sme: Core file support for Linux

This patch enables dumping SME state via gdb's gcore command and also
enables gdb to read SME state from a core file generated by the Linux
Kernel.

Regression-tested on aarch64-linux Ubuntu 22.04/20.04.

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/gdb/arch/aarch64-scalable-linux.c b/gdb/arch/aarch64-scalable-linux.c
index 3803acf..2e4aa92 100644
--- a/gdb/arch/aarch64-scalable-linux.c
+++ b/gdb/arch/aarch64-scalable-linux.c
@@ -19,3 +19,37 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include "arch/aarch64-scalable-linux.h"
+#include "arch/aarch64.h"
+#include "gdbsupport/byte-vector.h"
+#include "gdbsupport/common-regcache.h"
+
+/* See arch/aarch64-scalable-linux.h  */
+
+bool
+sve_state_is_empty (const struct reg_buffer_common *reg_buf)
+{
+  /* Instead of allocating a buffer with the size of the current vector
+     length, just use a buffer that is big enough for all cases.  */
+  gdb_byte zero_buffer[256];
+
+  /* Zero it out.  */
+  memset (zero_buffer, 0, 256);
+
+  /* Are any of the Z registers set (non-zero) after the first 128 bits?  */
+  for (int i = 0; i < AARCH64_SVE_Z_REGS_NUM; i++)
+    {
+      if (!reg_buf->raw_compare (AARCH64_SVE_Z0_REGNUM + i, zero_buffer,
+				 V_REGISTER_SIZE))
+	return false;
+    }
+
+  /* Are any of the P registers set (non-zero)?  */
+  for (int i = 0; i < AARCH64_SVE_P_REGS_NUM; i++)
+    {
+      if (!reg_buf->raw_compare (AARCH64_SVE_P0_REGNUM + i, zero_buffer, 0))
+	return false;
+    }
+
+  /* Is the FFR register set (non-zero)?  */
+  return reg_buf->raw_compare (AARCH64_SVE_FFR_REGNUM, zero_buffer, 0);
+}