Re: [PATCH v5 14/25] Refactor parsing of /proc//smaps

Simon Marchi via Gdb-patches
2021-02-05T03:38:57Z

> +/* See linux-tdep.h. */
> +
> +bool
> +linux_address_in_memtag_page (CORE_ADDR address)
> +{
> + if (current_inferior ()->fake_pid_p)
> + return false;
> +
> + pid_t pid = current_inferior ()->pid;
> +
> + std::string smaps_file = string_printf ("/proc/%d/smaps", pid);
> +
> + gdb::unique_xmalloc_ptr<char> data
> + = target_fileio_read_stralloc (NULL, smaps_file.c_str ());
> +
> + if (data == nullptr)
> + return false;
> +
> + std::vector<struct smaps_data> smaps;
> +
> + /* Parse the contents of smaps into a vector. */
> + smaps = parse_smaps_data (data.get (), smaps_file);

Declare and assign the vector directly:

std::vector<smaps_data> smaps = ...;

> +
> + for (const smaps_data &map : smaps)
> + {
> + /* Is the address within [start_address, end_address) in a page
> + mapped with memory tagging? */
> + if (address >= map.start_address
> + && address < map.end_address
> + && map.vmflags.memory_tagging)
> + return true;
> + }
> +
> + return false;
> +}
> +
> /* List memory regions in the inferior for a corefile. */
>
> static int
> @@ -1319,137 +1521,50 @@ linux_find_memory_regions_full (struct gdbarch *gdbarch,
> /* Older Linux kernels did not support /proc/PID/smaps. */
> maps_filename = string_printf ("/proc/%d/maps", pid);
> data = target_fileio_read_stralloc (NULL, maps_filename.c_str ());
> - }
> -
> - if (data != NULL)
> - {
> - char *line, *t;
> -
> - line = strtok_r (data.get (), "\n", &t);
> - while (line != NULL)
> - {
> - ULONGEST addr, endaddr, offset, inode;
> - const char *permissions, *device, *filename;
> - struct smaps_vmflags v;
> - size_t permissions_len, device_len;
> - int read, write, exec, priv;
> - int has_anonymous = 0;
> - int should_dump_p = 0;
> - int mapping_anon_p;
> - int mapping_file_p;
> -
> - memset (&v, 0, sizeof (v));
> - read_mapping (line, &addr, &endaddr, &permissions, &permissions_len,
> - &offset, &device, &device_len, &inode, &filename);
> - mapping_anon_p = mapping_is_anonymous_p (filename);
> - /* If the mapping is not anonymous, then we can consider it
> - to be file-backed. These two states (anonymous or
> - file-backed) seem to be exclusive, but they can actually
> - coexist. For example, if a file-backed mapping has
> - "Anonymous:" pages (see more below), then the Linux
> - kernel will dump this mapping when the user specified
> - that she only wants anonymous mappings in the corefile
> - (*even* when she explicitly disabled the dumping of
> - file-backed mappings). */
> - mapping_file_p = !mapping_anon_p;
> -
> - /* Decode permissions. */
> - read = (memchr (permissions, 'r', permissions_len) != 0);
> - write = (memchr (permissions, 'w', permissions_len) != 0);
> - exec = (memchr (permissions, 'x', permissions_len) != 0);
> - /* 'private' here actually means VM_MAYSHARE, and not
> - VM_SHARED. In order to know if a mapping is really
> - private or not, we must check the flag "sh" in the
> - VmFlags field. This is done by decode_vmflags. However,
> - if we are using a Linux kernel released before the commit
> - 834f82e2aa9a8ede94b17b656329f850c1471514 (3.10), we will
> - not have the VmFlags there. In this case, there is
> - really no way to know if we are dealing with VM_SHARED,
> - so we just assume that VM_MAYSHARE is enough. */
> - priv = memchr (permissions, 'p', permissions_len) != 0;
> -
> - /* Try to detect if region should be dumped by parsing smaps
> - counters. */
> - for (line = strtok_r (NULL, "\n", &t);
> - line != NULL && line[0] >= 'A' && line[0] <= 'Z';
> - line = strtok_r (NULL, "\n", &t))
> - {
> - char keyword[64 + 1];
>
> - if (sscanf (line, "%64s", keyword) != 1)
> - {
> - warning (_("Error parsing {s,}maps file '%s'"),
> - maps_filename.c_str ());
> - break;
> - }
> + if (data == nullptr)
> + return 1;
> + }
>
> - if (strcmp (keyword, "Anonymous:") == 0)
> - {
> - /* Older Linux kernels did not support the
> - "Anonymous:" counter. Check it here. */
> - has_anonymous = 1;
> - }
> - else if (strcmp (keyword, "VmFlags:") == 0)
> - decode_vmflags (line, &v);
> + std::vector<struct smaps_data> smaps;
>
> - if (strcmp (keyword, "AnonHugePages:") == 0
> - || strcmp (keyword, "Anonymous:") == 0)
> - {
> - unsigned long number;
> -
> - if (sscanf (line, "%*s%lu", &number) != 1)
> - {
> - warning (_("Error parsing {s,}maps file '%s' number"),
> - maps_filename.c_str ());
> - break;
> - }
> - if (number > 0)
> - {
> - /* Even if we are dealing with a file-backed
> - mapping, if it contains anonymous pages we
> - consider it to be *also* an anonymous
> - mapping, because this is what the Linux
> - kernel does:
> -
> - // Dump segments that have been written to.
> - if (vma->anon_vma && FILTER(ANON_PRIVATE))
> - goto whole;
> -
> - Note that if the mapping is already marked as
> - file-backed (i.e., mapping_file_p is
> - non-zero), then this is a special case, and
> - this mapping will be dumped either when the
> - user wants to dump file-backed *or* anonymous
> - mappings. */
> - mapping_anon_p = 1;
> - }
> - }
> - }
> + /* Parse the contents of smaps into a vector. */
> + smaps = parse_smaps_data (data.get (), maps_filename.c_str ());

Likewise here.

>
> - if (has_anonymous)
> - should_dump_p = should_dump_mapping_p (filterflags, &v, priv,
> - mapping_anon_p,
> - mapping_file_p,
> - filename, addr, offset);
> - else
> - {
> - /* Older Linux kernels did not support the "Anonymous:" counter.
> - If it is missing, we can't be sure - dump all the pages. */
> - should_dump_p = 1;
> - }
> + for (const struct smaps_data map : smaps)

You are missing the & to make it a reference (otherwise it makes a copy
of each item as it iterates, I don't think you want that.

Otherwise, LGTM.

Simon