Refactor parsing of /proc/<pid>/smaps
The Linux kernel exposes the information about MTE-protected pages via the proc filesystem, more specifically through the smaps file. What we're looking for is a mapping with the 'mt' flag, which tells us that mapping was created with a PROT_MTE flag and, thus, is capable of using memory tagging. We already parse that file for other purposes (core file generation/filtering), so this patch refactors the code to make the parsing of the smaps file reusable for memory tagging. The function linux_address_in_memtag_page uses the refactored code to allow querying for memory tag support in a particular address, and it gets used in the next patch. gdb/ChangeLog: 2021-03-24 Luis Machado <luis.machado@linaro.org> * linux-tdep.c (struct smaps_vmflags) <memory_tagging>: New flag bit. (struct smaps_data): New struct. (decode_vmflags): Handle the 'mt' flag. (parse_smaps_data): New function, refactored from linux_find_memory_regions_full. (linux_address_in_memtag_page): New function. (linux_find_memory_regions_full): Refactor into parse_smaps_data. * linux-tdep.h (linux_address_in_memtag_page): New prototype.
This commit is contained in:
Luis Machado
parent
93e447c605
commit
1e735120b9
3 changed files with 251 additions and 122 deletions
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@ -1,3 +1,15 @@
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2021-03-24 Luis Machado <luis.machado@linaro.org>
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* linux-tdep.c (struct smaps_vmflags) <memory_tagging>: New flag
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bit.
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(struct smaps_data): New struct.
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(decode_vmflags): Handle the 'mt' flag.
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(parse_smaps_data): New function, refactored from
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linux_find_memory_regions_full.
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(linux_address_in_memtag_page): New function.
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(linux_find_memory_regions_full): Refactor into parse_smaps_data.
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* linux-tdep.h (linux_address_in_memtag_page): New prototype.
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2021-03-24 Luis Machado <luis.machado@linaro.org>
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* linux-tdep.c (linux_find_memory_regions_full): Use std::string
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243
gdb/linux-tdep.c
243
gdb/linux-tdep.c
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@ -88,6 +88,31 @@ struct smaps_vmflags
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/* Is this a MAP_SHARED mapping (VM_SHARED, "sh"). */
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unsigned int shared_mapping : 1;
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/* Memory map has memory tagging enabled. */
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unsigned int memory_tagging : 1;
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};
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/* Data structure that holds the information contained in the
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/proc/<pid>/smaps file. */
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struct smaps_data
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{
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ULONGEST start_address;
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ULONGEST end_address;
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std::string filename;
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struct smaps_vmflags vmflags;
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bool read;
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bool write;
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bool exec;
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bool priv;
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bool has_anonymous;
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bool mapping_anon_p;
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bool mapping_file_p;
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ULONGEST inode;
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ULONGEST offset;
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};
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/* Whether to take the /proc/PID/coredump_filter into account when
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@ -476,6 +501,8 @@ decode_vmflags (char *p, struct smaps_vmflags *v)
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v->exclude_coredump = 1;
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else if (strcmp (s, "sh") == 0)
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v->shared_mapping = 1;
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else if (strcmp (s, "mt") == 0)
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v->memory_tagging = 1;
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}
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}
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@ -1271,63 +1298,24 @@ typedef int linux_dump_mapping_p_ftype (filter_flags filterflags,
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ULONGEST addr,
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ULONGEST offset);
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/* List memory regions in the inferior for a corefile. */
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/* Helper function to parse the contents of /proc/<pid>/smaps into a data
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structure, for easy access.
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static int
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linux_find_memory_regions_full (struct gdbarch *gdbarch,
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linux_dump_mapping_p_ftype *should_dump_mapping_p,
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linux_find_memory_region_ftype *func,
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void *obfd)
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{
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pid_t pid;
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/* Default dump behavior of coredump_filter (0x33), according to
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Documentation/filesystems/proc.txt from the Linux kernel
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tree. */
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filter_flags filterflags = (COREFILTER_ANON_PRIVATE
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| COREFILTER_ANON_SHARED
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| COREFILTER_ELF_HEADERS
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| COREFILTER_HUGETLB_PRIVATE);
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DATA is the contents of the smaps file. The parsed contents are stored
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into the SMAPS vector. */
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/* We need to know the real target PID to access /proc. */
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if (current_inferior ()->fake_pid_p)
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return 1;
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pid = current_inferior ()->pid;
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if (use_coredump_filter)
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{
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std::string core_dump_filter_name
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= string_printf ("/proc/%d/coredump_filter", pid);
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gdb::unique_xmalloc_ptr<char> coredumpfilterdata
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= target_fileio_read_stralloc (NULL, core_dump_filter_name.c_str ());
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if (coredumpfilterdata != NULL)
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{
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unsigned int flags;
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sscanf (coredumpfilterdata.get (), "%x", &flags);
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filterflags = (enum filter_flag) flags;
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}
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}
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std::string maps_filename = string_printf ("/proc/%d/smaps", pid);
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gdb::unique_xmalloc_ptr<char> data
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= target_fileio_read_stralloc (NULL, maps_filename.c_str ());
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if (data == NULL)
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{
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/* Older Linux kernels did not support /proc/PID/smaps. */
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maps_filename = string_printf ("/proc/%d/maps", pid);
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data = target_fileio_read_stralloc (NULL, maps_filename.c_str ());
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}
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if (data != NULL)
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static std::vector<struct smaps_data>
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parse_smaps_data (const char *data,
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const std::string maps_filename)
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{
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char *line, *t;
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line = strtok_r (data.get (), "\n", &t);
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gdb_assert (data != nullptr);
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line = strtok_r ((char *) data, "\n", &t);
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std::vector<struct smaps_data> smaps;
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while (line != NULL)
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{
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ULONGEST addr, endaddr, offset, inode;
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@ -1336,7 +1324,6 @@ linux_find_memory_regions_full (struct gdbarch *gdbarch,
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size_t permissions_len, device_len;
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int read, write, exec, priv;
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int has_anonymous = 0;
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int should_dump_p = 0;
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int mapping_anon_p;
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int mapping_file_p;
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@ -1427,12 +1414,138 @@ linux_find_memory_regions_full (struct gdbarch *gdbarch,
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}
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}
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}
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/* Save the smaps entry to the vector. */
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struct smaps_data map;
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if (has_anonymous)
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should_dump_p = should_dump_mapping_p (filterflags, &v, priv,
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mapping_anon_p,
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mapping_file_p,
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filename, addr, offset);
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map.start_address = addr;
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map.end_address = endaddr;
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map.filename = filename;
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map.vmflags = v;
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map.read = read? true : false;
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map.write = write? true : false;
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map.exec = exec? true : false;
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map.priv = priv? true : false;
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map.has_anonymous = has_anonymous;
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map.mapping_anon_p = mapping_anon_p? true : false;
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map.mapping_file_p = mapping_file_p? true : false;
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map.offset = offset;
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map.inode = inode;
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smaps.emplace_back (map);
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}
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return smaps;
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}
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/* See linux-tdep.h. */
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bool
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linux_address_in_memtag_page (CORE_ADDR address)
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{
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if (current_inferior ()->fake_pid_p)
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return false;
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pid_t pid = current_inferior ()->pid;
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std::string smaps_file = string_printf ("/proc/%d/smaps", pid);
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gdb::unique_xmalloc_ptr<char> data
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= target_fileio_read_stralloc (NULL, smaps_file.c_str ());
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if (data == nullptr)
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return false;
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/* Parse the contents of smaps into a vector. */
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std::vector<struct smaps_data> smaps
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= parse_smaps_data (data.get (), smaps_file);
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for (const smaps_data &map : smaps)
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{
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/* Is the address within [start_address, end_address) in a page
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mapped with memory tagging? */
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if (address >= map.start_address
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&& address < map.end_address
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&& map.vmflags.memory_tagging)
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return true;
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}
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return false;
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}
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/* List memory regions in the inferior for a corefile. */
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static int
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linux_find_memory_regions_full (struct gdbarch *gdbarch,
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linux_dump_mapping_p_ftype *should_dump_mapping_p,
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linux_find_memory_region_ftype *func,
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void *obfd)
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{
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pid_t pid;
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/* Default dump behavior of coredump_filter (0x33), according to
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Documentation/filesystems/proc.txt from the Linux kernel
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tree. */
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filter_flags filterflags = (COREFILTER_ANON_PRIVATE
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| COREFILTER_ANON_SHARED
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| COREFILTER_ELF_HEADERS
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| COREFILTER_HUGETLB_PRIVATE);
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/* We need to know the real target PID to access /proc. */
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if (current_inferior ()->fake_pid_p)
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return 1;
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pid = current_inferior ()->pid;
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if (use_coredump_filter)
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{
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std::string core_dump_filter_name
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= string_printf ("/proc/%d/coredump_filter", pid);
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gdb::unique_xmalloc_ptr<char> coredumpfilterdata
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= target_fileio_read_stralloc (NULL, core_dump_filter_name.c_str ());
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if (coredumpfilterdata != NULL)
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{
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unsigned int flags;
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sscanf (coredumpfilterdata.get (), "%x", &flags);
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filterflags = (enum filter_flag) flags;
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}
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}
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std::string maps_filename = string_printf ("/proc/%d/smaps", pid);
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gdb::unique_xmalloc_ptr<char> data
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= target_fileio_read_stralloc (NULL, maps_filename.c_str ());
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if (data == NULL)
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{
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/* Older Linux kernels did not support /proc/PID/smaps. */
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maps_filename = string_printf ("/proc/%d/maps", pid);
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data = target_fileio_read_stralloc (NULL, maps_filename.c_str ());
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if (data == nullptr)
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return 1;
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}
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/* Parse the contents of smaps into a vector. */
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std::vector<struct smaps_data> smaps
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= parse_smaps_data (data.get (), maps_filename.c_str ());
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for (const struct smaps_data &map : smaps)
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{
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int should_dump_p = 0;
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if (map.has_anonymous)
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{
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should_dump_p
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= should_dump_mapping_p (filterflags, &map.vmflags,
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map.priv,
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map.mapping_anon_p,
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map.mapping_file_p,
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map.filename.c_str (),
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map.start_address,
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map.offset);
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}
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else
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{
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/* Older Linux kernels did not support the "Anonymous:" counter.
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@ -1442,18 +1555,18 @@ linux_find_memory_regions_full (struct gdbarch *gdbarch,
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/* Invoke the callback function to create the corefile segment. */
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if (should_dump_p)
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func (addr, endaddr - addr, offset, inode,
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read, write, exec, 1, /* MODIFIED is true because we
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want to dump the mapping. */
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filename, obfd);
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{
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func (map.start_address, map.end_address - map.start_address,
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map.offset, map.inode, map.read, map.write, map.exec,
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1, /* MODIFIED is true because we want to dump
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the mapping. */
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map.filename.c_str (), obfd);
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}
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}
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return 0;
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}
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return 1;
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}
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/* A structure for passing information through
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linux_find_memory_regions_full. */
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@ -43,6 +43,10 @@ DEF_ENUM_FLAGS_TYPE (enum linux_siginfo_extra_field_values,
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struct type *linux_get_siginfo_type_with_fields (struct gdbarch *gdbarch,
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linux_siginfo_extra_fields);
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/* Return true if ADDRESS is within the boundaries of a page mapped with
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memory tagging protection. */
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bool linux_address_in_memtag_page (CORE_ADDR address);
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typedef char *(*linux_collect_thread_registers_ftype) (const struct regcache *,
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ptid_t,
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bfd *, char *, int *,
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