_dlclose_debug_enable()) {
+			munmap(dso->map, dso->map_len);
+		} else {
+			mprotect(dso->map, dso->map_len, PROT_NONE);
+		}
 	}
 }
 

porting/linux/user/ldso/ld_log.c

@@ -16,6 +16,7 @@
 #include "ld_log.h"
 
 static bool ld_log_enable = false;
+static bool ld_dlclose_debug = false;
 
 #ifdef OHOS_ENABLE_PARAMETER
 #include <fcntl.h>
@@ -73,11 +74,21 @@ static bool get_ld_log_value()
     }
     return (get_bool_sysparam(app_param_handle) || get_bool_sysparam(all_param_handle));
 }
+
+static bool get_ld_debug_dlclose_value()
+{
+    static CachedHandle param_handle = NULL;
+    if (param_handle == NULL) {
+        param_handle = CachedParameterCreate("musl.ld.debug.dlclose", "false");
+    }
+    return get_bool_sysparam(param_handle);
+}
 #endif
 
 void ld_log_reset()
 {
 #if (defined(OHOS_ENABLE_PARAMETER))
+    ld_dlclose_debug = get_ld_debug_dlclose_value();
     if (!is_musl_log_enable()) {
         ld_log_enable = false;
         return;
@@ -92,3 +103,8 @@ bool get_ld_log_enable()
 {
     return ld_log_enable;
 }
+
+bool is_dlclose_debug_enable()
+{
+    return ld_dlclose_debug;
+}

porting/linux/user/ldso/ld_log.h

@@ -34,6 +34,8 @@ extern "C" {
 hidden bool get_ld_log_enable();
 hidden void ld_log_reset();
 
+hidden bool is_dlclose_debug_enable();
+
 #if ((LD_LOG_LEVEL & LD_LOG_ERROR) && (defined(OHOS_ENABLE_PARAMETER) || defined(ENABLE_MUSL_LOG)))
 #define LD_LOGE(...) if (get_ld_log_enable()) {   \
     (void)HiLogAdapterPrint(MUSL_LOG_TYPE, LOG_ERROR, MUSL_LOG_DOMAIN, LD_LOG_TAG, __VA_ARGS__);    \