| Message ID | ce00dad5acdd4aff099b289843e30c83f7e31764.1695679700.git.falcon@tinylab.org (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | DCE/DSE: Add Dead Syscalls Elimination support, part1 | expand |
On Tue, Sep 26, 2023, at 00:42, Zhangjin Wu wrote: > For HAVE_TRIM_UNUSED_SYSCALLS, the syscall tables are hacked with the > inputing unused_syscalls. > > Firstly, the intermediate preprocessed .i files are generated from the > original C version of syscall tables respectively, and named with a > 'used' suffix: syscall_table_used.i, compat_syscall_table_used.i. > > Secondly, all of the unused syscalls are commented. > > At last, two new objective files sufixed with 'used' are generated from > the hacked .i files and they are linked into the eventual kernel image. > > Signed-off-by: Zhangjin Wu <falcon@tinylab.org> As mentioned in my comment on the mips patch, hacking the preprocessed file here is too much strain on the old infrastructure, the asm-generic/unistd.h file is already too hard to understand for anyone and in need of an overhaul, so let's work together on fixing it up first. Arnd
Hi, Arnd > On Tue, Sep 26, 2023, at 00:42, Zhangjin Wu wrote: > > For HAVE_TRIM_UNUSED_SYSCALLS, the syscall tables are hacked with the > > inputing unused_syscalls. > > > > Firstly, the intermediate preprocessed .i files are generated from the > > original C version of syscall tables respectively, and named with a > > 'used' suffix: syscall_table_used.i, compat_syscall_table_used.i. > > > > Secondly, all of the unused syscalls are commented. > > > > At last, two new objective files sufixed with 'used' are generated from > > the hacked .i files and they are linked into the eventual kernel image. > > > > Signed-off-by: Zhangjin Wu <falcon@tinylab.org> > > As mentioned in my comment on the mips patch, hacking the preprocessed > file here is too much strain on the old infrastructure, the > asm-generic/unistd.h file is already too hard to understand for > anyone and in need of an overhaul, so let's work together on fixing > it up first. > Ok, I was thinking about using asm/syscall_table.h instead of asm/unistd.h like mips. void * const sys_call_table[NR_syscalls] = { [0 ... NR_syscalls - 1] = __riscv_sys_ni_syscall, #include <asm/syscall_table.h> }; Therefore, we can generate syscall_table.h from asm/unist.h with a tool like scripts/syscallused.sh Another solution may be firstly generate a list of `#define __USED_NR_##call 1` for the used syscalls from Kconfig symbol, and then change __SYSCALL() macro to: #define __SYSCALL(nr, call) [nr] = __is_defined(__USED_NR_##call) ? __riscv_##call : __riscv_sys_ni_syscall, `include/linux/kconfig.h` defined the '__is_defined'. This method may work for the archs with .tbl files too. Thanks, Zhangjin > Arnd
On Sat, Oct 7, 2023, at 15:29, Zhangjin Wu wrote: >> On Tue, Sep 26, 2023, at 00:42, Zhangjin Wu wrote: >> > For HAVE_TRIM_UNUSED_SYSCALLS, the syscall tables are hacked with the >> > inputing unused_syscalls. >> > >> > Firstly, the intermediate preprocessed .i files are generated from the >> > original C version of syscall tables respectively, and named with a >> > 'used' suffix: syscall_table_used.i, compat_syscall_table_used.i. >> > >> > Secondly, all of the unused syscalls are commented. >> > >> > At last, two new objective files sufixed with 'used' are generated from >> > the hacked .i files and they are linked into the eventual kernel image. >> > >> > Signed-off-by: Zhangjin Wu <falcon@tinylab.org> >> >> As mentioned in my comment on the mips patch, hacking the preprocessed >> file here is too much strain on the old infrastructure, the >> asm-generic/unistd.h file is already too hard to understand for >> anyone and in need of an overhaul, so let's work together on fixing >> it up first. >> > > Ok, I was thinking about using asm/syscall_table.h instead of > asm/unistd.h like mips. > > void * const sys_call_table[NR_syscalls] = { > [0 ... NR_syscalls - 1] = __riscv_sys_ni_syscall, > #include <asm/syscall_table.h> > }; > > Therefore, we can generate syscall_table.h from asm/unist.h with a tool > like scripts/syscallused.sh > > Another solution may be firstly generate a list of `#define __USED_NR_##call 1` > for the used syscalls from Kconfig symbol, and then change __SYSCALL() macro > to: > > #define __SYSCALL(nr, call) [nr] = > __is_defined(__USED_NR_##call) ? __riscv_##call : > __riscv_sys_ni_syscall, > > `include/linux/kconfig.h` defined the '__is_defined'. > > This method may work for the archs with .tbl files too. Right, either way would be much better than than your first approach. For the mips version (and all the other traditional architectures that use the syscall.tbl method) I think I'd integrate the filtering in scripts/syscalltbl.sh if we decide to go that way. For the riscv version (and all the others using asm-generic/unistd.h), the __USED_NR_## macro would be fine as an intermediate step, until we manage to convert those to syscall.tbl parsing. On the other hand, based on the earlier findings, my overall feeling is that we're better off not adding the extra indirection at all, but instead add the more Kconfig symbols to control the largest groups of syscalls, with the hope of conditionally removing additional code for each of these symbols beyond the automatic gc-section logic. Arnd
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index d607ab0f7c6d..b5e726b49a6f 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -140,6 +140,7 @@ config RISCV select HAVE_RSEQ select HAVE_STACKPROTECTOR select HAVE_SYSCALL_TRACEPOINTS + select HAVE_TRIM_UNUSED_SYSCALLS if HAVE_LD_DEAD_CODE_DATA_ELIMINATION select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU select IRQ_DOMAIN select IRQ_FORCED_THREADING diff --git a/arch/riscv/kernel/syscalls/Makefile b/arch/riscv/kernel/syscalls/Makefile index 65abd0871ee5..3b5969aaa9e8 100644 --- a/arch/riscv/kernel/syscalls/Makefile +++ b/arch/riscv/kernel/syscalls/Makefile @@ -3,8 +3,45 @@ # Makefile for the RISC-V syscall tables # +ifndef CONFIG_TRIM_UNUSED_SYSCALLS + CFLAGS_syscall_table.o += $(call cc-option,-Wno-override-init,) CFLAGS_compat_syscall_table.o += $(call cc-option,-Wno-override-init,) obj-y += syscall_table.o obj-$(CONFIG_COMPAT) += compat_syscall_table.o +else # CONFIG_TRIM_UNUSED_SYSCALLS + +include $(srctree)/scripts/Makefile.syscalls + +CFLAGS_syscall_table_used.o += $(call cc-option,-Wno-override-init,) +CFLAGS_compat_syscall_table_used.o += $(call cc-option,-Wno-override-init,) + +obj-y += syscall_table_used.o +obj-$(CONFIG_COMPAT) += compat_syscall_table_used.o + +# comment the unused syscalls +quiet_cmd_used = USED $@ + cmd_used = sed -E -e '/^\[([0-9]+|\([0-9]+ \+ [0-9]+\))\] = /{/= *__riscv_(__sys_|sys_|compat_)*($(used_syscalls)),/!{s%^%/* %g;s%$$% */%g}}' -i $@; + +$(obj)/syscall_table_used.c: $(src)/syscall_table.c + $(Q)cp $< $@ + +$(obj)/syscall_table_used.i: $(src)/syscall_table_used.c $(used_syscalls_deps) FORCE + $(call if_changed_dep,cpp_i_c) + $(call cmd,used) + +$(obj)/syscall_table_used.o: $(obj)/syscall_table_used.i FORCE + $(call if_changed,cc_o_c) + +$(obj)/compat_syscall_table_used.c: $(src)/compat_syscall_table.c + $(Q)cp $< $@ + +$(obj)/compat_syscall_table_used.i: $(src)/compat_syscall_table_used.c $(used_syscalls_deps) FORCE + $(call if_changed_dep,cpp_i_c) + $(call cmd,used) + +$(obj)/compat_syscall_table_used.o: $(obj)/compat_syscall_table_used.i FORCE + $(call if_changed,cc_o_c) + +endif # CONFIG_TRIM_UNUSED_SYSCALLS
For HAVE_TRIM_UNUSED_SYSCALLS, the syscall tables are hacked with the inputing unused_syscalls. Firstly, the intermediate preprocessed .i files are generated from the original C version of syscall tables respectively, and named with a 'used' suffix: syscall_table_used.i, compat_syscall_table_used.i. Secondly, all of the unused syscalls are commented. At last, two new objective files sufixed with 'used' are generated from the hacked .i files and they are linked into the eventual kernel image. Signed-off-by: Zhangjin Wu <falcon@tinylab.org> --- arch/riscv/Kconfig | 1 + arch/riscv/kernel/syscalls/Makefile | 37 +++++++++++++++++++++++++++++ 2 files changed, 38 insertions(+)