[AArch64] When unavailable, fetch VG from ptrace.

[deliverable/binutils-gdb.git] / gdb / nat / aarch64-sve-linux-ptrace.c

diff --git a/gdb/nat/aarch64-sve-linux-ptrace.c b/gdb/nat/aarch64-sve-linux-ptrace.c
index b8f0711f9beb2eb902d7d27263405cead81f408a..2ce90ccfd7e3c1e0fbb742508b7ee6fd96524a2b 100644 (file)
--- a/gdb/nat/aarch64-sve-linux-ptrace.c
+++ b/gdb/nat/aarch64-sve-linux-ptrace.c
@@ -92,11 +92,26 @@ aarch64_sve_set_vq (int tid, uint64_t vq)
 bool
 aarch64_sve_set_vq (int tid, struct reg_buffer_common *reg_buf)
 {
+  uint64_t reg_vg = 0;
+
+  /* The VG register may not be valid if we've not collected any value yet.
+     This can happen, for example,  if we're restoring the regcache after an
+     inferior function call, and the VG register comes after the Z
+     registers.  */
   if (reg_buf->get_register_status (AARCH64_SVE_VG_REGNUM) != REG_VALID)
-    return false;
+  {
+    /* If vg is not available yet, fetch it from ptrace.  The VG value from
+       ptrace is likely the correct one.  */
+    uint64_t vq = aarch64_sve_get_vq (tid);
 
-  uint64_t reg_vg = 0;
-  reg_buf->raw_collect (AARCH64_SVE_VG_REGNUM, &reg_vg);
+    /* If something went wrong, just bail out.  */
+    if (vq == 0)
+      return false;
+
+    reg_vg = sve_vg_from_vq (vq);
+  }
+  else
+    reg_buf->raw_collect (AARCH64_SVE_VG_REGNUM, &reg_vg);
 
   return aarch64_sve_set_vq (tid, sve_vq_from_vg (reg_vg));
 }