diff options
Diffstat (limited to 'elf')
| -rw-r--r-- | elf/dl-close.c | 3 | ||||
| -rw-r--r-- | elf/dl-load.c | 9 | ||||
| -rw-r--r-- | elf/dl-open.c | 15 | ||||
| -rw-r--r-- | elf/rtld-debugger-interface.txt | 122 | ||||
| -rw-r--r-- | elf/rtld.c | 3 |
5 files changed, 149 insertions, 3 deletions
diff --git a/elf/dl-close.c b/elf/dl-close.c index a250ea5..45b2187 100644 --- a/elf/dl-close.c +++ b/elf/dl-close.c @@ -31,6 +31,7 @@ #include <sys/mman.h> #include <sysdep-cancel.h> #include <tls.h> +#include <stap-probe.h> /* Type of the constructor functions. */ @@ -468,6 +469,7 @@ _dl_close_worker (struct link_map *map) struct r_debug *r = _dl_debug_initialize (0, nsid); r->r_state = RT_DELETE; _dl_debug_state (); + LIBC_PROBE (unmap_start, 2, nsid, r); if (unload_global) { @@ -737,6 +739,7 @@ _dl_close_worker (struct link_map *map) /* Notify the debugger those objects are finalized and gone. */ r->r_state = RT_CONSISTENT; _dl_debug_state (); + LIBC_PROBE (unmap_complete, 2, nsid, r); /* Recheck if we need to retry, release the lock. */ out: diff --git a/elf/dl-load.c b/elf/dl-load.c index fe83f87..43e1269 100644 --- a/elf/dl-load.c +++ b/elf/dl-load.c @@ -35,6 +35,7 @@ #include <stackinfo.h> #include <caller.h> #include <sysdep.h> +#include <stap-probe.h> #include <dl-dst.h> @@ -882,7 +883,7 @@ _dl_init_paths (const char *llp) static void __attribute__ ((noreturn, noinline)) lose (int code, int fd, const char *name, char *realname, struct link_map *l, - const char *msg, struct r_debug *r) + const char *msg, struct r_debug *r, Lmid_t nsid) { /* The file might already be closed. */ if (fd != -1) @@ -896,6 +897,7 @@ lose (int code, int fd, const char *name, char *realname, struct link_map *l, { r->r_state = RT_CONSISTENT; _dl_debug_state (); + LIBC_PROBE (map_failed, 2, nsid, r); } _dl_signal_error (code, name, NULL, msg); @@ -934,7 +936,7 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp, errval = errno; call_lose: lose (errval, fd, name, realname, l, errstring, - make_consistent ? r : NULL); + make_consistent ? r : NULL, nsid); } /* Look again to see if the real name matched another already loaded. */ @@ -1041,6 +1043,7 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp, linking has not been used before. */ r->r_state = RT_ADD; _dl_debug_state (); + LIBC_PROBE (map_start, 2, nsid, r); make_consistent = true; } else @@ -1736,7 +1739,7 @@ open_verify (const char *name, struct filebuf *fbp, struct link_map *loader, name = strdupa (realname); free (realname); } - lose (errval, fd, name, NULL, NULL, errstring, NULL); + lose (errval, fd, name, NULL, NULL, errstring, NULL, 0); } /* See whether the ELF header is what we expect. */ diff --git a/elf/dl-open.c b/elf/dl-open.c index e2780a4..00781af 100644 --- a/elf/dl-open.c +++ b/elf/dl-open.c @@ -32,6 +32,7 @@ #include <caller.h> #include <sysdep-cancel.h> #include <tls.h> +#include <stap-probe.h> #include <dl-dst.h> @@ -291,6 +292,7 @@ dl_open_worker (void *a) struct r_debug *r = _dl_debug_initialize (0, args->nsid); r->r_state = RT_CONSISTENT; _dl_debug_state (); + LIBC_PROBE (map_complete, 3, args->nsid, r, new); /* Print scope information. */ if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_SCOPES, 0)) @@ -376,10 +378,19 @@ dl_open_worker (void *a) } } + int relocation_in_progress = 0; + for (size_t i = nmaps; i-- > 0; ) { l = maps[i]; + if (! relocation_in_progress) + { + /* Notify the debugger that relocations are about to happen. */ + LIBC_PROBE (reloc_start, 2, args->nsid, r); + relocation_in_progress = 1; + } + #ifdef SHARED if (__builtin_expect (GLRO(dl_profile) != NULL, 0)) { @@ -544,6 +555,10 @@ cannot load any more object with static TLS")); } } + /* Notify the debugger all new objects have been relocated. */ + if (relocation_in_progress) + LIBC_PROBE (reloc_complete, 3, args->nsid, r, new); + /* Run the initializer functions of new objects. */ _dl_init (new, args->argc, args->argv, args->env); diff --git a/elf/rtld-debugger-interface.txt b/elf/rtld-debugger-interface.txt new file mode 100644 index 0000000..61bc99e --- /dev/null +++ b/elf/rtld-debugger-interface.txt @@ -0,0 +1,122 @@ +Standard debugger interface +=========================== + +The run-time linker exposes a rendezvous structure to allow debuggers +to interface with it. This structure, r_debug, is defined in link.h. +If the executable's dynamic section has a DT_DEBUG element, the +run-time linker sets that element's value to the address where this +structure can be found. + +The r_debug structure contains (amongst others) the following fields: + + struct link_map *r_map: + A linked list of loaded objects. + + enum { RT_CONSISTENT, RT_ADD, RT_DELETE } r_state: + The current state of the r_map list. RT_CONSISTENT means that r_map + is not currently being modified and may safely be inspected. RT_ADD + means that an object is being added to r_map, and that the list is + not guaranteed to be consistent. Likewise RT_DELETE means that an + object is being removed from the list. + + ElfW(Addr) r_brk: + The address of a function internal to the run-time linker which is + called whenever r_state is changed. The debugger should set a + breakpoint at this address if it wants to notice mapping changes. + +This protocol is widely supported, but somewhat limited in that it +has no provision to provide access to multiple namespaces, and that +the notifications (via r_brk) only refer to changes to r_map--the +debugger is notified that a new object has been added, for instance, +but there is no way for the debugger to discover whether any of the +objects in the link-map have been relocated or not. + + +Probe-based debugger interface +============================== + +Systemtap is a dynamic tracing/instrumenting tool available on Linux. +Probes that are not fired at run time have close to zero overhead. +glibc contains a number of probes that debuggers can set breakpoints +on in order to notice certain events. + +All rtld probes have the following arguments: + + arg1: Lmid_t lmid: + The link-map ID of the link-map list that the object was loaded + into. This will be LM_ID_BASE for the application's main link-map + list, or some other value for different namespaces. + + arg2: struct r_debug *r_debug: + A pointer to the r_debug structure containing the link-map list + that the object was loaded into. This will be the value stored in + DT_DEBUG for the application's main link-map list, or some other + value for different namespaces. + +map_complete and reloc_complete may have the following additional +argument: + + arg3: struct link_map *new: + A pointer which, if not NULL, points to the entry in the specified + r_debug structure's link-map list corresponding to the first new + object to have been mapped or relocated, with new->l_next pointing + to the link-map of the next new object to have been mapped or + relocated, and so on. Note that because `new' is an entry in a + larger list, new->l_prev (if not NULL) will point to what was the + last link-map in the link-map list prior to the new objects being + mapped or relocated. + +The following probes are available: + + init_start: + This is called once, when the linker is about to fill in the main + r_debug structure at application startup. init_start always has + lmid set to LM_ID_BASE and r_debug set to the value stored in + DT_DEBUG. r_debug is not guaranteed to be consistent until + init_complete is fired. + + init_complete: + This is called once, when the linker has filled in the main + r_debug structure at application startup. init_complete always + has lmid set to LM_ID_BASE and r_debug set to the value stored + in DT_DEBUG. The r_debug structure is consistent and may be + inspected, and all objects in the link-map are guaranteed to + have been relocated. + + map_start: + The linker is about to map new objects into the specified + namespace. The namespace's r_debug structure is not guaranteed + to be consistent until a corresponding map_complete is fired. + + map_complete: + The linker has finished mapping new objects into the specified + namespace. The namespace's r_debug structure is consistent and + may be inspected, although objects in the namespace's link-map + are not guaranteed to have been relocated. + + map_failed: + The linker failed while attempting to map new objects into + the specified namespace. The namespace's r_debug structure + is consistent and may be inspected. + + reloc_start: + The linker is about to relocate all unrelocated objects in the + specified namespace. The namespace's r_debug structure is not + guaranteed to be consistent until a corresponding reloc_complete + is fired. + + reloc_complete: + The linker has relocated all objects in the specified namespace. + The namespace's r_debug structure is consistent and may be + inspected, and all objects in the namespace's link-map are + guaranteed to have been relocated. + + unmap_start: + The linker is about to remove objects from the specified + namespace. The namespace's r_debug structure is not guaranteed to + be consistent until a corresponding unmap_complete is fired. + + unmap_complete: + The linker has finished removing objects into the specified + namespace. The namespace's r_debug structure is consistent and + may be inspected. @@ -39,6 +39,7 @@ #include <dl-osinfo.h> #include <dl-procinfo.h> #include <tls.h> +#include <stap-probe.h> #include <stackinfo.h> #include <assert.h> @@ -1683,6 +1684,7 @@ ERROR: ld.so: object '%s' cannot be loaded as audit interface: %s; ignored.\n", /* We start adding objects. */ r->r_state = RT_ADD; _dl_debug_state (); + LIBC_PROBE (init_start, 2, LM_ID_BASE, r); /* Auditing checkpoint: we are ready to signal that the initial map is being constructed. */ @@ -2402,6 +2404,7 @@ ERROR: ld.so: object '%s' cannot be loaded as audit interface: %s; ignored.\n", r = _dl_debug_initialize (0, LM_ID_BASE); r->r_state = RT_CONSISTENT; _dl_debug_state (); + LIBC_PROBE (init_complete, 2, LM_ID_BASE, r); #ifndef MAP_COPY /* We must munmap() the cache file. */ |