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Diffstat (limited to 'tests/assembly/stack-protector/stack-protector-heuristics-effect.rs')
| -rw-r--r-- | tests/assembly/stack-protector/stack-protector-heuristics-effect.rs | 396 |
1 files changed, 396 insertions, 0 deletions
diff --git a/tests/assembly/stack-protector/stack-protector-heuristics-effect.rs b/tests/assembly/stack-protector/stack-protector-heuristics-effect.rs new file mode 100644 index 000000000..7c2b60550 --- /dev/null +++ b/tests/assembly/stack-protector/stack-protector-heuristics-effect.rs @@ -0,0 +1,396 @@ +// revisions: all strong basic none missing +// assembly-output: emit-asm +// ignore-macos slightly different policy on stack protection of arrays +// ignore-windows stack check code uses different function names +// ignore-nvptx64 stack protector is not supported +// [all] compile-flags: -Z stack-protector=all +// [strong] compile-flags: -Z stack-protector=strong +// [basic] compile-flags: -Z stack-protector=basic +// [none] compile-flags: -Z stack-protector=none +// compile-flags: -C opt-level=2 -Z merge-functions=disabled + +#![crate_type = "lib"] + +#![allow(incomplete_features)] + +#![feature(unsized_locals, unsized_fn_params)] + + +// CHECK-LABEL: emptyfn: +#[no_mangle] +pub fn emptyfn() { + // all: __stack_chk_fail + // strong-NOT: __stack_chk_fail + // basic-NOT: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} + +// CHECK-LABEL: array_char +#[no_mangle] +pub fn array_char(f: fn(*const char)) { + let a = ['c'; 1]; + let b = ['d'; 3]; + let c = ['e'; 15]; + + f(&a as *const _); + f(&b as *const _); + f(&c as *const _); + + // Any type of local array variable leads to stack protection with the + // "strong" heuristic. The 'basic' heuristic only adds stack protection to + // functions with local array variables of a byte-sized type, however. Since + // 'char' is 4 bytes in Rust, this function is not protected by the 'basic' + // heuristic + // + // (This test *also* takes the address of the local stack variables. We + // cannot know that this isn't what triggers the `strong` heuristic. + // However, the test strategy of passing the address of a stack array to an + // external function is sufficient to trigger the `basic` heuristic (see + // test `array_u8_large()`). Since the `basic` heuristic only checks for the + // presence of stack-local array variables, we can be confident that this + // test also captures this part of the `strong` heuristic specification.) + + // all: __stack_chk_fail + // strong: __stack_chk_fail + // basic-NOT: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} + +// CHECK-LABEL: array_u8_1 +#[no_mangle] +pub fn array_u8_1(f: fn(*const u8)) { + let a = [0u8; 1]; + f(&a as *const _); + + // The 'strong' heuristic adds stack protection to functions with local + // array variables regardless of their size. + + // all: __stack_chk_fail + // strong: __stack_chk_fail + // basic-NOT: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} + +// CHECK-LABEL: array_u8_small: +#[no_mangle] +pub fn array_u8_small(f: fn(*const u8)) { + let a = [0u8; 2]; + let b = [0u8; 7]; + f(&a as *const _); + f(&b as *const _); + + // Small arrays do not lead to stack protection by the 'basic' heuristic. + + // all: __stack_chk_fail + // strong: __stack_chk_fail + // basic-NOT: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} + +// CHECK-LABEL: array_u8_large: +#[no_mangle] +pub fn array_u8_large(f: fn(*const u8)) { + let a = [0u8; 9]; + f(&a as *const _); + + // Since `a` is a byte array with size greater than 8, the basic heuristic + // will also protect this function. + + // all: __stack_chk_fail + // strong: __stack_chk_fail + // basic: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} + +#[derive(Copy, Clone)] +pub struct ByteSizedNewtype(u8); + +// CHECK-LABEL: array_bytesizednewtype_9: +#[no_mangle] +pub fn array_bytesizednewtype_9(f: fn(*const ByteSizedNewtype)) { + let a = [ByteSizedNewtype(0); 9]; + f(&a as *const _); + + // Since `a` is a byte array in the LLVM output, the basic heuristic will + // also protect this function. + + // all: __stack_chk_fail + // strong: __stack_chk_fail + // basic: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} + +// CHECK-LABEL: local_var_addr_used_indirectly +#[no_mangle] +pub fn local_var_addr_used_indirectly(f: fn(bool)) { + let a = 5; + let a_addr = &a as *const _ as usize; + f(a_addr & 0x10 == 0); + + // This function takes the address of a local variable taken. Although this + // address is never used as a way to refer to stack memory, the `strong` + // heuristic adds stack smash protection. This is also the case in C++: + // ``` + // cat << EOF | clang++ -O2 -fstack-protector-strong -S -x c++ - -o - | grep stack_chk + // #include <cstdint> + // void f(void (*g)(bool)) { + // int32_t x; + // g((reinterpret_cast<uintptr_t>(&x) & 0x10U) == 0); + // } + // EOF + // ``` + + // all: __stack_chk_fail + // strong: __stack_chk_fail + // basic-NOT: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} + + +// CHECK-LABEL: local_string_addr_taken +#[no_mangle] +pub fn local_string_addr_taken(f: fn(&String)) { + let x = String::new(); + f(&x); + + // Taking the address of the local variable `x` leads to stack smash + // protection with the `strong` heuristic, but not with the `basic` + // heuristic. It does not matter that the reference is not mut. + // + // An interesting note is that a similar function in C++ *would* be + // protected by the `basic` heuristic, because `std::string` has a char + // array internally as a small object optimization: + // ``` + // cat <<EOF | clang++ -O2 -fstack-protector -S -x c++ - -o - | grep stack_chk + // #include <string> + // void f(void (*g)(const std::string&)) { + // std::string x; + // g(x); + // } + // EOF + // ``` + // + + // all: __stack_chk_fail + // strong: __stack_chk_fail + // basic-NOT: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} + +pub trait SelfByRef { + fn f(&self) -> i32; +} + +impl SelfByRef for i32 { + fn f(&self) -> i32 { + return self + 1; + } +} + +// CHECK-LABEL: local_var_addr_taken_used_locally_only +#[no_mangle] +pub fn local_var_addr_taken_used_locally_only(factory: fn() -> i32, sink: fn(i32)) { + let x = factory(); + let g = x.f(); + sink(g); + + // Even though the local variable conceptually has its address taken, as + // it's passed by reference to the trait function, the use of the reference + // is easily inlined. There is therefore no stack smash protection even with + // the `strong` heuristic. + + // all: __stack_chk_fail + // strong-NOT: __stack_chk_fail + // basic-NOT: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} + +pub struct Gigastruct { + does: u64, + not: u64, + have: u64, + array: u64, + members: u64 +} + +// CHECK-LABEL: local_large_var_moved +#[no_mangle] +pub fn local_large_var_moved(f: fn(Gigastruct)) { + let x = Gigastruct { does: 0, not: 1, have: 2, array: 3, members: 4 }; + f(x); + + // Even though the local variable conceptually doesn't have its address + // taken, it's so large that the "move" is implemented with a reference to a + // stack-local variable in the ABI. Consequently, this function *is* + // protected by the `strong` heuristic. This is also the case for + // rvalue-references in C++, regardless of struct size: + // ``` + // cat <<EOF | clang++ -O2 -fstack-protector-strong -S -x c++ - -o - | grep stack_chk + // #include <cstdint> + // #include <utility> + // void f(void (*g)(uint64_t&&)) { + // uint64_t x; + // g(std::move(x)); + // } + // EOF + // ``` + + // all: __stack_chk_fail + // strong: __stack_chk_fail + // basic-NOT: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} + +// CHECK-LABEL: local_large_var_cloned +#[no_mangle] +pub fn local_large_var_cloned(f: fn(Gigastruct)) { + f(Gigastruct { does: 0, not: 1, have: 2, array: 3, members: 4 }); + + // A new instance of `Gigastruct` is passed to `f()`, without any apparent + // connection to this stack frame. Still, since instances of `Gigastruct` + // are sufficiently large, it is allocated in the caller stack frame and + // passed as a pointer. As such, this function is *also* protected by the + // `strong` heuristic, just like `local_large_var_moved`. This is also the + // case for pass-by-value of sufficiently large structs in C++: + // ``` + // cat <<EOF | clang++ -O2 -fstack-protector-strong -S -x c++ - -o - | grep stack_chk + // #include <cstdint> + // #include <utility> + // struct Gigastruct { uint64_t a, b, c, d, e; }; + // void f(void (*g)(Gigastruct)) { + // g(Gigastruct{}); + // } + // EOF + // ``` + + + // all: __stack_chk_fail + // strong: __stack_chk_fail + // basic-NOT: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} + + +extern "C" { + // A call to an external `alloca` function is *not* recognized as an + // `alloca(3)` operation. This function is a compiler built-in, as the + // man page explains. Clang translates it to an LLVM `alloca` + // instruction with a count argument, which is also what the LLVM stack + // protector heuristics looks for. The man page for `alloca(3)` details + // a way to avoid using the compiler built-in: pass a -std=c11 + // argument, *and* don't include <alloca.h>. Though this leads to an + // external alloca() function being called, it doesn't lead to stack + // protection being included. It even fails with a linker error + // "undefined reference to `alloca'". Example: + // ``` + // cat<<EOF | clang -fstack-protector-strong -x c -std=c11 - -o /dev/null + // #include <stdlib.h> + // void * alloca(size_t); + // void f(void (*g)(void*)) { + // void * p = alloca(10); + // g(p); + // } + // int main() { return 0; } + // EOF + // ``` + // The following tests demonstrate that calls to an external `alloca` + // function in Rust also doesn't trigger stack protection. + + fn alloca(size: usize) -> *mut (); +} + +// CHECK-LABEL: alloca_small_compile_time_constant_arg +#[no_mangle] +pub fn alloca_small_compile_time_constant_arg(f: fn(*mut ())) { + f(unsafe { alloca(8) }); + + // all: __stack_chk_fail + // strong-NOT: __stack_chk_fail + // basic-NOT: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} + +// CHECK-LABEL: alloca_large_compile_time_constant_arg +#[no_mangle] +pub fn alloca_large_compile_time_constant_arg(f: fn(*mut ())) { + f(unsafe { alloca(9) }); + + // all: __stack_chk_fail + // strong-NOT: __stack_chk_fail + // basic-NOT: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} + + +// CHECK-LABEL: alloca_dynamic_arg +#[no_mangle] +pub fn alloca_dynamic_arg(f: fn(*mut ()), n: usize) { + f(unsafe { alloca(n) }); + + // all: __stack_chk_fail + // strong-NOT: __stack_chk_fail + // basic-NOT: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} + +// The question then is: in what ways can Rust code generate array-`alloca` +// LLVM instructions? This appears to only be generated by +// rustc_codegen_ssa::traits::Builder::array_alloca() through +// rustc_codegen_ssa::mir::operand::OperandValue::store_unsized(). FWICT +// this is support for the "unsized locals" unstable feature: +// https://doc.rust-lang.org/unstable-book/language-features/unsized-locals.html. + + +// CHECK-LABEL: unsized_fn_param +#[no_mangle] +pub fn unsized_fn_param(s: [u8], l: bool, f: fn([u8])) { + let n = if l { 1 } else { 2 }; + f(*Box::<[u8]>::from(&s[0..n])); // slice-copy with Box::from + + // Even though slices are conceptually passed by-value both into this + // function and into `f()`, this is implemented with pass-by-reference + // using a suitably constructed fat-pointer (as if the functions + // accepted &[u8]). This function therefore doesn't need dynamic array + // alloca, and is therefore not protected by the `strong` or `basic` + // heuristics. + + + // all: __stack_chk_fail + // strong-NOT: __stack_chk_fail + // basic-NOT: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} + +// CHECK-LABEL: unsized_local +#[no_mangle] +pub fn unsized_local(s: &[u8], l: bool, f: fn(&mut [u8])) { + let n = if l { 1 } else { 2 }; + let mut a: [u8] = *Box::<[u8]>::from(&s[0..n]); // slice-copy with Box::from + f(&mut a); + + // This function allocates a slice as a local variable in its stack + // frame. Since the size is not a compile-time constant, an array + // alloca is required, and the function is protected by both the + // `strong` and `basic` heuristic. + + // all: __stack_chk_fail + // strong: __stack_chk_fail + // basic: __stack_chk_fail + // none-NOT: __stack_chk_fail + // missing-NOT: __stack_chk_fail +} |