target/arm: Don't put FPEXC and FPSID in org.gnu.gdb.arm.vfp XML

Currently we send VFP XML which includes D0..D15 or D0..D31, plus
FPSID, FPSCR and FPEXC.  The upstream GDB tolerates this, but its
definition of this XML feature does not include FPSID or FPEXC.  In
particular, for M-profile cores there are no FPSID or FPEXC
registers, so advertising those is wrong.

Move FPSID and FPEXC into their own bit of XML which we only send for
A and R profile cores.  This brings our definition of the XML
org.gnu.gdb.arm.vfp feature into line with GDB's own (at least for
non-Neon cores...) and means we don't claim to have FPSID and FPEXC
on M-profile.

(It seems unlikely to me that any gdbstub users really care about
being able to look at FPEXC and FPSID; but we've supplied them to gdb
for a decade and it's not hard to keep doing so.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210921162901.17508-5-peter.maydell@linaro.org

1 files changed, 40 insertions, 16 deletions

diff --git a/target/arm/gdbstub.c b/target/arm/gdbstub.c
index cbf156d192..e0dcb33e32 100644
--- a/target/arm/gdbstub.c
+++ b/target/arm/gdbstub.c
@@ -144,11 +144,7 @@ static int vfp_gdb_get_reg(CPUARMState *env, GByteArray *buf, int reg)
     }
     switch (reg - nregs) {
     case 0:
-        return gdb_get_reg32(buf, env->vfp.xregs[ARM_VFP_FPSID]);
-    case 1:
         return gdb_get_reg32(buf, vfp_get_fpscr(env));
-    case 2:
-        return gdb_get_reg32(buf, env->vfp.xregs[ARM_VFP_FPEXC]);
     }
     return 0;
 }
@@ -173,12 +169,30 @@ static int vfp_gdb_set_reg(CPUARMState *env, uint8_t *buf, int reg)
     }
     switch (reg - nregs) {
     case 0:
-        env->vfp.xregs[ARM_VFP_FPSID] = ldl_p(buf);
+        vfp_set_fpscr(env, ldl_p(buf));
         return 4;
+    }
+    return 0;
+}
+
+static int vfp_gdb_get_sysreg(CPUARMState *env, GByteArray *buf, int reg)
+{
+    switch (reg) {
+    case 0:
+        return gdb_get_reg32(buf, env->vfp.xregs[ARM_VFP_FPSID]);
     case 1:
-        vfp_set_fpscr(env, ldl_p(buf));
+        return gdb_get_reg32(buf, env->vfp.xregs[ARM_VFP_FPEXC]);
+    }
+    return 0;
+}
+
+static int vfp_gdb_set_sysreg(CPUARMState *env, uint8_t *buf, int reg)
+{
+    switch (reg) {
+    case 0:
+        env->vfp.xregs[ARM_VFP_FPSID] = ldl_p(buf);
         return 4;
-    case 2:
+    case 1:
         env->vfp.xregs[ARM_VFP_FPEXC] = ldl_p(buf) & (1 << 30);
         return 4;
     }
@@ -434,15 +448,25 @@ void arm_cpu_register_gdb_regs_for_features(ARMCPU *cpu)
                                      34, "aarch64-fpu.xml", 0);
         }
 #endif
-    } else if (arm_feature(env, ARM_FEATURE_NEON)) {
-        gdb_register_coprocessor(cs, vfp_gdb_get_reg, vfp_gdb_set_reg,
-                                 51, "arm-neon.xml", 0);
-    } else if (cpu_isar_feature(aa32_simd_r32, cpu)) {
-        gdb_register_coprocessor(cs, vfp_gdb_get_reg, vfp_gdb_set_reg,
-                                 35, "arm-vfp3.xml", 0);
-    } else if (cpu_isar_feature(aa32_vfp_simd, cpu)) {
-        gdb_register_coprocessor(cs, vfp_gdb_get_reg, vfp_gdb_set_reg,
-                                 19, "arm-vfp.xml", 0);
+    } else {
+        if (arm_feature(env, ARM_FEATURE_NEON)) {
+            gdb_register_coprocessor(cs, vfp_gdb_get_reg, vfp_gdb_set_reg,
+                                     49, "arm-neon.xml", 0);
+        } else if (cpu_isar_feature(aa32_simd_r32, cpu)) {
+            gdb_register_coprocessor(cs, vfp_gdb_get_reg, vfp_gdb_set_reg,
+                                     33, "arm-vfp3.xml", 0);
+        } else if (cpu_isar_feature(aa32_vfp_simd, cpu)) {
+            gdb_register_coprocessor(cs, vfp_gdb_get_reg, vfp_gdb_set_reg,
+                                     17, "arm-vfp.xml", 0);
+        }
+        if (!arm_feature(env, ARM_FEATURE_M)) {
+            /*
+             * A and R profile have FP sysregs FPEXC and FPSID that we
+             * expose to gdb.
+             */
+            gdb_register_coprocessor(cs, vfp_gdb_get_sysreg, vfp_gdb_set_sysreg,
+                                     2, "arm-vfp-sysregs.xml", 0);
+        }
     }
     gdb_register_coprocessor(cs, arm_gdb_get_sysreg, arm_gdb_set_sysreg,
                              arm_gen_dynamic_sysreg_xml(cs, cs->gdb_num_regs),