Re: [PATCH RFC 1/1] TCG insn.c: Implement counting specific addresses

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

steffen_hirschmann@web.de writes:

> From: Steffen Hirschmann <steffen_hirschmann@web.de>
>
> This commit implements counting of executed instruction within certain
> virtual address ranges via libinsn.so

This seems reasonable. Do you have any specific use cases where this
information is useful?

> Signed-off-by: Steffen Hirschmann <steffen_hirschmann@web.de>
> ---
>  docs/about/emulation.rst |  2 +
>  tests/tcg/plugins/insn.c | 89 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 91 insertions(+)
>
> diff --git a/docs/about/emulation.rst b/docs/about/emulation.rst
> index a72591ee4d..1fd122bc50 100644
> --- a/docs/about/emulation.rst
> +++ b/docs/about/emulation.rst
> @@ -336,6 +336,8 @@ Behaviour can be tweaked with the following arguments:
>      - Give a summary of the instruction sizes for the execution
>    * - match=<string>
>      - Only instrument instructions matching the string prefix
> +  * - vaddr=<start>+<count>
> +    - Counts executed instructions in this virtual address range. <start> and <count> must be in base 16
>  
>  The ``match`` option will show some basic stats including how many
>  instructions have executed since the last execution. For
> diff --git a/tests/tcg/plugins/insn.c b/tests/tcg/plugins/insn.c
> index 0c723cb9ed..c6d5b07d05 100644
> --- a/tests/tcg/plugins/insn.c
> +++ b/tests/tcg/plugins/insn.c
> @@ -48,6 +48,14 @@ static GHashTable *match_insn_records;
>  static GMutex match_hash_lock;
>  
>  
> +typedef struct {
> +    uint64_t start;
> +    uint64_t end;
> +    qemu_plugin_u64 hits; /* Number of insn executed in this range */
> +} VaddrRange;
> +
> +static GArray *vaddr_ranges;
> +
>  static Instruction * get_insn_record(const char *disas, uint64_t vaddr, Match *m)
>  {
>      g_autofree char *str_hash = g_strdup_printf("%"PRIx64" %s", vaddr, disas);
> @@ -187,6 +195,15 @@ static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
>              }
>              g_free(insn_disas);
>          }
> +
> +        for (int j = 0; j < vaddr_ranges->len; j++) {
> +            VaddrRange *var = &g_array_index(vaddr_ranges, VaddrRange, j);
> +            uint64_t vaddr = qemu_plugin_insn_vaddr(insn);
> +            if (var->start <= vaddr && vaddr < var->end) {
> +                qemu_plugin_register_vcpu_insn_exec_inline_per_vcpu(
> +                    insn, QEMU_PLUGIN_INLINE_ADD_U64, var->hits, 1);
> +            }
> +        }
>      }
>  }
>  
> @@ -246,6 +263,19 @@ static void plugin_exit(qemu_plugin_id_t id, void *p)
>  
>      g_array_free(matches, TRUE);
>      g_array_free(sizes, TRUE);
> +
> +    for (i = 0; i < vaddr_ranges->len; ++i) {
> +        VaddrRange *var = &g_array_index(vaddr_ranges, VaddrRange, i);
> +        uint64_t hits = qemu_plugin_u64_sum(var->hits);
> +
> +        g_string_printf(out, "Vaddr range [0x%08lx, 0x%08lx): %"PRId64" hits\n",
> +                        var->start, var->end, hits);
> +        qemu_plugin_outs(out->str);
> +        qemu_plugin_scoreboard_free(var->hits.score);
> +    }
> +
> +
> +    g_array_free(vaddr_ranges, TRUE);
>  }
>  
>  
> @@ -258,6 +288,48 @@ static void parse_match(char *match)
>      g_array_append_val(matches, new_match);
>  }
>  
> +static void parse_vaddr(const char *arg)
> +{
> +    char *vaddr = g_strdup(arg);

We can make this:

   g_autofree char *vaddr = g_strdup(arg);

to save the g_free() later.

> +    char *saveptr, *token1, *token2;
> +    uint64_t start, len, end;
> +    token1 = strtok_r(vaddr, "+", &saveptr);
> +    token2 = strtok_r(NULL, "+", &saveptr);
> +    if (!token1 || !token2) {
> +        fprintf(stderr, "vaddr usage: vaddr=start+count (both base 16!)\n");
> +        exit(1);
> +    }

rather than manually messing about with strtok_r how about:

  uint64_t start = 0, len = 0;
  g_auto(GStrv) tokens = g_strsplit(vaddr, "+", 2);

  if (tokens[0] && tokens[2]) {
     start = g_ascii_strtoull(tokens[0], NULL, 16);
     len = g_ascii_strtoull(tokens[1], NULL, 16);
  }

  if ((start == 0 || start == GUINT64_MAX) ||
      (len == 0 || len == GUINT64_MAX)) {
     fprintf(stderr, "vaddr usage: vaddr=start+count (both base 16!)\n");
     return false;
  }

Alternatively we already export qemu_plugin_bool_parse() so maybe we
could consider re-factoring qemu_set_dfilter_ranges() to extract the
parser and make it available as a helper?

> +
> +    start = g_ascii_strtoull(token1, NULL, 16);
> +    len = g_ascii_strtoull(token2, NULL, 16);
> +    end = start + len;
> +
> +    g_free(vaddr);

see above

> +
> +    if (start == 0 || end == 0) {
> +        fprintf(stderr, "vaddr usage: vaddr=start+count (both base 16!)\n");
> +        exit(1);

exit is rude for a plugin, we should fall back to QEMU by returning -1

> +    }
> +
> +    if (UINT64_MAX - start < len) {
> +        fprintf(stderr, "integer overflow in vaddr end address calculation."
> +                        " Specified vaddr=start+count incorrect.\n");
> +        exit(1);
> +    }
> +
> +    g_autoptr(GString) out = g_string_new(NULL);
> +    g_string_printf(out, "Registering new Vaddr range"
> +                        " start=0x%08lx len=0x%08lx end=0x%08lx\n", start, len, end);
> +    qemu_plugin_outs(out->str);

Keep variable declarations at the top of a block, that said do we need
to echo here?

> +
> +    VaddrRange new_vaddrrange = {
> +        .start = start,
> +        .end = end,
> +        .hits = qemu_plugin_scoreboard_u64(
> +            qemu_plugin_scoreboard_new(sizeof(uint64_t))) };
> +    g_array_append_val(vaddr_ranges, new_vaddrrange);
> +}
> +
>  QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
>                                             const qemu_info_t *info,
>                                             int argc, char **argv)
> @@ -265,6 +337,7 @@ QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
>      matches = g_array_new(false, true, sizeof(Match));
>      /* null terminated so 0 is not a special case */
>      sizes = g_array_new(true, true, sizeof(unsigned long));
> +    vaddr_ranges = g_array_new(false, true, sizeof(VaddrRange));
>  
>      for (int i = 0; i < argc; i++) {
>          char *opt = argv[i];
> @@ -281,6 +354,8 @@ QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
>              }
>          } else if (g_strcmp0(tokens[0], "match") == 0) {
>              parse_match(tokens[1]);
> +        } else if (g_strcmp0(tokens[0], "vaddr") == 0) {
> +            parse_vaddr(tokens[1]);
>          } else if (g_strcmp0(tokens[0], "trace") == 0) {
>              if (!qemu_plugin_bool_parse(tokens[0], tokens[1], &do_trace)) {
>                  fprintf(stderr, "boolean argument parsing failed: %s\n", opt);
> @@ -292,6 +367,20 @@ QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
>          }
>      }
>  
> +    /* Check for invalid parameter combinations */
> +    if (vaddr_ranges->len > 0) {
> +        if (matches->len > 0) {
> +            fprintf(stderr, "match=... and vaddr=... are incompatible."
> +                            " Use only one of them.\n");
> +            return -1;
> +        }
> +
> +        if (!do_inline) {
> +            fprintf(stderr, "vaddr=... is only supported in conjunction with inline.\n");
> +            return -1;
> +        }
> +    }
> +
>      insn_count = qemu_plugin_scoreboard_u64(
>          qemu_plugin_scoreboard_new(sizeof(uint64_t)));

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro