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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Minios-devel] [UNIKRAFT PATCH v2 1/5] lib/syscall_shim: UK_LLSYSCALL_(R_)_DEFINE variants
Reviewed-by: Gaulthier Gain <gaulthier.gain@xxxxxxxxx>
> On 3 Apr 2020, at 18:29, Simon Kuenzer <simon.kuenzer@xxxxxxxxx> wrote:
>
> Some system calls have different signatures and return types on the
> libC API and the Linux system call ABI (e.g., brk, mount). In order
> to support implementing such libc-style wrappers manually on top of
> the syscall_shim library, we introduce so called low-level variants
> for the UK_SYSCALL_(R_)_DEFINE macros that only provide the
> uk_syscall_(e|r)_<syscall name> symbols: UK_LLSYSCALL_(R_)_DEFINE
>
> Signed-off-by: Simon Kuenzer <simon.kuenzer@xxxxxxxxx>
> ---
> doc/guides/developers-app.rst | 35 ++++++++++-
> lib/syscall_shim/include/uk/syscall.h | 91 ++++++++++++++++++++-------
> 2 files changed, 102 insertions(+), 24 deletions(-)
>
> diff --git a/doc/guides/developers-app.rst b/doc/guides/developers-app.rst
> index 6438333c..a7242e60 100644
> --- a/doc/guides/developers-app.rst
> +++ b/doc/guides/developers-app.rst
> @@ -428,10 +428,39 @@ Both macros create the following three symbols:
> <return_type> <syscall_name>(<arg1_type> <arg1_name>,
> <arg2_type> <arg2_name>, ...);
>
> +For the case that the libc-style wrapper does not match the signature and
> return
> +type of the underlying system call, a so called low-level variant of these
> two
> +macros are available: ``UK_LLSYSCALL_DEFINE``, ``UK_LLSYSCALL_R_DEFINE``.
> +These macros only generate the ``uk_syscall_e_<syscall_name>`` and
> +``uk_syscall_r_<syscall_name>`` symbols. You can then provide the custom
> +libc-style wrapper on top:
> +
> +.. code-block:: c
> +
> + #include <uk/syscall.h>
> +
> + UK_LLSYSCALL_R_DEFINE(ssize_t, write, int, fd, const void *, buf,
> size_t, count)
> + {
> + long ret;
> +
> + ret = (long) vfs_do_write(fd, buf, count);
> + if (ret < 0) {
> + return -EFAULT;
> + }
> + return ret;
> + }
> +
> + ssize_t write(int fd, const void *buf, size_t count)
> + {
> + return (ssize_t) uk_syscall_e_write((long) fd,
> + (long) buf, (long) count);
> + }
> +
> Note: When `syscall_shim` library is not enabled, the original design idea was
> -that the macros provide the libc-style wrapper only. However, both macros
> -provide always all three variants. This is done to support the case that a
> -system call is implemented on top of another.
> +that the macros provide the libc-style wrapper only. However, all the
> +described macros are still available and populate the symbols as documented
> +here. This is done to support the case that a system call is implemented by
> +calling another.
>
> If your library uses an ``exportsyms.uk`` file, you need to add the three
> symbols for making them public available: ::
> diff --git a/lib/syscall_shim/include/uk/syscall.h
> b/lib/syscall_shim/include/uk/syscall.h
> index cd5c6e67..a219365b 100644
> --- a/lib/syscall_shim/include/uk/syscall.h
> +++ b/lib/syscall_shim/include/uk/syscall.h
> @@ -37,6 +37,7 @@
> #ifndef __UK_SYSCALL_H__
> #define __UK_SYSCALL_H__
>
> +#include <uk/config.h>
> #include <uk/essentials.h>
> #include <errno.h>
> #include <uk/print.h>
> @@ -94,56 +95,83 @@ typedef long uk_syscall_arg_t;
> /* TODO: `void` as return type is currently not supported.
> * NOTE: Workaround is to use `int` instead.
> */
> -#define __UK_SYSCALL_DEFINE(x, rtype, name, ename, rname, ...)
> \
> - rtype name(UK_ARG_MAPx(x, UK_S_ARG_ACTUAL, __VA_ARGS__)); \
> +/*
> + * UK_LLSYSCALL_DEFINE()
> + * Low-level variant, does not provide a libc-style wrapper
> + */
> +#define __UK_LLSYSCALL_DEFINE(x, rtype, name, ename, rname, ...) \
> + long ename(UK_ARG_MAPx(x, UK_S_ARG_LONG, __VA_ARGS__)); \
> long rname(UK_ARG_MAPx(x, UK_S_ARG_LONG, __VA_ARGS__)) \
> { \
> int _errno = errno; \
> long ret; \
> \
> errno = 0; \
> - ret = (long) name( \
> - UK_ARG_MAPx(x, UK_S_ARG_CAST_ACTUAL, __VA_ARGS__)); \
> + ret = ename( \
> + UK_ARG_MAPx(x, UK_S_ARG_CAST_LONG, __VA_ARGS__)); \
> if (ret == -1) \
> ret = errno ? -errno : -EFAULT; \
> errno = _errno; \
> return ret; \
> } \
> + static inline rtype __##ename(UK_ARG_MAPx(x, \
> + UK_S_ARG_ACTUAL, __VA_ARGS__)); \
> long ename(UK_ARG_MAPx(x, UK_S_ARG_LONG, __VA_ARGS__)) \
> { \
> - return (long) name( \
> + return (long) __##ename( \
> UK_ARG_MAPx(x, UK_S_ARG_CAST_ACTUAL, __VA_ARGS__)); \
> } \
> - rtype name(UK_ARG_MAPx(x, UK_S_ARG_ACTUAL, __VA_ARGS__))
> + static inline rtype __##ename(UK_ARG_MAPx(x, \
> + UK_S_ARG_ACTUAL, __VA_ARGS__))
> +#define _UK_LLSYSCALL_DEFINE(...) __UK_LLSYSCALL_DEFINE(__VA_ARGS__)
> +#define UK_LLSYSCALL_DEFINE(rtype, name, ...)
> \
> + _UK_LLSYSCALL_DEFINE(__UK_SYSCALL_DEF_NARGS(__VA_ARGS__), \
> + rtype, \
> + name, \
> + __UK_NAME2SCALLE_FN(name), \
> + __UK_NAME2SCALLR_FN(name), \
> + __VA_ARGS__)
> +
> +/*
> + * UK_SYSCALL_DEFINE()
> + * Based on UK_LLSYSCALL_DEFINE and provides a libc-style wrapper
> + */
> +#define __UK_SYSCALL_DEFINE(x, rtype, name, ename, rname, ...)
> \
> + long ename(UK_ARG_MAPx(x, UK_S_ARG_LONG, __VA_ARGS__)); \
> + rtype name(UK_ARG_MAPx(x, UK_S_ARG_ACTUAL, __VA_ARGS__)) \
> + { \
> + return (rtype) ename( \
> + UK_ARG_MAPx(x, UK_S_ARG_CAST_LONG, __VA_ARGS__)); \
> + } \
> + __UK_LLSYSCALL_DEFINE(x, rtype, name, ename, rname, __VA_ARGS__)
> #define _UK_SYSCALL_DEFINE(...) __UK_SYSCALL_DEFINE(__VA_ARGS__)
> -#define UK_SYSCALL_DEFINE(rtype, name, ...) \
> - _UK_SYSCALL_DEFINE(__UK_SYSCALL_DEF_NARGS(__VA_ARGS__), \
> - rtype, \
> - name, \
> - __UK_NAME2SCALLE_FN(name), \
> - __UK_NAME2SCALLR_FN(name), \
> +#define UK_SYSCALL_DEFINE(rtype, name, ...) \
> + _UK_SYSCALL_DEFINE(__UK_SYSCALL_DEF_NARGS(__VA_ARGS__), \
> + rtype, \
> + name, \
> + __UK_NAME2SCALLE_FN(name), \
> + __UK_NAME2SCALLR_FN(name), \
> __VA_ARGS__)
>
> /* Raw system call implementation that is returning negative codes on errors
> */
> /* TODO: `void` as return type is currently not supported.
> * NOTE: Workaround is to use `int` instead.
> */
> -#define __UK_SYSCALL_R_DEFINE(x, rtype, name, ename, rname, ...) \
> +/*
> + * UK_LLSYSCALL_R_DEFINE()
> + * Low-level variant, does not provide a libc-style wrapper
> + */
> +#define __UK_LLSYSCALL_R_DEFINE(x, rtype, name, ename, rname, ...) \
> long rname(UK_ARG_MAPx(x, UK_S_ARG_LONG, __VA_ARGS__)); \
> - rtype name(UK_ARG_MAPx(x, UK_S_ARG_ACTUAL, __VA_ARGS__)) \
> + long ename(UK_ARG_MAPx(x, UK_S_ARG_LONG, __VA_ARGS__)) \
> { \
> long ret = rname( \
> UK_ARG_MAPx(x, UK_S_ARG_CAST_LONG, __VA_ARGS__)); \
> if (ret < 0) { \
> errno = (int) -ret; \
> - return (rtype) -1; \
> + return -1; \
> } \
> - return (rtype) ret; \
> - } \
> - long ename(UK_ARG_MAPx(x, UK_S_ARG_LONG, __VA_ARGS__)) \
> - { \
> - return (long) name( \
> - UK_ARG_MAPx(x, UK_S_ARG_CAST_ACTUAL, __VA_ARGS__)); \
> + return ret; \
> } \
> static inline long __##rname(UK_ARG_MAPx(x, UK_S_ARG_ACTUAL, \
> __VA_ARGS__)); \
> @@ -154,6 +182,27 @@ typedef long uk_syscall_arg_t;
> } \
> static inline long __##rname(UK_ARG_MAPx(x, UK_S_ARG_ACTUAL, \
> __VA_ARGS__))
> +#define _UK_LLSYSCALL_R_DEFINE(...) __UK_LLSYSCALL_R_DEFINE(__VA_ARGS__)
> +#define UK_LLSYSCALL_R_DEFINE(rtype, name, ...)
> \
> + _UK_LLSYSCALL_R_DEFINE(__UK_SYSCALL_DEF_NARGS(__VA_ARGS__), \
> + rtype, \
> + name, \
> + __UK_NAME2SCALLE_FN(name), \
> + __UK_NAME2SCALLR_FN(name), \
> + __VA_ARGS__)
> +
> +/*
> + * UK_SYSCALL_R_DEFINE()
> + * Based on UK_LLSYSCALL_R_DEFINE and provides a libc-style wrapper
> + */
> +#define __UK_SYSCALL_R_DEFINE(x, rtype, name, ename, rname, ...) \
> + long ename(UK_ARG_MAPx(x, UK_S_ARG_LONG, __VA_ARGS__)); \
> + rtype name(UK_ARG_MAPx(x, UK_S_ARG_ACTUAL, __VA_ARGS__)) \
> + { \
> + return (rtype) ename( \
> + UK_ARG_MAPx(x, UK_S_ARG_CAST_LONG, __VA_ARGS__)); \
> + } \
> + __UK_LLSYSCALL_R_DEFINE(x, rtype, name, ename, rname, __VA_ARGS__)
> #define _UK_SYSCALL_R_DEFINE(...) __UK_SYSCALL_R_DEFINE(__VA_ARGS__)
> #define UK_SYSCALL_R_DEFINE(rtype, name, ...) \
> _UK_SYSCALL_R_DEFINE(__UK_SYSCALL_DEF_NARGS(__VA_ARGS__), \
> --
> 2.20.1
>
>
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