[PATCH v2 for-6.2] target/arm: Advertise MVE to gdb when present

[Peter Maydell]

Cortex-M CPUs with MVE should advertise this fact to gdb, using the
org.gnu.gdb.arm.m-profile-mve XML feature, which defines the VPR
register.  Presence of this feature also tells gdb to create
pseudo-registers Q0..Q7, so we do not need to tell gdb about them
separately.

Note that unless you have a very recent GDB that includes this fix:
http://patches-tcwg.linaro.org/patch/58133/ gdb will mis-print the
individual fields of the VPR register as zero (but showing the whole
thing as hex, eg with "print /x $vpr" will give the correct value).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
Reposting this unchanged except to remove the 'RFC' tag, as
the gdb patches have now gone upstream and the XML layout is
therefore finalized.
---
 configs/targets/aarch64-softmmu.mak  |  2 +-
 configs/targets/arm-linux-user.mak   |  2 +-
 configs/targets/arm-softmmu.mak      |  2 +-
 configs/targets/armeb-linux-user.mak |  2 +-
 target/arm/gdbstub.c                 | 25 +++++++++++++++++++++++++
 gdb-xml/arm-m-profile-mve.xml        | 19 +++++++++++++++++++
 6 files changed, 48 insertions(+), 4 deletions(-)
 create mode 100644 gdb-xml/arm-m-profile-mve.xml

diff --git a/configs/targets/aarch64-softmmu.mak 
b/configs/targets/aarch64-softmmu.mak
index 13d40b55e6d..d489e6da830 100644
--- a/configs/targets/aarch64-softmmu.mak
+++ b/configs/targets/aarch64-softmmu.mak
@@ -1,5 +1,5 @@
 TARGET_ARCH=aarch64
 TARGET_BASE_ARCH=arm
 TARGET_SUPPORTS_MTTCG=y
-TARGET_XML_FILES= gdb-xml/aarch64-core.xml gdb-xml/aarch64-fpu.xml 
gdb-xml/arm-core.xml gdb-xml/arm-vfp.xml gdb-xml/arm-vfp3.xml 
gdb-xml/arm-vfp-sysregs.xml gdb-xml/arm-neon.xml gdb-xml/arm-m-profile.xml
+TARGET_XML_FILES= gdb-xml/aarch64-core.xml gdb-xml/aarch64-fpu.xml 
gdb-xml/arm-core.xml gdb-xml/arm-vfp.xml gdb-xml/arm-vfp3.xml 
gdb-xml/arm-vfp-sysregs.xml gdb-xml/arm-neon.xml gdb-xml/arm-m-profile.xml 
gdb-xml/arm-m-profile-mve.xml
 TARGET_NEED_FDT=y
diff --git a/configs/targets/arm-linux-user.mak 
b/configs/targets/arm-linux-user.mak
index acecc339e38..3e10d6b15d5 100644
--- a/configs/targets/arm-linux-user.mak
+++ b/configs/targets/arm-linux-user.mak
@@ -1,6 +1,6 @@
 TARGET_ARCH=arm
 TARGET_SYSTBL_ABI=common,oabi
 TARGET_SYSTBL=syscall.tbl
-TARGET_XML_FILES= gdb-xml/arm-core.xml gdb-xml/arm-vfp.xml 
gdb-xml/arm-vfp3.xml gdb-xml/arm-vfp-sysregs.xml gdb-xml/arm-neon.xml 
gdb-xml/arm-m-profile.xml
+TARGET_XML_FILES= gdb-xml/arm-core.xml gdb-xml/arm-vfp.xml 
gdb-xml/arm-vfp3.xml gdb-xml/arm-vfp-sysregs.xml gdb-xml/arm-neon.xml 
gdb-xml/arm-m-profile.xml gdb-xml/arm-m-profile-mve.xml
 TARGET_HAS_BFLT=y
 CONFIG_ARM_COMPATIBLE_SEMIHOSTING=y
diff --git a/configs/targets/arm-softmmu.mak b/configs/targets/arm-softmmu.mak
index f6c95ba07a4..92c8349b964 100644
--- a/configs/targets/arm-softmmu.mak
+++ b/configs/targets/arm-softmmu.mak
@@ -1,4 +1,4 @@
 TARGET_ARCH=arm
 TARGET_SUPPORTS_MTTCG=y
-TARGET_XML_FILES= gdb-xml/arm-core.xml gdb-xml/arm-vfp.xml 
gdb-xml/arm-vfp3.xml gdb-xml/arm-vfp-sysregs.xml gdb-xml/arm-neon.xml 
gdb-xml/arm-m-profile.xml
+TARGET_XML_FILES= gdb-xml/arm-core.xml gdb-xml/arm-vfp.xml 
gdb-xml/arm-vfp3.xml gdb-xml/arm-vfp-sysregs.xml gdb-xml/arm-neon.xml 
gdb-xml/arm-m-profile.xml gdb-xml/arm-m-profile-mve.xml
 TARGET_NEED_FDT=y
diff --git a/configs/targets/armeb-linux-user.mak 
b/configs/targets/armeb-linux-user.mak
index 662c73d8fbd..f81e5bf1fe4 100644
--- a/configs/targets/armeb-linux-user.mak
+++ b/configs/targets/armeb-linux-user.mak
@@ -2,6 +2,6 @@ TARGET_ARCH=arm
 TARGET_SYSTBL_ABI=common,oabi
 TARGET_SYSTBL=syscall.tbl
 TARGET_WORDS_BIGENDIAN=y
-TARGET_XML_FILES= gdb-xml/arm-core.xml gdb-xml/arm-vfp.xml 
gdb-xml/arm-vfp3.xml gdb-xml/arm-vfp-sysregs.xml gdb-xml/arm-neon.xml 
gdb-xml/arm-m-profile.xml
+TARGET_XML_FILES= gdb-xml/arm-core.xml gdb-xml/arm-vfp.xml 
gdb-xml/arm-vfp3.xml gdb-xml/arm-vfp-sysregs.xml gdb-xml/arm-neon.xml 
gdb-xml/arm-m-profile.xml gdb-xml/arm-m-profile-mve.xml
 TARGET_HAS_BFLT=y
 CONFIG_ARM_COMPATIBLE_SEMIHOSTING=y
diff --git a/target/arm/gdbstub.c b/target/arm/gdbstub.c
index e0dcb33e325..134da0d0ae3 100644
--- a/target/arm/gdbstub.c
+++ b/target/arm/gdbstub.c
@@ -199,6 +199,27 @@ static int vfp_gdb_set_sysreg(CPUARMState *env, uint8_t 
*buf, int reg)
     return 0;
 }
 
+static int mve_gdb_get_reg(CPUARMState *env, GByteArray *buf, int reg)
+{
+    switch (reg) {
+    case 0:
+        return gdb_get_reg32(buf, env->v7m.vpr);
+    default:
+        return 0;
+    }
+}
+
+static int mve_gdb_set_reg(CPUARMState *env, uint8_t *buf, int reg)
+{
+    switch (reg) {
+    case 0:
+        env->v7m.vpr = ldl_p(buf);
+        return 4;
+    default:
+        return 0;
+    }
+}
+
 /**
  * arm_get/set_gdb_*: get/set a gdb register
  * @env: the CPU state
@@ -468,6 +489,10 @@ void arm_cpu_register_gdb_regs_for_features(ARMCPU *cpu)
                                      2, "arm-vfp-sysregs.xml", 0);
         }
     }
+    if (cpu_isar_feature(aa32_mve, cpu)) {
+        gdb_register_coprocessor(cs, mve_gdb_get_reg, mve_gdb_set_reg,
+                                 1, "arm-m-profile-mve.xml", 0);
+    }
     gdb_register_coprocessor(cs, arm_gdb_get_sysreg, arm_gdb_set_sysreg,
                              arm_gen_dynamic_sysreg_xml(cs, cs->gdb_num_regs),
                              "system-registers.xml", 0);
diff --git a/gdb-xml/arm-m-profile-mve.xml b/gdb-xml/arm-m-profile-mve.xml
new file mode 100644
index 00000000000..cba664c4c5b
--- /dev/null
+++ b/gdb-xml/arm-m-profile-mve.xml
@@ -0,0 +1,19 @@
+<?xml version="1.0"?>
+<!-- Copyright (C) 2021 Free Software Foundation, Inc.
+
+     Copying and distribution of this file, with or without modification,
+     are permitted in any medium without royalty provided the copyright
+     notice and this notice are preserved.  -->
+
+<!DOCTYPE feature SYSTEM "gdb-target.dtd">
+<feature name="org.gnu.gdb.arm.m-profile-mve">
+  <flags id="vpr_reg" size="4">
+    <!-- ARMv8.1-M and MVE: Unprivileged and privileged Access.  -->
+    <field name="P0" start="0" end="15"/>
+    <!-- ARMv8.1-M: Privileged Access only.  -->
+    <field name="MASK01" start="16" end="19"/>
+    <!-- ARMv8.1-M: Privileged Access only.  -->
+    <field name="MASK23" start="20" end="23"/>
+  </flags>
+  <reg name="vpr" bitsize="32" type="vpr_reg"/>
+</feature>
-- 
2.20.1