Re: [PATCH 1/2] contrib/plugins/execlog: Add tab to the separator search of insn_disas

["Alex Bennée" <alex.bennee@linaro.org>]

Yodel Eldar <yodel.eldar@gmail.com> writes:

> On 6/29/25 1:50 PM, Alex Bennée wrote:
>> Yodel Eldar <yodel.eldar@gmail.com> writes:
>>
>>> Currently, execlog searches for a space separator between the
>>> instruction mnemonic and operands, but some disassemblers, e.g. Alpha's,
>>> use a tab separator instead; this results in a null pointer being passed
>>> as the haystack in g_strstr during a subsequent register search, i.e.
>>> undefined behavior, because of a missing null check.
>>>
>>> This patch adds tab to the separator search and a null check on the
>>> result.
>>>
>>> Also, existing, affected pointers are changed to const.
>>>
>>> Lastly, a break statement was added to immediately terminate the
>>> register search when a user-requested register is found in the current
>>> instruction as a trivial optimization, because searching for the
>>> remaining requested registers is unnecessary once one is found.
>>>
>>> Signed-off-by: Yodel Eldar <yodel.eldar@gmail.com>
>>> ---
>>>   contrib/plugins/execlog.c | 15 +++++++++------
>>>   1 file changed, 9 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/contrib/plugins/execlog.c b/contrib/plugins/execlog.c
>>> index d67d010761..08fc1f12d4 100644
>>> --- a/contrib/plugins/execlog.c
>>> +++ b/contrib/plugins/execlog.c
>>> @@ -232,12 +232,15 @@ static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
>>>            */
>>>           if (disas_assist && rmatches) {
>>>               check_regs_next = false;
>>> -            gchar *args = g_strstr_len(insn_disas, -1, " ");
>>> -            for (int n = 0; n < all_reg_names->len; n++) {
>>> -                gchar *reg = g_ptr_array_index(all_reg_names, n);
>>> -                if (g_strrstr(args, reg)) {
>>> -                    check_regs_next = true;
>>> -                    skip = false;
>>> +            const gchar *args = strpbrk(insn_disas, " \t");
>> We have a general preference for glib here, could we use g_strsplit_set?
>>
>> Something like:
>>
>> modified   contrib/plugins/execlog.c
>> @@ -232,12 +232,14 @@ static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
>>            */
>>           if (disas_assist && rmatches) {
>>               check_regs_next = false;
>> -            gchar *args = g_strstr_len(insn_disas, -1, " ");
>> -            for (int n = 0; n < all_reg_names->len; n++) {
>> -                gchar *reg = g_ptr_array_index(all_reg_names, n);
>> -                if (g_strrstr(args, reg)) {
>> -                    check_regs_next = true;
>> -                    skip = false;
>> +            g_auto(GStrv) args = g_strsplit_set(insn_disas, " \t", 2);
>> +            if (args && args[1]) {
>> +                for (int n = 0; n < all_reg_names->len; n++) {
>> +                    gchar *reg = g_ptr_array_index(all_reg_names, n);
>> +                    if (g_strrstr(args[1], reg)) {
>> +                        check_regs_next = true;
>> +                        skip = false;
>> +                    }
>>
>
> Certainly, and thanks for the suggestion! May I credit you with a
> "Suggested-by" or "Co-authored-by" tag in v2 of the patch?

Suggested-by is fine ;-)

>
>
>>> +            if (args) {
>>> +                for (int n = 0; n < all_reg_names->len; n++) {
>>> +                    const gchar *reg = g_ptr_array_index(all_reg_names, n);
>>> +                    if (g_strrstr(args, reg)) {
>>> +                        check_regs_next = true;
>>> +                        skip = false;
>>> +                        break;
>>> +                    }
>>>                   }
>>>               }
>>>           }

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro