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:

> 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;
+                    }


> +            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