[lldb] [lit] Introduce tests for reading x86 general purpose registers

[mgorny]

Summary

Introduce tests for reading the eight x86 general purpose registers,
i.e. RAX/RBX/RCX/RDX/RBP/RSP/RSI/RDI and their shorter counterparts.
The test comes in separate 32-bit and 64-bit variant, targeting
appropriate processors.

While technically the 32-bit test could run on amd64, it would be
redundant to the 64-bit version, so just run one of them on each arch.

[mgorny]

GCC refuses to build this with:

Inputs/x86-64-gp-read.cpp: In function ‘int main()’:
Inputs/x86-64-gp-read.cpp:31:1: error: bp cannot be used in asm here
 }
 ^
Inputs/x86-gp-read.cpp: In function ‘int main()’:
Inputs/x86-gp-read.cpp:31:1: error: bp cannot be used in asm here
 }
 ^

Clang doesn't complain but it also seems to generally exhibit special assumptions about *bp not being touched by assembly. In this particular case, it seems to generate correct code (with push/pop for rbp around my code).

[mgorny]

Oh wait, that push/pop doesn't really work when I modify the stack pointer ;-). I suppose this doesn't really cause any problems because we don't continue the program past int3 though.

[mgorny]

Updated to avoid returning to the program with corrupt RSP/RBP. In the 64-bit version, I'm saving the initial values in %r8 and %r9; in the 32-bit version, I'm using %mm0 and %mm1.

[mgorny]

Also included -fomit-frame-pointer, for CLI compatibility with gcc (i.e. in case clang becomes more strict in the future).

[labath]

Looks good to me. In your place, I wouldn't bother with making sure that the process can correctly terminate after we have read the registers, but now that you have done it, there's no reason to take it out. :)

lit/Register/Inputs/x86-64-gp-read.cpp

+#include <cstdint>
+
+int main() {
+  constexpr uint64_t rax = 0x0102030405060708;
+  constexpr uint64_t rbx = 0x1112131415161718;
+  constexpr uint64_t rcx = 0x2122232425262728;
+  constexpr uint64_t rdx = 0x3132333435363738;
+  constexpr uint64_t rsp = 0x4142434445464748;
+  constexpr uint64_t rbp = 0x5152535455565758;
+  constexpr uint64_t rsi = 0x6162636465666768;
+  constexpr uint64_t rdi = 0x7172737475767778;
+
+  asm volatile(
+    // save rsp & rbp
+    "movq    %%rsp, %%r8\n\t"
+    "movq    %%rbp, %%r9\n\t"
+    "\n\t"
+    "movq    %0, %%rax\n\t"
+    "movq    %1, %%rbx\n\t"
+    "movq    %2, %%rcx\n\t"
+    "movq    %3, %%rdx\n\t"
+    "movq    %4, %%rsp\n\t"
+    "movq    %5, %%rbp\n\t"
+    "movq    %6, %%rsi\n\t"
+    "movq    %7, %%rdi\n\t"
+    "\n\t"
+    "int3\n\t"
+    "\n\t"
+    // restore rsp & rbp
+    "movq    %%r8, %%rsp\n\t"
+    "movq    %%r9, %%rbp"
+    :
+    : "i"(rax), "i"(rbx), "i"(rcx), "i"(rdx), "i"(rsp), "i"(rbp), "i"(rsi),
+      "i"(rdi)
+    : "%rax", "%rbx", "%rcx", "%rdx", "%rsp", "%rbp", "%rsi", "%rdi", "%r8",
+      "%r9"
+  );
+
+  return 0;
+}

lit/Register/Inputs/x86-gp-read.cpp

+#include <cstdint>
+
+int main() {
+  constexpr uint32_t eax = 0x05060708;
+  constexpr uint32_t ebx = 0x15161718;
+  constexpr uint32_t ecx = 0x25262728;
+  constexpr uint32_t edx = 0x35363738;
+  constexpr uint32_t esp = 0x45464748;
+  constexpr uint32_t ebp = 0x55565758;
+  constexpr uint32_t esi = 0x65666768;
+  constexpr uint32_t edi = 0x75767778;
+
+  asm volatile(
+    // save esp & ebp
+    "movd    %%esp, %%mm0\n\t"
+    "movd    %%ebp, %%mm1\n\t"
+    "\n\t"
+    "movl    %0, %%eax\n\t"
+    "movl    %1, %%ebx\n\t"
+    "movl    %2, %%ecx\n\t"
+    "movl    %3, %%edx\n\t"
+    "movl    %4, %%esp\n\t"
+    "movl    %5, %%ebp\n\t"
+    "movl    %6, %%esi\n\t"
+    "movl    %7, %%edi\n\t"
+    "\n\t"
+    "int3\n\t"
+    "\n\t"
+    // restore esp & ebp
+    "movd    %%mm0, %%esp\n\t"
+    "movd    %%mm1, %%ebp\n\t"
+    :
+    : "i"(eax), "i"(ebx), "i"(ecx), "i"(edx), "i"(esp), "i"(ebp), "i"(esi),
+      "i"(edi)
+    : "%eax", "%ebx", "%ecx", "%edx", "%esp", "%ebp", "%esi", "%edi", "%mm0",
+      "%mm1"
+  );
+
+  return 0;
+}

lit/Register/x86-64-gp-read.test

+# XFAIL: system-windows
+# REQUIRES: native && target-x86_64
+# RUN: %clangxx -fomit-frame-pointer %p/Inputs/x86-64-gp-read.cpp -o %t
+# RUN: %lldb -b -s %s %t | FileCheck %s
+process launch
+
+register read --all
+# CHECK-DAG: rax = 0x0102030405060708
+# CHECK-DAG: rbx = 0x1112131415161718
+# CHECK-DAG: rcx = 0x2122232425262728
+# CHECK-DAG: rdx = 0x3132333435363738
+# CHECK-DAG: rdi = 0x7172737475767778
+# CHECK-DAG: rsi = 0x6162636465666768
+# CHECK-DAG: rbp = 0x5152535455565758
+# CHECK-DAG: rsp = 0x4142434445464748
+# CHECK-DAG: eax = 0x05060708
+# CHECK-DAG: ebx = 0x15161718
+# CHECK-DAG: ecx = 0x25262728
+# CHECK-DAG: edx = 0x35363738
+# CHECK-DAG: edi = 0x75767778
+# CHECK-DAG: esi = 0x65666768
+# CHECK-DAG: ebp = 0x55565758
+# CHECK-DAG: esp = 0x45464748
+# CHECK-DAG: ax = 0x0708
+# CHECK-DAG: bx = 0x1718
+# CHECK-DAG: cx = 0x2728
+# CHECK-DAG: dx = 0x3738
+# CHECK-DAG: di = 0x7778
+# CHECK-DAG: si = 0x6768
+# CHECK-DAG: bp = 0x5758
+# CHECK-DAG: sp = 0x4748
+# CHECK-DAG: ah = 0x07
+# CHECK-DAG: bh = 0x17
+# CHECK-DAG: ch = 0x27
+# CHECK-DAG: dh = 0x37
+# CHECK-DAG: al = 0x08
+# CHECK-DAG: bl = 0x18
+# CHECK-DAG: cl = 0x28
+# CHECK-DAG: dl = 0x38
+
+process continue
+# CHECK: Process {{[0-9]+}} exited with status = 0

lit/Register/x86-gp-read.test

+# XFAIL: system-windows
+# REQUIRES: native && target-x86
+# RUN: %clangxx -fomit-frame-pointer %p/Inputs/x86-gp-read.cpp -o %t
+# RUN: %lldb -b -s %s %t | FileCheck %s
+process launch
+
+register read --all
+# CHECK-DAG: eax = 0x05060708
+# CHECK-DAG: ebx = 0x15161718
+# CHECK-DAG: ecx = 0x25262728
+# CHECK-DAG: edx = 0x35363738
+# CHECK-DAG: edi = 0x75767778
+# CHECK-DAG: esi = 0x65666768
+# CHECK-DAG: ebp = 0x55565758
+# CHECK-DAG: esp = 0x45464748
+# CHECK-DAG: ax = 0x0708
+# CHECK-DAG: bx = 0x1718
+# CHECK-DAG: cx = 0x2728
+# CHECK-DAG: dx = 0x3738
+# CHECK-DAG: di = 0x7778
+# CHECK-DAG: si = 0x6768
+# CHECK-DAG: bp = 0x5758
+# CHECK-DAG: sp = 0x4748
+# CHECK-DAG: ah = 0x07
+# CHECK-DAG: bh = 0x17
+# CHECK-DAG: ch = 0x27
+# CHECK-DAG: dh = 0x37
+# CHECK-DAG: al = 0x08
+# CHECK-DAG: bl = 0x18
+# CHECK-DAG: cl = 0x28
+# CHECK-DAG: dl = 0x38
+
+process continue
+# CHECK: Process {{[0-9]+}} exited with status = 0