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x86/traps: Move control protection handler to separate file

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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: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Tested-by: Pengfei Xu <pengfei.xu@intel.com>
Tested-by: John Allen <john.allen@amd.com>
Tested-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/all/20230613001108.3040476-8-rick.p.edgecombe%40intel.com
This commit is contained in:
Rick Edgecombe 2023-06-12 17:10:33 -07:00
parent 18e66b695e
commit 2da5b91fe4
3 changed files with 78 additions and 75 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/kernel/Makefile
View File

@ -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)

76
arch/x86/kernel/cet.c Normal file
View File

@ -0,0 +1,76 @@
// 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);

75
arch/x86/kernel/traps.c
View File

@ -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