Commit 530dce27 authored by Xin Li's avatar Xin Li Committed by Borislav Petkov (AMD)
Browse files

x86/syscall: Split IDT syscall setup code into idt_syscall_init() 



Because FRED uses the ring 3 FRED entrypoint for SYSCALL and SYSENTER and
ERETU is the only legit instruction to return to ring 3, there is NO need
to setup SYSCALL and SYSENTER MSRs for FRED, except the IA32_STAR MSR.

Split IDT syscall setup code into idt_syscall_init() to make it easy to
skip syscall setup code when FRED is enabled.

Suggested-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarXin Li <xin3.li@intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Tested-by: default avatarShan Kang <shan.kang@intel.com>
Link: https://lore.kernel.org/r/20231205105030.8698-34-xin3.li@intel.com
parent 70d0fe5d

arch/x86/kernel/cpu/common.c

+10 −3
Original line number Diff line number Diff line
@@ -2066,10 +2066,8 @@ static void wrmsrl_cstar(unsigned long val) 
		wrmsrl(MSR_CSTAR, val);

}



/* May not be marked __init: used by software suspend */

void syscall_init(void)

static inline void idt_syscall_init(void)

{

	wrmsr(MSR_STAR, 0, (__USER32_CS << 16) | __KERNEL_CS);

	wrmsrl(MSR_LSTAR, (unsigned long)entry_SYSCALL_64);



	if (ia32_enabled()) {
@@ -2103,6 +2101,15 @@ void syscall_init(void) 
	       X86_EFLAGS_AC|X86_EFLAGS_ID);

}



/* May not be marked __init: used by software suspend */

void syscall_init(void)

{

	/* The default user and kernel segments */

	wrmsr(MSR_STAR, 0, (__USER32_CS << 16) | __KERNEL_CS);



	idt_syscall_init();

}



#else	/* CONFIG_X86_64 */



#ifdef CONFIG_STACKPROTECTOR