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*Total -- 529.94kb -> 339.12kb (36.01%) /src/librustdoc/html/static/favicon-16x16.png -- 2.16kb -> 1.02kb (52.98%) /src/librustdoc/html/static/favicon-32x32.png -- 2.85kb -> 1.40kb (50.91%) /src/doc/unstable-book/src/compiler-flags/img/llvm-cov-show-01.png -- 406.98kb -> 242.19kb (40.49%) /src/doc/rustc/src/images/image1.png -- 14.93kb -> 11.67kb (21.89%) /src/doc/rustc/src/images/image3.png -- 70.71kb -> 56.50kb (20.1%) /src/doc/rustc/src/images/image2.png -- 28.10kb -> 22.50kb (19.92%) /src/librustdoc/html/static/favicon.svg -- 4.20kb -> 3.84kb (8.54%) Signed-off-by: ImgBotApp <[email protected]>
pthariensflame
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Feb 20, 2021
HWAddressSanitizer support # Motivation Compared to regular ASan, HWASan has a [smaller overhead](https://source.android.com/devices/tech/debug/hwasan). The difference in practice is that HWASan'ed code is more usable, e.g. Android device compiled with HWASan can be used as a daily driver. # Example ``` fn main() { let xs = vec![0, 1, 2, 3]; let _y = unsafe { *xs.as_ptr().offset(4) }; } ``` ``` ==223==ERROR: HWAddressSanitizer: tag-mismatch on address 0xefdeffff0050 at pc 0xaaaad00b3468 READ of size 4 at 0xefdeffff0050 tags: e5/00 (ptr/mem) in thread T0 #0 0xaaaad00b3464 (/root/main+0x53464) #1 0xaaaad00b39b4 (/root/main+0x539b4) #2 0xaaaad00b3dd0 (/root/main+0x53dd0) #3 0xaaaad00b61dc (/root/main+0x561dc) #4 0xaaaad00c0574 (/root/main+0x60574) #5 0xaaaad00b6290 (/root/main+0x56290) rust-lang#6 0xaaaad00b6170 (/root/main+0x56170) rust-lang#7 0xaaaad00b3578 (/root/main+0x53578) rust-lang#8 0xffff81345e70 (/lib64/libc.so.6+0x20e70) rust-lang#9 0xaaaad0096310 (/root/main+0x36310) [0xefdeffff0040,0xefdeffff0060) is a small allocated heap chunk; size: 32 offset: 16 0xefdeffff0050 is located 0 bytes to the right of 16-byte region [0xefdeffff0040,0xefdeffff0050) allocated here: #0 0xaaaad009bcdc (/root/main+0x3bcdc) #1 0xaaaad00b1eb0 (/root/main+0x51eb0) #2 0xaaaad00b20d4 (/root/main+0x520d4) #3 0xaaaad00b2800 (/root/main+0x52800) #4 0xaaaad00b1cf4 (/root/main+0x51cf4) #5 0xaaaad00b33d4 (/root/main+0x533d4) rust-lang#6 0xaaaad00b39b4 (/root/main+0x539b4) rust-lang#7 0xaaaad00b61dc (/root/main+0x561dc) rust-lang#8 0xaaaad00b3578 (/root/main+0x53578) rust-lang#9 0xaaaad0096310 (/root/main+0x36310) Thread: T0 0xeffe00002000 stack: [0xffffc0590000,0xffffc0d90000) sz: 8388608 tls: [0xffff81521020,0xffff815217d0) Memory tags around the buggy address (one tag corresponds to 16 bytes): 0xfefcefffef80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefcefffef90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefcefffefa0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefcefffefb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefcefffefc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefcefffefd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefcefffefe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefcefffeff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 =>0xfefceffff000: a2 a2 05 00 e5 [00] 00 00 00 00 00 00 00 00 00 00 0xfefceffff010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefceffff020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefceffff030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefceffff040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefceffff050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefceffff060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefceffff070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefceffff080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Tags for short granules around the buggy address (one tag corresponds to 16 bytes): 0xfefcefffeff0: .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. =>0xfefceffff000: .. .. c5 .. .. [..] .. .. .. .. .. .. .. .. .. .. 0xfefceffff010: .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. See https://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html#short-granules for a description of short granule tags Registers where the failure occurred (pc 0xaaaad00b3468): x0 e500efdeffff0050 x1 0000000000000004 x2 0000ffffc0d8f5a0 x3 0200efff00000000 x4 0000ffffc0d8f4c0 x5 000000000000004f x6 00000ffffc0d8f36 x7 0000efff00000000 x8 e500efdeffff0050 x9 0200efff00000000 x10 0000000000000000 x11 0200efff00000000 x12 0200effe000006b0 x13 0200effe000006b0 x14 0000000000000008 x15 00000000c00000cf x16 0000aaaad00a0afc x17 0000000000000003 x18 0000000000000001 x19 0000ffffc0d8f718 x20 ba00ffffc0d8f7a0 x21 0000aaaad00962e0 x22 0000000000000000 x23 0000000000000000 x24 0000000000000000 x25 0000000000000000 x26 0000000000000000 x27 0000000000000000 x28 0000000000000000 x29 0000ffffc0d8f650 x30 0000aaaad00b3468 ``` # Comments/Caveats * HWASan is only supported on arm64. * I'm not sure if I should add a feature gate or piggyback on the existing one for sanitizers. * HWASan requires `-C target-feature=+tagged-globals`. That flag should probably be set transparently to the user. Not sure how to go about that. # TODO * Need more tests. * Update documentation. * Fix symbolization. * Integrate with CI
pthariensflame
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Sep 14, 2025
match clang's `va_arg` assembly on arm targets tracking issue: rust-lang#44930 For this example ```rust #![feature(c_variadic)] #[unsafe(no_mangle)] unsafe extern "C" fn variadic(a: f64, mut args: ...) -> f64 { let b = args.arg::<f64>(); let c = args.arg::<f64>(); a + b + c } ``` We currently generate (via llvm): ```asm variadic: sub sp, sp, rust-lang#12 stmib sp, {r2, r3} vmov d0, r0, r1 add r0, sp, #4 vldr d1, [sp, #4] add r0, r0, rust-lang#15 bic r0, r0, rust-lang#7 vadd.f64 d0, d0, d1 add r1, r0, rust-lang#8 str r1, [sp] vldr d1, [r0] vadd.f64 d0, d0, d1 vmov r0, r1, d0 add sp, sp, rust-lang#12 bx lr ``` LLVM is not doing a good job. In fact, it's well-known that LLVM's implementation of `va_arg` is kind of bad, and we implement it ourselves (based on clang) for many targets already. For arm, our own `emit_ptr_va_arg` saves 3 instructions. Next, it turns out it's important for LLVM to explicitly start and end the lifetime of the `va_list`. In rust-lang#146059 I already end the lifetime, but when looking at this again, I noticed that it is important to also start it, see https://godbolt.org/z/EGqvKTTsK: failing to explicitly start the lifetime uses an extra register. So, the combination of `emit_ptr_va_arg` with starting/ending the lifetime makes rustc emit exactly the instructions that clang generates:: ```asm variadic: sub sp, sp, rust-lang#12 stmib sp, {r2, r3} vmov d16, r0, r1 vldr d17, [sp, #4] vadd.f64 d16, d16, d17 vldr d17, [sp, rust-lang#12] vadd.f64 d16, d16, d17 vmov r0, r1, d16 add sp, sp, rust-lang#12 bx lr ``` The arguments to `emit_ptr_va_arg` are based on [the clang implementation](https://github.com/llvm/llvm-project/blob/03dc2a41f3d9a500e47b513de5c5008c06860d65/clang/lib/CodeGen/Targets/ARM.cpp#L798-L844). r? ``@workingjubilee`` (I can re-roll if your queue is too full, but you do seem like the right person here) try-job: armhf-gnu
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