[PATCH v6 11/15] gdbserver: Add a function to set the XSAVE mask and size.

John Baldwin
2023-07-14T15:57:39Z

Make x86_xcr0 private to i387-fp.cc and use i387_set_xsave_mask to set
the value instead. Add a static global instance of x86_xsave_layout
and initialize it in the new function as well to be used in a future
commit to parse XSAVE extended state regions.

Update the Linux port to use this function rather than setting
x86_xcr0 directly. In the case that XML is not supported, don't
bother setting x86_xcr0 to the default value but just omit the call to
i387_set_xsave_mask as i387-fp.cc defaults to the SSE case used for
non-XML.

In addition, use x86_xsave_length to determine the size of the XSAVE
register set via CPUID.
---
gdbserver/configure.srv | 12 ++++++++----
gdbserver/i387-fp.cc | 16 ++++++++++++++--
gdbserver/i387-fp.h | 4 +++-
gdbserver/linux-x86-low.cc | 10 ++++++----
4 files changed, 31 insertions(+), 11 deletions(-)

diff --git a/gdbserver/configure.srv b/gdbserver/configure.srv
index f0101994529..72256f82871 100644
--- a/gdbserver/configure.srv
+++ b/gdbserver/configure.srv
@@ -102,7 +102,8 @@ case "${gdbserver_host}" in
i[34567]86-*-linux*) srv_tgtobj="${srv_tgtobj} arch/i386.o"
srv_tgtobj="${srv_tgtobj} $srv_linux_obj"
srv_tgtobj="${srv_tgtobj} linux-x86-low.o x86-low.o"
- srv_tgtobj="${srv_tgtobj} nat/x86-dregs.o i387-fp.o"
+ srv_tgtobj="${srv_tgtobj} nat/x86-dregs.o"
+ srv_tgtobj="${srv_tgtobj} nat/x86-xstate.o i387-fp.o"
srv_tgtobj="${srv_tgtobj} linux-x86-tdesc.o"
srv_tgtobj="${srv_tgtobj} nat/linux-btrace.o"
srv_tgtobj="${srv_tgtobj} nat/x86-linux.o"
@@ -362,7 +363,8 @@ case "${gdbserver_host}" in
srv_linux_thread_db=yes
;;
x86_64-*-linux*) srv_tgtobj="$srv_linux_obj linux-x86-low.o x86-low.o"
- srv_tgtobj="${srv_tgtobj} nat/x86-dregs.o i387-fp.o"
+ srv_tgtobj="${srv_tgtobj} nat/x86-dregs.o"
+ srv_tgtobj="${srv_tgtobj} nat/x86-xstate.o i387-fp.o"
srv_tgtobj="${srv_tgtobj} arch/i386.o arch/amd64.o"
srv_tgtobj="${srv_tgtobj} linux-x86-tdesc.o"
srv_tgtobj="${srv_tgtobj} nat/linux-btrace.o"
@@ -377,14 +379,16 @@ case "${gdbserver_host}" in
ipa_obj="${ipa_obj} arch/amd64-ipa.o"
;;
x86_64-*-mingw*) srv_regobj=""
- srv_tgtobj="x86-low.o nat/x86-dregs.o i387-fp.o"
+ srv_tgtobj="x86-low.o nat/x86-dregs.o"
+ srv_tgtobj="${srv_tgtobj} nat/x86-xstate.o i387-fp.o"
srv_tgtobj="${srv_tgtobj} win32-low.o win32-i386-low.o"
srv_tgtobj="${srv_tgtobj} nat/windows-nat.o"
srv_tgtobj="${srv_tgtobj} arch/amd64.o arch/i386.o"
srv_mingw=yes
;;
x86_64-*-cygwin*) srv_regobj=""
- srv_tgtobj="x86-low.o nat/x86-dregs.o i387-fp.o"
+ srv_tgtobj="x86-low.o nat/x86-dregs.o"
+ srv_tgtobj="${srv_tgtobj} nat/x86-xstate.o i387-fp.o"
srv_tgtobj="${srv_tgtobj} win32-low.o win32-i386-low.o"
srv_tgtobj="${srv_tgtobj} nat/windows-nat.o"
srv_tgtobj="${srv_tgtobj} arch/amd64.o arch/i386.o"
diff --git a/gdbserver/i387-fp.cc b/gdbserver/i387-fp.cc
index 49795ace9a9..b8d7a912f26 100644
--- a/gdbserver/i387-fp.cc
+++ b/gdbserver/i387-fp.cc
@@ -19,12 +19,18 @@
#include "server.h"
#include "i387-fp.h"
#include "gdbsupport/x86-xstate.h"
+#include "nat/x86-xstate.h"
+
+/* Default to SSE. */
+static unsigned long long x86_xcr0 = X86_XSTATE_SSE_MASK;

static const int num_mpx_bnd_registers = 4;
static const int num_mpx_cfg_registers = 2;
static const int num_avx512_k_registers = 8;
static const int num_pkeys_registers = 1;

+static x86_xsave_layout xsave_layout;
+
/* Note: These functions preserve the reserved bits in control registers.
However, gdbserver promptly throws away that information. */

@@ -974,5 +980,11 @@ i387_xsave_to_cache (struct regcache *regcache, const void *buf)
}
}

-/* Default to SSE. */
-unsigned long long x86_xcr0 = X86_XSTATE_SSE_MASK;
+/* See i387-fp.h. */
+
+void
+i387_set_xsave_mask (uint64_t xcr0, int len)
+{
+ x86_xcr0 = xcr0;
+ xsave_layout = x86_fetch_xsave_layout (xcr0, len);
+}
diff --git a/gdbserver/i387-fp.h b/gdbserver/i387-fp.h
index f536a2be15a..09b6a91aa25 100644
--- a/gdbserver/i387-fp.h
+++ b/gdbserver/i387-fp.h
@@ -28,6 +28,8 @@ void i387_fxsave_to_cache (struct regcache *regcache, const void *buf);
void i387_cache_to_xsave (struct regcache *regcache, void *buf);
void i387_xsave_to_cache (struct regcache *regcache, const void *buf);

-extern unsigned long long x86_xcr0;
+/* Set the XSAVE mask and fetch the XSAVE layout via CPUID. */
+
+void i387_set_xsave_mask (uint64_t xcr0, int len);

#endif /* GDBSERVER_I387_FP_H */
diff --git a/gdbserver/linux-x86-low.cc b/gdbserver/linux-x86-low.cc
index 4a538b107be..1483e2a66d7 100644
--- a/gdbserver/linux-x86-low.cc
+++ b/gdbserver/linux-x86-low.cc
@@ -25,6 +25,7 @@
#include "i387-fp.h"
#include "x86-low.h"
#include "gdbsupport/x86-xstate.h"
+#include "nat/x86-xstate.h"
#include "nat/gdb_ptrace.h"

#ifdef __x86_64__
@@ -873,6 +874,7 @@ x86_linux_read_description (void)
int xcr0_features;
int tid;
static uint64_t xcr0;
+ static int xsave_len;
struct regset_info *regset;

tid = lwpid_of (current_thread);
@@ -907,8 +909,6 @@ x86_linux_read_description (void)

if (!use_xml)
{
- x86_xcr0 = X86_XSTATE_SSE_MASK;
-
/* Don't use XML. */
#ifdef __x86_64__
if (machine == EM_X86_64)
@@ -938,11 +938,13 @@ x86_linux_read_description (void)
xcr0 = xstateregs[(I386_LINUX_XSAVE_XCR0_OFFSET
/ sizeof (uint64_t))];

+ xsave_len = x86_xsave_length ();
+
/* Use PTRACE_GETREGSET if it is available. */
for (regset = x86_regsets;
regset->fill_function != NULL; regset++)
if (regset->get_request == PTRACE_GETREGSET)
- regset->size = X86_XSTATE_SIZE (xcr0);
+ regset->size = xsave_len;
else if (regset->type != GENERAL_REGS)
regset->size = 0;
}
@@ -953,7 +955,7 @@ x86_linux_read_description (void)
&& (xcr0 & X86_XSTATE_ALL_MASK));

if (xcr0_features)
- x86_xcr0 = xcr0;
+ i387_set_xsave_mask (xcr0, xsave_len);

if (machine == EM_X86_64)
{
--
2.40.0