[llvm] [BOLT][binary-analysis] Add initial pac-ret gadget scanner (PR #122304)

[Anatoly Trosinenko via llvm-commits]

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@@ -0,0 +1,46 @@
+// RUN: %clang %cflags -march=armv8.3-a -mbranch-protection=pac-ret %s %p/../../Inputs/asm_main.c -o %t.exe
+// RUN: llvm-bolt-binary-analysis --scanners=pacret %t.exe 2>&1 | FileCheck -check-prefix=CHECK --allow-empty %s
+
+
+// Verify that we can also detect gadgets across basic blocks
+
+        .globl f_crossbb1
+        .type   f_crossbb1, at function
+f_crossbb1:
+        hint    #25
+        stp     x29, x30, [sp, #-16]!
+        ldp     x29, x30, [sp], #16
+        cbnz    x0, 1f
+        autiasp
+1:
+        ret
+        .size f_crossbb1, .-f_crossbb1
+// CHECK-LABEL:     GS-PACRET: non-protected ret found in function f_crossbb1, basic block .L{{[^,]+}}, at address
+// CHECK-NEXT:  The return instruction is     {{[0-9a-f]+}}:       ret
+// CHECK-NEXT:  The 2 instructions that write to the return register after any authentication are:
+// CHECK-NEXT:  1.     {{[0-9a-f]+}}:      ldp     x29, x30, [sp], #0x10
+// CHECK-NEXT:  2.     {{[0-9a-f]+}}:      autiasp
+
+// A test that checks that the dataflow state tracking across when merging BBs
+// seems to work:
+        .globl f_mergebb1
+        .type   f_mergebb1, at function
+f_mergebb1:
+        hint    #25
+2:
+        stp     x29, x30, [sp, #-16]!
+        ldp     x29, x30, [sp], #16
+        sub     x0, x0, #1
+        cbnz    x0, 1f
+        autiasp
+        b       2b
+1:
+        ret
+        .size f_mergebb1, .-f_mergebb1
+// CHECK-LABEL: GS-PACRET: non-protected ret found in function f_mergebb1, basic block .L{{[^,]+}}, at address
+// CHECK-NEXT:    The return instruction is     {{[0-9a-f]+}}:       ret
+// CHECK-NEXT:    The 1 instructions that write to the return register after any authentication are:
+// CHECK-NEXT:    1.     {{[0-9a-f]+}}:      ldp     x29, x30, [sp], #0x10
+
----------------
atrosinenko wrote:

A test case similar to shrink-wrapping could probably be interesting, too:
```
        cbz     x0, 1f
        hint    #25
        stp     x29, x30, [sp, #-16]!
        ldp     x29, x30, [sp], #16
        autiasp
1:
        ret
```

https://github.com/llvm/llvm-project/pull/122304