[Qemu-arm] [PATCH v3 4/4] target/arm: Add arm_gdb_set_sysreg() callback

[Abdallah Bouassida]

This is a callback to set the cp-regs registered by the dynamic XML.

Signed-off-by: Abdallah Bouassida <address@hidden>
---
>> Some of our customers need to connect to Qemu using our tool TRACE32® 
>> via GDB,
>> and for some use case they need to have write access to some particular 
>> cpregs.
>> So, it will be nice to have this capability!
>> Usually, a user won't modify these registers unless he knows what he is 
>> doing!

> I also still don't really like using write_raw_cp_reg() here --
> it will bypass some behaviour you want and in some cases will
> just break the emulation because invariants we assume will
> hold no longer hold. It would be a lot lot safer to not
> provide write access at all, only read access.

Adding to that our customers may need this write access, our tool TRACE32®
needs this also in some particular cases. For example: temporary disabling MMU
to do a physical memory access.

 target/arm/cpu.h     |  2 ++
 target/arm/gdbstub.c | 21 ++++++++++++++++++++-
 target/arm/helper.c  |  2 +-
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index 0e35f64..f4fea98 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -2120,6 +2120,8 @@ static inline bool cp_access_ok(int current_el,
 /* Raw read of a coprocessor register (as needed for migration, etc) */
 uint64_t read_raw_cp_reg(CPUARMState *env, const ARMCPRegInfo *ri);
 
+void write_raw_cp_reg(CPUARMState *env, const ARMCPRegInfo *ri, uint64_t v);
+
 /**
  * write_list_to_cpustate
  * @cpu: ARMCPU
diff --git a/target/arm/gdbstub.c b/target/arm/gdbstub.c
index e08ad79..57bd418 100644
--- a/target/arm/gdbstub.c
+++ b/target/arm/gdbstub.c
@@ -183,12 +183,31 @@ static int arm_gdb_get_sysreg(CPUARMState *env, uint8_t 
*buf, int reg)
     return 0;
 }
 
+static int arm_gdb_set_sysreg(CPUARMState *env, uint8_t *buf, int reg)
+{
+    ARMCPU *cpu = arm_env_get_cpu(env);
+    const ARMCPRegInfo *ri;
+    uint32_t key;
+    uint32_t tmp;
+
+    tmp = ldl_p(buf);
+    key = cpu->dyn_xml.cpregs_keys[reg];
+    ri = get_arm_cp_reginfo(arm_env_get_cpu(env)->cp_regs, key);
+    if (ri) {
+        if (!(ri->type & ARM_CP_CONST)) {
+            write_raw_cp_reg(env, ri, tmp);
+            return cpreg_field_is_64bit(ri) ? 8 : 4;
+        }
+    }
+    return 0;
+}
+
 void arm_register_gdb_regs_for_features(CPUState *cs)
 {
     int n;
 
     n = arm_gen_dynamic_xml(cs);
-    gdb_register_coprocessor(cs, arm_gdb_get_sysreg, NULL,
+    gdb_register_coprocessor(cs, arm_gdb_get_sysreg, arm_gdb_set_sysreg,
                              n, "system-registers.xml", 0);
 
 }
diff --git a/target/arm/helper.c b/target/arm/helper.c
index 1594ec45..4a4afbf 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -200,7 +200,7 @@ uint64_t read_raw_cp_reg(CPUARMState *env, const 
ARMCPRegInfo *ri)
     }
 }
 
-static void write_raw_cp_reg(CPUARMState *env, const ARMCPRegInfo *ri,
+void write_raw_cp_reg(CPUARMState *env, const ARMCPRegInfo *ri,
                              uint64_t v)
 {
     /* Raw write of a coprocessor register (as needed for migration, etc).
-- 
2.7.4