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output/elf: Don't set data symbol type/size in ABS sections

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I'm dealing with a FreeBSD-derived embedded target that ends up
showing such symbols (which is mainly NASM struct definitions)
in backtraces after calling NULL function pointers, since these
symbols _are_ technically covering bytes around address zero.

Needless to say, this is extremely confusing and generates
nonsensical bug reports. (Essentially, random unrelated crashes
get cross-referenced to a random ASM struct, whatever the linker
picked for address 0).

These symbols are already a bit strange to begin with (they're
purely an artifact of how NASM happens to implement structs),
leaving their sizes at 0 seems reasonable.

Signed-off-by: Fabian Giesen <fabian.giesen@epicgames.com>
This commit is contained in:
Fabian Giesen 2022-08-30 14:20:09 -07:00
parent 3aebb20f12
commit 04f981e0e6
1 changed files with 5 additions and 1 deletions
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6
output/outelf.c
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@ -2696,7 +2696,11 @@ static void debug_typevalue(int32_t type)
stype = STT_NOTYPE;
break;
}
if (stype == STT_OBJECT && lastsym && !lastsym->type) {
/* Set type and size info on most recently seen symbol if we haven't set it already.
But avoid setting size info on object (data) symbols in absolute sections (which
is primarily structs); some environments get confused with non-zero-extent absolute
object symbols and end up showing them in backtraces for NULL fn pointer calls. */
if (stype == STT_OBJECT && lastsym && !lastsym->type && lastsym->section != XSHN_ABS) {
lastsym->size = ssize;
lastsym->type = stype;
}