From 7810b4c37c7d03772215102a8db5e84d29fe2221 Mon Sep 17 00:00:00 2001
From: Ben Gamari <ben@smart-cactus.org>
Date: Fri, 8 Mar 2024 11:58:58 -0500
Subject: [PATCH] rts/linker: Don't unload native objects when dlinfo isn't
available
To do so is unsafe as we have no way of identifying references to
symbols provided by the object.
Fixes #24513. Fixes #23993.
---
rts/CheckUnload.c | 15 +++++++++++----
rts/Linker.c | 2 ++
rts/LinkerInternals.h | 10 +++++++++-
rts/linker/Elf.c | 4 ++++
.../linker_unload_multiple_objs.c | 2 +-
5 files changed, 27 insertions(+), 6 deletions(-)
diff --git a/rts/CheckUnload.c b/rts/CheckUnload.c
index e7e04bcd388d..e787f2d68afb 100644
--- a/rts/CheckUnload.c
+++ b/rts/CheckUnload.c
@@ -492,8 +492,6 @@ void checkUnload(void)
next = oc->next;
ASSERT(oc->status == OBJECT_UNLOADED);
- removeOCSectionIndices(s_indices, oc);
-
// Symbols should be removed by unloadObj_.
// NB (osa): If this assertion doesn't hold then freeObjectCode below
// will corrupt symhash as keys of that table live in ObjectCodes. If
@@ -501,8 +499,17 @@ void checkUnload(void)
// RTS) then it's probably because this assertion did not hold.
ASSERT(oc->symbols == NULL);
- freeObjectCode(oc);
- n_unloaded_objects -= 1;
+ if (oc->unloadable) {
+ removeOCSectionIndices(s_indices, oc);
+ freeObjectCode(oc);
+ n_unloaded_objects -= 1;
+ } else {
+ // If we don't have enough information to
+ // accurately determine the reachability of
+ // the object then hold onto it.
+ oc->next = objects;
+ objects = oc;
+ }
}
old_objects = NULL;
diff --git a/rts/Linker.c b/rts/Linker.c
index 66fbf7907028..64f54cf0eaa2 100644
--- a/rts/Linker.c
+++ b/rts/Linker.c
@@ -1385,6 +1385,8 @@ mkOc( ObjectType type, pathchar *path, char *image, int imageSize,
oc->prev = NULL;
oc->next_loaded_object = NULL;
oc->mark = object_code_mark_bit;
+ /* this will get cleared by the caller if object is not safely unloadable */
+ oc->unloadable = true;
oc->dependencies = allocHashSet();
#if defined(NEED_M32)
diff --git a/rts/LinkerInternals.h b/rts/LinkerInternals.h
index 271611a249da..cbfd3ef686c3 100644
--- a/rts/LinkerInternals.h
+++ b/rts/LinkerInternals.h
@@ -313,8 +313,14 @@ struct _ObjectCode {
struct _ObjectCode *next_loaded_object;
// Mark bit
+ // N.B. This is a full word as we CAS it.
StgWord mark;
+ // Can this object be safely unloaded? Not true for
+ // dynamic objects when dlinfo is not available as
+ // we cannot determine liveness.
+ bool unloadable;
+
// Set of dependencies (ObjectCode*) of the object file. Traverse
// dependencies using `iterHashTable`.
//
@@ -376,7 +382,9 @@ struct _ObjectCode {
/* handle returned from dlopen */
void *dlopen_handle;
- /* virtual memory ranges of loaded code */
+ /* virtual memory ranges of loaded code. NULL if no range information is
+ * available (e.g. if dlinfo is unavailable on the current platform).
+ */
NativeCodeRange *nc_ranges;
};
diff --git a/rts/linker/Elf.c b/rts/linker/Elf.c
index b0acfcfb5469..f668cfe31338 100644
--- a/rts/linker/Elf.c
+++ b/rts/linker/Elf.c
@@ -2186,6 +2186,10 @@ void * loadNativeObj_ELF (pathchar *path, char **errmsg)
copyErrmsg(errmsg, "dl_iterate_phdr failed to find obj");
goto dl_iterate_phdr_fail;
}
+ nc->unloadable = true;
+#else
+ nc->nc_ranges = NULL;
+ nc->unloadable = false;
#endif /* defined (HAVE_DLINFO) */
insertOCSectionIndices(nc);
diff --git a/testsuite/tests/rts/linker/unload_multiple_objs/linker_unload_multiple_objs.c b/testsuite/tests/rts/linker/unload_multiple_objs/linker_unload_multiple_objs.c
index b076809a6b15..910663caa57a 100644
--- a/testsuite/tests/rts/linker/unload_multiple_objs/linker_unload_multiple_objs.c
+++ b/testsuite/tests/rts/linker/unload_multiple_objs/linker_unload_multiple_objs.c
@@ -64,7 +64,7 @@ void check_object_freed(char *obj_path) {
OStatus st;
st = getObjectLoadStatus(toPathchar(obj_path));
if (st != OBJECT_NOT_LOADED) {
- errorBelch("object %s status != OBJECT_NOT_LOADED", obj_path);
+ errorBelch("object %s status != OBJECT_NOT_LOADED, is %d instead", obj_path, st);
exit(1);
}
}
--
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