[ Upstream commit f19fbd5ed642dc31c809596412dab1ed56f2f156 ]
Add CONFIG_EXPOLINE to enable the use of the new -mindirect-branch= and
-mfunction_return= compiler options to create a kernel fortified against
the specte v2 attack.
With CONFIG_EXPOLINE=y all indirect branches will be issued with an
execute type instruction. For z10 or newer the EXRL instruction will
be used, for older machines the EX instruction. The typical indirect
call
basr %r14,%r1
is replaced with a PC relative call to a new thunk
brasl %r14,__s390x_indirect_jump_r1
The thunk contains the EXRL/EX instruction to the indirect branch
__s390x_indirect_jump_r1:
exrl 0,0f
j .
0: br %r1
The detour via the execute type instruction has a performance impact.
To get rid of the detour the new kernel parameter "nospectre_v2" and
"spectre_v2=[on,off,auto]" can be used. If the parameter is specified
the kernel and module code will be patched at runtime.
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
---
arch/s390/Kconfig | 28 +++++++++
arch/s390/Makefile | 10 +++
arch/s390/include/asm/lowcore.h | 4 +-
arch/s390/include/asm/nospec-branch.h | 18 ++++++
arch/s390/kernel/Makefile | 3 +
arch/s390/kernel/entry.S | 113 ++++++++++++++++++++++++++--------
arch/s390/kernel/module.c | 62 ++++++++++++++++---
arch/s390/kernel/nospec-branch.c | 101 ++++++++++++++++++++++++++++++
arch/s390/kernel/setup.c | 4 ++
arch/s390/kernel/smp.c | 1 +
arch/s390/kernel/vmlinux.lds.S | 14 +++++
drivers/s390/char/Makefile | 2 +
12 files changed, 325 insertions(+), 35 deletions(-)
create mode 100644 arch/s390/include/asm/nospec-branch.h
create mode 100644 arch/s390/kernel/nospec-branch.c
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 391255169396..89bab36b98ac 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -722,6 +722,34 @@ config KERNEL_NOBP
If unsure, say N.
+config EXPOLINE
+ def_bool n
+ prompt "Avoid speculative indirect branches in the kernel"
+ help
+ Compile the kernel with the expoline compiler options to guard
+ against kernel-to-user data leaks by avoiding speculative indirect
+ branches.
+ Requires a compiler with -mindirect-branch=thunk support for full
+ protection. The kernel may run slower.
+
+ If unsure, say N.
+
+choice
+ prompt "Expoline default"
+ depends on EXPOLINE
+ default EXPOLINE_FULL
+
+config EXPOLINE_OFF
+ bool "spectre_v2=off"
+
+config EXPOLINE_MEDIUM
+ bool "spectre_v2=auto"
+
+config EXPOLINE_FULL
+ bool "spectre_v2=on"
+
+endchoice
+
endmenu
menu "Power Management"
diff --git a/arch/s390/Makefile b/arch/s390/Makefile
index e8d4423e4f85..9ff5714eafaf 100644
--- a/arch/s390/Makefile
+++ b/arch/s390/Makefile
@@ -77,6 +77,16 @@ ifeq ($(call cc-option-yn,-mwarn-dynamicstack),y)
cflags-$(CONFIG_WARN_DYNAMIC_STACK) += -mwarn-dynamicstack
endif
+ifdef CONFIG_EXPOLINE
+ ifeq ($(call cc-option-yn,$(CC_FLAGS_MARCH) -mindirect-branch=thunk),y)
+ CC_FLAGS_EXPOLINE := -mindirect-branch=thunk
+ CC_FLAGS_EXPOLINE += -mfunction-return=thunk
+ CC_FLAGS_EXPOLINE += -mindirect-branch-table
+ export CC_FLAGS_EXPOLINE
+ cflags-y += $(CC_FLAGS_EXPOLINE)
+ endif
+endif
+
ifdef CONFIG_FUNCTION_TRACER
# make use of hotpatch feature if the compiler supports it
cc_hotpatch := -mhotpatch=0,3
diff --git a/arch/s390/include/asm/lowcore.h b/arch/s390/include/asm/lowcore.h
index 2f8809671151..8520c23e419b 100644
--- a/arch/s390/include/asm/lowcore.h
+++ b/arch/s390/include/asm/lowcore.h
@@ -155,7 +155,9 @@ struct _lowcore {
/* Per cpu primary space access list */
__u32 paste[16]; /* 0x0400 */
- __u8 pad_0x04c0[0x0e00-0x0440]; /* 0x0440 */
+ /* br %r1 trampoline */
+ __u16 br_r1_trampoline; /* 0x0440 */
+ __u8 pad_0x0442[0x0e00-0x0442]; /* 0x0442 */
/*
* 0xe00 contains the address of the IPL Parameter Information
diff --git a/arch/s390/include/asm/nospec-branch.h b/arch/s390/include/asm/nospec-branch.h
new file mode 100644
index 000000000000..7df48e5cf36f
--- /dev/null
+++ b/arch/s390/include/asm/nospec-branch.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_S390_EXPOLINE_H
+#define _ASM_S390_EXPOLINE_H
+
+#ifndef __ASSEMBLY__
+
+#include <linux/types.h>
+
+extern int nospec_call_disable;
+extern int nospec_return_disable;
+
+void nospec_init_branches(void);
+void nospec_call_revert(s32 *start, s32 *end);
+void nospec_return_revert(s32 *start, s32 *end);
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ASM_S390_EXPOLINE_H */
diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile
index a4c95c847905..9c9cf5331d6f 100644
--- a/arch/s390/kernel/Makefile
+++ b/arch/s390/kernel/Makefile
@@ -48,6 +48,9 @@ obj-y += entry.o reipl.o relocate_kernel.o alternative.o
extra-y += head.o head64.o vmlinux.lds
+obj-$(CONFIG_EXPOLINE) += nospec-branch.o
+CFLAGS_REMOVE_expoline.o += $(CC_FLAGS_EXPOLINE)
+
obj-$(CONFIG_MODULES) += s390_ksyms.o module.o
obj-$(CONFIG_SMP) += smp.o
obj-$(CONFIG_SCHED_BOOK) += topology.o
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 7fdf7c2efaf6..beda1c33ca12 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -225,12 +225,74 @@ _PIF_WORK = (_PIF_PER_TRAP)
.popsection
.endm
+#ifdef CONFIG_EXPOLINE
+
+ .macro GEN_BR_THUNK name,reg,tmp
+ .section .text.\name,"axG",@progbits,\name,comdat
+ .globl \name
+ .hidden \name
+ .type \name,@function
+\name:
+ .cfi_startproc
+#ifdef CONFIG_HAVE_MARCH_Z10_FEATURES
+ exrl 0,0f
+#else
+ larl \tmp,0f
+ ex 0,0(\tmp)
+#endif
+ j .
+0: br \reg
+ .cfi_endproc
+ .endm
+
+ GEN_BR_THUNK __s390x_indirect_jump_r1use_r9,%r9,%r1
+ GEN_BR_THUNK __s390x_indirect_jump_r1use_r14,%r14,%r1
+ GEN_BR_THUNK __s390x_indirect_jump_r11use_r14,%r14,%r11
+
+ .macro BASR_R14_R9
+0: brasl %r14,__s390x_indirect_jump_r1use_r9
+ .pushsection .s390_indirect_branches,"a",@progbits
+ .long 0b-.
+ .popsection
+ .endm
+
+ .macro BR_R1USE_R14
+0: jg __s390x_indirect_jump_r1use_r14
+ .pushsection .s390_indirect_branches,"a",@progbits
+ .long 0b-.
+ .popsection
+ .endm
+
+ .macro BR_R11USE_R14
+0: jg __s390x_indirect_jump_r11use_r14
+ .pushsection .s390_indirect_branches,"a",@progbits
+ .long 0b-.
+ .popsection
+ .endm
+
+#else /* CONFIG_EXPOLINE */
+
+ .macro BASR_R14_R9
+ basr %r14,%r9
+ .endm
+
+ .macro BR_R1USE_R14
+ br %r14
+ .endm
+
+ .macro BR_R11USE_R14
+ br %r14
+ .endm
+
+#endif /* CONFIG_EXPOLINE */
+
+
.section .kprobes.text, "ax"
ENTRY(__bpon)
.globl __bpon
BPON
- br %r14
+ BR_R1USE_R14
/*
* Scheduler resume function, called by switch_to
@@ -258,9 +320,9 @@ ENTRY(__switch_to)
mvc __LC_CURRENT_PID(4,%r0),__TASK_pid(%r3) # store pid of next
lmg %r6,%r15,__SF_GPRS(%r15) # load gprs of next task
TSTMSK __LC_MACHINE_FLAGS,MACHINE_FLAG_LPP
- bzr %r14
+ jz 0f
.insn s,0xb2800000,__LC_LPP # set program parameter
- br %r14
+0: BR_R1USE_R14
.L__critical_start:
@@ -326,7 +388,7 @@ sie_exit:
xgr %r5,%r5
lmg %r6,%r14,__SF_GPRS(%r15) # restore kernel registers
lg %r2,__SF_EMPTY+16(%r15) # return exit reason code
- br %r14
+ BR_R1USE_R14
.Lsie_fault:
lghi %r14,-EFAULT
stg %r14,__SF_EMPTY+16(%r15) # set exit reason code
@@ -383,7 +445,7 @@ ENTRY(system_call)
lgf %r9,0(%r8,%r10) # get system call add.
TSTMSK __TI_flags(%r12),_TIF_TRACE
jnz .Lsysc_tracesys
- basr %r14,%r9 # call sys_xxxx
+ BASR_R14_R9 # call sys_xxxx
stg %r2,__PT_R2(%r11) # store return value
.Lsysc_return:
@@ -523,7 +585,7 @@ ENTRY(system_call)
lmg %r3,%r7,__PT_R3(%r11)
stg %r7,STACK_FRAME_OVERHEAD(%r15)
lg %r2,__PT_ORIG_GPR2(%r11)
- basr %r14,%r9 # call sys_xxx
+ BASR_R14_R9 # call sys_xxx
stg %r2,__PT_R2(%r11) # store return value
.Lsysc_tracenogo:
TSTMSK __TI_flags(%r12),_TIF_TRACE
@@ -547,7 +609,7 @@ ENTRY(ret_from_fork)
lmg %r9,%r10,__PT_R9(%r11) # load gprs
ENTRY(kernel_thread_starter)
la %r2,0(%r10)
- basr %r14,%r9
+ BASR_R14_R9
j .Lsysc_tracenogo
/*
@@ -621,9 +683,9 @@ ENTRY(pgm_check_handler)
nill %r10,0x007f
sll %r10,2
je .Lpgm_return
- lgf %r1,0(%r10,%r1) # load address of handler routine
+ lgf %r9,0(%r10,%r1) # load address of handler routine
lgr %r2,%r11 # pass pointer to pt_regs
- basr %r14,%r1 # branch to interrupt-handler
+ BASR_R14_R9 # branch to interrupt-handler
.Lpgm_return:
LOCKDEP_SYS_EXIT
tm __PT_PSW+1(%r11),0x01 # returning to user ?
@@ -900,7 +962,7 @@ ENTRY(psw_idle)
stpt __TIMER_IDLE_ENTER(%r2)
.Lpsw_idle_lpsw:
lpswe __SF_EMPTY(%r15)
- br %r14
+ BR_R1USE_R14
.Lpsw_idle_end:
/*
@@ -914,7 +976,7 @@ ENTRY(save_fpu_regs)
lg %r2,__LC_CURRENT
aghi %r2,__TASK_thread
TSTMSK __LC_CPU_FLAGS,_CIF_FPU
- bor %r14
+ jo .Lsave_fpu_regs_exit
stfpc __THREAD_FPU_fpc(%r2)
.Lsave_fpu_regs_fpc_end:
lg %r3,__THREAD_FPU_regs(%r2)
@@ -944,7 +1006,8 @@ ENTRY(save_fpu_regs)
std 15,120(%r3)
.Lsave_fpu_regs_done:
oi __LC_CPU_FLAGS+7,_CIF_FPU
- br %r14
+.Lsave_fpu_regs_exit:
+ BR_R1USE_R14
.Lsave_fpu_regs_end:
/*
@@ -961,7 +1024,7 @@ load_fpu_regs:
lg %r4,__LC_CURRENT
aghi %r4,__TASK_thread
TSTMSK __LC_CPU_FLAGS,_CIF_FPU
- bnor %r14
+ jno .Lload_fpu_regs_exit
lfpc __THREAD_FPU_fpc(%r4)
TSTMSK __LC_MACHINE_FLAGS,MACHINE_FLAG_VX
lg %r4,__THREAD_FPU_regs(%r4) # %r4 <- reg save area
@@ -990,7 +1053,8 @@ load_fpu_regs:
ld 15,120(%r4)
.Lload_fpu_regs_done:
ni __LC_CPU_FLAGS+7,255-_CIF_FPU
- br %r14
+.Lload_fpu_regs_exit:
+ BR_R1USE_R14
.Lload_fpu_regs_end:
.L__critical_end:
@@ -1163,7 +1227,7 @@ cleanup_critical:
jl 0f
clg %r9,BASED(.Lcleanup_table+104) # .Lload_fpu_regs_end
jl .Lcleanup_load_fpu_regs
-0: br %r14
+0: BR_R11USE_R14
.align 8
.Lcleanup_table:
@@ -1193,7 +1257,7 @@ cleanup_critical:
ni __SIE_PROG0C+3(%r9),0xfe # no longer in SIE
lctlg %c1,%c1,__LC_USER_ASCE # load primary asce
larl %r9,sie_exit # skip forward to sie_exit
- br %r14
+ BR_R11USE_R14
#endif
.Lcleanup_system_call:
@@ -1250,7 +1314,7 @@ cleanup_critical:
stg %r15,56(%r11) # r15 stack pointer
# set new psw address and exit
larl %r9,.Lsysc_do_svc
- br %r14
+ BR_R11USE_R14
.Lcleanup_system_call_insn:
.quad system_call
.quad .Lsysc_stmg
@@ -1260,7 +1324,7 @@ cleanup_critical:
.Lcleanup_sysc_tif:
larl %r9,.Lsysc_tif
- br %r14
+ BR_R11USE_R14
.Lcleanup_sysc_restore:
# check if stpt has been executed
@@ -1277,14 +1341,14 @@ cleanup_critical:
mvc 0(64,%r11),__PT_R8(%r9)
lmg %r0,%r7,__PT_R0(%r9)
1: lmg %r8,%r9,__LC_RETURN_PSW
- br %r14
+ BR_R11USE_R14
.Lcleanup_sysc_restore_insn:
.quad .Lsysc_exit_timer
.quad .Lsysc_done - 4
.Lcleanup_io_tif:
larl %r9,.Lio_tif
- br %r14
+ BR_R11USE_R14
.Lcleanup_io_restore:
# check if stpt has been executed
@@ -1298,7 +1362,7 @@ cleanup_critical:
mvc 0(64,%r11),__PT_R8(%r9)
lmg %r0,%r7,__PT_R0(%r9)
1: lmg %r8,%r9,__LC_RETURN_PSW
- br %r14
+ BR_R11USE_R14
.Lcleanup_io_restore_insn:
.quad .Lio_exit_timer
.quad .Lio_done - 4
@@ -1350,17 +1414,17 @@ cleanup_critical:
# prepare return psw
nihh %r8,0xfcfd # clear irq & wait state bits
lg %r9,48(%r11) # return from psw_idle
- br %r14
+ BR_R11USE_R14
.Lcleanup_idle_insn:
.quad .Lpsw_idle_lpsw
.Lcleanup_save_fpu_regs:
larl %r9,save_fpu_regs
- br %r14
+ BR_R11USE_R14
.Lcleanup_load_fpu_regs:
larl %r9,load_fpu_regs
- br %r14
+ BR_R11USE_R14
/*
* Integer constants
@@ -1376,7 +1440,6 @@ cleanup_critical:
.Lsie_critical_length:
.quad .Lsie_done - .Lsie_gmap
#endif
-
.section .rodata, "a"
#define SYSCALL(esame,emu) .long esame
.globl sys_call_table
diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c
index 06c7e82342cd..86b49f209251 100644
--- a/arch/s390/kernel/module.c
+++ b/arch/s390/kernel/module.c
@@ -32,6 +32,8 @@
#include <linux/moduleloader.h>
#include <linux/bug.h>
#include <asm/alternative.h>
+#include <asm/nospec-branch.h>
+#include <asm/facility.h>
#if 0
#define DEBUGP printk
@@ -164,7 +166,11 @@ int module_frob_arch_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
me->arch.got_offset = me->core_size;
me->core_size += me->arch.got_size;
me->arch.plt_offset = me->core_size;
- me->core_size += me->arch.plt_size;
+ if (me->arch.plt_size) {
+ if (IS_ENABLED(CONFIG_EXPOLINE) && !nospec_call_disable)
+ me->arch.plt_size += PLT_ENTRY_SIZE;
+ me->core_size += me->arch.plt_size;
+ }
return 0;
}
@@ -318,9 +324,21 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
unsigned int *ip;
ip = me->module_core + me->arch.plt_offset +
info->plt_offset;
- ip[0] = 0x0d10e310; /* basr 1,0; lg 1,10(1); br 1 */
- ip[1] = 0x100a0004;
- ip[2] = 0x07f10000;
+ ip[0] = 0x0d10e310; /* basr 1,0 */
+ ip[1] = 0x100a0004; /* lg 1,10(1) */
+ if (IS_ENABLED(CONFIG_EXPOLINE) &&
+ !nospec_call_disable) {
+ unsigned int *ij;
+ ij = me->module_core +
+ me->arch.plt_offset +
+ me->arch.plt_size - PLT_ENTRY_SIZE;
+ ip[2] = 0xa7f40000 + /* j __jump_r1 */
+ (unsigned int)(u16)
+ (((unsigned long) ij - 8 -
+ (unsigned long) ip) / 2);
+ } else {
+ ip[2] = 0x07f10000; /* br %r1 */
+ }
ip[3] = (unsigned int) (val >> 32);
ip[4] = (unsigned int) val;
info->plt_initialized = 1;
@@ -426,16 +444,42 @@ int module_finalize(const Elf_Ehdr *hdr,
struct module *me)
{
const Elf_Shdr *s;
- char *secstrings;
+ char *secstrings, *secname;
+ void *aseg;
+
+ if (IS_ENABLED(CONFIG_EXPOLINE) &&
+ !nospec_call_disable && me->arch.plt_size) {
+ unsigned int *ij;
+
+ ij = me->module_core + me->arch.plt_offset +
+ me->arch.plt_size - PLT_ENTRY_SIZE;
+ if (test_facility(35)) {
+ ij[0] = 0xc6000000; /* exrl %r0,.+10 */
+ ij[1] = 0x0005a7f4; /* j . */
+ ij[2] = 0x000007f1; /* br %r1 */
+ } else {
+ ij[0] = 0x44000000 | (unsigned int)
+ offsetof(struct _lowcore, br_r1_trampoline);
+ ij[1] = 0xa7f40000; /* j . */
+ }
+ }
secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
- if (!strcmp(".altinstructions", secstrings + s->sh_name)) {
- /* patch .altinstructions */
- void *aseg = (void *)s->sh_addr;
+ aseg = (void *) s->sh_addr;
+ secname = secstrings + s->sh_name;
+ if (!strcmp(".altinstructions", secname))
+ /* patch .altinstructions */
apply_alternatives(aseg, aseg + s->sh_size);
- }
+
+ if (IS_ENABLED(CONFIG_EXPOLINE) &&
+ (!strcmp(".nospec_call_table", secname)))
+ nospec_call_revert(aseg, aseg + s->sh_size);
+
+ if (IS_ENABLED(CONFIG_EXPOLINE) &&
+ (!strcmp(".nospec_return_table", secname)))
+ nospec_return_revert(aseg, aseg + s->sh_size);
}
jump_label_apply_nops(me);
diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c
new file mode 100644
index 000000000000..86ee26a612cf
--- /dev/null
+++ b/arch/s390/kernel/nospec-branch.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/module.h>
+#include <asm/facility.h>
+#include <asm/nospec-branch.h>
+
+int nospec_call_disable = IS_ENABLED(EXPOLINE_OFF);
+int nospec_return_disable = !IS_ENABLED(EXPOLINE_FULL);
+
+static int __init nospectre_v2_setup_early(char *str)
+{
+ nospec_call_disable = 1;
+ nospec_return_disable = 1;
+ return 0;
+}
+early_param("nospectre_v2", nospectre_v2_setup_early);
+
+static int __init spectre_v2_setup_early(char *str)
+{
+ if (str && !strncmp(str, "on", 2)) {
+ nospec_call_disable = 0;
+ nospec_return_disable = 0;
+ }
+ if (str && !strncmp(str, "off", 3)) {
+ nospec_call_disable = 1;
+ nospec_return_disable = 1;
+ }
+ if (str && !strncmp(str, "auto", 4)) {
+ nospec_call_disable = 0;
+ nospec_return_disable = 1;
+ }
+ 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 */
+ memcpy(insnbuf + 2, (char[]) { 0x47, 0x00, 0x00, 0x00 }, 4);
+ 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;
+ if (br[0] != 0x07 || (br[1] & 0xf0) != 0xf0)
+ continue;
+ switch (type) {
+ case BRCL_EXPOLINE:
+ /* brcl to thunk, replace with br + nop */
+ insnbuf[0] = br[0];
+ insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f);
+ break;
+ case BRASL_EXPOLINE:
+ /* brasl to thunk, replace with basr + nop */
+ insnbuf[0] = 0x0d;
+ insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f);
+ break;
+ }
+
+ s390_kernel_write(instr, insnbuf, 6);
+ }
+}
+
+void __init_or_module nospec_call_revert(s32 *start, s32 *end)
+{
+ if (nospec_call_disable)
+ __nospec_revert(start, end);
+}
+
+void __init_or_module nospec_return_revert(s32 *start, s32 *end)
+{
+ if (nospec_return_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_call_revert(__nospec_call_start, __nospec_call_end);
+ nospec_return_revert(__nospec_return_start, __nospec_return_end);
+}
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index e5627d4d910c..959e7646cec7 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -64,6 +64,7 @@
#include <asm/sysinfo.h>
#include <asm/numa.h>
#include <asm/alternative.h>
+#include <asm/nospec-branch.h>
#include "entry.h"
/*
@@ -373,6 +374,7 @@ static void __init setup_lowcore(void)
#ifdef CONFIG_SMP
lc->spinlock_lockval = arch_spin_lockval(0);
#endif
+ lc->br_r1_trampoline = 0x07f1; /* br %r1 */
set_prefix((u32)(unsigned long) lc);
lowcore_ptr[0] = lc;
@@ -897,6 +899,8 @@ void __init setup_arch(char **cmdline_p)
set_preferred_console();
apply_alternative_instructions();
+ if (IS_ENABLED(CONFIG_EXPOLINE))
+ nospec_init_branches();
/* Setup zfcpdump support */
setup_zfcpdump();
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 6de44b6bbb0d..77f4f334a465 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -200,6 +200,7 @@ static int pcpu_alloc_lowcore(struct pcpu *pcpu, int cpu)
lc->panic_stack = panic_stack + PANIC_FRAME_OFFSET;
lc->cpu_nr = cpu;
lc->spinlock_lockval = arch_spin_lockval(cpu);
+ lc->br_r1_trampoline = 0x07f1; /* br %r1 */
if (MACHINE_HAS_VX)
lc->vector_save_area_addr =
(unsigned long) &lc->vector_save_area;
diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
index 6cff68a84bb3..a4ae08e416e6 100644
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -101,6 +101,20 @@ SECTIONS
*(.altinstr_replacement)
}
+ /*
+ * Table with the patch locations to undo expolines
+ */
+ .nospec_call_table : {
+ __nospec_call_start = . ;
+ *(.s390_indirect*)
+ __nospec_call_end = . ;
+ }
+ .nospec_return_table : {
+ __nospec_return_start = . ;
+ *(.s390_return*)
+ __nospec_return_end = . ;
+ }
+
/* early.c uses stsi, which requires page aligned data. */
. = ALIGN(PAGE_SIZE);
INIT_DATA_SECTION(0x100)
diff --git a/drivers/s390/char/Makefile b/drivers/s390/char/Makefile
index 6fa9364d1c07..835f1054976b 100644
--- a/drivers/s390/char/Makefile
+++ b/drivers/s390/char/Makefile
@@ -2,6 +2,8 @@
# S/390 character devices
#
+CFLAGS_REMOVE_sclp_early_core.o += $(CC_FLAGS_EXPOLINE)
+
obj-y += ctrlchar.o keyboard.o defkeymap.o sclp.o sclp_rw.o sclp_quiesce.o \
sclp_cmd.o sclp_config.o sclp_cpi_sys.o sclp_ocf.o sclp_ctl.o \
sclp_early.o
--
2.13.5