linux: support for monitoring syscall

[pixclk]

[BenBE]

Any chance this kind of information is available on other platforms too?

[pixclk]

Any chance this kind of information is available on other platforms too?

Theoretically possible, but currently only intended to support Linux.

[Explorer09]

One more thing. We should allow the user to disable this "syscall" monitoring at compile time time. Since the /proc/<pid>/syscall file is only present when the kernel is compiled with CONFIG_HAVE_ARCH_TRACEHOOK, it may be useless for users without such kernel. Another reason for having this compile option is we can save code size by not compiling the syscall number-to-name mapping table into htop binary, in case we implement one in the future.

[BenBE]

@Explorer09 Or disable the column, when the feature is not available at runtime.

[Explorer09]

@ Explorer09 Or disable the column, when the feature is not available at runtime.

I wish a compile time option to disable it as well.

[BenBE]

@ Explorer09 Or disable the column, when the feature is not available at runtime.

I wish a compile time option to disable it as well.

Like so?

# Check for syscall feature option
AC_ARG_ENABLE(
   [syscall],
   [
      AS_HELP_STRING(
         [--enable-syscall],
         [Enable 'syscall' feature. Possible values: off, buildtime-check, runtime-check, always-on. Default is 'off'.]
      )
   ],
   [case "${enableval}" in
      off) syscall_feature=0 ;;
      buildtime-check) syscall_feature=1 ;;
      runtime-check) syscall_feature=2 ;;
      always-on) syscall_feature=3 ;;
      *) AC_MSG_ERROR([Invalid value for --enable-syscall]) ;;
   esac],
   [syscall_feature=0]
)

# If buildtime-check is enabled, check if /proc/self/syscall exists and is non-empty
AS_IF(
   [test "x$syscall_feature" = "x1"],
   [
      AC_CHECK_FILE(
         [/proc/self/syscall],
         [syscall_exists=yes],
         [syscall_exists=no]
      )
      AS_IF(
         [test "x$syscall_exists" = "xyes" && test -s /proc/self/syscall],
         [],
         [syscall_feature=0]
      )
   ]
)

# Set the result of the check to a preprocessor directive
AC_DEFINE_UNQUOTED([SYSCALL_FEATURE], [$syscall_feature], [Define to the selected syscall feature state.])

[Explorer09]

@BenBE

• I merged your "runtime-check" and "always-on" into one option, because checking the thing at runtime is trivial.
• When cross-compiling, checking /proc/self/syscall won't help. It's better just enable it in that case.

AC_ARG_ENABLE([syscall],
   [AS_HELP_STRING([--enable-syscall],
   [enable 'syscall' monitoring. @<:@default=check@:>@])],
   [],
   [enable_syscall=check]
)

if test "x$enable_syscall" = xcheck; then
   if "$cross_compiling" != no; then
      enable_syscall=yes
   elif test -f /proc/self/syscall && test -s /proc/self/syscall; then
      enable_syscall=yes
   else
      enable_syscall=no
   fi
fi
if test "x$enable_syscall" = xyes; then
   AC_DEFINE([HAVE_SYSCALL], [1], [Define to 1 is syscall monitoring is enabled.])
fi

[pixclk]

@BenBE

* I merged your "runtime-check" and "always-on" into one option, because checking the thing at runtime is trivial.

* When cross-compiling, checking `/proc/self/syscall` won't help. It's better just enable it in that case.

AC_ARG_ENABLE([syscall],
   [AS_HELP_STRING([--enable-syscall],
   [enable 'syscall' monitoring. @<:@default=check@:>@])],
   [],
   [enable_syscall=check]
)

if test "x$enable_syscall" = xcheck; then
   if "$cross_compiling" != no; then
      enable_syscall=yes
   elif test -f /proc/self/syscall && test -s /proc/self/syscall; then
      enable_syscall=yes
   else
      enable_syscall=no
   fi
fi
if test "x$enable_syscall" = xyes; then
   AC_DEFINE([HAVE_SYSCALL], [1], [Define to 1 is syscall monitoring is enabled.])
fi

Very good job, I will merge it

[pixclk]

@Explorer09

@JohnSanpe You should handle the running string as special and assign a placeholder number for it. The reason is it allows us to display running string with colors. This status should be special in sorting/collating anyway.

Using special placeholder number may conflict with future syscalls, so storing possible states separately may be a better choice? This is also more convenient for us to use lookup tables in the future.

[Explorer09]

You should handle the running string as special and assign a placeholder number for it. The reason is it allows us to display running string with colors. This status should be special in sorting/collating anyway.

Using special placeholder number may conflict with future syscalls, so storing possible states separately may be a better choice? This is also more convenient for us to use lookup tables in the future.

Use a negative number. E.g. -2, or maybe -1000 which has an even less chance to cause conflict.

[pixclk]

You should handle the running string as special and assign a placeholder number for it. The reason is it allows us to display running string with colors. This status should be special in sorting/collating anyway.

Using special placeholder number may conflict with future syscalls, so storing possible states separately may be a better choice? This is also more convenient for us to use lookup tables in the future.

Use a negative number. E.g. -2, or maybe -1000 which has an even less chance to cause conflict.

I have already fixed it 😄

[pixclk]

Does CI seem to have some issues?

[BenBE]

Does CI seem to have some issues?

No. CI is waiting for approval by one of the maintainers as this is your first pull request for this project.