diff options
Diffstat (limited to 'sysdeps/generic')
| -rw-r--r-- | sysdeps/generic/dl-tls.c | 74 | ||||
| -rw-r--r-- | sysdeps/generic/ldsodefs.h | 2 |
2 files changed, 66 insertions, 10 deletions
diff --git a/sysdeps/generic/dl-tls.c b/sysdeps/generic/dl-tls.c index a51e3f7bc7..ccad53c59f 100644 --- a/sysdeps/generic/dl-tls.c +++ b/sysdeps/generic/dl-tls.c @@ -117,9 +117,10 @@ internal_function _dl_determine_tlsoffset (void) { struct dtv_slotinfo *slotinfo; - size_t max_align = __alignof__ (void *); + size_t max_align; size_t offset; size_t cnt; + size_t freebytes; /* The first element of the dtv slot info list is allocated. */ assert (GL(dl_tls_dtv_slotinfo_list) != NULL); @@ -127,24 +128,78 @@ _dl_determine_tlsoffset (void) dl_tls_dtv_slotinfo_list list. */ assert (GL(dl_tls_dtv_slotinfo_list)->next == NULL); + /* Determining the offset of the various parts of the static TLS + block has several dependencies. In addition we have to work + around bugs in some toolchains. + + Each TLS block from the objects available at link time has a size + and an alignment requirement. The GNU ld computes the alignment + requirements for the data at the positions *in the file*, though. + I.e, it is not simply possible to allocate a block with the size + of the TLS program header entry. The data is layed out assuming + that the first byte of the TLS block fulfills + + p_vaddr mod p_align == &TLS_BLOCK mod p_align + + This means we have to add artificial padding at the beginning of + the TLS block. These bytes are never used for the TLS data in + this module but the first byte allocated must be aligned + according to mod p_align == 0 so that the first byte of the TLS + block is aligned according to p_vaddr mod p_align. This is ugly + and the linker can help by computing the offsets in the TLS block + assuming the first byte of the TLS block is aligned according to + p_align. + + We can handle this wrong behavior because of another bug in GNU + ld. The p_vaddr field of the TLS segment must be zero (according + to the spec) since the linker does not know the address or offset + where it will end up at. Once a linker is available which + handles the alignment correctly it should set p_addr to zero and + all will automatically fall into place. + + The extra space which might be allocated before the first byte of + the TLS block need not go unused. The code below tries to use + that memory for the next TLS block. This can work if the total + memory requirement for the next TLS block is smaller than the + gap. */ + # if TLS_TCB_AT_TP /* We simply start with zero. */ + max_align = __alignof (void *); offset = 0; + freebytes = 0; slotinfo = GL(dl_tls_dtv_slotinfo_list)->slotinfo; for (cnt = 1; slotinfo[cnt].map != NULL; ++cnt) { assert (cnt < GL(dl_tls_dtv_slotinfo_list)->len); - max_align = MAX (max_align, slotinfo[cnt].map->l_tls_align); + size_t blsize = (slotinfo[cnt].map->l_tls_blocksize + + slotinfo[cnt].map->l_tls_firstbyte_offset); - /* Compute the offset of the next TLS block. */ - offset = roundup (offset + slotinfo[cnt].map->l_tls_blocksize, - slotinfo[cnt].map->l_tls_align); + if (blsize <= freebytes) + { + /* When we come here the amount of memory we was "wasted" + for the correct alignment of the previous block is larger + than what we need for this module. So use it. */ + size_t n = (freebytes - blsize) / slotinfo[cnt].map->l_tls_align; + freebytes = (n * slotinfo[cnt].map->l_tls_align + + slotinfo[cnt].map->l_tls_firstbyte_offset); + } + else + { + /* There is either no gap from the bottom of the static TLS + block to the first used byte or the gap is too small. + Extend the static TLS block. */ + offset += roundup (blsize, max_align); + freebytes = slotinfo[cnt].map->l_tls_firstbyte_offset; + } + + max_align = MAX (max_align, slotinfo[cnt].map->l_tls_align); /* XXX For some architectures we perhaps should store the negative offset. */ - slotinfo[cnt].map->l_tls_offset = offset; + slotinfo[cnt].map->l_tls_offset = offset - freebytes; } /* The thread descriptor (pointed to by the thread pointer) has its @@ -156,11 +211,12 @@ _dl_determine_tlsoffset (void) // XXX model. GL(dl_tls_static_used) = offset; - GL(dl_tls_static_size) = roundup (offset + TLS_STATIC_SURPLUS + TLS_TCB_SIZE, - TLS_TCB_ALIGN); + GL(dl_tls_static_size) = (offset + roundup (TLS_STATIC_SURPLUS, max_align) + + TLS_TCB_SIZE); # elif TLS_DTV_AT_TP /* The TLS blocks start right after the TCB. */ offset = TLS_TCB_SIZE; + max_align = __alignof (void *); /* The first block starts right after the TCB. */ slotinfo = GL(dl_tls_dtv_slotinfo_list)->slotinfo; @@ -201,7 +257,7 @@ _dl_determine_tlsoffset (void) # endif /* The alignment requirement for the static TLS block. */ - GL(dl_tls_static_align) = MAX (TLS_TCB_ALIGN, max_align); + GL(dl_tls_static_align) = max_align; } diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index 570b52261b..565edb3fd8 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -797,7 +797,7 @@ rtld_hidden_proto (_dl_allocate_tls) extern void _dl_get_tls_static_info (size_t *sizep, size_t *alignp) internal_function; -extern void _dl_allocate_static_tls (struct link_map *map) +extern int _dl_allocate_static_tls (struct link_map *map) internal_function attribute_hidden; /* These are internal entry points to the two halves of _dl_allocate_tls, |