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| author | Szabolcs Nagy <szabolcs.nagy@arm.com> | 2020-06-09 09:57:28 +0100 |
|---|---|---|
| committer | Szabolcs Nagy <szabolcs.nagy@arm.com> | 2020-07-08 17:32:56 +0100 |
| commit | 0c7b002fac12dcb2f53ba83ee56bb3b5d2439447 (patch) | |
| tree | cc07f5e054d4aefa382ceeacd458c06fc4205169 /sysdeps | |
| parent | ae7a94e5e3edf78f4da562edc05ece229614c716 (diff) | |
| download | glibc-0c7b002fac12dcb2f53ba83ee56bb3b5d2439447.tar.gz glibc-0c7b002fac12dcb2f53ba83ee56bb3b5d2439447.tar.xz glibc-0c7b002fac12dcb2f53ba83ee56bb3b5d2439447.zip | |
rtld: Add rtld.nns tunable for the number of supported namespaces
TLS_STATIC_SURPLUS is 1664 bytes currently which is not enough to support DL_NNS (== 16) number of dynamic link namespaces, if we assume 192 bytes of TLS are reserved for libc use and 144 bytes are reserved for other system libraries that use IE TLS. A new tunable is introduced to control the number of supported namespaces and to adjust the surplus static TLS size as follows: surplus_tls = 192 * (rtld.nns-1) + 144 * rtld.nns + 512 The default is rtld.nns == 4 and then the surplus TLS size is the same as before, so the behaviour is unchanged by default. If an application creates more namespaces than the rtld.nns setting allows, then it is not guaranteed to work, but the limit is not checked. So existing usage will continue to work, but in the future if an application creates more than 4 dynamic link namespaces then the tunable will need to be set. In this patch DL_NNS is a fixed value and provides a maximum to the rtld.nns setting. Static linking used fixed 2048 bytes surplus TLS, this is changed so the same contract is used as for dynamic linking. With static linking DL_NNS == 1 so rtld.nns tunable is forced to 1, so by default the surplus TLS is reduced to 144 + 512 = 656 bytes. This change is not expected to cause problems. Tested on aarch64-linux-gnu and x86_64-linux-gnu. Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Diffstat (limited to 'sysdeps')
| -rw-r--r-- | sysdeps/generic/ldsodefs.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index c525ffa12c..3b0c6d9620 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -583,6 +583,11 @@ struct rtld_global_ro binaries, don't honor for PIEs). */ EXTERN ElfW(Addr) _dl_use_load_bias; + /* Size of surplus space in the static TLS area for dynamically + loaded modules with IE-model TLS or for TLSDESC optimization. + See comments in elf/dl-tls.c where it is initialized. */ + EXTERN size_t _dl_tls_static_surplus; + /* Name of the shared object to be profiled (if any). */ EXTERN const char *_dl_profile; /* Filename of the output file. */ @@ -1101,6 +1106,9 @@ extern size_t _dl_count_modids (void) attribute_hidden; /* Calculate offset of the TLS blocks in the static TLS block. */ extern void _dl_determine_tlsoffset (void) attribute_hidden; +/* Calculate the size of the static TLS surplus. */ +void _dl_tls_static_surplus_init (void) attribute_hidden; + #ifndef SHARED /* Set up the TCB for statically linked applications. This is called early during startup because we always use TLS (for errno and the |