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
@ -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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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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* linux-tdep.c (linux_find_memory_regions_full): Use std::string
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357
gdb/linux-tdep.c
357
gdb/linux-tdep.c
@ -88,8 +88,33 @@ struct smaps_vmflags
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/* Is this a MAP_SHARED mapping (VM_SHARED, "sh"). */
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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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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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};
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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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/* Whether to take the /proc/PID/coredump_filter into account when
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generating a corefile. */
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generating a corefile. */
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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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v->exclude_coredump = 1;
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else if (strcmp (s, "sh") == 0)
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else if (strcmp (s, "sh") == 0)
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v->shared_mapping = 1;
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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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}
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}
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@ -1271,6 +1298,180 @@ typedef int linux_dump_mapping_p_ftype (filter_flags filterflags,
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ULONGEST addr,
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ULONGEST addr,
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ULONGEST offset);
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ULONGEST offset);
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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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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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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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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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const char *permissions, *device, *filename;
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struct smaps_vmflags v;
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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 mapping_anon_p;
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int mapping_file_p;
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memset (&v, 0, sizeof (v));
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read_mapping (line, &addr, &endaddr, &permissions, &permissions_len,
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&offset, &device, &device_len, &inode, &filename);
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mapping_anon_p = mapping_is_anonymous_p (filename);
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/* If the mapping is not anonymous, then we can consider it
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to be file-backed. These two states (anonymous or
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file-backed) seem to be exclusive, but they can actually
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coexist. For example, if a file-backed mapping has
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"Anonymous:" pages (see more below), then the Linux
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kernel will dump this mapping when the user specified
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that she only wants anonymous mappings in the corefile
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(*even* when she explicitly disabled the dumping of
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file-backed mappings). */
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mapping_file_p = !mapping_anon_p;
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/* Decode permissions. */
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read = (memchr (permissions, 'r', permissions_len) != 0);
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write = (memchr (permissions, 'w', permissions_len) != 0);
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exec = (memchr (permissions, 'x', permissions_len) != 0);
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/* 'private' here actually means VM_MAYSHARE, and not
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VM_SHARED. In order to know if a mapping is really
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private or not, we must check the flag "sh" in the
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VmFlags field. This is done by decode_vmflags. However,
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if we are using a Linux kernel released before the commit
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834f82e2aa9a8ede94b17b656329f850c1471514 (3.10), we will
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not have the VmFlags there. In this case, there is
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really no way to know if we are dealing with VM_SHARED,
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so we just assume that VM_MAYSHARE is enough. */
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priv = memchr (permissions, 'p', permissions_len) != 0;
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/* Try to detect if region should be dumped by parsing smaps
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counters. */
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for (line = strtok_r (NULL, "\n", &t);
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line != NULL && line[0] >= 'A' && line[0] <= 'Z';
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line = strtok_r (NULL, "\n", &t))
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{
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char keyword[64 + 1];
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if (sscanf (line, "%64s", keyword) != 1)
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{
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warning (_("Error parsing {s,}maps file '%s'"),
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maps_filename.c_str ());
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break;
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}
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if (strcmp (keyword, "Anonymous:") == 0)
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{
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/* Older Linux kernels did not support the
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"Anonymous:" counter. Check it here. */
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has_anonymous = 1;
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}
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else if (strcmp (keyword, "VmFlags:") == 0)
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decode_vmflags (line, &v);
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if (strcmp (keyword, "AnonHugePages:") == 0
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|| strcmp (keyword, "Anonymous:") == 0)
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{
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unsigned long number;
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if (sscanf (line, "%*s%lu", &number) != 1)
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{
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warning (_("Error parsing {s,}maps file '%s' number"),
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maps_filename.c_str ());
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break;
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}
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if (number > 0)
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{
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/* Even if we are dealing with a file-backed
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mapping, if it contains anonymous pages we
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consider it to be *also* an anonymous
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mapping, because this is what the Linux
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kernel does:
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// Dump segments that have been written to.
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if (vma->anon_vma && FILTER(ANON_PRIVATE))
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goto whole;
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Note that if the mapping is already marked as
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file-backed (i.e., mapping_file_p is
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non-zero), then this is a special case, and
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this mapping will be dumped either when the
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user wants to dump file-backed *or* anonymous
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mappings. */
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mapping_anon_p = 1;
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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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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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/* List memory regions in the inferior for a corefile. */
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static int
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static int
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@ -1321,137 +1522,49 @@ linux_find_memory_regions_full (struct gdbarch *gdbarch,
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/* Older Linux kernels did not support /proc/PID/smaps. */
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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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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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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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}
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if (data != NULL)
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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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{
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char *line, *t;
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int should_dump_p = 0;
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line = strtok_r (data.get (), "\n", &t);
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if (map.has_anonymous)
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while (line != NULL)
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{
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{
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ULONGEST addr, endaddr, offset, inode;
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should_dump_p
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const char *permissions, *device, *filename;
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= should_dump_mapping_p (filterflags, &map.vmflags,
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struct smaps_vmflags v;
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map.priv,
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size_t permissions_len, device_len;
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map.mapping_anon_p,
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int read, write, exec, priv;
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map.mapping_file_p,
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int has_anonymous = 0;
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map.filename.c_str (),
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int should_dump_p = 0;
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map.start_address,
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int mapping_anon_p;
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map.offset);
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int mapping_file_p;
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}
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else
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memset (&v, 0, sizeof (v));
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{
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read_mapping (line, &addr, &endaddr, &permissions, &permissions_len,
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/* Older Linux kernels did not support the "Anonymous:" counter.
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&offset, &device, &device_len, &inode, &filename);
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If it is missing, we can't be sure - dump all the pages. */
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mapping_anon_p = mapping_is_anonymous_p (filename);
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should_dump_p = 1;
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/* If the mapping is not anonymous, then we can consider it
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to be file-backed. These two states (anonymous or
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file-backed) seem to be exclusive, but they can actually
|
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coexist. For example, if a file-backed mapping has
|
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"Anonymous:" pages (see more below), then the Linux
|
|
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kernel will dump this mapping when the user specified
|
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that she only wants anonymous mappings in the corefile
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(*even* when she explicitly disabled the dumping of
|
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file-backed mappings). */
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mapping_file_p = !mapping_anon_p;
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/* Decode permissions. */
|
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read = (memchr (permissions, 'r', permissions_len) != 0);
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write = (memchr (permissions, 'w', permissions_len) != 0);
|
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exec = (memchr (permissions, 'x', permissions_len) != 0);
|
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/* 'private' here actually means VM_MAYSHARE, and not
|
|
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VM_SHARED. In order to know if a mapping is really
|
|
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private or not, we must check the flag "sh" in the
|
|
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VmFlags field. This is done by decode_vmflags. However,
|
|
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if we are using a Linux kernel released before the commit
|
|
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834f82e2aa9a8ede94b17b656329f850c1471514 (3.10), we will
|
|
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not have the VmFlags there. In this case, there is
|
|
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really no way to know if we are dealing with VM_SHARED,
|
|
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so we just assume that VM_MAYSHARE is enough. */
|
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priv = memchr (permissions, 'p', permissions_len) != 0;
|
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|
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/* Try to detect if region should be dumped by parsing smaps
|
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counters. */
|
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for (line = strtok_r (NULL, "\n", &t);
|
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line != NULL && line[0] >= 'A' && line[0] <= 'Z';
|
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line = strtok_r (NULL, "\n", &t))
|
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{
|
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char keyword[64 + 1];
|
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|
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if (sscanf (line, "%64s", keyword) != 1)
|
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{
|
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warning (_("Error parsing {s,}maps file '%s'"),
|
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maps_filename.c_str ());
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break;
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}
|
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|
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if (strcmp (keyword, "Anonymous:") == 0)
|
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{
|
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/* Older Linux kernels did not support the
|
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"Anonymous:" counter. Check it here. */
|
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has_anonymous = 1;
|
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}
|
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else if (strcmp (keyword, "VmFlags:") == 0)
|
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decode_vmflags (line, &v);
|
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|
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if (strcmp (keyword, "AnonHugePages:") == 0
|
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|| strcmp (keyword, "Anonymous:") == 0)
|
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{
|
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unsigned long number;
|
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|
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if (sscanf (line, "%*s%lu", &number) != 1)
|
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{
|
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warning (_("Error parsing {s,}maps file '%s' number"),
|
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maps_filename.c_str ());
|
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break;
|
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}
|
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if (number > 0)
|
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{
|
|
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/* Even if we are dealing with a file-backed
|
|
||||||
mapping, if it contains anonymous pages we
|
|
||||||
consider it to be *also* an anonymous
|
|
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mapping, because this is what the Linux
|
|
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kernel does:
|
|
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|
|
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// Dump segments that have been written to.
|
|
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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;
|
|
||||||
}
|
|
||||||
}
|
|
||||||
}
|
|
||||||
|
|
||||||
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;
|
|
||||||
}
|
|
||||||
|
|
||||||
/* Invoke the callback function to create the corefile segment. */
|
|
||||||
if (should_dump_p)
|
|
||||||
func (addr, endaddr - addr, offset, inode,
|
|
||||||
read, write, exec, 1, /* MODIFIED is true because we
|
|
||||||
want to dump the mapping. */
|
|
||||||
filename, obfd);
|
|
||||||
}
|
}
|
||||||
|
|
||||||
return 0;
|
/* Invoke the callback function to create the corefile segment. */
|
||||||
|
if (should_dump_p)
|
||||||
|
{
|
||||||
|
func (map.start_address, map.end_address - map.start_address,
|
||||||
|
map.offset, map.inode, map.read, map.write, map.exec,
|
||||||
|
1, /* MODIFIED is true because we want to dump
|
||||||
|
the mapping. */
|
||||||
|
map.filename.c_str (), obfd);
|
||||||
|
}
|
||||||
}
|
}
|
||||||
|
|
||||||
return 1;
|
return 0;
|
||||||
}
|
}
|
||||||
|
|
||||||
/* A structure for passing information through
|
/* A structure for passing information through
|
||||||
|
|||||||
@ -43,6 +43,10 @@ DEF_ENUM_FLAGS_TYPE (enum linux_siginfo_extra_field_values,
|
|||||||
struct type *linux_get_siginfo_type_with_fields (struct gdbarch *gdbarch,
|
struct type *linux_get_siginfo_type_with_fields (struct gdbarch *gdbarch,
|
||||||
linux_siginfo_extra_fields);
|
linux_siginfo_extra_fields);
|
||||||
|
|
||||||
|
/* Return true if ADDRESS is within the boundaries of a page mapped with
|
||||||
|
memory tagging protection. */
|
||||||
|
bool linux_address_in_memtag_page (CORE_ADDR address);
|
||||||
|
|
||||||
typedef char *(*linux_collect_thread_registers_ftype) (const struct regcache *,
|
typedef char *(*linux_collect_thread_registers_ftype) (const struct regcache *,
|
||||||
ptid_t,
|
ptid_t,
|
||||||
bfd *, char *, int *,
|
bfd *, char *, int *,
|
||||||
|
|||||||
Loading…
Reference in New Issue
Block a user