* [PATCH v2 1/6] target_fileio_read_stralloc: add an optional length parameter
2026-08-25 10:09 [PATCH v2 0/6] gdb: introduce file_reader_t to read procfs files Matthieu Longo
@ 2026-08-25 10:09 ` Matthieu Longo
2026-08-25 10:09 ` [PATCH v2 2/6] gdb support: add gdb::ranges::replace algorithm Matthieu Longo
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: Matthieu Longo @ 2026-08-25 10:09 UTC (permalink / raw)
To: gdb-patches
Cc: Simon Marchi, Thiago Jung Bauermann, Luis Machado, Luis Machado,
Christina Joos, Kevin Buettner, Matthieu Longo
Extend target_fileio_read_stralloc with an optional output parameter
that returns the number of bytes read, excluding the terminating NUL
byte.
Most callers only need the returned NUL-terminated buffer and can
ignore the new parameter, but callers that need the number of bytes
read can now obtain it without recomputing it.
While updating the function, make a couple of minor cleanups by using
'\0' instead of 0 for character literals and clarifying the function
documentation.
Reviewed-By: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
---
gdb/target.c | 11 ++++++++---
gdb/target.h | 20 ++++++++++++--------
2 files changed, 20 insertions(+), 11 deletions(-)
diff --git a/gdb/target.c b/gdb/target.c
index 5d937f3ae85..ebf0f30092c 100644
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -3547,7 +3547,8 @@ target_fileio_read_alloc (struct inferior *inf, const char *filename,
/* See target.h. */
gdb::unique_xmalloc_ptr<char>
-target_fileio_read_stralloc (struct inferior *inf, const char *filename)
+target_fileio_read_stralloc (struct inferior *inf, const char *filename,
+ LONGEST *len)
{
gdb_byte *buffer;
char *bufstr;
@@ -3556,17 +3557,21 @@ target_fileio_read_stralloc (struct inferior *inf, const char *filename)
transferred = target_fileio_read_alloc_1 (inf, filename, &buffer, 1);
bufstr = (char *) buffer;
+ /* Note: on failure, target_fileio_read_alloc_1 returns -1. */
+ if (len != nullptr)
+ *len = transferred;
+
if (transferred < 0)
return gdb::unique_xmalloc_ptr<char> (nullptr);
if (transferred == 0)
return make_unique_xstrdup ("");
- bufstr[transferred] = 0;
+ bufstr[transferred] = '\0';
/* Check for embedded NUL bytes; but allow trailing NULs. */
for (i = strlen (bufstr); i < transferred; i++)
- if (bufstr[i] != 0)
+ if (bufstr[i] != '\0')
{
warning (_("target file %s "
"contained unexpected null characters"),
diff --git a/gdb/target.h b/gdb/target.h
index 6d1c21f29f6..819279c08fc 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -2327,15 +2327,19 @@ extern LONGEST target_fileio_read_alloc (struct inferior *inf,
const char *filename,
gdb_byte **buf_p);
-/* Read target file FILENAME, in the filesystem as seen by INF. If
- INF is NULL, use the filesystem seen by the debugger (GDB or, for
- remote targets, the remote stub). The result is NUL-terminated and
- returned as a string, allocated using xmalloc. If an error occurs
- or the transfer is unsupported, NULL is returned. Empty objects
- are returned as allocated but empty strings. A warning is issued
- if the result contains any embedded NUL bytes. */
+/* Read the content of the target file FILENAME from the filesystem as
+ seen by INF. If INF is NULL, use the filesystem seen by the debugger
+ (GDB or, for remote targets, the remote stub).
+
+ If LEN is not NULL, store the number of bytes read, excluding the
+ terminating NUL byte.
+
+ The returned buffer is NUL-terminated and allocated using xmalloc.
+ On error, or if the transfer is unsupported, return NULL and set
+ LEN to -1. Empty files are returned as allocated but empty strings.
+ A warning is issued if the file content contains embedded NUL bytes. */
extern gdb::unique_xmalloc_ptr<char> target_fileio_read_stralloc
- (struct inferior *inf, const char *filename);
+ (struct inferior *inf, const char *filename, LONGEST *len = nullptr);
/* Invalidate the target associated with open handles that were open
on target TARG, since we're about to close (and maybe destroy) the
--
2.55.0
^ permalink raw reply [flat|nested] 7+ messages in thread* [PATCH v2 2/6] gdb support: add gdb::ranges::replace algorithm
2026-08-25 10:09 [PATCH v2 0/6] gdb: introduce file_reader_t to read procfs files Matthieu Longo
2026-08-25 10:09 ` [PATCH v2 1/6] target_fileio_read_stralloc: add an optional length parameter Matthieu Longo
@ 2026-08-25 10:09 ` Matthieu Longo
2026-08-25 10:09 ` [PATCH v2 3/6] gdb: introduce helper class file_reader_t Matthieu Longo
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: Matthieu Longo @ 2026-08-25 10:09 UTC (permalink / raw)
To: gdb-patches
Cc: Simon Marchi, Thiago Jung Bauermann, Luis Machado, Luis Machado,
Christina Joos, Kevin Buettner, Matthieu Longo
Provide a C++17-compatible replacement for the C++20 std::ranges::replace
algorithm, allowing callers to use a consistent interface until GDB
transitions to C++20. The helper should be removed once the C++ standard
library implementation become available.
https://en.cppreference.com/cpp/algorithm/ranges/replace
---
gdbsupport/array-view.h | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/gdbsupport/array-view.h b/gdbsupport/array-view.h
index 8431d7f5add..f9842ecff30 100644
--- a/gdbsupport/array-view.h
+++ b/gdbsupport/array-view.h
@@ -225,6 +225,22 @@ void copy (gdb::array_view<U> src, gdb::array_view<T> dest)
std::copy_backward (src.begin (), src.end (), dest.end ());
}
+namespace ranges {
+
+/* Replace all occurrences of a value in the provided range.
+
+ Note: this helper is a reimplementation of std::ranges::replace, only
+ available from C++20 onwards, and consequently, should be replaced by
+ std::ranges::replace once GDB switches to C++20. */
+
+template <class Range, typename T>
+void replace (Range r, const T &old_value, const T &new_value)
+{
+ std::replace (r.begin (), r.end (), old_value, new_value);
+}
+
+} /* namespace ranges */
+
/* Compare LHS and RHS for (deep) equality. That is, whether LHS and
RHS have the same sizes, and whether each pair of elements of LHS
and RHS at the same position compares equal. */
--
2.55.0
^ permalink raw reply [flat|nested] 7+ messages in thread* [PATCH v2 3/6] gdb: introduce helper class file_reader_t
2026-08-25 10:09 [PATCH v2 0/6] gdb: introduce file_reader_t to read procfs files Matthieu Longo
2026-08-25 10:09 ` [PATCH v2 1/6] target_fileio_read_stralloc: add an optional length parameter Matthieu Longo
2026-08-25 10:09 ` [PATCH v2 2/6] gdb support: add gdb::ranges::replace algorithm Matthieu Longo
@ 2026-08-25 10:09 ` Matthieu Longo
2026-08-25 10:09 ` [PATCH v2 4/6] gdb/linux-tdep: migrate linux_info_proc to file_reader_t Matthieu Longo
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: Matthieu Longo @ 2026-08-25 10:09 UTC (permalink / raw)
To: gdb-patches
Cc: Simon Marchi, Thiago Jung Bauermann, Luis Machado, Luis Machado,
Christina Joos, Kevin Buettner, Matthieu Longo
Wrap all the boilerplate code required to read a file in a new helper
class: file_reader_t. The class owns the file contents together with
the file path, and provides convenient accessors for the data, size and
typed views. It supports both null-terminated text files and binary files.
This helper eliminates repeated calls to target_fileio_read_stralloc
and target_fileio_read_alloc, remove explicit memory management with
gdb::unique_xmalloc_ptr, and simplifies the casting logic when working
with binary data.
The patch converts some of the existing Linux, AMD64, and SPARC code that
reads files from /proc to use file_reader_t. As a side effect,
amd64_linux_lam_untag_mask and linux_process_address_in_memtag_page
may now return earlier in case the file is empty.
Reviewed-By: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Reviewed-By: Christina Joos <christina.joos@intel.com>
---
gdb/amd64-linux-tdep.c | 12 ++--
gdb/linux-tdep.c | 122 ++++++++++++++++++-----------------------
gdb/sparc64-tdep.c | 15 +++--
gdb/target.h | 78 ++++++++++++++++++++++++++
4 files changed, 143 insertions(+), 84 deletions(-)
diff --git a/gdb/amd64-linux-tdep.c b/gdb/amd64-linux-tdep.c
index 9b23db72bbe..52f16c953d1 100644
--- a/gdb/amd64-linux-tdep.c
+++ b/gdb/amd64-linux-tdep.c
@@ -1848,14 +1848,11 @@ amd64_linux_lam_untag_mask ()
if (inf->fake_pid_p)
return DEFAULT_TAG_MASK;
- const std::string filename = string_printf ("/proc/%d/status", inf->pid);
- gdb::unique_xmalloc_ptr<char> status_file
- = target_fileio_read_stralloc (nullptr, filename.c_str ());
-
- if (status_file == nullptr)
+ file_reader_t<char> proc_status (string_printf ("/proc/%d/status", inf->pid));
+ if (!proc_status)
return DEFAULT_TAG_MASK;
- std::string_view status_file_view (status_file.get ());
+ std::string_view status_file_view (proc_status.data ());
constexpr std::string_view untag_mask_str = "untag_mask:\t";
const size_t found = status_file_view.find (untag_mask_str);
if (found != std::string::npos)
@@ -1867,7 +1864,8 @@ amd64_linux_lam_untag_mask ()
unsigned long long result = std::strtoul (start, &endptr, 0);
if (errno != 0 || endptr == start)
error (_("Failed to parse untag_mask from file %ps."),
- styled_string (file_name_style.style (), filename.c_str ()));
+ styled_string (file_name_style.style (),
+ proc_status.c_filepath ()));
return result;
}
diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c
index 588984a1ca4..84614bc91a0 100644
--- a/gdb/linux-tdep.c
+++ b/gdb/linux-tdep.c
@@ -1551,7 +1551,7 @@ parse_smaps_key_value (const char *keyword, const char *line,
DATA is the contents of the smaps file. The parsed contents are stored
into the SMAPS vector. */
-static std::vector<struct smaps_data>
+static std::vector<smaps_data>
parse_smaps_data (const char *data,
const std::string &maps_filename)
{
@@ -1561,7 +1561,7 @@ parse_smaps_data (const char *data,
line = strtok_r ((char *) data, "\n", &t);
- std::vector<struct smaps_data> smaps;
+ std::vector<smaps_data> smaps;
while (line != NULL)
{
@@ -1673,7 +1673,7 @@ parse_smaps_data (const char *data,
}
}
/* Save the smaps entry to the vector. */
- struct smaps_data map;
+ smaps_data map;
map.start_address = m.addr;
map.end_address = m.endaddr;
@@ -1697,6 +1697,12 @@ parse_smaps_data (const char *data,
return smaps;
}
+static std::vector<smaps_data>
+parse_smaps_data (const file_reader_t<char> &freader)
+{
+ return parse_smaps_data (freader.data (), freader.filepath ());
+}
+
/* Helper that checks if an address is in a memory tag page for a live
process. */
@@ -1708,17 +1714,13 @@ linux_process_address_in_memtag_page (CORE_ADDR address)
ptid_t ptid = get_process_reference_ptid ();
- std::string smaps_file = string_printf ("/proc/%ld/smaps", ptid.lwp ());
-
- gdb::unique_xmalloc_ptr<char> data
- = target_fileio_read_stralloc (NULL, smaps_file.c_str ());
-
- if (data == nullptr)
+ file_reader_t<char> smaps_freader
+ (string_printf ("/proc/%ld/smaps", ptid.lwp ()));
+ if (!smaps_freader)
return false;
/* Parse the contents of smaps into a vector. */
- std::vector<struct smaps_data> smaps
- = parse_smaps_data (data.get (), smaps_file);
+ std::vector<smaps_data> smaps = parse_smaps_data (smaps_freader);
for (const smaps_data &map : smaps)
{
@@ -1782,17 +1784,13 @@ linux_find_memory_regions_full (struct gdbarch *gdbarch,
if (use_coredump_filter)
{
- std::string core_dump_filter_name
- = string_printf ("/proc/%ld/coredump_filter", ptid.lwp ());
-
- gdb::unique_xmalloc_ptr<char> coredumpfilterdata
- = target_fileio_read_stralloc (NULL, core_dump_filter_name.c_str ());
-
- if (coredumpfilterdata != NULL)
+ file_reader_t<char> coredump_filter_freader
+ (string_printf ("/proc/%ld/coredump_filter", ptid.lwp ()));
+ if (coredump_filter_freader)
{
unsigned int flags;
- sscanf (coredumpfilterdata.get (), "%x", &flags);
+ sscanf (coredump_filter_freader.data (), "%x", &flags);
filterflags = (enum filter_flag) flags;
}
}
@@ -1813,10 +1811,9 @@ linux_find_memory_regions_full (struct gdbarch *gdbarch,
}
/* Parse the contents of smaps into a vector. */
- std::vector<struct smaps_data> smaps
- = parse_smaps_data (data.get (), maps_filename);
+ std::vector<smaps_data> smaps = parse_smaps_data (data.get (), maps_filename);
- for (const struct smaps_data &map : smaps)
+ for (const smaps_data &map: smaps)
{
/* Invoke the callback function to create the corefile segment. */
if (should_dump_mapping_p (filterflags, map))
@@ -2295,9 +2292,6 @@ linux_corefile_parse_exec_context (struct gdbarch *gdbarch, bfd *cbfd)
static bool
linux_fill_prpsinfo (struct elf_internal_linux_prpsinfo *p)
{
- /* The filename which we will use to obtain some info about the process.
- We will basically use this to store the `/proc/PID/FILENAME' file. */
- char filename[100];
/* The basename of the executable. */
const char *basename;
/* Temporary buffer. */
@@ -2319,24 +2313,27 @@ linux_fill_prpsinfo (struct elf_internal_linux_prpsinfo *p)
gdb_assert (p != nullptr);
- /* Obtaining PID and filename. */
- xsnprintf (filename, sizeof (filename), "/proc/%ld/cmdline", ptid.lwp ());
- /* The full name of the program which generated the corefile. */
- gdb_byte *buf = nullptr;
- LONGEST buf_len = target_fileio_read_alloc (nullptr, filename, &buf);
- gdb::unique_xmalloc_ptr<char> fname ((char *)buf);
+ file_reader_t<gdb_byte> cmdline_freader
+ (string_printf ("/proc/%ld/cmdline", ptid.lwp ()));
+ if (!cmdline_freader)
+ return false;
- if (buf_len < 1 || fname.get () == nullptr || fname.get ()[0] == '\0')
+ /* /proc/<pid>/cmdline stores the command-line arguments as a sequence of
+ NUL-separated strings. */
+ gdb::array_view<char> cmdline = cmdline_freader.cast_view<char> ();
+ /* The buffer points to the full name of the program which generated the
+ corefile. */
+ if (cmdline.size () < 1 || cmdline[0] == '\0')
{
/* No program name was read, so we won't be able to retrieve more
information about the process. */
return false;
}
- if (fname.get ()[buf_len - 1] != '\0')
+ if (cmdline[cmdline.size () - 1] != '\0')
{
warning (_("target file %s "
"does not contain a trailing null character"),
- filename);
+ cmdline_freader.c_filepath ());
return false;
}
@@ -2346,27 +2343,24 @@ linux_fill_prpsinfo (struct elf_internal_linux_prpsinfo *p)
p->pr_pid = ptid.pid ();
/* Copying the program name. Only the basename matters. */
- basename = lbasename (fname.get ());
+ basename = lbasename (cmdline.data ());
strncpy (p->pr_fname, basename, sizeof (p->pr_fname) - 1);
p->pr_fname[sizeof (p->pr_fname) - 1] = '\0';
const std::string &infargs = current_inferior ()->args ();
/* The arguments of the program. */
- std::string psargs = fname.get ();
+ std::string psargs = cmdline.data ();
if (!infargs.empty ())
psargs += ' ' + infargs;
strncpy (p->pr_psargs, psargs.c_str (), sizeof (p->pr_psargs) - 1);
p->pr_psargs[sizeof (p->pr_psargs) - 1] = '\0';
- xsnprintf (filename, sizeof (filename), "/proc/%ld/stat", ptid.lwp ());
- /* The contents of `/proc/PID/stat'. */
- gdb::unique_xmalloc_ptr<char> proc_stat_contents
- = target_fileio_read_stralloc (NULL, filename);
- char *proc_stat = proc_stat_contents.get ();
-
- if (proc_stat == NULL || *proc_stat == '\0')
+ file_reader_t<char> stat_freader
+ (string_printf ("/proc/%ld/stat", ptid.lwp ()));
+ const char *proc_stat = stat_freader.data ();
+ if (!stat_freader || *proc_stat == '\0')
{
/* Despite being unable to read more information about the
process, we return true here because at least we have its
@@ -2438,13 +2432,10 @@ linux_fill_prpsinfo (struct elf_internal_linux_prpsinfo *p)
/* Finally, obtaining the UID and GID. For that, we read and parse the
contents of the `/proc/PID/status' file. */
- xsnprintf (filename, sizeof (filename), "/proc/%ld/status", ptid.lwp ());
- /* The contents of `/proc/PID/status'. */
- gdb::unique_xmalloc_ptr<char> proc_status_contents
- = target_fileio_read_stralloc (NULL, filename);
- char *proc_status = proc_status_contents.get ();
-
- if (proc_status == NULL || *proc_status == '\0')
+ file_reader_t<char> status_freader
+ (string_printf ("/proc/%ld/status", ptid.lwp ()));
+ char *proc_status = status_freader.data ();
+ if (!status_freader || *proc_status == '\0')
{
/* Returning true since we already have a bunch of information. */
return true;
@@ -2837,9 +2828,6 @@ linux_gdb_signal_to_target (struct gdbarch *gdbarch,
static bool
linux_vsyscall_range_raw (struct gdbarch *gdbarch, struct mem_range *range)
{
- char filename[100];
- long pid;
-
if (target_auxv_search (AT_SYSINFO_EHDR, &range->start) <= 0)
return false;
@@ -2877,7 +2865,7 @@ linux_vsyscall_range_raw (struct gdbarch *gdbarch, struct mem_range *range)
if (current_inferior ()->fake_pid_p)
return false;
- pid = current_inferior ()->pid;
+ long pid = current_inferior ()->pid;
/* Note that reading /proc/PID/task/PID/maps (1) is much faster than
reading /proc/PID/maps (2). The later identifies thread stacks
@@ -2887,15 +2875,14 @@ linux_vsyscall_range_raw (struct gdbarch *gdbarch, struct mem_range *range)
a few thousand threads, (1) takes a few milliseconds, while (2)
takes several seconds. Also note that "smaps", what we read for
determining core dump mappings, is even slower than "maps". */
- xsnprintf (filename, sizeof filename, "/proc/%ld/task/%ld/maps", pid, pid);
- gdb::unique_xmalloc_ptr<char> data
- = target_fileio_read_stralloc (NULL, filename);
- if (data != NULL)
+ file_reader_t<char> task_maps_freader
+ (string_printf ("/proc/%ld/task/%ld/maps", pid, pid));
+ if (task_maps_freader)
{
char *line;
char *saveptr = NULL;
- for (line = strtok_r (data.get (), "\n", &saveptr);
+ for (line = strtok_r (task_maps_freader.data (), "\n", &saveptr);
line != NULL;
line = strtok_r (NULL, "\n", &saveptr))
{
@@ -2913,8 +2900,9 @@ linux_vsyscall_range_raw (struct gdbarch *gdbarch, struct mem_range *range)
}
}
}
- else
- warning (_("unable to open /proc file '%s'"), filename);
+ else if (task_maps_freader.error ())
+ warning (_("unable to open /proc file '%s'"),
+ task_maps_freader.c_filepath ());
return false;
}
@@ -3241,16 +3229,12 @@ linux_address_in_shadow_stack_mem_range
ptid_t ptid = get_process_reference_ptid ();
- std::string smaps_file = string_printf ("/proc/%ld/smaps", ptid.lwp ());
-
- gdb::unique_xmalloc_ptr<char> data
- = target_fileio_read_stralloc (nullptr, smaps_file.c_str ());
-
- if (data == nullptr)
+ file_reader_t<char> smaps_freader
+ (string_printf ("/proc/%ld/smaps", ptid.lwp ()));
+ if (!smaps_freader)
return false;
- const std::vector<smaps_data> smaps
- = parse_smaps_data (data.get (), smaps_file);
+ const std::vector<smaps_data> smaps = parse_smaps_data (smaps_freader);
auto find_addr_mem_range = [&addr] (const smaps_data &map)
{
diff --git a/gdb/sparc64-tdep.c b/gdb/sparc64-tdep.c
index 93db3417a2a..97f8fa72e52 100644
--- a/gdb/sparc64-tdep.c
+++ b/gdb/sparc64-tdep.c
@@ -301,18 +301,16 @@ adi_tag_fd ()
static bool
adi_is_addr_mapped (CORE_ADDR vaddr, size_t cnt)
{
- char filename[MAX_PROC_NAME_SIZE];
size_t i = 0;
pid_t pid = inferior_ptid.pid ();
- snprintf (filename, sizeof filename, "/proc/%ld/adi/maps", (long) pid);
- gdb::unique_xmalloc_ptr<char> data
- = target_fileio_read_stralloc (NULL, filename);
- if (data)
+ file_reader_t<char> adi_maps_freader
+ (string_printf ("/proc/%d/adi/maps", pid));
+ if (adi_maps_freader)
{
adi_stat_t adi_stat = get_adi_info (pid);
char *saveptr;
- for (char *line = strtok_r (data.get (), "\n", &saveptr);
+ for (char *line = strtok_r (adi_maps_freader.data (), "\n", &saveptr);
line;
line = strtok_r (NULL, "\n", &saveptr))
{
@@ -328,8 +326,9 @@ adi_is_addr_mapped (CORE_ADDR vaddr, size_t cnt)
}
}
}
- else
- warning (_("unable to open /proc file '%s'"), filename);
+ else if (adi_maps_freader.error ())
+ warning (_("unable to open /proc file '%s'"),
+ adi_maps_freader.c_filepath ());
return false;
}
diff --git a/gdb/target.h b/gdb/target.h
index 819279c08fc..017918b6582 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -2341,6 +2341,84 @@ extern LONGEST target_fileio_read_alloc (struct inferior *inf,
extern gdb::unique_xmalloc_ptr<char> target_fileio_read_stralloc
(struct inferior *inf, const char *filename, LONGEST *len = nullptr);
+/* Helper class for reading the content of a file on the target. */
+template <typename T>
+class file_reader_t
+{
+ /* The filepath of the file being read. */
+ std::string m_filepath;
+ /* Smart pointer to the data. */
+ gdb::unique_xmalloc_ptr<T> m_data;
+ /* Number of bytes read. */
+ LONGEST m_size;
+
+public:
+ file_reader_t (const std::string &filepath)
+ : m_filepath (filepath)
+ , m_size (0)
+ {
+ if constexpr (std::is_same_v<T, char>)
+ m_data = target_fileio_read_stralloc (nullptr, m_filepath.c_str (),
+ &m_size);
+ else
+ {
+ gdb_byte *buf = nullptr;
+ m_size = target_fileio_read_alloc (nullptr, m_filepath.c_str (), &buf);
+ m_data = gdb::unique_xmalloc_ptr<T> (reinterpret_cast<T *>(buf));
+ }
+ }
+
+ file_reader_t (file_reader_t &&) = default;
+ file_reader_t &operator= (file_reader_t &&) = default;
+
+ DISABLE_COPY_AND_ASSIGN (file_reader_t);
+
+ /* Return true if the file was read successfully but contained no data. */
+ bool empty () const noexcept
+ { return m_data != nullptr && m_size == 0; }
+
+ /* Return true if the file could not be read. */
+ bool error () const noexcept
+ { return m_data == nullptr || m_size < 0; }
+
+ /* Return true if the file was read successfully and is non-empty. */
+ explicit operator bool () const noexcept
+ { return !(error () || empty ()); }
+
+ /* Return a pointer to the data. */
+ T *data () const noexcept
+ { return m_data.get (); }
+
+ /* Return the number of bytes read. */
+ LONGEST size () const noexcept
+ {
+ /* For char buffers, size() corresponds to the size of the read data. Some
+ null-terminator characters are possibly scattered throughout the data.
+ Consequently, strlen() might not reflect the actual size. */
+ return m_size;
+ }
+
+ /* Return a span of the data. */
+ gdb::array_view<T> view () const noexcept
+ { return gdb::array_view<T> (m_data.get (), size ()); }
+
+ /* Return a span of the data, reinterpreted as U objects. */
+ template <typename U>
+ gdb::array_view<U> cast_view () const noexcept
+ {
+ return gdb::array_view<U> (reinterpret_cast<U *> (m_data.get ()),
+ size () * sizeof (T) / sizeof (U));
+ }
+
+ /* Return the path of the file that was read. */
+ const std::string &filepath () const noexcept
+ { return m_filepath; }
+
+ /* Return the path of the file that was read as a C string. */
+ const char *c_filepath () const noexcept
+ { return m_filepath.c_str (); }
+};
+
/* Invalidate the target associated with open handles that were open
on target TARG, since we're about to close (and maybe destroy) the
target. The handles remain open from the client's perspective, but
--
2.55.0
^ permalink raw reply [flat|nested] 7+ messages in thread* [PATCH v2 4/6] gdb/linux-tdep: migrate linux_info_proc to file_reader_t
2026-08-25 10:09 [PATCH v2 0/6] gdb: introduce file_reader_t to read procfs files Matthieu Longo
` (2 preceding siblings ...)
2026-08-25 10:09 ` [PATCH v2 3/6] gdb: introduce helper class file_reader_t Matthieu Longo
@ 2026-08-25 10:09 ` Matthieu Longo
2026-08-25 10:09 ` [PATCH v2 5/6] gdb/linux-tdep: migrate linux_find_memory_regions_full " Matthieu Longo
2026-08-25 10:09 ` [PATCH v2 6/6] gdb/linux-tdep: remove legacy parse_smaps_data overload Matthieu Longo
5 siblings, 0 replies; 7+ messages in thread
From: Matthieu Longo @ 2026-08-25 10:09 UTC (permalink / raw)
To: gdb-patches
Cc: Simon Marchi, Thiago Jung Bauermann, Luis Machado, Luis Machado,
Christina Joos, Kevin Buettner, Matthieu Longo
The patch migrates the code of linux_info_proc to use file_reader_t to
read the procfs files.
The availability of array_views allows to also simplify the logic in
several places, where null-terminating characters are replaced by spaces,
or where the file content is iterated line by line.
In the last case, a new helper function, extract_string_view_from_buffer,
encapsulates the logic for such iterations where string are separated by
tokens.
Reviewed-By: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
---
gdb/linux-tdep.c | 135 +++++++++++++++++++++++++++++------------------
1 file changed, 84 insertions(+), 51 deletions(-)
diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c
index 84614bc91a0..e2c5b2d8815 100644
--- a/gdb/linux-tdep.c
+++ b/gdb/linux-tdep.c
@@ -866,6 +866,39 @@ dump_note_entry_p (filter_flags filterflags, const smaps_data &map)
return true;
}
+/* Extract a string view from BUFFER starting at START and ending at the
+ first occurrence of SEPARATOR.
+ Return the extracted view together with an iterator to the beginning of
+ the next entry, skipping any successive separators. If no separator
+ is found, return the remainder of BUFFER starting at START. If there is
+ no following entry, the returned iterator is BUFFER.end (). */
+
+static std::pair<gdb::array_view<char>, gdb::array_view<char>::iterator>
+extract_string_view_from_buffer (gdb::array_view<char> &buffer,
+ gdb::array_view<char>::iterator start,
+ char separator = '\0')
+{
+ auto next_start = buffer.end ();
+
+ /* Reject a START iterator that does not point into BUFFER. */
+ if (start < buffer.begin () || start >= buffer.end ())
+ return {gdb::array_view<char> (), next_start};
+
+ auto it = std::find (start, buffer.end (), separator);
+
+ /* If no separator is found, the remainder of BUFFER is the final string. */
+ if (it != buffer.end ())
+ {
+ /* Otherwise, skip successive separators so that NEXT_START points to
+ the beginning of the next string, if any. */
+ for (next_start = std::next (it);
+ next_start != buffer.end () && *next_start == separator;
+ next_start = std::next (next_start));
+ }
+
+ return {gdb::array_view<char> (start, it), next_start};
+}
+
/* Implement the "info proc" command. */
static void
@@ -914,25 +947,23 @@ linux_info_proc (struct gdbarch *gdbarch, const char *args,
if (cmdline_f)
{
- xsnprintf (filename, sizeof filename, "/proc/%ld/cmdline", ptid.lwp ());
- gdb_byte *buffer;
- LONGEST len = target_fileio_read_alloc (nullptr, filename, &buffer);
-
- if (len > 0)
+ file_reader_t<gdb_byte> cmdline_freader
+ (string_printf ("/proc/%ld/cmdline", ptid.lwp ()));
+ if (cmdline_freader)
{
- gdb::unique_xmalloc_ptr<char> cmdline ((char *) buffer);
- ssize_t pos;
-
- for (pos = 0; pos < len - 1; pos++)
- {
- if (buffer[pos] == '\0')
- buffer[pos] = ' ';
- }
- buffer[len - 1] = '\0';
- gdb_printf ("cmdline = '%s'\n", buffer);
+ /* /proc/<pid>/cmdline stores the command-line arguments as a
+ sequence of NUL-separated strings. */
+ gdb::array_view<char> cmdline = cmdline_freader.cast_view<char> ();
+ gdb_assert (cmdline[cmdline.size () - 1] == '\0');
+ /* Replace null characters splitting the arguments in the command
+ line by spaces, except for the last one. */
+ gdb::ranges::replace
+ (cmdline.slice (0, cmdline.size () - 1), '\0', ' ');
+ gdb_printf ("cmdline = '%s'\n", cmdline.data ());
}
else
- warning (_("unable to open /proc file '%s'"), filename);
+ warning (_("unable to open /proc file '%s'"),
+ cmdline_freader.c_filepath ());
}
if (cwd_f)
{
@@ -946,27 +977,25 @@ linux_info_proc (struct gdbarch *gdbarch, const char *args,
}
if (environ_f)
{
- xsnprintf (filename, sizeof filename, "/proc/%ld/environ", ptid.lwp ());
- gdb_byte *buffer;
- LONGEST len = target_fileio_read_alloc (nullptr, filename, &buffer);
-
- if (len > 0)
+ file_reader_t<gdb_byte> environ_freader
+ (string_printf ("/proc/%ld/environ", ptid.lwp ()));
+ if (environ_freader)
{
- gdb::unique_xmalloc_ptr<char> dealloc ((char *) buffer);
gdb_printf (_("Environment variables:\n\n"));
-
+ gdb::array_view<char> buffer = environ_freader.cast_view<char> ();
/* Entries are separated by the null character.
Print each environment variable, line by line. */
- gdb_byte *buffer_end = buffer + len;
- while (buffer < buffer_end)
+ for (auto it = buffer.begin (); it != buffer.end ();)
{
- gdb_printf (" %s\n", buffer);
- /* +1 for the null character. */
- buffer += strlen ((char *) buffer) + 1;
+ auto [ntbs, next_start]
+ = extract_string_view_from_buffer (buffer, it, '\0');
+ gdb_printf (" %s\n", ntbs.data ());
+ it = next_start;
}
}
else
- warning (_("unable to open /proc file '%s'"), filename);
+ warning (_("unable to open /proc file '%s'"),
+ environ_freader.c_filepath ());
}
if (exe_f)
{
@@ -980,10 +1009,9 @@ linux_info_proc (struct gdbarch *gdbarch, const char *args,
}
if (mappings_f)
{
- xsnprintf (filename, sizeof filename, "/proc/%ld/maps", ptid.lwp ());
- gdb::unique_xmalloc_ptr<char> map
- = target_fileio_read_stralloc (NULL, filename);
- if (map != NULL)
+ file_reader_t<char> map_freader
+ (string_printf ("/proc/%ld/maps", ptid.lwp ()));
+ if (map_freader)
{
gdb_printf (_("Mapped address spaces:\n\n"));
ui_out_emit_table emitter (current_uiout, 6, -1, "ProcMappings");
@@ -997,12 +1025,16 @@ linux_info_proc (struct gdbarch *gdbarch, const char *args,
current_uiout->table_header (0, ui_left, "objfile", "File");
current_uiout->table_body ();
- char *saveptr;
- for (const char *line = strtok_r (map.get (), "\n", &saveptr);
- line != nullptr;
- line = strtok_r (nullptr, "\n", &saveptr))
+ auto content = map_freader.view ();
+ for (auto it = content.begin (); it != content.end ();)
{
- struct mapping m = read_mapping (line);
+ auto [line, next_line_begin]
+ = extract_string_view_from_buffer (content, it, '\n');
+ it = next_line_begin;
+
+ /* read_mapping() expects a null-terminated string. */
+ *std::prev (it) = '\0';
+ struct mapping m = read_mapping (line.data ());
ui_out_emit_tuple tuple_emitter (current_uiout);
current_uiout->field_core_addr ("start", gdbarch, m.addr);
@@ -1021,26 +1053,26 @@ linux_info_proc (struct gdbarch *gdbarch, const char *args,
}
}
else
- warning (_("unable to open /proc file '%s'"), filename);
+ warning (_("unable to open /proc file '%s'"),
+ map_freader.c_filepath ());
}
if (status_f)
{
- xsnprintf (filename, sizeof filename, "/proc/%ld/status", ptid.lwp ());
- gdb::unique_xmalloc_ptr<char> status
- = target_fileio_read_stralloc (NULL, filename);
- if (status)
- gdb_puts (status.get ());
+ file_reader_t<char> status_freader
+ (string_printf ("/proc/%ld/status", ptid.lwp ()));
+ if (status_freader)
+ gdb_puts (status_freader.data ());
else
- warning (_("unable to open /proc file '%s'"), filename);
+ warning (_("unable to open /proc file '%s'"),
+ status_freader.c_filepath ());
}
if (stat_f)
{
- xsnprintf (filename, sizeof filename, "/proc/%ld/stat", ptid.lwp ());
- gdb::unique_xmalloc_ptr<char> statstr
- = target_fileio_read_stralloc (NULL, filename);
- if (statstr)
+ file_reader_t<char> stat_freader
+ (string_printf ("/proc/%ld/stat", ptid.lwp ()));
+ if (stat_freader)
{
- const char *p = statstr.get ();
+ const char *p = stat_freader.data ();
gdb_printf (_("Process: %s\n"),
pulongest (strtoulst (p, &p, 10)));
@@ -1167,7 +1199,8 @@ linux_info_proc (struct gdbarch *gdbarch, const char *args,
#endif
}
else
- warning (_("unable to open /proc file '%s'"), filename);
+ warning (_("unable to open /proc file '%s'"),
+ stat_freader.c_filepath ());
}
}
--
2.55.0
^ permalink raw reply [flat|nested] 7+ messages in thread* [PATCH v2 5/6] gdb/linux-tdep: migrate linux_find_memory_regions_full to file_reader_t
2026-08-25 10:09 [PATCH v2 0/6] gdb: introduce file_reader_t to read procfs files Matthieu Longo
` (3 preceding siblings ...)
2026-08-25 10:09 ` [PATCH v2 4/6] gdb/linux-tdep: migrate linux_info_proc to file_reader_t Matthieu Longo
@ 2026-08-25 10:09 ` Matthieu Longo
2026-08-25 10:09 ` [PATCH v2 6/6] gdb/linux-tdep: remove legacy parse_smaps_data overload Matthieu Longo
5 siblings, 0 replies; 7+ messages in thread
From: Matthieu Longo @ 2026-08-25 10:09 UTC (permalink / raw)
To: gdb-patches
Cc: Simon Marchi, Thiago Jung Bauermann, Luis Machado, Luis Machado,
Christina Joos, Kevin Buettner, Matthieu Longo
The previous implementation of linux_find_memory_regions_full could
still return success even when none of the /proc/PID/[s]maps files
existed, or all reads returned 0 bytes (this last case can happen on
Linux when the thread-group leader has exited).
As a result, the function could incorrectly succeed, allowing core
dump generation via the gcore command.
This logical defect was allowing, by chance, the function to return
success and hence, allowing fortuitously the coredump generation via
gcore command (see gcore-stale-thread test for more details).
A previous patch in this patch series fixed this issue by using the
first LWP ID of the current inferior instead of relying on the PID.
This patch adapts the code to use file_reader_t and makes the function
return an error if reading any of the procfs files fails.
Reviewed-By: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
---
gdb/linux-tdep.c | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)
diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c
index e2c5b2d8815..2833d8a4bb6 100644
--- a/gdb/linux-tdep.c
+++ b/gdb/linux-tdep.c
@@ -1828,24 +1828,22 @@ linux_find_memory_regions_full (struct gdbarch *gdbarch,
}
}
- std::string maps_filename = string_printf ("/proc/%ld/smaps", ptid.lwp ());
-
- gdb::unique_xmalloc_ptr<char> data
- = target_fileio_read_stralloc (NULL, maps_filename.c_str ());
+ std::vector<smaps_data> smaps;
- if (data == NULL)
+ file_reader_t<char> smaps_freader
+ (string_printf ("/proc/%ld/smaps", ptid.lwp ()));
+ if (smaps_freader)
+ smaps = parse_smaps_data (smaps_freader);
+ else
{
/* Older Linux kernels did not support /proc/PID/smaps. */
- maps_filename = string_printf ("/proc/%ld/maps", ptid.lwp ());
- data = target_fileio_read_stralloc (NULL, maps_filename.c_str ());
-
- if (data == nullptr)
+ file_reader_t<char> maps_freader
+ (string_printf ("/proc/%ld/maps", ptid.lwp ()));
+ if (!maps_freader)
return false;
+ smaps = parse_smaps_data (maps_freader);
}
- /* Parse the contents of smaps into a vector. */
- std::vector<smaps_data> smaps = parse_smaps_data (data.get (), maps_filename);
-
for (const smaps_data &map: smaps)
{
/* Invoke the callback function to create the corefile segment. */
--
2.55.0
^ permalink raw reply [flat|nested] 7+ messages in thread* [PATCH v2 6/6] gdb/linux-tdep: remove legacy parse_smaps_data overload
2026-08-25 10:09 [PATCH v2 0/6] gdb: introduce file_reader_t to read procfs files Matthieu Longo
` (4 preceding siblings ...)
2026-08-25 10:09 ` [PATCH v2 5/6] gdb/linux-tdep: migrate linux_find_memory_regions_full " Matthieu Longo
@ 2026-08-25 10:09 ` Matthieu Longo
5 siblings, 0 replies; 7+ messages in thread
From: Matthieu Longo @ 2026-08-25 10:09 UTC (permalink / raw)
To: gdb-patches
Cc: Simon Marchi, Thiago Jung Bauermann, Luis Machado, Luis Machado,
Christina Joos, Kevin Buettner, Matthieu Longo
Now that all callers use the file_reader_t overload of parse_smaps_data,
the legacy interface taking a raw buffer and filename separately is no
longer needed.
Fold its implementation into the file_reader_t version and remove the
obsolete wrapper. This also simplifies the implementation by using the
file_reader_t accessors directly.
Reviewed-By: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Reviewed-By: Luis Machado <luis.machado.foss@gmail.com>
---
gdb/linux-tdep.c | 30 ++++++++++++------------------
1 file changed, 12 insertions(+), 18 deletions(-)
diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c
index 2833d8a4bb6..4cdb02b9c09 100644
--- a/gdb/linux-tdep.c
+++ b/gdb/linux-tdep.c
@@ -1581,18 +1581,17 @@ parse_smaps_key_value (const char *keyword, const char *line,
/* Helper function to parse the contents of /proc/<pid>/smaps into a data
structure, for easy access.
- DATA is the contents of the smaps file. The parsed contents are stored
- into the SMAPS vector. */
+ FREADER is a wrapper around the contents of the smaps file.
+ The parsed contents are stored into the SMAPS vector. */
static std::vector<smaps_data>
-parse_smaps_data (const char *data,
- const std::string &maps_filename)
+parse_smaps_data (const file_reader_t<char> &freader)
{
char *line, *t;
- gdb_assert (data != nullptr);
+ gdb_assert (freader);
- line = strtok_r ((char *) data, "\n", &t);
+ line = strtok_r (freader.data (), "\n", &t);
std::vector<smaps_data> smaps;
@@ -1648,8 +1647,8 @@ parse_smaps_data (const char *data,
if (sscanf (line, "%64s", keyword) != 1)
{
- warning (_("Error parsing {s,}maps file '%s'"),
- maps_filename.c_str ());
+ warning (_("Error parsing keyword in {s,}maps file '%s'"),
+ freader.c_filepath ());
break;
}
@@ -1663,12 +1662,12 @@ parse_smaps_data (const char *data,
decode_vmflags (line, &v);
if (parse_smaps_key_value (keyword, line, "Rss:",
- maps_filename,
+ freader.filepath (),
&rss))
continue;
if (parse_smaps_key_value (keyword, line, "Swap:",
- maps_filename,
+ freader.filepath (),
&swap))
continue;
@@ -1679,8 +1678,9 @@ parse_smaps_data (const char *data,
if (sscanf (line, "%*s%lu", &number) != 1)
{
- warning (_("Error parsing {s,}maps file '%s' number"),
- maps_filename.c_str ());
+ warning (_("Error parsing numeric value associated with "
+ "key '%s' in {s,}maps file '%s'"),
+ keyword, freader.c_filepath ());
break;
}
if (number > 0)
@@ -1730,12 +1730,6 @@ parse_smaps_data (const char *data,
return smaps;
}
-static std::vector<smaps_data>
-parse_smaps_data (const file_reader_t<char> &freader)
-{
- return parse_smaps_data (freader.data (), freader.filepath ());
-}
-
/* Helper that checks if an address is in a memory tag page for a live
process. */
--
2.55.0
^ permalink raw reply [flat|nested] 7+ messages in thread