On 7/31/15 3:18 AM, Wangnan (F) wrote:
However with the newest llvm + clang the DWARF info is still incorrect:
$ objdump --dwarf=info ./out.o
...
<1><3f>: Abbrev Number: 3 (DW_TAG_structure_type)
<40> DW_AT_name : (indirect string, offset: 0x0): clang
version 3.8.0 (http://llvm.org/git/clang.git
f0fcd3432cbed83500df70c18f275d8affb89e5e) (http://llvm.org/git/llvm.git
c8ccd78d31d4949fa1c14e954ccb06253e18cf37)
<44> DW_AT_byte_size : 8
<45> DW_AT_decl_file : 1
<46> DW_AT_decl_line : 4
<2><47>: Abbrev Number: 4 (DW_TAG_member)
<48> DW_AT_name : (indirect string, offset: 0x0): clang
version 3.8.0 (http://llvm.org/git/clang.git
f0fcd3432cbed83500df70c18f275d8affb89e5e) (http://llvm.org/git/llvm.git
c8ccd78d31d4949fa1c14e954ccb06253e18cf37)
<4c> DW_AT_type : <0x60>
<50> DW_AT_decl_file : 1
<51> DW_AT_decl_line : 5
<52> DW_AT_data_member_location: 0
<2><53>: Abbrev Number: 4 (DW_TAG_member)
<54> DW_AT_name : (indirect string, offset: 0x0): clang
version 3.8.0 (http://llvm.org/git/clang.git
f0fcd3432cbed83500df70c18f275d8affb89e5e) (http://llvm.org/git/llvm.git
c8ccd78d31d4949fa1c14e954ccb06253e18cf37)
<58> DW_AT_type : <0x60>
<5c> DW_AT_decl_file : 1
<5d> DW_AT_decl_line : 6
<5e> DW_AT_data_member_location: 4
...
The DW_AT_name is missing.
didn't have time to look at it.
from your llvm patches looks like you've got quite experienced
with it already :)
I'll post 2 LLVM patches by replying this mail. Please have a look and
help me
send them to LLVM if you think my code is correct.
patch 1:
I don't quite understand the purpose of builtin_dwarf_cfa
returning R11. It's a special register seen inside llvm codegen
only. It doesn't have kernel meaning.
patch 2:
do we really need to hack clang?
Can you just define a function that aliases to intrinsic,
like we do for ld_abs/ld_ind ?
void bpf_store_half(void *skb, u64 off, u64 val) asm("llvm.bpf.store.half");
then no extra patches necessary.
struct my_str {
int x;
int y;
};
struct my_str __str_my_str;
struct my_str2 {
int x;
int y;
int z;
};
struct my_str2 __str_my_str2;
test_func(__builtin_bpf_typeid(&__str_my_str));
test_func(__builtin_bpf_typeid(&__str_my_str2));
mov r1, 1
call 4660
mov r1, 2
call 4660
this part looks good. I think it's usable.
> 1. llvm.eh_typeid_for can be used on global variables only. So for each
> output
> structure we have to define a global varable.
why? I think it should work with local pointers as well.
> 2. We still need to find a way to connect the fetchd typeid with DWARF
> info.
> Inserting that ID into DWARF may workable?
hmm, that id should be the same id we're seeing in dwarf, right?
I think it's used in exception handling which is reusing some of
the dwarf stuff for this, so the must be a way to connect that id
to actual type info. Though last time I looked at EH was
during g++ hacking days. No idea how llvm does it exactly, but
I'm assuming the logic for rtti should be similar.
btw, for any deep llvm stuff you may need to move the thread to llvmdev.
May be folks there will have other ideas.
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