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author | H.J. Lu <hjl.tools@gmail.com> | 2021-08-17 19:35:48 -0700 |
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committer | H.J. Lu <hjl.tools@gmail.com> | 2021-09-19 13:51:35 -0700 |
commit | a93d9e03a31ec14405cb3a09aa95413b67067380 (patch) | |
tree | 532f865c7241b3cf363433272e5923c468ea2969 /elf/dl-debug.c | |
parent | 885762aa31d75de8b9fea4c0e2e372b582d4c548 (diff) | |
download | glibc-a93d9e03a31ec14405cb3a09aa95413b67067380.zip glibc-a93d9e03a31ec14405cb3a09aa95413b67067380.tar.gz glibc-a93d9e03a31ec14405cb3a09aa95413b67067380.tar.bz2 |
Extend struct r_debug to support multiple namespaces [BZ #15971]
Glibc does not provide an interface for debugger to access libraries
loaded in multiple namespaces via dlmopen.
The current rtld-debugger interface is described in the file:
elf/rtld-debugger-interface.txt
under the "Standard debugger interface" heading. This interface only
provides access to the first link-map (LM_ID_BASE).
1. Bump r_version to 2 when multiple namespaces are used. This triggers
the GDB bug:
https://sourceware.org/bugzilla/show_bug.cgi?id=28236
2. Add struct r_debug_extended to extend struct r_debug into a linked-list,
where each element correlates to an unique namespace.
3. Initialize the r_debug_extended structure. Bump r_version to 2 for
the new namespace and add the new namespace to the namespace linked list.
4. Add _dl_debug_update to return the address of struct r_debug' of a
namespace.
5. Add a hidden symbol, _r_debug_extended, for struct r_debug_extended.
6. Provide the symbol, _r_debug, with size of struct r_debug, as an alias
of _r_debug_extended, for programs which reference _r_debug.
This fixes BZ #15971.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Diffstat (limited to 'elf/dl-debug.c')
-rw-r--r-- | elf/dl-debug.c | 81 |
1 files changed, 62 insertions, 19 deletions
diff --git a/elf/dl-debug.c b/elf/dl-debug.c index 2cd5f09..f637d4b 100644 --- a/elf/dl-debug.c +++ b/elf/dl-debug.c @@ -30,37 +30,80 @@ extern const int verify_link_map_members[(VERIFY_MEMBER (l_addr) && VERIFY_MEMBER (l_prev)) ? 1 : -1]; -/* This structure communicates dl state to the debugger. The debugger - normally finds it via the DT_DEBUG entry in the dynamic section, but in - a statically-linked program there is no dynamic section for the debugger - to examine and it looks for this particular symbol name. */ -struct r_debug _r_debug; +/* Update the `r_map' member and return the address of `struct r_debug' + of the namespace NS. */ +struct r_debug * +_dl_debug_update (Lmid_t ns) +{ + struct r_debug_extended *r; + if (ns == LM_ID_BASE) + r = &_r_debug_extended; + else + r = &GL(dl_ns)[ns]._ns_debug; + if (r->base.r_map == NULL) + atomic_store_release (&r->base.r_map, + (void *) GL(dl_ns)[ns]._ns_loaded); + return &r->base; +} -/* Initialize _r_debug if it has not already been done. The argument is - the run-time load address of the dynamic linker, to be put in - _r_debug.r_ldbase. Returns the address of _r_debug. */ +/* 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. */ struct r_debug * _dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns) { - struct r_debug *r; + struct r_debug_extended *r, **pp = NULL; if (ns == LM_ID_BASE) - r = &_r_debug; - else - r = &GL(dl_ns)[ns]._ns_debug; + { + r = &_r_debug_extended; + /* Initialize r_version to 1. */ + if (_r_debug_extended.base.r_version == 0) + _r_debug_extended.base.r_version = 1; + } + else if (DL_NNS > 1) + { + r = &GL(dl_ns)[ns]._ns_debug; + if (r->base.r_brk == 0) + { + /* Add the new namespace to the linked list. After a namespace + is initialized, r_brk becomes non-zero. A namespace becomes + empty (r_map == NULL) when it is unused. But it is never + removed from the linked list. */ + struct r_debug_extended *p; + for (pp = &_r_debug_extended.r_next; + (p = *pp) != NULL; + pp = &p->r_next) + ; + + r->base.r_version = 2; + } + } + + if (r->base.r_brk == 0) + { + /* Tell the debugger where to find the map of loaded objects. + This function is called from dlopen. Initialize the namespace + only once. */ + r->base.r_ldbase = ldbase ?: _r_debug_extended.base.r_ldbase; + r->base.r_brk = (ElfW(Addr)) &_dl_debug_state; + r->r_next = NULL; + } + + if (r->base.r_map == NULL) + atomic_store_release (&r->base.r_map, + (void *) GL(dl_ns)[ns]._ns_loaded); - if (r->r_map == NULL || ldbase != 0) + if (pp != NULL) { - /* Tell the debugger where to find the map of loaded objects. */ - r->r_version = 1 /* R_DEBUG_VERSION XXX */; - r->r_ldbase = ldbase ?: _r_debug.r_ldbase; - r->r_map = (void *) GL(dl_ns)[ns]._ns_loaded; - r->r_brk = (ElfW(Addr)) &_dl_debug_state; + atomic_store_release (pp, r); + /* Bump r_version to 2 for the new namespace. */ + atomic_store_release (&_r_debug_extended.base.r_version, 2); } - return r; + return &r->base; } |