[Lldb-commits] [lldb] r249379 - Bug 25050: X87 FPU Special Purpose Registers

[Zachary Turner via lldb-commits]

Please don't submit CLs like this without a test in the future.  This
should be testable by writing some assembly to move a value into an FPU
register, setting a breakpoint, then querying the register values.  Can you
submit this as a followup?

On Tue, Oct 6, 2015 at 12:05 AM Abhishek Aggarwal via lldb-commits <
lldb-commits at lists.llvm.org> wrote:

> Author: abhishek
> Date: Tue Oct  6 02:04:03 2015
> New Revision: 249379
>
> URL: http://llvm.org/viewvc/llvm-project?rev=249379&view=rev
> Log:
> Bug 25050: X87 FPU Special Purpose Registers
>
> Summary:
>   - For x86_64-FreeBSD Platform:
>     -- LLDB now provides correct values of X87 FPU
>        Special Purpose Registers like fstat, ftag, fctrl etc..
>
> Signed-off-by: Abhishek Aggarwal <abhishek.a.aggarwal at intel.com>
>
> Reviewers: emaste, mikesart, clayborg
>
> Subscribers: emaste
>
> Differential Revision: http://reviews.llvm.org/D13434
>
> Modified:
>
> lldb/trunk/source/Plugins/Process/FreeBSD/RegisterContextPOSIXProcessMonitor_x86.cpp
>
> lldb/trunk/source/Plugins/Process/FreeBSD/RegisterContextPOSIXProcessMonitor_x86.h
>
> Modified:
> lldb/trunk/source/Plugins/Process/FreeBSD/RegisterContextPOSIXProcessMonitor_x86.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Plugins/Process/FreeBSD/RegisterContextPOSIXProcessMonitor_x86.cpp?rev=249379&r1=249378&r2=249379&view=diff
>
> ==============================================================================
> ---
> lldb/trunk/source/Plugins/Process/FreeBSD/RegisterContextPOSIXProcessMonitor_x86.cpp
> (original)
> +++
> lldb/trunk/source/Plugins/Process/FreeBSD/RegisterContextPOSIXProcessMonitor_x86.cpp
> Tue Oct  6 02:04:03 2015
> @@ -58,6 +58,9 @@ RegisterContextPOSIXProcessMonitor_x86_6
>
>             lldb_private::RegisterInfoInterface *register_info)
>      : RegisterContextPOSIX_x86(thread, concrete_frame_idx, register_info)
>  {
> +    // Store byte offset of fctrl (i.e. first register of FPR) wrt
> 'UserArea'
> +    const RegisterInfo *reg_info_fctrl = GetRegisterInfoByName("fctrl");
> +    m_fctrl_offset_in_userarea = reg_info_fctrl->byte_offset;
>  }
>
>  ProcessMonitor &
> @@ -254,8 +257,15 @@ RegisterContextPOSIXProcessMonitor_x86_6
>      }
>
>      // Get pointer to m_fpr.xstate.fxsave variable and set the data from
> it.
> -    assert (reg_info->byte_offset < sizeof(m_fpr));
> -    uint8_t *src = (uint8_t *)&m_fpr + reg_info->byte_offset;
> +    // Byte offsets of all registers are calculated wrt 'UserArea'
> structure.
> +    // However, ReadFPR() reads fpu registers {using
> ptrace(PT_GETFPREGS,..)}
> +    // and stores them in 'm_fpr' (of type FPR structure). To extract
> values of fpu
> +    // registers, m_fpr should be read at byte offsets calculated wrt to
> FPR structure.
> +
> +    // Since, FPR structure is also one of the member of UserArea
> structure.
> +    // byte_offset(fpu wrt FPR) = byte_offset(fpu wrt UserArea) -
> byte_offset(fctrl wrt UserArea)
> +    assert ( (reg_info->byte_offset - m_fctrl_offset_in_userarea) <
> sizeof(m_fpr));
> +    uint8_t *src = (uint8_t *)&m_fpr + reg_info->byte_offset -
> m_fctrl_offset_in_userarea;
>      switch (reg_info->byte_size)
>      {
>          case 2:
> @@ -308,8 +318,15 @@ RegisterContextPOSIXProcessMonitor_x86_6
>          else
>          {
>              // Get pointer to m_fpr.xstate.fxsave variable and set the
> data to it.
> -            assert (reg_info->byte_offset < sizeof(m_fpr));
> -            uint8_t *dst = (uint8_t *)&m_fpr + reg_info->byte_offset;
> +            // Byte offsets of all registers are calculated wrt
> 'UserArea' structure.
> +            // However, WriteFPR() takes m_fpr (of type FPR structure)
> and writes only fpu
> +            // registers using ptrace(PT_SETFPREGS,..) API. Hence fpu
> registers should
> +            // be written in m_fpr at byte offsets calculated wrt FPR
> structure.
> +
> +            // Since, FPR structure is also one of the member of UserArea
> structure.
> +            // byte_offset(fpu wrt FPR) = byte_offset(fpu wrt UserArea) -
> byte_offset(fctrl wrt UserArea)
> +            assert ( (reg_info->byte_offset - m_fctrl_offset_in_userarea)
> < sizeof(m_fpr));
> +            uint8_t *dst = (uint8_t *)&m_fpr + reg_info->byte_offset -
> m_fctrl_offset_in_userarea;
>              switch (reg_info->byte_size)
>              {
>                  case 2:
>
> Modified:
> lldb/trunk/source/Plugins/Process/FreeBSD/RegisterContextPOSIXProcessMonitor_x86.h
> URL:
> http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Plugins/Process/FreeBSD/RegisterContextPOSIXProcessMonitor_x86.h?rev=249379&r1=249378&r2=249379&view=diff
>
> ==============================================================================
> ---
> lldb/trunk/source/Plugins/Process/FreeBSD/RegisterContextPOSIXProcessMonitor_x86.h
> (original)
> +++
> lldb/trunk/source/Plugins/Process/FreeBSD/RegisterContextPOSIXProcessMonitor_x86.h
> Tue Oct  6 02:04:03 2015
> @@ -91,6 +91,7 @@ protected:
>  private:
>      ProcessMonitor &
>      GetMonitor();
> +    uint32_t m_fctrl_offset_in_userarea;  // Offset of 'fctrl' in
> 'UserArea' Structure
>  };
>
>  #endif
>
>
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