@@ -519,6 +519,23 @@ config ARCH_RANDOM
If unsure, say Y.
+config KERNEL_NOBP
+ def_bool n
+ prompt "Enable modified branch prediction for the kernel by default"
+ help
+ If this option is selected the kernel will switch to a modified
+ branch prediction mode if the firmware interface is available.
+ The modified branch prediction mode improves the behaviour in
+ regard to speculative execution.
+
+ With the option enabled the kernel parameter "nobp=0" or "nospec"
+ can be used to run the kernel in the normal branch prediction mode.
+
+ With the option disabled the modified branch prediction mode is
+ enabled with the "nobp=1" kernel parameter.
+
+ If unsure, say N.
+
endmenu
menu "Memory setup"
@@ -14,6 +14,24 @@
#define MAX_FACILITY_BIT (sizeof(((struct lowcore *)0)->stfle_fac_list) * 8)
+static inline void __set_facility(unsigned long nr, void *facilities)
+{
+ unsigned char *ptr = (unsigned char *) facilities;
+
+ if (nr >= MAX_FACILITY_BIT)
+ return;
+ ptr[nr >> 3] |= 0x80 >> (nr & 7);
+}
+
+static inline void __clear_facility(unsigned long nr, void *facilities)
+{
+ unsigned char *ptr = (unsigned char *) facilities;
+
+ if (nr >= MAX_FACILITY_BIT)
+ return;
+ ptr[nr >> 3] &= ~(0x80 >> (nr & 7));
+}
+
static inline int __test_facility(unsigned long nr, void *facilities)
{
unsigned char *ptr;
@@ -154,7 +154,8 @@ struct lowcore {
__u8 pad_0x0e20[0x0f00-0x0e20]; /* 0x0e20 */
/* Extended facility list */
- __u64 stfle_fac_list[32]; /* 0x0f00 */
+ __u64 stfle_fac_list[16]; /* 0x0f00 */
+ __u64 alt_stfle_fac_list[16]; /* 0x0f80 */
__u8 pad_0x1000[0x11b0-0x1000]; /* 0x1000 */
/* Pointer to the machine check extended save area */
@@ -14,18 +14,35 @@ static int __init disable_alternative_instructions(char *str)
early_param("noaltinstr", disable_alternative_instructions);
-extern struct alt_instr __alt_nobp[], __alt_nobp_end[];
-static int __init nobp_setup(char *str)
+static int __init nobp_setup_early(char *str)
{
bool enabled;
int rc;
rc = kstrtobool(str, &enabled);
- if (!rc && enabled)
- apply_alternatives(__alt_nobp, __alt_nobp_end);
- return rc;
+ if (rc)
+ return rc;
+ if (enabled && test_facility(82))
+ __set_facility(82, S390_lowcore.alt_stfle_fac_list);
+ 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 nogmb_setup_early(char *str)
+{
+ __clear_facility(81, S390_lowcore.alt_stfle_fac_list);
+ return 0;
}
-__setup("nobp=", nobp_setup);
+early_param("nogmb", nogmb_setup_early);
struct brcl_insn {
u16 opc;
@@ -87,7 +104,8 @@ static void __init_or_module __apply_alternatives(struct alt_instr *start,
instr = (u8 *)&a->instr_offset + a->instr_offset;
replacement = (u8 *)&a->repl_offset + a->repl_offset;
- if (!test_facility(a->facility))
+ if (!__test_facility(a->facility,
+ S390_lowcore.alt_stfle_fac_list))
continue;
if (unlikely(a->instrlen % 2 || a->replacementlen % 2)) {
@@ -327,6 +327,11 @@ static noinline __init void setup_facility_list(void)
{
stfle(S390_lowcore.stfle_fac_list,
ARRAY_SIZE(S390_lowcore.stfle_fac_list));
+ memcpy(S390_lowcore.alt_stfle_fac_list,
+ S390_lowcore.stfle_fac_list,
+ sizeof(S390_lowcore.alt_stfle_fac_list));
+ if (!IS_ENABLED(CONFIG_KERNEL_NOBP))
+ __clear_facility(82, S390_lowcore.alt_stfle_fac_list);
}
static __init void detect_diag9c(void)
@@ -162,7 +162,7 @@ _PIF_WORK = (_PIF_PER_TRAP | _PIF_SYSCALL_RESTART)
660: .long 0xb2e8c000
.popsection
661: .long 0x47000000
- .pushsection .altnobp, "a"
+ .pushsection .altinstructions, "a"
.long 661b - .
.long 660b - .
.word 82
@@ -176,7 +176,7 @@ _PIF_WORK = (_PIF_PER_TRAP | _PIF_SYSCALL_RESTART)
662: .long 0xb2e8d000
.popsection
663: .long 0x47000000
- .pushsection .altnobp, "a"
+ .pushsection .altinstructions, "a"
.long 663b - .
.long 662b - .
.word 82
@@ -339,7 +339,9 @@ static void __init setup_lowcore(void)
lc->preempt_count = S390_lowcore.preempt_count;
lc->stfl_fac_list = S390_lowcore.stfl_fac_list;
memcpy(lc->stfle_fac_list, S390_lowcore.stfle_fac_list,
- MAX_FACILITY_BIT/8);
+ sizeof(lc->stfle_fac_list));
+ memcpy(lc->alt_stfle_fac_list, S390_lowcore.alt_stfle_fac_list,
+ sizeof(lc->alt_stfle_fac_list));
if (MACHINE_HAS_VX || MACHINE_HAS_GS) {
unsigned long bits, size;
@@ -280,7 +280,9 @@ static void pcpu_prepare_secondary(struct pcpu *pcpu, int cpu)
__ctl_store(lc->cregs_save_area, 0, 15);
save_access_regs((unsigned int *) lc->access_regs_save_area);
memcpy(lc->stfle_fac_list, S390_lowcore.stfle_fac_list,
- MAX_FACILITY_BIT/8);
+ sizeof(lc->stfle_fac_list));
+ memcpy(lc->alt_stfle_fac_list, S390_lowcore.alt_stfle_fac_list,
+ sizeof(lc->alt_stfle_fac_list));
}
static void pcpu_attach_task(struct pcpu *pcpu, struct task_struct *tsk)
@@ -115,9 +115,6 @@ SECTIONS
__alt_instructions = .;
*(.altinstructions)
__alt_instructions_end = .;
- __alt_nobp = .;
- *(.altnobp)
- __alt_nobp_end = .;
}
/*