Commit 2da5b91f authored by Rick Edgecombe's avatar Rick Edgecombe
Browse files

x86/traps: Move control protection handler to separate file 



Today the control protection handler is defined in traps.c and used only
for the kernel IBT feature. To reduce ifdeffery, move it to it's own file.
In future patches, functionality will be added to make this handler also
handle user shadow stack faults. So name the file cet.c.

No functional change.

Signed-off-by: default avatarRick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarMike Rapoport (IBM) <rppt@kernel.org>
Tested-by: default avatarPengfei Xu <pengfei.xu@intel.com>
Tested-by: default avatarJohn Allen <john.allen@amd.com>
Tested-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/all/20230613001108.3040476-8-rick.p.edgecombe%40intel.com
parent 18e66b69

arch/x86/kernel/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -145,6 +145,8 @@ obj-$(CONFIG_CFI_CLANG) += cfi.o 


obj-$(CONFIG_CALL_THUNKS)		+= callthunks.o



obj-$(CONFIG_X86_CET)			+= cet.o



###

# 64 bit specific files

ifeq ($(CONFIG_X86_64),y)

arch/x86/kernel/cet.c

0 → 100644
+76 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



#include <linux/ptrace.h>

#include <asm/bugs.h>

#include <asm/traps.h>



static __ro_after_init bool ibt_fatal = true;



extern void ibt_selftest_ip(void); /* code label defined in asm below */



enum cp_error_code {

	CP_EC        = (1 << 15) - 1,



	CP_RET       = 1,

	CP_IRET      = 2,

	CP_ENDBR     = 3,

	CP_RSTRORSSP = 4,

	CP_SETSSBSY  = 5,



	CP_ENCL	     = 1 << 15,

};



DEFINE_IDTENTRY_ERRORCODE(exc_control_protection)

{

	if (!cpu_feature_enabled(X86_FEATURE_IBT)) {

		pr_err("Unexpected #CP\n");

		BUG();

	}



	if (WARN_ON_ONCE(user_mode(regs) || (error_code & CP_EC) != CP_ENDBR))

		return;



	if (unlikely(regs->ip == (unsigned long)&ibt_selftest_ip)) {

		regs->ax = 0;

		return;

	}



	pr_err("Missing ENDBR: %pS\n", (void *)instruction_pointer(regs));

	if (!ibt_fatal) {

		printk(KERN_DEFAULT CUT_HERE);

		__warn(__FILE__, __LINE__, (void *)regs->ip, TAINT_WARN, regs, NULL);

		return;

	}

	BUG();

}



/* Must be noinline to ensure uniqueness of ibt_selftest_ip. */

noinline bool ibt_selftest(void)

{

	unsigned long ret;



	asm ("	lea ibt_selftest_ip(%%rip), %%rax\n\t"

	     ANNOTATE_RETPOLINE_SAFE

	     "	jmp *%%rax\n\t"

	     "ibt_selftest_ip:\n\t"

	     UNWIND_HINT_FUNC

	     ANNOTATE_NOENDBR

	     "	nop\n\t"



	     : "=a" (ret) : : "memory");



	return !ret;

}



static int __init ibt_setup(char *str)

{

	if (!strcmp(str, "off"))

		setup_clear_cpu_cap(X86_FEATURE_IBT);



	if (!strcmp(str, "warn"))

		ibt_fatal = false;



	return 1;

}



__setup("ibt=", ibt_setup);

arch/x86/kernel/traps.c

+0 −75
Original line number Diff line number Diff line
@@ -213,81 +213,6 @@ DEFINE_IDTENTRY(exc_overflow) 
	do_error_trap(regs, 0, "overflow", X86_TRAP_OF, SIGSEGV, 0, NULL);

}



#ifdef CONFIG_X86_KERNEL_IBT



static __ro_after_init bool ibt_fatal = true;



extern void ibt_selftest_ip(void); /* code label defined in asm below */



enum cp_error_code {

	CP_EC        = (1 << 15) - 1,



	CP_RET       = 1,

	CP_IRET      = 2,

	CP_ENDBR     = 3,

	CP_RSTRORSSP = 4,

	CP_SETSSBSY  = 5,



	CP_ENCL	     = 1 << 15,

};



DEFINE_IDTENTRY_ERRORCODE(exc_control_protection)

{

	if (!cpu_feature_enabled(X86_FEATURE_IBT)) {

		pr_err("Unexpected #CP\n");

		BUG();

	}



	if (WARN_ON_ONCE(user_mode(regs) || (error_code & CP_EC) != CP_ENDBR))

		return;



	if (unlikely(regs->ip == (unsigned long)&ibt_selftest_ip)) {

		regs->ax = 0;

		return;

	}



	pr_err("Missing ENDBR: %pS\n", (void *)instruction_pointer(regs));

	if (!ibt_fatal) {

		printk(KERN_DEFAULT CUT_HERE);

		__warn(__FILE__, __LINE__, (void *)regs->ip, TAINT_WARN, regs, NULL);

		return;

	}

	BUG();

}



/* Must be noinline to ensure uniqueness of ibt_selftest_ip. */

noinline bool ibt_selftest(void)

{

	unsigned long ret;



	asm ("	lea ibt_selftest_ip(%%rip), %%rax\n\t"

	     ANNOTATE_RETPOLINE_SAFE

	     "	jmp *%%rax\n\t"

	     "ibt_selftest_ip:\n\t"

	     UNWIND_HINT_FUNC

	     ANNOTATE_NOENDBR

	     "	nop\n\t"



	     : "=a" (ret) : : "memory");



	return !ret;

}



static int __init ibt_setup(char *str)

{

	if (!strcmp(str, "off"))

		setup_clear_cpu_cap(X86_FEATURE_IBT);



	if (!strcmp(str, "warn"))

		ibt_fatal = false;



	return 1;

}



__setup("ibt=", ibt_setup);



#endif /* CONFIG_X86_KERNEL_IBT */



#ifdef CONFIG_X86_F00F_BUG

void handle_invalid_op(struct pt_regs *regs)

#else