ASR_BASE
Change-Id: Icf3719cc0afe3eeb3edc7fa80a2eb5199ca9dda1
diff --git a/marvell/linux/arch/s390/kernel/nospec-branch.c b/marvell/linux/arch/s390/kernel/nospec-branch.c
new file mode 100644
index 0000000..29e511f
--- /dev/null
+++ b/marvell/linux/arch/s390/kernel/nospec-branch.c
@@ -0,0 +1,176 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/cpu.h>
+#include <asm/nospec-branch.h>
+
+static int __init nobp_setup_early(char *str)
+{
+ bool enabled;
+ int rc;
+
+ rc = kstrtobool(str, &enabled);
+ if (rc)
+ return rc;
+ if (enabled && test_facility(82)) {
+ /*
+ * The user explicitely requested nobp=1, enable it and
+ * disable the expoline support.
+ */
+ __set_facility(82, S390_lowcore.alt_stfle_fac_list);
+ if (IS_ENABLED(CONFIG_EXPOLINE))
+ nospec_disable = 1;
+ } else {
+ __clear_facility(82, S390_lowcore.alt_stfle_fac_list);
+ }
+ return 0;
+}
+early_param("nobp", nobp_setup_early);
+
+static int __init nospec_setup_early(char *str)
+{
+ __clear_facility(82, S390_lowcore.alt_stfle_fac_list);
+ return 0;
+}
+early_param("nospec", nospec_setup_early);
+
+static int __init nospec_report(void)
+{
+ if (test_facility(156))
+ pr_info("Spectre V2 mitigation: etokens\n");
+ if (__is_defined(CC_USING_EXPOLINE) && !nospec_disable)
+ pr_info("Spectre V2 mitigation: execute trampolines\n");
+ if (__test_facility(82, S390_lowcore.alt_stfle_fac_list))
+ pr_info("Spectre V2 mitigation: limited branch prediction\n");
+ return 0;
+}
+arch_initcall(nospec_report);
+
+#ifdef CONFIG_EXPOLINE
+
+int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF);
+
+static int __init nospectre_v2_setup_early(char *str)
+{
+ nospec_disable = 1;
+ return 0;
+}
+early_param("nospectre_v2", nospectre_v2_setup_early);
+
+void __init nospec_auto_detect(void)
+{
+ if (test_facility(156) || cpu_mitigations_off()) {
+ /*
+ * The machine supports etokens.
+ * Disable expolines and disable nobp.
+ */
+ if (__is_defined(CC_USING_EXPOLINE))
+ nospec_disable = 1;
+ __clear_facility(82, S390_lowcore.alt_stfle_fac_list);
+ } else if (__is_defined(CC_USING_EXPOLINE)) {
+ /*
+ * The kernel has been compiled with expolines.
+ * Keep expolines enabled and disable nobp.
+ */
+ nospec_disable = 0;
+ __clear_facility(82, S390_lowcore.alt_stfle_fac_list);
+ }
+ /*
+ * If the kernel has not been compiled with expolines the
+ * nobp setting decides what is done, this depends on the
+ * CONFIG_KERNEL_NP option and the nobp/nospec parameters.
+ */
+}
+
+static int __init spectre_v2_setup_early(char *str)
+{
+ if (str && !strncmp(str, "on", 2)) {
+ nospec_disable = 0;
+ __clear_facility(82, S390_lowcore.alt_stfle_fac_list);
+ }
+ if (str && !strncmp(str, "off", 3))
+ nospec_disable = 1;
+ if (str && !strncmp(str, "auto", 4))
+ nospec_auto_detect();
+ return 0;
+}
+early_param("spectre_v2", spectre_v2_setup_early);
+
+static void __init_or_module __nospec_revert(s32 *start, s32 *end)
+{
+ enum { BRCL_EXPOLINE, BRASL_EXPOLINE } type;
+ u8 *instr, *thunk, *br;
+ u8 insnbuf[6];
+ s32 *epo;
+
+ /* Second part of the instruction replace is always a nop */
+ for (epo = start; epo < end; epo++) {
+ instr = (u8 *) epo + *epo;
+ if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x04)
+ type = BRCL_EXPOLINE; /* brcl instruction */
+ else if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x05)
+ type = BRASL_EXPOLINE; /* brasl instruction */
+ else
+ continue;
+ thunk = instr + (*(int *)(instr + 2)) * 2;
+ if (thunk[0] == 0xc6 && thunk[1] == 0x00)
+ /* exrl %r0,<target-br> */
+ br = thunk + (*(int *)(thunk + 2)) * 2;
+ else if (thunk[0] == 0xc0 && (thunk[1] & 0x0f) == 0x00 &&
+ thunk[6] == 0x44 && thunk[7] == 0x00 &&
+ (thunk[8] & 0x0f) == 0x00 && thunk[9] == 0x00 &&
+ (thunk[1] & 0xf0) == (thunk[8] & 0xf0))
+ /* larl %rx,<target br> + ex %r0,0(%rx) */
+ br = thunk + (*(int *)(thunk + 2)) * 2;
+ else
+ continue;
+ /* Check for unconditional branch 0x07f? or 0x47f???? */
+ if ((br[0] & 0xbf) != 0x07 || (br[1] & 0xf0) != 0xf0)
+ continue;
+
+ memcpy(insnbuf + 2, (char[]) { 0x47, 0x00, 0x07, 0x00 }, 4);
+ switch (type) {
+ case BRCL_EXPOLINE:
+ insnbuf[0] = br[0];
+ insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f);
+ if (br[0] == 0x47) {
+ /* brcl to b, replace with bc + nopr */
+ insnbuf[2] = br[2];
+ insnbuf[3] = br[3];
+ } else {
+ /* brcl to br, replace with bcr + nop */
+ }
+ break;
+ case BRASL_EXPOLINE:
+ insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f);
+ if (br[0] == 0x47) {
+ /* brasl to b, replace with bas + nopr */
+ insnbuf[0] = 0x4d;
+ insnbuf[2] = br[2];
+ insnbuf[3] = br[3];
+ } else {
+ /* brasl to br, replace with basr + nop */
+ insnbuf[0] = 0x0d;
+ }
+ break;
+ }
+
+ s390_kernel_write(instr, insnbuf, 6);
+ }
+}
+
+void __init_or_module nospec_revert(s32 *start, s32 *end)
+{
+ if (nospec_disable)
+ __nospec_revert(start, end);
+}
+
+extern s32 __nospec_call_start[], __nospec_call_end[];
+extern s32 __nospec_return_start[], __nospec_return_end[];
+void __init nospec_init_branches(void)
+{
+ nospec_revert(__nospec_call_start, __nospec_call_end);
+ nospec_revert(__nospec_return_start, __nospec_return_end);
+}
+
+#endif /* CONFIG_EXPOLINE */