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
> <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> 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
>>
>>
>>
>
>
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