When I mentioned upstream, I was talking about Rust repository, since as
you said, I am not sure if this is LLVM problem yet. There is already a
similar bug filed in rust repo about u128 division causing exception
[1], and there is a possible fix [2] (which does not work for the page
fault). I have also found 1 more edge case in numbers to cause `General
Exception`, which just like the other two seems to be related to rust
intrinsic or LLVM, but since I am not sure, and simply haven't done any
testing on, I cannot really say.
Anyway, filing them in Rust repository is helpful since the bug might
affect other `msvc-like` tier-2 and tier-3 targets. There is also
renewed interest in making UEFI targets Tier-2 from Tier-3 (sponsored by
Red Hat), so it's possible that someone else might pick it up before I
am done with the std errors I am trying to fix.
Ayush Singh
[1]: https://github.com/rust-lang/rust/issues/86494
[2]: https://github.com/rust-lang/compiler-builtins/pull/475
On 7/27/22 00:42, Pedro Falcato wrote:
Fyi, please don't file bugs upstream just now. You're not sure if
they're LLVM problems (and they're likely not, else they would affect
everyone else, not just UEFI code). Try to get a simpler, reliable
repro (and do share with us!) before saying it's an LLVM bug.
In my experience, most "what the hell" "compiler bugs" ended up being
things I accidentally set up wrong, or didn't set up at all, and broke
things in a subtle way.
On Tue, Jul 26, 2022 at 6:43 AM Ayush Singh <ayushdevel1...@gmail.com>
wrote:
Hi Andrew. Thanks for all your work. The more I look at this, the
more it feels like it might be a problem on the LLVM side instead
of Rust. I also found some more tests (all related to numbers btw)
which can cause different types of exceptions, so I think I will
try filing bugs upstream.
Yours Sincerely,
Ayush Singh
On 7/26/22 00:24, Andrew Fish wrote:
I guess I could at least dump to the end (req)…. Going backwards
is a bit painful in x86.
(lldb) dis -s 0x0000000140001B60 -b -c 30
hello_world_std.efi[0x140001b60]: 48 8b 09
movq (%rcx), %rcx
hello_world_std.efi[0x140001b63]: 48 01 c1
addq %rax, %rcx
hello_world_std.efi[0x140001b66]: 4c 89 c2
movq %r8, %rdx
hello_world_std.efi[0x140001b69]: 48 11 c2
adcq %rax, %rdx
hello_world_std.efi[0x140001b6c]: 48 31 c1
xorq %rax, %rcx
hello_world_std.efi[0x140001b6f]: 48 31 c2
xorq %rax, %rdx
hello_world_std.efi[0x140001b72]: 48 be 00 00 00 00 00 00 00 80
movabsq $-0x8000000000000000, %rsi ; imm = 0x8000000000000000
hello_world_std.efi[0x140001b7c]: 4c 21 c6
andq %r8, %rsi
hello_world_std.efi[0x140001b7f]: e8 5c 55 00 00
callq 0x1400070e0
hello_world_std.efi[0x140001b84]: 48 09 f0
orq %rsi, %rax
hello_world_std.efi[0x140001b87]: 48 83 c4 20
addq $0x20, %rsp
hello_world_std.efi[0x140001b8b]: 5e
popq %rsi
hello_world_std.efi[0x140001b8c]: c3
retq
hello_world_std.efi[0x140001b8d]: cc
int3
hello_world_std.efi[0x140001b8e]: cc
int3
hello_world_std.efi[0x140001b8f]: cc
int3
hello_world_std.efi[0x140001b90]: e9 db 55 00 00
jmp 0x140007170
hello_world_std.efi[0x140001b95]: cc
int3
…
Then we can guess based on how functions get aligned to find the
start….
hello_world_std.efi[0x140001b50]: 56
pushq %rsi
hello_world_std.efi[0x140001b51]: 48 83 ec 20
subq $0x20, %rsp
hello_world_std.efi[0x140001b55]: 4c 8b 41 08
movq 0x8(%rcx), %r8
hello_world_std.efi[0x140001b59]: 4c 89 c0
movq %r8, %rax
hello_world_std.efi[0x140001b5c]: 48 c1 f8 3f
sarq $0x3f, %rax
hello_world_std.efi[0x140001b60]: 48 8b 09
movq (%rcx), %rcx
hello_world_std.efi[0x140001b63]: 48 01 c1
addq %rax, %rcx
hello_world_std.efi[0x140001b66]: 4c 89 c2
movq %r8, %rdx
hello_world_std.efi[0x140001b69]: 48 11 c2
adcq %rax, %rdx
hello_world_std.efi[0x140001b6c]: 48 31 c1
xorq %rax, %rcx
hello_world_std.efi[0x140001b6f]: 48 31 c2
xorq %rax, %rdx
hello_world_std.efi[0x140001b72]: 48 be 00 00 00 00 00 00 00 80
movabsq $-0x8000000000000000, %rsi ; imm = 0x8000000000000000
hello_world_std.efi[0x140001b7c]: 4c 21 c6
andq %r8, %rsi
hello_world_std.efi[0x140001b7f]: e8 5c 55 00 00
callq 0x1400070e0
hello_world_std.efi[0x140001b84]: 48 09 f0
orq %rsi, %rax
hello_world_std.efi[0x140001b87]: 48 83 c4 20
addq $0x20, %rsp
hello_world_std.efi[0x140001b8b]: 5e
popq %rsi
hello_world_std.efi[0x140001b8c]: c3
retq
So the faulting function is getting passed a bad pointer as its
1st arg.
Thanks,
Andrew Fish
On Jul 25, 2022, at 11:45 AM, Andrew Fish <af...@apple.com>
<mailto:af...@apple.com> wrote:
Ops… Looks like your PE/COFF is linked at 0x0000000140000000,
so 0x140001b60 is the interesting bit.
(lldb) dis -s 0x0000000140001B60 -b
hello_world_std.efi[0x140001b60]: 48 8b 09
movq (%rcx), %rcx
hello_world_std.efi[0x140001b63]: 48 01 c1
addq %rax, %rcx
hello_world_std.efi[0x140001b66]: 4c 89 c2
movq %r8, %rdx
hello_world_std.efi[0x140001b69]: 48 11 c2
adcq %rax, %rdx
hello_world_std.efi[0x140001b6c]: 48 31 c1
xorq %rax, %rcx
hello_world_std.efi[0x140001b6f]: 48 31 c2
xorq %rax, %rdx
hello_world_std.efi[0x140001b72]: 48 be 00 00 00 00 00 00 00 80
movabsq $-0x8000000000000000, %rsi ; imm = 0x8000000000000000
hello_world_std.efi[0x140001b7c]: 4c 21 c6
andq %r8, %rsi
RCX - FFFFFFFFFFFFFFFF
So yea that looks like the fault.
I don’t see that pattern in your .s file….
Can you figure out what function is @ 0x140001b60 in the PE/COFF
image. Do you have a map file from the linker?
Thanks,
Andrew Fish
PS Again sorry I don’t have anything installed to crack PDB files.
Thanks,
Andrew Fish
On Jul 25, 2022, at 10:51 AM, Andrew Fish via groups.io
<http://groups.io> <afish=apple....@groups.io>
<mailto:afish=apple....@groups.io> wrote:
Ayush,
CR2 is the fault address so 0xFFFFFFFFFFFFFFFF. Given for EFI
Virt == Physical the fault address looks like a bad pointer.
Sorry I’ve not used VC++ in a long time so I don’t know how to
debug with VC++, but If I was using clang/lldb I’d look at the
source and assembly for the fault address.
The image base is: 0x000000000603C000
The fault PC/RIP is: 000000000603DB60
So the faulting code is at 0x1B60 in the image. Given the
images are linked at zero you should be able to load the build
product into the debugger and look at what code is at offset
0x1B60. The same should work for any tools that dump the binary.
Thanks,
Andrew Fish
On Jul 25, 2022, at 10:33 AM, Ayush Singh
<ayushdevel1...@gmail.com> <mailto:ayushdevel1...@gmail.com>
wrote:
Hello everyone.While running Rust tests in UEFI environment, I
have come across a numeric test that causes a pagefault. A
simple reproducible example for this is given below:
```rust
fn main() {
use std::hint::black_box as b;
let z: i128 = b(1);
assert!((-z as f64) < 0.0);
}
```
The exception output is as follows:
```
!!!! X64 Exception Type - 0E(#PF - Page-Fault) CPU Apic ID -
00000000 !!!!
ExceptionData - 0000000000000000 I:0 R:0 U:0 W:0 P:0 PK:0 SS:0
SGX:0
RIP - 000000000603DB60, CS - 0000000000000038, RFLAGS -
0000000000000246
RAX - 0000000000000000, RCX - FFFFFFFFFFFFFFFF, RDX -
FFFFFFFFFFFFFFFF
RBX - 0000000000000000, RSP - 0000000007EDF1D0, RBP -
0000000007EDF4C0
RSI - 0000000007EDF360, RDI - 0000000007EDF3C0
R8 - 0000000000000000, R9 - 0000000000000038, R10 -
0000000000000000
R11 - 0000000000000000, R12 - 00000000060C6018, R13 -
0000000007EDF520
R14 - 0000000007EDF6A8, R15 - 0000000005FA9490
DS - 0000000000000030, ES - 0000000000000030, FS -
0000000000000030
GS - 0000000000000030, SS - 0000000000000030
CR0 - 0000000080010033, CR2 - FFFFFFFFFFFFFFFF, CR3 -
0000000007C01000
CR4 - 0000000000000668, CR8 - 0000000000000000
DR0 - 0000000000000000, DR1 - 0000000000000000, DR2 -
0000000000000000
DR3 - 0000000000000000, DR6 - 00000000FFFF0FF0, DR7 -
0000000000000400
GDTR - 00000000079DE000 0000000000000047, LDTR - 0000000000000000
IDTR - 0000000007418018 0000000000000FFF, TR - 0000000000000000
FXSAVE_STATE - 0000000007EDEE30
!!!! Find image based on IP(0x603DB60)
/var/home/ayush/Documents/Programming/Rust/uefi/hello_world_std/target/x86_64-unknown-uefi/debug/deps/hello_world_std-338028f9369e2d42.pdb
(ImageBase=000000000603C000, EntryPoint=000000000603D8C0) !!!!
```
From my testing, the exception only occurs when a few
conditions are met.
1. The binary is compiled in Debug mode. No error in Release mode.
2. `i128` is in a black_box [1]. Does not occur if `black_box`
is not present.
3. It has to be `i128`. `i64` or something else work fine.
4. The cast has to be done on `-z`. Doing the same with `+z`
is fine.
I have also been discussing this in the Rust zulipchat [2], so
feel free to chime in there.
Additionally, here are links for more information about this
program:
1.
Assembly:https://rust-lang.zulipchat.com/user_uploads/4715/od51Y9Dkfjahcg9HHcOud8Fm/hello_world_std-338028f9369e2d42.s
2. EFI
Binary:https://rust-lang.zulipchat.com/user_uploads/4715/CknqtXLR8SaJZmyOnXctQkpL/hello_world_std.efi
3. PDB
file:https://rust-lang.zulipchat.com/user_uploads/4715/zV4i6DsjgQXotp_gS1naEsU0/hello_world_std-338028f9369e2d42.pdb
Yours Sincerely,
Ayush Singh
[1]:https://doc.rust-lang.org/std/hint/fn.black_box.html
[2]:https://rust-lang.zulipchat.com/#narrow/stream/182449-t-compiler.2Fhelp/topic/Casting.20i128.20to.20f64.20in.20black_box.20causes.20exception.20in.20UEFI
--
Pedro Falcato
-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#91857): https://edk2.groups.io/g/devel/message/91857
Mute This Topic: https://groups.io/mt/92610101/21656
Group Owner: devel+ow...@edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com]
-=-=-=-=-=-=-=-=-=-=-=-
