Re: [PATCH] Loongarch: entry: fix syscall_get_arguments() VS no-bultin-memcpy

["Wentao Guan" <guanwentao@uniontech.com>]

Hello Ruoyao,

The quick test results are very interesting...:
UnixBench syscall on 3A6000 platform:
./Run syscall -i 10 -c 8
kernel source: v6.16
kernel config:
https://github.com/deepin-community/kernel/blob/linux-6.12.y/arch/loongarch/configs/deepin_loongarch_desktop_defconfig
Use this GCC 15[1]:

result: 
1. with no patch:
System Call Overhead                          15000.0    8893011.8   5928.7
2. with patch [2] to disable -fno-builtin-memcpy -fno-builtin-memmove -fno-builtin-memset:
System Call Overhead                          15000.0    8510415.2   5673.6
lower than patch???
3. with my origin patch [3](+4.9%): 
System Call Overhead                          15000.0    9336022.1   6224.0

BRs
Wentao Guan

[1]: https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/15.2.0
[2]:
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 4b19f9337..53bbcf31c 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -746,6 +746,9 @@ config ARCH_SUSPEND_POSSIBLE
 config ARCH_HIBERNATION_POSSIBLE
        def_bool y
 
+config ARCH_MEMORY_LIBCALL_DISABLE
+       def_bool KASAN || GCC_VERSION >= 140000
+
 source "kernel/power/Kconfig"
 source "drivers/acpi/Kconfig"
 source "drivers/cpufreq/Kconfig"
diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
index b0703a4e0..fba837b22 100644
--- a/arch/loongarch/Makefile
+++ b/arch/loongarch/Makefile
@@ -120,7 +120,7 @@ endif
 
 cflags-y += $(call cc-option, -mno-check-zero-division)
 
-ifndef CONFIG_KASAN
+ifeq ($(CONFIG_ARCH_MEMORY_LIBCALL_DISABLE),)
 cflags-y += -fno-builtin-memcpy -fno-builtin-memmove -fno-builtin-memset
 endif
[3]:
diff --git a/arch/loongarch/include/asm/syscall.h b/arch/loongarch/include/asm/syscall.h
index 81d2733f7..171af2edd 100644
--- a/arch/loongarch/include/asm/syscall.h
+++ b/arch/loongarch/include/asm/syscall.h
@@ -65,7 +65,11 @@ static inline void syscall_get_arguments(struct task_struct *task,
                                         unsigned long *args)
 {
        args[0] = regs->orig_a0;
-       memcpy(&args[1], &regs->regs[5], 5 * sizeof(long));
+       args[1] = regs->regs[5];
+       args[2] = regs->regs[6];
+       args[3] = regs->regs[7];
+       args[4] = regs->regs[8];
+       args[5] = regs->regs[9];
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,

[4]: perf diff
# Event 'cycles:P'
#
# Baseline  Delta Abs  Shared Object                       Symbol                                               >
# ........  .........  ..................................  .....................................................>
#
    12.72%     -7.07%  [kernel.kallsyms]                   [k] syscall_trace_enter
     0.00%     +2.94%  [kernel.kallsyms]                   [k] __memcpy_fast
    33.69%     +1.41%  [kernel.kallsyms]                   [k] do_syscall
     2.64%     +0.32%  [kernel.kallsyms]                   [k] __audit_syscall_entry
     4.92%     +0.32%  libc.so.6                           [.] __GI___umask
     3.54%     +0.30%  [kernel.kallsyms]                   [k] alloc_fd
     4.36%     +0.24%  libc.so.6                           [.] __GI___getuid
     4.63%     +0.24%  libc.so.6                           [.] syscall
     4.50%     +0.22%  libc.so.6                           [.] __GI___dup
     4.84%     +0.22%  [kernel.kallsyms]                   [k] syscall_exit_work
     4.81%     +0.22%  libc.so.6                           [.] __close
               +0.20%  [kernel.kallsyms]                   [k] __memcpy
     1.48%     +0.15%  [kernel.kallsyms]                   [k] audit_reset_context
     0.69%     +0.13%  [kernel.kallsyms]                   [k] __se_sys_close
     2.13%     +0.10%  [kernel.kallsyms]                   [k] file_close_fd_locked
     0.86%     +0.08%  [kernel.kallsyms]                   [k] map_id_range_up
     0.71%     +0.06%  [kernel.kallsyms]                   [k] __task_pid_nr_ns
     0.41%     +0.04%  [kernel.kallsyms]                   [k] fd_install
     0.56%     +0.04%  [kernel.kallsyms]                   [k] __rcu_read_unlock
     0.57%     +0.04%  [kernel.kallsyms]                   [k] fput_close_sync
     0.07%     -0.04%  [kernel.kallsyms]                   [k] idle_exit
     1.37%     +0.04%  [kernel.kallsyms]                   [k] _raw_spin_lock
     0.69%     +0.03%  [kernel.kallsyms]                   [k] filp_flush
     0.76%     +0.03%  syscall                             [.] main
     0.52%     +0.03%  [kernel.kallsyms]                   [k] from_kuid_munged
     0.45%     +0.03%  [kernel.kallsyms]                   [k] _raw_spin_unlock
     0.07%     -0.03%  [kernel.kallsyms]                   [k] finish_task_switch.isra.0
     1.72%     +0.03%  [kernel.kallsyms]                   [k] ktime_get_coarse_real_ts64
     0.67%     +0.03%  [kernel.kallsyms]                   [k] __rcu_read_lock
     0.03%     -0.03%  deepin-deepinid-daemon              [.] 0x0000000000003018
     1.28%     -0.02%  [kernel.kallsyms]                   [k] __audit_syscall_exit
     0.12%     +0.02%  syscall                             [.] getuid@plt
     0.02%     -0.02%  dde-session-daemon                  [.] 0x0000000000299d10
     0.02%     -0.02%  ld-linux-loongarch-lp64d.so.1       [.] do_lookup_x
     0.03%     -0.01%  [kernel.kallsyms]                   [k] _raw_spin_unlock_irqrestore
     0.01%     -0.01%  ld-linux-loongarch-lp64d.so.1       [.] _dl_lookup_symbol_x
     0.30%     +0.01%  [kernel.kallsyms]                   [k] sys_getpid
     0.14%     -0.01%  syscall                             [.] umask@plt
     0.01%     -0.01%  libdbus-1.so.3.32.4                 [.] 0x0000000000015ac0
     0.02%     -0.01%  [kernel.kallsyms]                   [k] clear_page
     0.01%     -0.01%  deepin-sync-helper                  [.] 0x0000000000003a84
     0.14%     +0.01%  syscall                             [.] close@plt