Re: [PATCH v2 7/8] Windows gdb: Implement XState (Intel AVX) support

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Am Montag, 27. Juli 2026 um 19:47:52 MESZ hat Hannes Domani <[email protected]> Folgendes geschrieben:

> This adds support for the Intel AVX and AVX-512 registers on Windows.
> It enables accessing registers $ymm0 - $ymm31, $zmm0 - $zmm31, and
> $k0 - $k7 where they are available.
> 
> It also enables reading the shadow stack pointer register $pl3_ssp (for
> executables marked compatible with CET shadow stack [1]), but modifying
> it seems to be restricted restricted by windows.
> 
> After this patch the tests gdb.arch/i386-avx.exp and gdb.arch/i386-avx512.exp
> pass on windows.
> 
> [1] https://learn.microsoft.com/en-us/cpp/build/reference/cetcompat
> ---
> v2:
>   - Extended commit message and NEWS entry
>   - Remove PKRU support
>   - Fixed context offset of $pl3_ssp
> ---
> gdb/NEWS              |  6 +++
> gdb/x86-windows-nat.c | 108 ++++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 111 insertions(+), 3 deletions(-)
> 
> diff --git a/gdb/NEWS b/gdb/NEWS
> index 8f40ca5cb11..71ff5508d6d 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -116,6 +116,12 @@
>   intent to remove it in a future release.
>   The s390 64-bit target (s390x-*) remains supported.
> 
> +* Support for Intel AVX registers on Windows.
> +  Support displaying and modifying Intel AVX registers $ymm0 - $ymm31.
> +  Support displaying and modifying Intel AVX-512 registers $zmm0 - $zmm31
> +  and $k0 - $k7.
> +  Support displaying the shadow stack pointer register $pl3_ssp.
> +
> * Configure changes
> 
> ** --with-babeltrace has been removed.  The babeltrace library was
> diff --git a/gdb/x86-windows-nat.c b/gdb/x86-windows-nat.c
> index 3af5ef4dae0..270f9eae8e7 100644
> --- a/gdb/x86-windows-nat.c
> +++ b/gdb/x86-windows-nat.c
> @@ -27,6 +27,9 @@
> 
> #include "i386-tdep.h"
> #include "i387-tdep.h"
> +#ifdef __x86_64__
> +#include "amd64-tdep.h"
> +#endif
> 
> using namespace windows_nat;
> 
> @@ -70,6 +73,8 @@ struct x86_windows_nat_target final : public x86_nat_target<windows_nat_target>
>               windows_thread_info *th, int r) override;
> 
>   bool is_sw_breakpoint (const EXCEPTION_RECORD *er) const override;
> +
> +  const struct target_desc *read_description () override;
> };
> 
> /* The current process.  */
> @@ -109,7 +114,31 @@ x86_windows_per_inferior::fill_thread_context (windows_thread_info *th)
>       if (context->ContextFlags == 0)
>     {
>       context->ContextFlags = WindowsContext<decltype(context)>::all;
> +      if (xstate_features != 0)
> +        {
> +          context->ContextFlags |= CONTEXT_XSTATE_FLAG;
> +          set_xstate_features_mask (context, xstate_features);
> +        }
>       CHECK (get_thread_context (th->h, context));
> +
> +      if (xstate_features != 0)
> +        {
> +          DWORD64 features = 0;
> +          CHECK (get_xstate_features_mask (context, &features));
> +          DWORD64 zeroed_features = xstate_features & ~features;
> +
> +          for (int f = X86_XSTATE_AVX_ID; f <= X86_XSTATE_CET_U_ID; f++)
> +        {
> +          DWORD64 flag = 1ULL << f;
> +          if ((zeroed_features & flag) != 0)
> +            {
> +              DWORD size = 0;
> +              void *loc = locate_xstate_feature (context, f, &size);
> +              if (loc != nullptr && size > 0)
> +            memset (loc, 0, size);
> +            }
> +        }
> +        }
>     }
>     });
> }
> @@ -198,6 +227,14 @@ x86_windows_nat_target::thread_context_continue (windows_thread_info *th,
>       if (GetExitCodeThread (th->h, &ec)
>           && ec == STILL_ACTIVE)
>         {
> +          DWORD debug_registers = WindowsContext<decltype(context)>::debug;
> +          if (xstate_features != 0
> +          && (context->ContextFlags & ~debug_registers) != 0)
> +        {
> +          context->ContextFlags |= CONTEXT_XSTATE_FLAG;
> +          set_xstate_features_mask (context, xstate_features);
> +        }
> +
>           BOOL status = set_thread_context (th->h, context);
> 
>           if (!killed)
> @@ -227,7 +264,7 @@ x86_windows_nat_target::thread_context_step (windows_thread_info *th,
> 
> template<typename Context>
> static char *
> -get_context_reg_ptr (Context *context, int r)
> +get_context_reg_ptr (Context *context, int r, i386_gdbarch_tdep *tdep)
> {
>   const int *mappings;
>   int mappings_count;
> @@ -247,6 +284,54 @@ get_context_reg_ptr (Context *context, int r)
>   char *context_offset;
>   if (r < mappings_count)
>     context_offset = (char *) context + mappings[r];
> +  else if (I387_ZMM0H_REGNUM (tdep) > 0 && r >= I387_ZMM0H_REGNUM (tdep)
> +      && r < I387_ZMM16H_REGNUM (tdep) && r < I387_ZMMENDH_REGNUM (tdep))
> +    {
> +      context_offset = (char *) locate_xstate_feature
> +    (context, X86_XSTATE_ZMM_H_ID, NULL);
> +      context_offset += 32 * (r - I387_ZMM0H_REGNUM (tdep));
> +    }
> +  else if (I387_ZMM0H_REGNUM (tdep) > 0 && r >= I387_ZMM16H_REGNUM (tdep)
> +      && r < I387_ZMMENDH_REGNUM (tdep))
> +    {
> +      context_offset = (char *) locate_xstate_feature
> +    (context, X86_XSTATE_ZMM_ID, NULL);
> +      context_offset += 32 + 64 * (r - I387_ZMM16H_REGNUM (tdep));
> +    }
> +  else if (I387_K0_REGNUM (tdep) > 0 && r >= I387_K0_REGNUM (tdep)
> +      && r < I387_KEND_REGNUM (tdep))
> +    {
> +      context_offset = (char *) locate_xstate_feature
> +    (context, X86_XSTATE_K_ID, NULL);
> +      context_offset += 8 * (r - I387_K0_REGNUM (tdep));
> +    }
> +  else if (I387_YMM16H_REGNUM (tdep) > 0 && r >= I387_YMM16H_REGNUM (tdep)
> +      && r < I387_YMMH_AVX512_END_REGNUM (tdep))
> +    {
> +      context_offset = (char *) locate_xstate_feature
> +    (context, X86_XSTATE_ZMM_ID, NULL);
> +      context_offset += 16 + 64 * (r - I387_YMM16H_REGNUM (tdep));
> +    }
> +  else if (I387_XMM16_REGNUM (tdep) > 0 && r >= I387_XMM16_REGNUM (tdep)
> +      && r < I387_XMM_AVX512_END_REGNUM (tdep))
> +    {
> +      context_offset = (char *) locate_xstate_feature
> +    (context, X86_XSTATE_ZMM_ID, NULL);
> +      context_offset += 64 * (r - I387_XMM16_REGNUM (tdep));
> +    }
> +  else if (I387_YMM0H_REGNUM (tdep) > 0 && r >= I387_YMM0H_REGNUM (tdep)
> +      && r < I387_YMMENDH_REGNUM (tdep))
> +    {
> +      context_offset = (char *) locate_xstate_feature
> +    (context, X86_XSTATE_AVX_ID, NULL);
> +      context_offset += 16 * (r - I387_YMM0H_REGNUM (tdep));
> +    }
> +  else if (tdep->ssp_regnum > 0 && r == tdep->ssp_regnum)
> +    {
> +      context_offset = (char *) locate_xstate_feature
> +    (context, X86_XSTATE_CET_U_ID, NULL);
> +      context_offset += 8;
> +    }
>   else
>     gdb_assert_not_reached ("invalid register number %d", r);
> 
> @@ -267,7 +352,7 @@ x86_windows_nat_target::fetch_one_register (struct regcache *regcache,
>   char *context_offset
>     = x86_windows_process.with_context (th, [&] (auto *context)
>     {
> -      return get_context_reg_ptr (context, r);
> +      return get_context_reg_ptr (context, r, tdep);
>     });
> 
>   gdb_assert (!gdbarch_read_pc_p (gdbarch));
> @@ -333,7 +418,7 @@ x86_windows_nat_target::store_one_register (const struct regcache *regcache,
>     = x86_windows_process.with_context (th, [&] (auto *context)
>     {
>       gdb_assert (context->ContextFlags != 0);
> -      return get_context_reg_ptr (context, r);
> +      return get_context_reg_ptr (context, r, tdep);
>     });
> 
>   /* GDB treats some registers as 32-bit, where they are in fact only
> @@ -368,6 +453,23 @@ x86_windows_nat_target::is_sw_breakpoint (const EXCEPTION_RECORD *er) const
>       || er->ExceptionCode == STATUS_WX86_BREAKPOINT);
> }
> 
> +const struct target_desc *
> +x86_windows_nat_target::read_description ()
> +{
> +  if (inferior_ptid == null_ptid)
> +    return this->beneath ()->read_description ();
> +
> +  if (xstate_features == 0)
> +    return nullptr;
> +
> +#ifdef __x86_64__
> +  if (!x86_windows_process.wow64_process)
> +    return amd64_target_description (xstate_features, false);
> +  else
> +#endif
> +    return i386_target_description (xstate_features, false);
> +}
> +
> /* Hardware watchpoint support, adapted from go32-nat.c code.  */
> 
> /* Pass the address ADDR to the inferior in the I'th debug register.
> -- 
> 2.54.0