[PATCH v2 2/3] elf: Introduce _dl_debug_change_state
Florian Weimer
fweimer@redhat.com
Tue Sep 6 10:27:29 GMT 2022
It combines updating r_state with the debugger notification.
The change to _dl_open introduces an additional debugger notification
for dlmopen, but debuggers are expected to ignore it.
---
elf/dl-close.c | 6 ++----
elf/dl-debug.c | 7 +++++++
elf/dl-load.c | 6 ++----
elf/dl-open.c | 5 ++---
elf/rtld.c | 6 ++----
sysdeps/generic/ldsodefs.h | 14 ++++++++++++--
6 files changed, 27 insertions(+), 17 deletions(-)
diff --git a/elf/dl-close.c b/elf/dl-close.c
index bcd6e206e9..c300999e5b 100644
--- a/elf/dl-close.c
+++ b/elf/dl-close.c
@@ -460,8 +460,7 @@ _dl_close_worker (struct link_map *map, bool force)
/* Notify the debugger we are about to remove some loaded objects. */
struct r_debug *r = _dl_debug_update (nsid);
- r->r_state = RT_DELETE;
- _dl_debug_state ();
+ _dl_debug_change_state (r, RT_DELETE);
LIBC_PROBE (unmap_start, 2, nsid, r);
if (unload_global)
@@ -765,8 +764,7 @@ _dl_close_worker (struct link_map *map, bool force)
while (GL(dl_ns)[GL(dl_nns) - 1]._ns_loaded == NULL);
/* Notify the debugger those objects are finalized and gone. */
- r->r_state = RT_CONSISTENT;
- _dl_debug_state ();
+ _dl_debug_change_state (r, RT_CONSISTENT);
LIBC_PROBE (unmap_complete, 2, nsid, r);
/* Recheck if we need to retry, release the lock. */
diff --git a/elf/dl-debug.c b/elf/dl-debug.c
index 66f9ad375d..47961236cf 100644
--- a/elf/dl-debug.c
+++ b/elf/dl-debug.c
@@ -67,6 +67,13 @@ _dl_debug_update (Lmid_t ns)
return &r->base;
}
+void
+_dl_debug_change_state (struct r_debug *r, int state)
+{
+ atomic_store_release (&r->r_state, state);
+ _dl_debug_state ();
+}
+
/* Initialize _r_debug_extended for the namespace NS. LDBASE is the
run-time load address of the dynamic linker, to be put in
_r_debug_extended.r_ldbase. Return the address of _r_debug. */
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 1ad0868dad..d23ad557fc 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -987,8 +987,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
if (make_consistent && r != NULL)
{
- r->r_state = RT_CONSISTENT;
- _dl_debug_state ();
+ _dl_debug_change_state (r, RT_CONSISTENT);
LIBC_PROBE (map_failed, 2, nsid, r);
}
@@ -1507,8 +1506,7 @@ cannot enable executable stack as shared object requires");
/* Notify the debugger we have added some objects. We need to
call _dl_debug_initialize in a static program in case dynamic
linking has not been used before. */
- r->r_state = RT_ADD;
- _dl_debug_state ();
+ _dl_debug_change_state (r, RT_ADD);
LIBC_PROBE (map_start, 2, nsid, r);
make_consistent = true;
}
diff --git a/elf/dl-open.c b/elf/dl-open.c
index 46e8066fd8..b67c2e099f 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -617,8 +617,7 @@ dl_open_worker_begin (void *a)
/* Notify the debugger all new objects are now ready to go. */
struct r_debug *r = _dl_debug_update (args->nsid);
- r->r_state = RT_CONSISTENT;
- _dl_debug_state ();
+ _dl_debug_change_state (r, RT_CONSISTENT);
LIBC_PROBE (map_complete, 3, args->nsid, r, new);
_dl_open_check (new);
@@ -853,7 +852,7 @@ no more namespaces available for dlmopen()"));
memset (&GL(dl_ns)[nsid], 0, sizeof (GL(dl_ns)[nsid]));
__rtld_lock_initialize (GL(dl_ns)[nsid]._ns_unique_sym_table.lock);
- _dl_debug_update (nsid)->r_state = RT_CONSISTENT;
+ _dl_debug_change_state (_dl_debug_update (nsid), RT_CONSISTENT);
}
/* Never allow loading a DSO in a namespace which is empty. Such
direct placements is only causing problems. Also don't allow
diff --git a/elf/rtld.c b/elf/rtld.c
index 3e771a93d8..ad67d7e4c5 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -1835,8 +1835,7 @@ dl_main (const ElfW(Phdr) *phdr,
elf_setup_debug_entry (main_map, r);
/* We start adding objects. */
- r->r_state = RT_ADD;
- _dl_debug_state ();
+ _dl_debug_change_state (r, RT_ADD);
LIBC_PROBE (init_start, 2, LM_ID_BASE, r);
/* Auditing checkpoint: we are ready to signal that the initial map
@@ -2409,8 +2408,7 @@ dl_main (const ElfW(Phdr) *phdr,
/* Notify the debugger all new objects are now ready to go. We must re-get
the address since by now the variable might be in another object. */
r = _dl_debug_update (LM_ID_BASE);
- r->r_state = RT_CONSISTENT;
- _dl_debug_state ();
+ _dl_debug_change_state (r, RT_CONSISTENT);
LIBC_PROBE (init_complete, 2, LM_ID_BASE, r);
#if defined USE_LDCONFIG && !defined MAP_COPY
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index b088f6b1ae..31fb19c871 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -1060,8 +1060,14 @@ extern void _dl_debug_state (void);
rtld_hidden_proto (_dl_debug_state)
/* Initialize `struct r_debug_extended' for the namespace NS. LDBASE
- is the run-time load address of the dynamic linker, to be put in the
- `r_ldbase' member. Return the address of the structure. */
+ is the run-time load address of the dynamic linker, to be put in
+ the `r_ldbase' member.
+
+ This function returns the address of the r_debug structure for the
+ namespace. This is not merely a convenience or optimization, but
+ it is necessary for the LIBC_PROBE Systemtap/debugger probes to
+ work reliably: direct variable access can create probes that tools
+ cannot consume. */
extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns)
attribute_hidden;
@@ -1069,6 +1075,10 @@ extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns)
of the namespace NS. */
extern struct r_debug *_dl_debug_update (Lmid_t ns) attribute_hidden;
+/* Updates R->r_state to STATE and notifies the debugger by calling
+ _dl_debug_state. */
+void _dl_debug_change_state (struct r_debug *r, int state) attribute_hidden;
+
/* Initialize the basic data structure for the search paths. SOURCE
is either "LD_LIBRARY_PATH" or "--library-path".
GLIBC_HWCAPS_PREPEND adds additional glibc-hwcaps subdirectories to
--
2.37.2
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