delve/pkg/proc/native/registers_linux_arm64.go
Alessandro Arzilli 200994bc8f
proc/*: only load floating point registers when needed (#1981)
Changes implementations of proc.Registers interface and the
op.DwarfRegisters struct so that floating point registers can be loaded
only when they are needed.
Removes the floatingPoint parameter from proc.Thread.Registers.
This accomplishes three things:

1. it simplifies the proc.Thread.Registers interface
2. it makes it impossible to accidentally create a broken set of saved
   registers or of op.DwarfRegisters by accidentally calling
   Registers(false)
3. it improves general performance of Delve by avoiding to load
   floating point registers as much as possible

Floating point registers are loaded under two circumstances:

1. When the Slice method is called with floatingPoint == true
2. When the Copy method is called

Benchmark before:

BenchmarkConditionalBreakpoints-4   	       1	4327350142 ns/op

Benchmark after:

BenchmarkConditionalBreakpoints-4   	       1	3852642917 ns/op

Updates #1549
2020-05-13 11:56:50 -07:00

102 lines
2.7 KiB
Go

package native
import (
"debug/elf"
"fmt"
"syscall"
"unsafe"
sys "golang.org/x/sys/unix"
"github.com/go-delve/delve/pkg/proc"
"github.com/go-delve/delve/pkg/proc/linutil"
)
const (
_AARCH64_GREGS_SIZE = 34 * 8
_AARCH64_FPREGS_SIZE = 32*16 + 8
)
func ptraceGetGRegs(pid int, regs *linutil.ARM64PtraceRegs) (err error) {
iov := sys.Iovec{Base: (*byte)(unsafe.Pointer(regs)), Len: _AARCH64_GREGS_SIZE}
_, _, err = syscall.Syscall6(syscall.SYS_PTRACE, sys.PTRACE_GETREGSET, uintptr(pid), uintptr(elf.NT_PRSTATUS), uintptr(unsafe.Pointer(&iov)), 0, 0)
if err == syscall.Errno(0) {
err = nil
}
return
}
func ptraceSetGRegs(pid int, regs *linutil.ARM64PtraceRegs) (err error) {
iov := sys.Iovec{Base: (*byte)(unsafe.Pointer(regs)), Len: _AARCH64_GREGS_SIZE}
_, _, err = syscall.Syscall6(syscall.SYS_PTRACE, sys.PTRACE_SETREGSET, uintptr(pid), uintptr(elf.NT_PRSTATUS), uintptr(unsafe.Pointer(&iov)), 0, 0)
if err == syscall.Errno(0) {
err = nil
}
return
}
// ptraceGetFpRegset returns floating point registers of the specified thread
// using PTRACE.
func ptraceGetFpRegset(tid int) (fpregset []byte, err error) {
var arm64_fpregs [_AARCH64_FPREGS_SIZE]byte
iov := sys.Iovec{Base: &arm64_fpregs[0], Len: _AARCH64_FPREGS_SIZE}
_, _, err = syscall.Syscall6(syscall.SYS_PTRACE, sys.PTRACE_GETREGSET, uintptr(tid), uintptr(elf.NT_FPREGSET), uintptr(unsafe.Pointer(&iov)), 0, 0)
if err != syscall.Errno(0) {
if err == syscall.ENODEV {
err = nil
}
return
} else {
err = nil
}
fpregset = arm64_fpregs[:iov.Len-8]
return fpregset, err
}
// SetPC sets PC to the value specified by 'pc'.
func (thread *nativeThread) SetPC(pc uint64) error {
ir, err := registers(thread)
if err != nil {
return err
}
r := ir.(*linutil.ARM64Registers)
r.Regs.Pc = pc
thread.dbp.execPtraceFunc(func() { err = ptraceSetGRegs(thread.ID, r.Regs) })
return err
}
// SetSP sets RSP to the value specified by 'sp'
func (thread *nativeThread) SetSP(sp uint64) (err error) {
var ir proc.Registers
ir, err = registers(thread)
if err != nil {
return err
}
r := ir.(*linutil.ARM64Registers)
r.Regs.Sp = sp
thread.dbp.execPtraceFunc(func() { err = ptraceSetGRegs(thread.ID, r.Regs) })
return
}
func (thread *nativeThread) SetDX(dx uint64) (err error) {
return fmt.Errorf("not supported")
}
func registers(thread *nativeThread) (proc.Registers, error) {
var (
regs linutil.ARM64PtraceRegs
err error
)
thread.dbp.execPtraceFunc(func() { err = ptraceGetGRegs(thread.ID, &regs) })
if err != nil {
return nil, err
}
r := linutil.NewARM64Registers(&regs, func(r *linutil.ARM64Registers) error {
var floatLoadError error
r.Fpregs, r.Fpregset, floatLoadError = thread.fpRegisters()
return floatLoadError
})
return r, nil
}