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Clang 3.4 will sometimes emit DIE for struct/union member before

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emitting the DIE for the type of that member. ctfconvert can not
handle this properly and will calculate a wrong member bit offset.
Same struct/union type from different .o file will be treated as
different types when their member bit offsets are different, and
gets added/merged multiple times. This will in turn cause many other
structs/pointers/typedefs that refer to the duplicated struct/union
gets added/merged multiple times and eventually causes numerous
duplicated CTF types in the kernel.debug file.

The simple workaround here is to make use of DW_AT_byte_size attribute
of the member DIE to calculate the bits occupied by the member's type,
without actually resolving the type.
This commit is contained in:
Kai Wang 2014-01-20 01:35:14 +00:00
parent e3fa6e64ee
commit d32f014939
1 changed files with 21 additions and 3 deletions
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24
cddl/contrib/opensolaris/tools/ctf/cvt/dwarf.c
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@ -938,7 +938,7 @@ static void
die_sou_create(dwarf_t *dw, Dwarf_Die str, Dwarf_Off off, tdesc_t *tdp,
int type, const char *typename)
{
Dwarf_Unsigned sz, bitsz, bitoff, maxsz=0;
Dwarf_Unsigned sz, bysz, bitsz, bitoff, maxsz=0;
Dwarf_Die mem;
mlist_t *ml, **mlastp;
iidesc_t *ii;
@ -1013,8 +1013,26 @@ die_sou_create(dwarf_t *dw, Dwarf_Die str, Dwarf_Off off, tdesc_t *tdp,
#if BYTE_ORDER == _BIG_ENDIAN
ml->ml_offset += bitoff;
#else
ml->ml_offset += tdesc_bitsize(ml->ml_type) - bitoff -
ml->ml_size;
/*
* Note that Clang 3.4 will sometimes generate
* member DIE before generating the DIE for the
* member's type. The code can not handle this
* properly so that tdesc_bitsize(ml->ml_type) will
* return 0 because ml->ml_type is unknown. As a
* result, a wrong member offset will be calculated.
* To workaround this, we can instead try to
* retrieve the value of DW_AT_byte_size attribute
* which stores the byte size of the space occupied
* by the type. If this attribute exists, its value
* should equal to tdesc_bitsize(ml->ml_type)/NBBY.
*/
if (die_unsigned(dw, mem, DW_AT_byte_size, &bysz, 0) &&
bysz > 0)
ml->ml_offset += bysz * NBBY - bitoff -
ml->ml_size;
else
ml->ml_offset += tdesc_bitsize(ml->ml_type) -
bitoff - ml->ml_size;
#endif
}