Hi, This series adds nolibc support for x86 32-bit. There are 3 patches in this series: 1) Use `__NR_mmap2` instead of `__NR_mmap` for x86 32-bit. 2) Provide `get_page_size()` function for x86 32-bit. 3) Add x86 32-bit native syscall support. The most noticeable changes is the patch 3. Unlike x86-64, only use native syscall from the __do_syscall macros when CONFIG_NOLIBC is enabled for 32-bit build. The reason is because the libc syscall wrapper can do better in 32-bit. The libc syscall wrapper can dispatch the best syscall instruction that the environment is supported, there are at least two variants syscall instruction for x86 32-bit, they are: `int $0x80` and `sysenter`. The `int $0x80` instruction is always available, but `sysenter` is not, it relies on VDSO. liburing always uses `int $0x80` for syscall if it's compiled with CONFIG_NOLIBC, otherwise it uses whatever the libc provides. Extra notes for __do_syscall6() macro: On i386, the 6th argument of syscall goes in %ebp. However, both Clang and GCC cannot use %ebp in the clobber list and in the "r" constraint without using -fomit-frame-pointer. To make it always available for any kind of compilation, the below workaround is implemented: 1) Push the 6-th argument. 2) Push %ebp. 3) Load the 6-th argument from 4(%esp) to %ebp. 4) Do the syscall (int $0x80). 5) Pop %ebp (restore the old value of %ebp). 6) Add %esp by 4 (undo the stack pointer). WARNING: Don't use register variables for __do_syscall6(), there is a known GCC bug that results in an endless loop. BugLink: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105032 ===== How is this tested? ===== This has been tested on x86-64 Linux (compiled with 32-bit bin support) with the following commands: sudo apt-get install gcc-i686-linux-gnu g++-i686-linux-gnu -y; ./configure --cc=i686-linux-gnu-gcc --cxx=i686-linux-gnu-g++ --nolibc; sudo make -j8 runtests; Signed-off-by: Alviro Iskandar Setiawan <alviro.iskandar@xxxxxxxxxxx> Signed-off-by: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx> --- Ammar Faizi (3): arch/syscall-defs: Use `__NR_mmap2` instead of `__NR_mmap` for x86 32-bit arch/x86/lib: Provide `get_page_size()` function for x86 32-bit arch/x86/syscall: Add x86 32-bit native syscall support src/arch/syscall-defs.h | 11 ++- src/arch/x86/lib.h | 17 ----- src/arch/x86/syscall.h | 150 +++++++++++++++++++++++++++++++++++++++- 3 files changed, 157 insertions(+), 21 deletions(-) base-commit: c47b44afb686d794f8ed62feb77e9c42431c8444 -- Ammar Faizi
