On 04/03/2021 07:47, Johannes Berg wrote:
On Thu, 2021-03-04 at 14:38 +0900, Hajime Tazaki wrote:
Now, I don't know how to fix it (short of changing your nsswitch
configuration) - maybe we could somehow rename sem_init()? Or maybe we
can somehow give the kernel binary a lower symbol resolution than the
libc/libpthread.
objcopy (from binutils) can localize symbols (i.e., objcopy -L
sem_init $orig_file $new_file). It also does renaming symbols. But
not sure this is the ideal solution.
Yes, we started thinking about it but it was too late at night when I
replied ...
I think there's basically a way to have an external list of symbols to
export, for symbol versioning, that we could/should use to basically not
export any of the kernel symbols out to libs.
How does UML handle symbol conflicts between userspace code and Linux
kernel (like this case sem_init) ? AFAIK, libnl has a same symbol as
Linux kernel (genlmsg_put) and others can possibly do as well.
I fear it doesn't?
Let's assume it does not, and try to fix this by de-conflicting the symbol.
For the time being, also, let's aim for a Debian specific patch just to go into their
"patches" dir for build so that UML is not dropped out of the release.
This should make all internal uses of sem_init be um_sem_init in the actual
object files. I will chase the issue of it picking up glibc memcpy separately.
Upon close inspection it looks like a different issue - it is in the other
direction (picking a dynamic symbol instead of the one from the tree). I spent
all day chasing it today and I cannot reproduce it. At the same time it was
reproducible yesterday without any problems :(
Ritesh, can you give the following a spin - it renames sem_init as um_sem_init
for UML only?
diff --git a/ipc/sem.c b/ipc/sem.c
index f6c30a85dadf..5157796daf54 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -263,7 +263,11 @@ void sem_exit_ns(struct ipc_namespace *ns)
}
#endif
+#ifdef CONFIG_UML
+void __init um_sem_init(void)
+#else
void __init sem_init(void)
+#endif
{
sem_init_ns(&init_ipc_ns);
ipc_init_proc_interface("sysvipc/sem",
diff --git a/ipc/util.h b/ipc/util.h
index 5766c61aed0e..b3356efb3c96 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -47,7 +47,12 @@ extern int ipc_min_cycle;
#define IPCMNI_IDX_MASK ((1 << IPCMNI_SHIFT) - 1)
#endif /* CONFIG_SYSVIPC_SYSCTL */
+#ifdef CONFIG_UML
+void um_sem_init(void);
+#define sem_init() um_sem_init()
+#else
void sem_init(void);
+#endif
void msg_init(void);
void shm_init(void);
johannes
--
Anton R. Ivanov
https://www.kot-begemot.co.uk/
