From 5d28a8962dcb6ec056b81d730e3c6fb57185a210 Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Tue, 28 Dec 2021 22:52:56 +0100 Subject: elf: Add _dl_find_object function It can be used to speed up the libgcc unwinder, and the internal _dl_find_dso_for_object function (which is used for caller identification in dlopen and related functions, and in dladdr). _dl_find_object is in the internal namespace due to bug 28503. If libgcc switches to _dl_find_object, this namespace issue will be fixed. It is located in libc for two reasons: it is necessary to forward the call to the static libc after static dlopen, and there is a link ordering issue with -static-libgcc and libgcc_eh.a because libc.so is not a linker script that includes ld.so in the glibc build tree (so that GCC's internal -lc after libgcc_eh.a does not pick up ld.so). It is necessary to do the i386 customization in the sysdeps/x86/bits/dl_find_object.h header shared with x86-64 because otherwise, multilib installations are broken. The implementation uses software transactional memory, as suggested by Torvald Riegel. Two copies of the supporting data structures are used, also achieving full async-signal-safety. Reviewed-by: Adhemerval Zanella --- include/atomic_wide_counter.h | 14 ++++++++++++++ include/bits/dl_find_object.h | 1 + include/dlfcn.h | 2 ++ include/link.h | 3 +++ 4 files changed, 20 insertions(+) create mode 100644 include/bits/dl_find_object.h (limited to 'include') diff --git a/include/atomic_wide_counter.h b/include/atomic_wide_counter.h index 31f009d..d1c40cd 100644 --- a/include/atomic_wide_counter.h +++ b/include/atomic_wide_counter.h @@ -31,6 +31,12 @@ __atomic_wide_counter_load_relaxed (__atomic_wide_counter *c) } static inline uint64_t +__atomic_wide_counter_load_acquire (__atomic_wide_counter *c) +{ + return atomic_load_acquire (&c->__value64); +} + +static inline uint64_t __atomic_wide_counter_fetch_add_relaxed (__atomic_wide_counter *c, unsigned int val) { @@ -64,6 +70,14 @@ __atomic_wide_counter_fetch_xor_release (__atomic_wide_counter *c, uint64_t __atomic_wide_counter_load_relaxed (__atomic_wide_counter *c) attribute_hidden; +static inline uint64_t +__atomic_wide_counter_load_acquire (__atomic_wide_counter *c) +{ + uint64_t r = __atomic_wide_counter_load_relaxed (c); + atomic_thread_fence_acquire (); + return r; +} + uint64_t __atomic_wide_counter_fetch_add_relaxed (__atomic_wide_counter *c, unsigned int op) attribute_hidden; diff --git a/include/bits/dl_find_object.h b/include/bits/dl_find_object.h new file mode 100644 index 0000000..7a323d7 --- /dev/null +++ b/include/bits/dl_find_object.h @@ -0,0 +1 @@ +#include_next diff --git a/include/dlfcn.h b/include/dlfcn.h index e73294b..ae25f05 100644 --- a/include/dlfcn.h +++ b/include/dlfcn.h @@ -4,6 +4,8 @@ #include /* For ElfW. */ #include +rtld_hidden_proto (_dl_find_object) + /* Internally used flag. */ #define __RTLD_DLOPEN 0x80000000 #define __RTLD_SPROF 0x40000000 diff --git a/include/link.h b/include/link.h index 6a9f788..b49be89 100644 --- a/include/link.h +++ b/include/link.h @@ -211,6 +211,9 @@ struct link_map freed, ie. not allocated with the dummy malloc in ld.so. */ unsigned int l_ld_readonly:1; /* Nonzero if dynamic section is readonly. */ + unsigned int l_find_object_processed:1; /* Zero if _dl_find_object_update + needs to process this + lt_library map. */ /* NODELETE status of the map. Only valid for maps of type lt_loaded. Lazy binding sets l_nodelete_active directly, -- cgit v1.1