Re: [edk2-devel] Casting i128 into f64 in UEFI Rust pagefaults
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 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 0x000140001B60 -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 $-0x8000, %rsi ; imm = 0x8000 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 $-0x8000, %rsi ; imm =
Re: [edk2-devel] Casting i128 into f64 in UEFI Rust pagefaults
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 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 0x000140001B60 -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 > $-0x8000, %rsi ; imm = 0x8000 > > 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 20addq > $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 $-0x8000, %rsi ; imm = 0x8000 > > 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 > wrote: > > Ops… Looks like your PE/COFF is linked at 0x00014000, > so 0x140001b60 is the interesting bit. > > (lldb) dis -s 0x000140001B60 -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 > $-0x8000, %rsi ; imm = 0x8000 > hello_world_std.efi[0x140001b7c]: 4c 21 c6 andq > %r8, %rsi > > RCX - > > So yea that looks like the fault. > > I don’t see
Re: [edk2-devel] Casting i128 into f64 in UEFI Rust pagefaults
> On Jul 25, 2022, at 10:43 PM, Ayush Singh 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. Ayush, In general If we want to move to Rust we are going to need a way to debug issues like this down to the root cause. I think figuring out how to debug will make it easier to move forward with the Rust port in general. It will time well spent. The best way to get LLVM fixed, if it is even broken, is to provide a simple test case that reproduces the behavior. I don’t think at this point we know what is going on. It is very unlikely that some random LLVM developer is going to invest the time in trying to setup some UEFI environment to try and root cause this bug. I general find I have to create a simple at desk example and then I get stuff fixed quickly. Basically a test case the LLVM developer can compile at their desk and see the error in assembler, or at least run it at desk and have bogus output. I’m not 100% sure what toolchain you are using. Can you `objdump -d hello_world_std.efi`and get some symbols with the disassembly? For VC++ I think it would be `DUMPBIN /DISASM`. What are you planning on using for source level debugging Rust? I wrote some gdb[1] and lldb[2] debugging commands in Python. I’m guessing loading Rust symbols from PE/COFF images should be similar, as long as the debugger knows about rust. I’m happy to help you figure out stuff related to debugging Rust. [1] https://github.com/tianocore/edk2/blob/master/BaseTools/Scripts/efi_gdb.py [2] https://github.com/tianocore/edk2/blob/master/BaseTools/Scripts/efi_lldb.py Thanks, Andrew Fish > 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 0x000140001B60 -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 >> $-0x8000, %rsi ; imm = 0x8000 >> 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 20addq >> $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 $-0x8000, %rsi ; imm = 0x8000 >>
Re: [edk2-devel] Casting i128 into f64 in UEFI Rust pagefaults
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 0x000140001B60 -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 $-0x8000, %rsi ; imm = 0x8000 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 $-0x8000, %rsi ; imm = 0x8000 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 wrote: Ops… Looks like your PE/COFF is linked at 0x00014000, so 0x140001b60 is the interesting bit. (lldb) dis -s 0x000140001B60 -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 $-0x8000, %rsi ; imm = 0x8000 hello_world_std.efi[0x140001b7c]: 4c 21 c6 andq %r8, %rsi RCX - 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?
Re: [edk2-devel] Casting i128 into f64 in UEFI Rust pagefaults
I guess I could at least dump to the end (req)…. Going backwards is a bit painful in x86. (lldb) dis -s 0x000140001B60 -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 $-0x8000, %rsi ; imm = 0x8000 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 20addq $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 80movabsq $-0x8000, %rsi ; imm = 0x8000 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 wrote: > > Ops… Looks like your PE/COFF is linked at 0x00014000, so 0x140001b60 > is the interesting bit. > > (lldb) dis -s 0x000140001B60 -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 > $-0x8000, %rsi ; imm = 0x8000 > hello_world_std.efi[0x140001b7c]: 4c 21 c6 andq %r8, > %rsi > > RCX - > > 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 >> wrote: >> >> Ayush, >> >> CR2 is the fault address so 0x. Given for EFI Virt == >> Physical the fault address looks like a bad
Re: [edk2-devel] Casting i128 into f64 in UEFI Rust pagefaults
Ops… Looks like your PE/COFF is linked at 0x00014000, so 0x140001b60 is
the interesting bit.
(lldb) dis -s 0x000140001B60 -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
$-0x8000, %rsi ; imm = 0x8000
hello_world_std.efi[0x140001b7c]: 4c 21 c6 andq %r8,
%rsi
RCX -
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
> wrote:
>
> Ayush,
>
> CR2 is the fault address so 0x. 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: 0x0603C000
> The fault PC/RIP is: 0603DB60
>
> 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 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 -
>> ExceptionData - I:0 R:0 U:0 W:0 P:0 PK:0 SS:0 SGX:0
>> RIP - 0603DB60, CS - 0038, RFLAGS - 0246
>> RAX - , RCX - , RDX -
>> RBX - , RSP - 07EDF1D0, RBP - 07EDF4C0
>> RSI - 07EDF360, RDI - 07EDF3C0
>> R8 - , R9 - 0038, R10 -
>> R11 - , R12 - 060C6018, R13 - 07EDF520
>> R14 - 07EDF6A8, R15 - 05FA9490
>> DS - 0030, ES - 0030, FS - 0030
>> GS - 0030, SS - 0030
>> CR0 - 80010033, CR2 - , CR3 - 07C01000
>> CR4 - 0668, CR8 -
>> DR0 - , DR1 - , DR2 -
>> DR3 - , DR6 - 0FF0, DR7 - 0400
>> GDTR - 079DE000 0047, LDTR -
>> IDTR - 07418018 0FFF, TR -
>> FXSAVE_STATE - 07EDEE30
>> 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=0603C000, EntryPoint=0603D8C0)
>>
>> ```
>>
>>
>> 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]:
>>
Re: [edk2-devel] Casting i128 into f64 in UEFI Rust pagefaults
Ayush,
CR2 is the fault address so 0x. 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: 0x0603C000
The fault PC/RIP is: 0603DB60
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 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 -
> ExceptionData - I:0 R:0 U:0 W:0 P:0 PK:0 SS:0 SGX:0
> RIP - 0603DB60, CS - 0038, RFLAGS - 0246
> RAX - , RCX - , RDX -
> RBX - , RSP - 07EDF1D0, RBP - 07EDF4C0
> RSI - 07EDF360, RDI - 07EDF3C0
> R8 - , R9 - 0038, R10 -
> R11 - , R12 - 060C6018, R13 - 07EDF520
> R14 - 07EDF6A8, R15 - 05FA9490
> DS - 0030, ES - 0030, FS - 0030
> GS - 0030, SS - 0030
> CR0 - 80010033, CR2 - , CR3 - 07C01000
> CR4 - 0668, CR8 -
> DR0 - , DR1 - , DR2 -
> DR3 - , DR6 - 0FF0, DR7 - 0400
> GDTR - 079DE000 0047, LDTR -
> IDTR - 07418018 0FFF, TR -
> FXSAVE_STATE - 07EDEE30
> 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=0603C000, EntryPoint=0603D8C0)
>
> ```
>
>
> 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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[edk2-devel] Casting i128 into f64 in UEFI Rust pagefaults
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 -
ExceptionData - I:0 R:0 U:0 W:0 P:0 PK:0 SS:0 SGX:0
RIP - 0603DB60, CS - 0038, RFLAGS - 0246
RAX - , RCX - , RDX -
RBX - , RSP - 07EDF1D0, RBP - 07EDF4C0
RSI - 07EDF360, RDI - 07EDF3C0
R8 - , R9 - 0038, R10 -
R11 - , R12 - 060C6018, R13 - 07EDF520
R14 - 07EDF6A8, R15 - 05FA9490
DS - 0030, ES - 0030, FS - 0030
GS - 0030, SS - 0030
CR0 - 80010033, CR2 - , CR3 - 07C01000
CR4 - 0668, CR8 -
DR0 - , DR1 - , DR2 -
DR3 - , DR6 - 0FF0, DR7 - 0400
GDTR - 079DE000 0047, LDTR -
IDTR - 07418018 0FFF, TR -
FXSAVE_STATE - 07EDEE30
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=0603C000, EntryPoint=0603D8C0)
```
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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