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elf: Use TLS_DTV_OFFSET in __tls_get_addr

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This fixes commit 5e249192cac7354af02a7347a0d8c984e0c88ed3 ("elf:
Remove the GET_ADDR_ARGS and related macros from the TLS code"):
GET_ADDR_ARGS was indeed unused, but GET_ADDR_OFFSET was used
on several targets, those that define TLS_DTV_OFFSET.  Instead
of reintroducing GET_ADDR_OFFSET, use TLS_DTV_OFFSET directly,
now that it is defined on all targets.

In the new tls_get_addr_adjust helper function, add a cast to
uintptr_t to help the s390 case, where the offset can be positive or
negative, depending on the addresses malloc returns.  The cast avoids
pointer wraparound/overflow.  The outer uintptr_t cast is needed
to suppress a warning on x86-64 x32 about mismatched integer/pointer
sizes.

Eventually this offset should be folded into the DTV addresses
themselves, to eliminate the subtraction on the TLS fast path.
This will require an adjustment to libthread_db because the
debugger interface currently returns unadjusted pointers.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
Florian Weimer 2025-01-02 13:45:27 +01:00
parent 91ee75abcf
commit 30e32da6aa
1 changed files with 16 additions and 4 deletions
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20
elf/dl-tls.c
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@ -890,6 +890,18 @@ _dl_update_slotinfo (unsigned long int req_modid, size_t new_gen)
return the_map;
}
/* Adjust the TLS variable pointer using the TLS descriptor offset and
the ABI-specific offset. */
static inline void *
tls_get_addr_adjust (void *from_dtv, tls_index *ti)
{
/* Perform arithmetic in uintptr_t to avoid pointer wraparound
issues. The outer cast to uintptr_t suppresses a warning about
pointer/integer size mismatch on ILP32 targets with 64-bit
ti_offset. */
return (void *) (uintptr_t) ((uintptr_t) from_dtv + ti->ti_offset
+ TLS_DTV_OFFSET);
}
static void *
__attribute_noinline__
@ -939,7 +951,7 @@ tls_get_addr_tail (tls_index *ti, dtv_t *dtv, struct link_map *the_map)
dtv[ti->ti_module].pointer.to_free = NULL;
dtv[ti->ti_module].pointer.val = p;
return (char *) p + ti->ti_offset;
return tls_get_addr_adjust (p, ti);
}
else
__rtld_lock_unlock_recursive (GL(dl_load_tls_lock));
@ -948,7 +960,7 @@ tls_get_addr_tail (tls_index *ti, dtv_t *dtv, struct link_map *the_map)
dtv[ti->ti_module].pointer = result;
assert (result.to_free != NULL);
return (char *) result.val + ti->ti_offset;
return tls_get_addr_adjust (result.val, ti);
}
@ -964,7 +976,7 @@ update_get_addr (tls_index *ti, size_t gen)
if (__glibc_unlikely (p == TLS_DTV_UNALLOCATED))
return tls_get_addr_tail (ti, dtv, the_map);
return (void *) p + ti->ti_offset;
return tls_get_addr_adjust (p, ti);
}
/* For all machines that have a non-macro version of __tls_get_addr, we
@ -1015,7 +1027,7 @@ __tls_get_addr (tls_index *ti)
if (__glibc_unlikely (p == TLS_DTV_UNALLOCATED))
return tls_get_addr_tail (ti, dtv, NULL);
return (char *) p + ti->ti_offset;
return tls_get_addr_adjust (p, ti);
}
#endif /* SHARED */