linux-kernel - [RFC][PATCH 01/24] x86/syscall: Add wrapper for invoking syscall function

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Date:   Mon,  9 Nov 2020 15:44:02 +0100
From:   Alexandre Chartre <alexandre.chartre@...cle.com>
To:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        x86@...nel.org, dave.hansen@...ux.intel.com, luto@...nel.org,
        peterz@...radead.org, linux-kernel@...r.kernel.org,
        thomas.lendacky@....com, jroedel@...e.de
Cc:     konrad.wilk@...cle.com, jan.setjeeilers@...cle.com,
        junaids@...gle.com, oweisse@...gle.com, rppt@...ux.vnet.ibm.com,
        graf@...zon.de, mgross@...ux.intel.com, kuzuno@...il.com,
        alexandre.chartre@...cle.com
Subject: [RFC][PATCH 01/24] x86/syscall: Add wrapper for invoking syscall function

Add a wrapper function for invoking a syscall function.

Signed-off-by: Alexandre Chartre <alexandre.chartre@...cle.com>
---
 arch/x86/entry/common.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 870efeec8bda..d222212908ad 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -35,6 +35,15 @@
 #include <asm/syscall.h>
 #include <asm/irq_stack.h>
 
+static __always_inline void run_syscall(sys_call_ptr_t sysfunc,
+					struct pt_regs *regs)
+{
+	if (!sysfunc)
+		return;
+
+	regs->ax = sysfunc(regs);
+}
+
 #ifdef CONFIG_X86_64
 __visible noinstr void do_syscall_64(unsigned long nr, struct pt_regs *regs)
 {
@@ -43,15 +52,16 @@ __visible noinstr void do_syscall_64(unsigned long nr, struct pt_regs *regs)
 	instrumentation_begin();
 	if (likely(nr < NR_syscalls)) {
 		nr = array_index_nospec(nr, NR_syscalls);
-		regs->ax = sys_call_table[nr](regs);
+		run_syscall(sys_call_table[nr], regs);
 #ifdef CONFIG_X86_X32_ABI
 	} else if (likely((nr & __X32_SYSCALL_BIT) &&
 			  (nr & ~__X32_SYSCALL_BIT) < X32_NR_syscalls)) {
 		nr = array_index_nospec(nr & ~__X32_SYSCALL_BIT,
 					X32_NR_syscalls);
-		regs->ax = x32_sys_call_table[nr](regs);
+		run_syscall(x32_sys_call_table[nr], regs);
 #endif
 	}
+
 	instrumentation_end();
 	syscall_exit_to_user_mode(regs);
 }
@@ -75,7 +85,7 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs,
 	if (likely(nr < IA32_NR_syscalls)) {
 		instrumentation_begin();
 		nr = array_index_nospec(nr, IA32_NR_syscalls);
-		regs->ax = ia32_sys_call_table[nr](regs);
+		run_syscall(ia32_sys_call_table[nr], regs);
 		instrumentation_end();
 	}
 }
-- 
2.18.4