sme: Signal frame support

Teach gdb about the ZA/SSVE state on signal frames and how to restore
the contents of the registers.

There is a new ZA_MAGIC context that the Linux Kernel uses to communicate
the ZA register state to gdb.

The SVE_MAGIC context has also been adjusted to contain a flag indicating
whether it is a SVE or SSVE state.

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

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

diff --git a/gdb/aarch64-linux-tdep.c b/gdb/aarch64-linux-tdep.c
index bdd5cb05c106c93b9418b5bafafd93f9ca1e96e7..f76d18880720bb15cd1c745a26a804461ca4e158 100644 (file)
--- a/gdb/aarch64-linux-tdep.c
+++ b/gdb/aarch64-linux-tdep.c
@@ -48,6 +48,7 @@
 #include "linux-record.h"
 
 #include "arch/aarch64-mte-linux.h"
+#include "arch/aarch64-scalable-linux.h"
 
 #include "arch-utils.h"
 #include "value.h"
@@ -152,6 +153,7 @@
 #define AARCH64_EXTRA_MAGIC                    0x45585401
 #define AARCH64_FPSIMD_MAGIC                   0x46508001
 #define AARCH64_SVE_MAGIC                      0x53564501
+#define AARCH64_ZA_MAGIC                       0x54366345
 
 /* Defines for the extra_context that follows an AARCH64_EXTRA_MAGIC.  */
 #define AARCH64_EXTRA_DATAP_OFFSET             8
@@ -164,13 +166,23 @@
 
 /* Defines for the sve structure that follows an AARCH64_SVE_MAGIC.  */
 #define AARCH64_SVE_CONTEXT_VL_OFFSET          8
+#define AARCH64_SVE_CONTEXT_FLAGS_OFFSET       10
 #define AARCH64_SVE_CONTEXT_REGS_OFFSET                16
 #define AARCH64_SVE_CONTEXT_P_REGS_OFFSET(vq) (32 * vq * 16)
 #define AARCH64_SVE_CONTEXT_FFR_OFFSET(vq) \
   (AARCH64_SVE_CONTEXT_P_REGS_OFFSET (vq) + (16 * vq * 2))
 #define AARCH64_SVE_CONTEXT_SIZE(vq) \
   (AARCH64_SVE_CONTEXT_FFR_OFFSET (vq) + (vq * 2))
+/* Flag indicating the SVE Context describes streaming mode.  */
+#define SVE_SIG_FLAG_SM                                0x1
 
+/* SME constants.  */
+#define AARCH64_SME_CONTEXT_SVL_OFFSET         8
+#define AARCH64_SME_CONTEXT_REGS_OFFSET                16
+#define AARCH64_SME_CONTEXT_ZA_SIZE(svq) \
+  ((sve_vl_from_vq (svq) * sve_vl_from_vq (svq)))
+#define AARCH64_SME_CONTEXT_SIZE(svq) \
+  (AARCH64_SME_CONTEXT_REGS_OFFSET + AARCH64_SME_CONTEXT_ZA_SIZE (svq))
 
 /* Read an aarch64_ctx, returning the magic value, and setting *SIZE to the
    size, or return 0 on error.  */
@@ -324,7 +336,10 @@ aarch64_linux_sigframe_init (const struct tramp_frame *self,
   CORE_ADDR section_end = section + AARCH64_SIGCONTEXT_RESERVED_SIZE;
   CORE_ADDR fpsimd = 0;
   CORE_ADDR sve_regs = 0;
+  CORE_ADDR za_state = 0;
+  uint64_t svcr = 0;
   uint32_t size, magic;
+  size_t vq = 0, svq = 0;
   bool extra_found = false;
   int num_regs = gdbarch_num_regs (gdbarch);
 
@@ -360,7 +375,7 @@ aarch64_linux_sigframe_init (const struct tramp_frame *self,
            /* Check if the section is followed by a full SVE dump, and set
               sve_regs if it is.  */
            gdb_byte buf[4];
-           uint16_t vq;
+           uint16_t flags;
 
            if (!tdep->has_sve ())
              break;
@@ -373,9 +388,23 @@ aarch64_linux_sigframe_init (const struct tramp_frame *self,
              }
            vq = sve_vq_from_vl (extract_unsigned_integer (buf, 2, byte_order));
 
-           if (vq != tdep->vq)
-             error (_("Invalid vector length in signal frame %d vs %s."), vq,
-                    pulongest (tdep->vq));
+           /* If SME is supported, also read the flags field.  It may
+              indicate if this SVE context is for streaming mode (SSVE).  */
+           if (tdep->has_sme ())
+             {
+               if (target_read_memory (section
+                                       + AARCH64_SVE_CONTEXT_FLAGS_OFFSET,
+                                       buf, 2) != 0)
+                 {
+                   section += size;
+                   break;
+                 }
+               flags = extract_unsigned_integer (buf, 2, byte_order);
+
+               /* Is this SSVE data? If so, enable the SM bit in SVCR.  */
+               if (flags & SVE_SIG_FLAG_SM)
+                 svcr |= SVCR_SM_BIT;
+             }
 
            if (size >= AARCH64_SVE_CONTEXT_SIZE (vq))
              sve_regs = section + AARCH64_SVE_CONTEXT_REGS_OFFSET;
@@ -384,6 +413,38 @@ aarch64_linux_sigframe_init (const struct tramp_frame *self,
            break;
          }
 
+       case AARCH64_ZA_MAGIC:
+         {
+           if (!tdep->has_sme ())
+             {
+               section += size;
+               break;
+             }
+
+           /* Check if the section is followed by a full ZA dump, and set
+              za_state if it is.  */
+           gdb_byte buf[2];
+
+           if (target_read_memory (section + AARCH64_SME_CONTEXT_SVL_OFFSET,
+                                   buf, 2) != 0)
+             {
+               section += size;
+               break;
+             }
+           svq = sve_vq_from_vl (extract_unsigned_integer (buf, 2,
+                                                           byte_order));
+
+           if (size >= AARCH64_SME_CONTEXT_SIZE (svq))
+             {
+               za_state = section + AARCH64_SME_CONTEXT_REGS_OFFSET;
+               /* We have ZA data.  Enable the ZA bit in SVCR.  */
+               svcr |= SVCR_ZA_BIT;
+             }
+
+           section += size;
+           break;
+         }
+
        case AARCH64_EXTRA_MAGIC:
          {
            /* Extra is always the last valid section in reserved and points to
@@ -422,7 +483,7 @@ aarch64_linux_sigframe_init (const struct tramp_frame *self,
 
       for (int i = 0; i < 32; i++)
        {
-         offset = sve_regs + (i * tdep->vq * 16);
+         offset = sve_regs + (i * vq * 16);
          trad_frame_set_reg_addr (this_cache, AARCH64_SVE_Z0_REGNUM + i,
                                   offset);
          trad_frame_set_reg_addr (this_cache,
@@ -440,12 +501,12 @@ aarch64_linux_sigframe_init (const struct tramp_frame *self,
                                   offset);
        }
 
-      offset = sve_regs + AARCH64_SVE_CONTEXT_P_REGS_OFFSET (tdep->vq);
+      offset = sve_regs + AARCH64_SVE_CONTEXT_P_REGS_OFFSET (vq);
       for (int i = 0; i < 16; i++)
        trad_frame_set_reg_addr (this_cache, AARCH64_SVE_P0_REGNUM + i,
-                                offset + (i * tdep->vq * 2));
+                                offset + (i * vq * 2));
 
-      offset = sve_regs + AARCH64_SVE_CONTEXT_FFR_OFFSET (tdep->vq);
+      offset = sve_regs + AARCH64_SVE_CONTEXT_FFR_OFFSET (vq);
       trad_frame_set_reg_addr (this_cache, AARCH64_SVE_FFR_REGNUM, offset);
     }
 
@@ -461,6 +522,17 @@ aarch64_linux_sigframe_init (const struct tramp_frame *self,
        aarch64_linux_restore_vregs (gdbarch, this_cache, fpsimd);
     }
 
+  if (za_state != 0)
+    {
+      /* Restore the ZA state.  */
+      trad_frame_set_reg_addr (this_cache, tdep->sme_za_regnum,
+                              za_state);
+    }
+
+  /* If SME is supported, set SVCR as well.  */
+  if (tdep->has_sme ())
+    trad_frame_set_reg_value (this_cache, tdep->sme_svcr_regnum, svcr);
+
   trad_frame_set_id (this_cache, frame_id_build (sp, func));
 }
 

diff --git a/gdb/nat/aarch64-scalable-linux-sigcontext.h b/gdb/nat/aarch64-scalable-linux-sigcontext.h
index 74407bd266a0db950d07514fb276ebce22887050..18623443744d636e6815f19ac3524d256ed64c0e 100644 (file)
--- a/gdb/nat/aarch64-scalable-linux-sigcontext.h
+++ b/gdb/nat/aarch64-scalable-linux-sigcontext.h
@@ -30,7 +30,10 @@
 struct sve_context {
        struct _aarch64_ctx head;
        __u16 vl;
-       __u16 __reserved[3];
+       /* Holds flags.  This field was defined for SME support.  Prior to it,
+          this used to be a reserved 16-bit value.  */
+       __u16 flags;
+       __u16 __reserved[2];
 };
 
 /*