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Implement inline break for linux using syscalls #28

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Implement inline break for linux using syscalls #28

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3 changes: 3 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -106,6 +106,7 @@ main () at test/break-c++.cc:6
7 std::cout << "hello, world\n";
```

On linux arm/aarch64 inlined syscall used
On AArch64, **debug_break()** generates **.inst 0xd4200000**.

See table below for the behavior of **debug_break()** on other architecturs.
Expand All @@ -116,8 +117,10 @@ Behavior on Different Architectures
| Architecture | debug_break() |
| ------------- | ------------- |
| x86/x86-64 | `int3` |
| ARM/Thumb, 32-bit, linux | `SYS_tgkill(SYS_getpid(),SYS_gettid(),SIGTRAP)` |
| ARM mode, 32-bit | `.inst 0xe7f001f0` |
| Thumb mode, 32-bit | `.inst 0xde01` |
| AArch64, ARMv8, linux | `SYS_tgkill(SYS_getpid(),SYS_gettid(),SIGTRAP)` |
| AArch64, ARMv8 | `.inst 0xd4200000` |
| POWER | `.4byte 0x7d821008` |
| RISC-V | `.4byte 0x00100073` |
Expand Down
48 changes: 48 additions & 0 deletions debugbreak.h
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Expand Up @@ -39,13 +39,35 @@ extern "C" {
#define DEBUG_BREAK_USE_TRAP_INSTRUCTION 1
#define DEBUG_BREAK_USE_BULTIN_TRAP 2
#define DEBUG_BREAK_USE_SIGTRAP 3
#define DEBUG_BREAK_USE_SYSCALL 4

#if defined(__i386__) || defined(__x86_64__)
#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_TRAP_INSTRUCTION
__inline__ static void trap_instruction(void)
{
__asm__ volatile("int $0x03");
}
#elif defined(__linux__) && (defined(__arm__) || defined(__thumb__))
#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_SYSCALL
#define INLINE_SYS_RAISE(x) do \
{ \
int raise_sig = (x); \
__asm__ volatile ( \
"mov r3, r7\n\t" \
"mov r7,#178\n\t" /* gettid */ \
"svc 0\n\t" \
"mov r1, r0\n\t" /* getpid */ \
"mov r7,#172\n\t" \
"svc 0\n\t" \
"mov r7,#268\n\t" /* tgkill */ \
"mov r2,%0\n\t" \
"svc 0\n\t" \
"mov r7, r3\n\t" \
: \
:"r"(raise_sig) \
: "r0", "r1", "r2", "r3", "memory" \
); \
} while(0)
#elif defined(__thumb__)
#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_TRAP_INSTRUCTION
/* FIXME: handle __THUMB_INTERWORK__ */
Expand Down Expand Up @@ -90,6 +112,25 @@ __inline__ static void trap_instruction(void)
/* Known problem:
* Same problem and workaround as Thumb mode */
}
#elif defined(__aarch64__) && defined(__linux__)
#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_SYSCALL
#define INLINE_SYS_RAISE(x) do \
{ \
unsigned long long raise_sig = (x); \
__asm__ volatile ( \
"mov x8,#178\n\t" /* gettid */ \
"svc 0\n\t" \
"mov x1, x0\n\t" \
"mov x8,#172\n\t" /* getpid */ \
"svc 0\n\t" \
"mov x8,#131\n\t" /* tgkill */ \
"mov x2,%0\n\t" \
"svc 0\n\t" \
: \
: "r"(raise_sig) \
: "x0", "x1", "x2", "x8", "memory", "cc" \
); \
} while(0)
#elif defined(__aarch64__) && defined(__APPLE__)
#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_BULTIN_DEBUGTRAP
#elif defined(__aarch64__)
Expand Down Expand Up @@ -136,6 +177,13 @@ __inline__ static void trap_instruction(void)

#ifndef DEBUG_BREAK_IMPL
#error "debugbreak.h is not supported on this target"
#elif DEBUG_BREAK_IMPL == DEBUG_BREAK_USE_SYSCALL
__attribute__((always_inline))
__inline__ static void debug_break(void)
{
/* SIGTRAP */
INLINE_SYS_RAISE(5);
}
#elif DEBUG_BREAK_IMPL == DEBUG_BREAK_USE_TRAP_INSTRUCTION
__attribute__((always_inline))
__inline__ static void debug_break(void)
Expand Down