Re: [RFC PATCH 15/24] target/arm: Fill new members of GDBFeature

[Akihiko Odaki <akihiko.odaki@daynix.com>]

On 2023/08/14 23:56, Alex Bennée wrote:
> 
> Akihiko Odaki <akihiko.odaki@daynix.com> writes:
> 
>> These members will be used to help plugins to identify registers.
>>
>> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
>> ---
>>   target/arm/gdbstub.c   | 46 +++++++++++++++++++++++++++---------------
>>   target/arm/gdbstub64.c | 42 +++++++++++++++++++++++++-------------
>>   2 files changed, 58 insertions(+), 30 deletions(-)
>>
>> diff --git a/target/arm/gdbstub.c b/target/arm/gdbstub.c
>> index 100a6eed15..56d24028f6 100644
>> --- a/target/arm/gdbstub.c
>> +++ b/target/arm/gdbstub.c
>> @@ -270,6 +270,7 @@ static void arm_gen_one_feature_sysreg(GString *s,
>>       g_string_append_printf(s, " regnum=\"%d\"", regnum);
>>       g_string_append_printf(s, " group=\"cp_regs\"/>");
>>       dyn_feature->data.cpregs.keys[dyn_feature->desc.num_regs] = ri_key;
>> +    ((const char **)dyn_feature->desc.regs)[dyn_feature->desc.num_regs] = ri->name;
>>       dyn_feature->desc.num_regs++;
>>   }
>>   
>> @@ -316,6 +317,8 @@ static GDBFeature *arm_gen_dynamic_sysreg_feature(CPUState *cs, int base_reg)
>>       DynamicGDBFeatureInfo *dyn_feature = &cpu->dyn_sysreg_feature;
>>       gsize num_regs = g_hash_table_size(cpu->cp_regs);
>>   
>> +    dyn_feature->desc.name = "org.qemu.gdb.arm.sys.regs";
>> +    dyn_feature->desc.regs = g_new(const char *, num_regs);
> 
> AIUI this means we now have an array of register names which mirrors the
> names embedded in the XML. This smells like a few steps away from just
> abstracting the whole XML away from the targets and generating them
> inside gdbstub when we need them. As per my stalled attempt I referenced
> earlier.

The abstraction is strictly limited for identifiers. Most plugin should 
already have some knowledge of how registers are used. For example, a 
plugin that tracks stack frame for RISC-V should know sp is the stack 
pointer register. Similarly, a cycle simulator plugin should know how 
registers are used in a program. Only identifiers matter in such cases.

I'm definitely *not* in favor of abstracting the whole XML for plugins. 
It will be too hard to maintain ABI compatibility when a new attribute 
emerges, for example.

> 
> 
>>       dyn_feature->desc.num_regs = 0;
>>       dyn_feature->data.cpregs.keys = g_new(uint32_t, num_regs);
>>       g_string_printf(s, "<?xml version=\"1.0\"?>");
>> @@ -418,30 +421,34 @@ static int arm_gdb_set_m_systemreg(CPUARMState *env, uint8_t *buf, int reg)
>>   }
>>   
>>   static GDBFeature *arm_gen_dynamic_m_systemreg_feature(CPUState *cs,
>> -                                                       int orig_base_reg)
>> +                                                       int base_reg)
>>   {
>>       ARMCPU *cpu = ARM_CPU(cs);
>>       CPUARMState *env = &cpu->env;
>>       GString *s = g_string_new(NULL);
>> -    int base_reg = orig_base_reg;
>> -    int i;
>> +    const char **regs = g_new(const char *, ARRAY_SIZE(m_sysreg_def));
>> +    int i = 0;
>> +    int j;
>>   
>>       g_string_printf(s, "<?xml version=\"1.0\"?>");
>>       g_string_append_printf(s, "<!DOCTYPE target SYSTEM \"gdb-target.dtd\">");
>>       g_string_append_printf(s, "<feature name=\"org.gnu.gdb.arm.m-system\">\n");
>>   
>> -    for (i = 0; i < ARRAY_SIZE(m_sysreg_def); i++) {
>> -        if (arm_feature(env, m_sysreg_def[i].feature)) {
>> +    for (j = 0; j < ARRAY_SIZE(m_sysreg_def); j++) {
>> +        if (arm_feature(env, m_sysreg_def[j].feature)) {
>> +            regs[i] = m_sysreg_def[j].name;
>>               g_string_append_printf(s,
>>                   "<reg name=\"%s\" bitsize=\"32\" regnum=\"%d\"/>\n",
>> -                m_sysreg_def[i].name, base_reg++);
>> +                m_sysreg_def[j].name, base_reg + i++);
>>           }
>>       }
>>   
>>       g_string_append_printf(s, "</feature>");
>> +    cpu->dyn_m_systemreg_feature.desc.name = "org.gnu.gdb.arm.m-system";
>>       cpu->dyn_m_systemreg_feature.desc.xmlname = "arm-m-system.xml";
>>       cpu->dyn_m_systemreg_feature.desc.xml = g_string_free(s, false);
>> -    cpu->dyn_m_systemreg_feature.desc.num_regs = base_reg - orig_base_reg;
>> +    cpu->dyn_m_systemreg_feature.desc.regs = regs;
>> +    cpu->dyn_m_systemreg_feature.desc.num_regs = i;
>>   
>>       return &cpu->dyn_m_systemreg_feature.desc;
>>   }
>> @@ -462,30 +469,37 @@ static int arm_gdb_set_m_secextreg(CPUARMState *env, uint8_t *buf, int reg)
>>   }
>>   
>>   static GDBFeature *arm_gen_dynamic_m_secextreg_feature(CPUState *cs,
>> -                                                       int orig_base_reg)
>> +                                                       int base_reg)
>>   {
>>       ARMCPU *cpu = ARM_CPU(cs);
>>       GString *s = g_string_new(NULL);
>> -    int base_reg = orig_base_reg;
>> -    int i;
>> +    const char **regs = g_new(const char *, ARRAY_SIZE(m_sysreg_def) * 2);
>> +    int i = 0;
>> +    int j;
>>   
>>       g_string_printf(s, "<?xml version=\"1.0\"?>");
>>       g_string_append_printf(s, "<!DOCTYPE target SYSTEM \"gdb-target.dtd\">");
>>       g_string_append_printf(s, "<feature name=\"org.gnu.gdb.arm.secext\">\n");
>>   
>> -    for (i = 0; i < ARRAY_SIZE(m_sysreg_def); i++) {
>> +    for (j = 0; j < ARRAY_SIZE(m_sysreg_def); j++) {
>> +        regs[i] = g_strconcat(m_sysreg_def[j].name, "_ns", NULL);
>>           g_string_append_printf(s,
>> -            "<reg name=\"%s_ns\" bitsize=\"32\" regnum=\"%d\"/>\n",
>> -            m_sysreg_def[i].name, base_reg++);
>> +            "<reg name=\"%s\" bitsize=\"32\" regnum=\"%d\"/>\n",
>> +            regs[i], base_reg + i);
>> +        i++;
>> +        regs[i] = g_strconcat(m_sysreg_def[j].name, "_s", NULL);
>>           g_string_append_printf(s,
>> -            "<reg name=\"%s_s\" bitsize=\"32\" regnum=\"%d\"/>\n",
>> -            m_sysreg_def[i].name, base_reg++);
>> +            "<reg name=\"%s\" bitsize=\"32\" regnum=\"%d\"/>\n",
>> +            regs[i], base_reg + i);
>> +        i++;
>>       }
>>   
>>       g_string_append_printf(s, "</feature>");
>> +    cpu->dyn_m_secextreg_feature.desc.name = "org.gnu.gdb.arm.secext";
>>       cpu->dyn_m_secextreg_feature.desc.xmlname = "arm-m-secext.xml";
>>       cpu->dyn_m_secextreg_feature.desc.xml = g_string_free(s, false);
>> -    cpu->dyn_m_secextreg_feature.desc.num_regs = base_reg - orig_base_reg;
>> +    cpu->dyn_m_secextreg_feature.desc.regs = regs;
>> +    cpu->dyn_m_secextreg_feature.desc.num_regs = i;
>>   
>>       return &cpu->dyn_m_secextreg_feature.desc;
>>   }
>> diff --git a/target/arm/gdbstub64.c b/target/arm/gdbstub64.c
>> index 20483ef9bc..c5ed7c0aa3 100644
>> --- a/target/arm/gdbstub64.c
>> +++ b/target/arm/gdbstub64.c
>> @@ -316,15 +316,21 @@ static void output_vector_union_type(GString *s, int reg_width,
>>       g_string_append(s, "</union>");
>>   }
>>   
>> -GDBFeature *arm_gen_dynamic_svereg_feature(CPUState *cs, int orig_base_reg)
>> +GDBFeature *arm_gen_dynamic_svereg_feature(CPUState *cs, int base_reg)
>>   {
>>       ARMCPU *cpu = ARM_CPU(cs);
>>       GString *s = g_string_new(NULL);
>>       DynamicGDBFeatureInfo *info = &cpu->dyn_svereg_feature;
>> +    const char **regs;
>>       int reg_width = cpu->sve_max_vq * 128;
>>       int pred_width = cpu->sve_max_vq * 16;
>> -    int base_reg = orig_base_reg;
>> -    int i;
>> +    int i = 0;
>> +    int j;
>> +
>> +    info->desc.name = "org.gnu.gdb.aarch64.sve";
>> +    info->desc.num_regs = 32 + 16 + 4;
>> +    regs = g_new(const char *, info->desc.num_regs);
>> +    info->desc.regs = regs;
>>   
>>       g_string_printf(s, "<?xml version=\"1.0\"?>");
>>       g_string_append_printf(s, "<!DOCTYPE target SYSTEM \"gdb-target.dtd\">");
>> @@ -339,44 +345,52 @@ GDBFeature *arm_gen_dynamic_svereg_feature(CPUState *cs, int orig_base_reg)
>>                              pred_width / 8);
>>   
>>       /* Define the vector registers. */
>> -    for (i = 0; i < 32; i++) {
>> +    for (j = 0; j < 32; j++) {
>> +        regs[i] = g_strdup_printf("z%d", j);
>>           g_string_append_printf(s,
>> -                               "<reg name=\"z%d\" bitsize=\"%d\""
>> +                               "<reg name=\"%s\" bitsize=\"%d\""
>>                                  " regnum=\"%d\" type=\"svev\"/>",
>> -                               i, reg_width, base_reg++);
>> +                               regs[i], reg_width, base_reg + i);
>> +        i++;
>>       }
>>   
>>       /* fpscr & status registers */
>> +    regs[i] = "fpsr";
>>       g_string_append_printf(s, "<reg name=\"fpsr\" bitsize=\"32\""
>>                              " regnum=\"%d\" group=\"float\""
>> -                           " type=\"int\"/>", base_reg++);
>> +                           " type=\"int\"/>", base_reg + i++);
>> +    regs[i] = "fpcr";
>>       g_string_append_printf(s, "<reg name=\"fpcr\" bitsize=\"32\""
>>                              " regnum=\"%d\" group=\"float\""
>> -                           " type=\"int\"/>", base_reg++);
>> +                           " type=\"int\"/>", base_reg + i++);
>>   
>>       /* Define the predicate registers. */
>> -    for (i = 0; i < 16; i++) {
>> +    for (j = 0; j < 16; j++) {
>> +        regs[i] = g_strdup_printf("p%d", j);
>>           g_string_append_printf(s,
>> -                               "<reg name=\"p%d\" bitsize=\"%d\""
>> +                               "<reg name=\"%s\" bitsize=\"%d\""
>>                                  " regnum=\"%d\" type=\"svep\"/>",
>> -                               i, pred_width, base_reg++);
>> +                               regs[i], pred_width, base_reg + i);
>> +        i++;
>>       }
>> +    regs[i] = "ffr";
>>       g_string_append_printf(s,
>>                              "<reg name=\"ffr\" bitsize=\"%d\""
>>                              " regnum=\"%d\" group=\"vector\""
>>                              " type=\"svep\"/>",
>> -                           pred_width, base_reg++);
>> +                           pred_width, base_reg + i++);
>>   
>>       /* Define the vector length pseudo-register. */
>> +    regs[i] = "vg";
>>       g_string_append_printf(s,
>>                              "<reg name=\"vg\" bitsize=\"64\""
>>                              " regnum=\"%d\" type=\"int\"/>",
>> -                           base_reg++);
>> +                           base_reg + i++);
>>   
>>       g_string_append_printf(s, "</feature>");
>>   
>>       info->desc.xmlname = "sve-registers.xml";
>>       info->desc.xml = g_string_free(s, false);
>> -    info->desc.num_regs = base_reg - orig_base_reg;
>> +    assert(info->desc.num_regs == i);
>>       return &info->desc;
>>   }
> 
>