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author | 2023-06-12 17:10:33 -0700 | |
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committer | 2023-07-11 14:12:18 -0700 | |
commit | 2da5b91fe4092aab9d92138c78b68e9856b078d0 (patch) | |
tree | f8736e7ec3071c900ee507b029ba4ed8dfb2fe3e /arch/x86/kernel/cet.c | |
parent | x86/shstk: Add Kconfig option for shadow stack (diff) | |
download | linux-2da5b91fe4092aab9d92138c78b68e9856b078d0.tar.gz linux-2da5b91fe4092aab9d92138c78b68e9856b078d0.tar.bz2 linux-2da5b91fe4092aab9d92138c78b68e9856b078d0.zip |
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: 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
Diffstat (limited to 'arch/x86/kernel/cet.c')
-rw-r--r-- | arch/x86/kernel/cet.c | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c new file mode 100644 index 000000000000..7ad22b705b64 --- /dev/null +++ b/arch/x86/kernel/cet.c @@ -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); |