[PATCH] gdbserver: convert program_args to a single string
Andrew Burgess
aburgess@redhat.com
Tue Jan 14 13:39:03 GMT 2025
This commit changes how gdbserver stores the inferior arguments from
being a vector of separate arguments into a single string with all of
the arguments combined together.
Making this change might feel a little strange; intuitively it feels
like we would be better off storing the arguments as a vector, but
this change is part of a larger series of work that aims to improve
GDB's inferior argument handling. The full series was posted here:
https://inbox.sourceware.org/gdb-patches/cover.1730731085.git.aburgess@redhat.com
But asking people to review a 14 patch series in unreasonable, so I'm
instead posting the patches in smaller batches. This patch can stand
alone, and I do think this change makes sense on its own:
First, GDB already stores the inferior arguments as a single string,
so doing this moves gdbserver into line with GDB. The common code
into which gdbserver calls requires the arguments to be a single
string, so currently each target's create_inferior implementation
merged the arguments anyway, so all this commit really does is move
the merging up the call stack, and store the merged result rather than
storing the separate parts.
However, the biggest reason for why this commit is needed, is an issue
with passing arguments from GDB to gdbserver when starting a new
inferior.
Consider:
(gdb) set args $VAR
(gdb) run
...
When using a native target the inferior will see the value of $VAR
expanded by the shell GDB uses to start the inferior. However, if
using an extended-remote target the inferior will see literally $VAR,
the unexpanded name of the variable, the reason for this is that,
although GDB sends '$VAR' to gdbserver, when gdbserver receives this,
it converts this to '\$VAR', which prevents the variable from being
expanded by the shell.
The reason for this is that construct_inferior_arguments escapes all
special shell characters within its arguments, and it is
construct_inferior_arguments that is used to combine the separate
arguments into a single string.
In the future I will change construct_inferior_arguments so that
it can apply different escaping strategies. When this happens we will
want to escape arguments coming from the gdbserver command line
differently than arguments coming from GDB (via a vRun packet), which
means we need to call construct_inferior_arguments earlier, at the
point where we know if the arguments came from the gdbserver command
line, or from the vRun packet.
This argument escaping issue is discussed in PR gdb/28392.
This commit doesn't fix any issues, nor does it change
construct_inferior_arguments to actually do different escaping, that
will all come later. This is purely a restructuring.
There should be no user visible changes after this commit.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28392
Tested-By: Guinevere Larsen <guinevere@redhat.com>
---
gdbserver/linux-low.cc | 5 ++---
gdbserver/linux-low.h | 2 +-
gdbserver/netbsd-low.cc | 6 ++----
gdbserver/netbsd-low.h | 2 +-
gdbserver/server.cc | 24 +++++++++++++++++++-----
gdbserver/target.h | 6 +++---
gdbserver/win32-low.cc | 7 +++----
gdbserver/win32-low.h | 2 +-
8 files changed, 32 insertions(+), 22 deletions(-)
diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
index 50ce2b44927..65268a6ee6c 100644
--- a/gdbserver/linux-low.cc
+++ b/gdbserver/linux-low.cc
@@ -974,7 +974,7 @@ linux_ptrace_fun ()
int
linux_process_target::create_inferior (const char *program,
- const std::vector<char *> &program_args)
+ const std::string &program_args)
{
client_state &cs = get_client_state ();
struct lwp_info *new_lwp;
@@ -984,10 +984,9 @@ linux_process_target::create_inferior (const char *program,
{
maybe_disable_address_space_randomization restore_personality
(cs.disable_randomization);
- std::string str_program_args = construct_inferior_arguments (program_args);
pid = fork_inferior (program,
- str_program_args.c_str (),
+ program_args.c_str (),
get_environ ()->envp (), linux_ptrace_fun,
NULL, NULL, NULL, NULL);
}
diff --git a/gdbserver/linux-low.h b/gdbserver/linux-low.h
index 5be00b8c98c..75af38d898f 100644
--- a/gdbserver/linux-low.h
+++ b/gdbserver/linux-low.h
@@ -141,7 +141,7 @@ class linux_process_target : public process_stratum_target
public:
int create_inferior (const char *program,
- const std::vector<char *> &program_args) override;
+ const std::string &program_args) override;
void post_create_inferior () override;
diff --git a/gdbserver/netbsd-low.cc b/gdbserver/netbsd-low.cc
index 04e103563e7..9e7314b02a9 100644
--- a/gdbserver/netbsd-low.cc
+++ b/gdbserver/netbsd-low.cc
@@ -78,11 +78,9 @@ netbsd_ptrace_fun ()
int
netbsd_process_target::create_inferior (const char *program,
- const std::vector<char *> &program_args)
+ const std::string &program_args)
{
- std::string str_program_args = construct_inferior_arguments (program_args);
-
- pid_t pid = fork_inferior (program, str_program_args.c_str (),
+ pid_t pid = fork_inferior (program, program_args.c_str (),
get_environ ()->envp (), netbsd_ptrace_fun,
nullptr, nullptr, nullptr, nullptr);
diff --git a/gdbserver/netbsd-low.h b/gdbserver/netbsd-low.h
index 53200ddffc4..aef1ce40cb9 100644
--- a/gdbserver/netbsd-low.h
+++ b/gdbserver/netbsd-low.h
@@ -42,7 +42,7 @@ class netbsd_process_target : public process_stratum_target
public:
int create_inferior (const char *program,
- const std::vector<char *> &program_args) override;
+ const std::string &program_args) override;
void post_create_inferior () override;
diff --git a/gdbserver/server.cc b/gdbserver/server.cc
index 55898f59556..efe63ae7515 100644
--- a/gdbserver/server.cc
+++ b/gdbserver/server.cc
@@ -121,7 +121,20 @@ private:
/* The program name, adjusted if needed. */
std::string m_path;
} program_path;
-static std::vector<char *> program_args;
+
+/* All program arguments are merged into a single string. This is similar
+ to how GDB manages the inferior arguments, and actually makes our lives
+ easier; the rules for how arguments are merged into a single string
+ differ depending on where the arguments come from. Arguments arriving
+ form the gdbserver command line are quoted, while arguments arriving
+ from GDB (via a vRun packet) are already quoted.
+
+ NOTE: The comment above is ahead of its time. The differences between
+ how the PROGRAM_ARGS string is built up have not yet been implemented.
+ A later patch in this series will make this change, and remove this
+ note. */
+static std::string program_args;
+
static std::string wrapper_argv;
/* The PID of the originally created or attached inferior. Used to
@@ -3484,9 +3497,8 @@ handle_v_run (char *own_buf)
else
program_path.set (new_program_name.get ());
- /* Free the old argv and install the new one. */
- free_vector_argv (program_args);
- program_args = new_argv;
+ program_args = construct_inferior_arguments (new_argv);
+ free_vector_argv (new_argv);
try
{
@@ -4376,8 +4388,10 @@ captured_main (int argc, char *argv[])
n = argc - (next_arg - argv);
program_path.set (next_arg[0]);
+ std::vector<char *> temp_arg_vector;
for (i = 1; i < n; i++)
- program_args.push_back (xstrdup (next_arg[i]));
+ temp_arg_vector.push_back (next_arg[i]);
+ program_args = construct_inferior_arguments (temp_arg_vector);
/* Wait till we are at first instruction in program. */
target_create_inferior (program_path.get (), program_args);
diff --git a/gdbserver/target.h b/gdbserver/target.h
index 3643b9110da..1a013bb83db 100644
--- a/gdbserver/target.h
+++ b/gdbserver/target.h
@@ -77,13 +77,13 @@ class process_stratum_target
/* Start a new process.
PROGRAM is a path to the program to execute.
- PROGRAM_ARGS is a standard NULL-terminated array of arguments,
- to be passed to the inferior as ``argv'' (along with PROGRAM).
+ PROGRAM_ARGS is a string containing all of the arguments that will be
+ used to start the inferior.
Returns the new PID on success, -1 on failure. Registers the new
process with the process list. */
virtual int create_inferior (const char *program,
- const std::vector<char *> &program_args) = 0;
+ const std::string &program_args) = 0;
/* Do additional setup after a new process is created, including
exec-wrapper completion. */
diff --git a/gdbserver/win32-low.cc b/gdbserver/win32-low.cc
index da858b65e6f..139c945a2ba 100644
--- a/gdbserver/win32-low.cc
+++ b/gdbserver/win32-low.cc
@@ -492,12 +492,12 @@ create_process (const char *program, char *args,
/* Start a new process.
PROGRAM is the program name.
- PROGRAM_ARGS is the vector containing the inferior's args.
+ PROGRAM_ARGS is a string containing all the inferior's arguments.
Returns the new PID on success, -1 on failure. Registers the new
process with the process list. */
int
win32_process_target::create_inferior (const char *program,
- const std::vector<char *> &program_args)
+ const std::string &program_args)
{
client_state &cs = get_client_state ();
#ifndef USE_WIN32API
@@ -508,8 +508,7 @@ win32_process_target::create_inferior (const char *program,
DWORD flags;
PROCESS_INFORMATION pi;
DWORD err;
- std::string str_program_args = construct_inferior_arguments (program_args);
- char *args = (char *) str_program_args.c_str ();
+ char *args = (char *) program_args.c_str ();
/* win32_wait needs to know we're not attaching. */
windows_process.attaching = 0;
diff --git a/gdbserver/win32-low.h b/gdbserver/win32-low.h
index daed16a6ae6..e9dd6adc5a8 100644
--- a/gdbserver/win32-low.h
+++ b/gdbserver/win32-low.h
@@ -101,7 +101,7 @@ class win32_process_target : public process_stratum_target
public:
int create_inferior (const char *program,
- const std::vector<char *> &program_args) override;
+ const std::string &program_args) override;
int attach (unsigned long pid) override;
base-commit: 127f733f88717bdb52f03c12c0c2d240bbc892e3
--
2.47.1
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