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-rw-r--r--arch/s390/Kconfig28
-rw-r--r--arch/s390/Makefile10
-rw-r--r--arch/s390/include/asm/lowcore.h6
-rw-r--r--arch/s390/include/asm/nospec-branch.h18
-rw-r--r--arch/s390/kernel/Makefile4
-rw-r--r--arch/s390/kernel/entry.S113
-rw-r--r--arch/s390/kernel/module.c62
-rw-r--r--arch/s390/kernel/nospec-branch.c100
-rw-r--r--arch/s390/kernel/setup.c4
-rw-r--r--arch/s390/kernel/smp.c1
-rw-r--r--arch/s390/kernel/vmlinux.lds.S14
-rw-r--r--drivers/s390/char/Makefile2
12 files changed, 327 insertions, 35 deletions
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index d514e25095c2..0636229dae22 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -557,6 +557,34 @@ 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 "Memory setup"
diff --git a/arch/s390/Makefile b/arch/s390/Makefile
index fd691c4ff89e..2ced3239cb84 100644
--- a/arch/s390/Makefile
+++ b/arch/s390/Makefile
@@ -78,6 +78,16 @@ 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 += $(CC_FLAGS_EXPOLINE)
+ endif
+endif
+
ifdef CONFIG_FUNCTION_TRACER
# make use of hotpatch feature if the compiler supports it
cc_hotpatch := -mhotpatch=0,3
diff --git a/arch/s390/include/asm/lowcore.h b/arch/s390/include/asm/lowcore.h
index c63986aee942..5bc888841eaf 100644
--- a/arch/s390/include/asm/lowcore.h
+++ b/arch/s390/include/asm/lowcore.h
@@ -136,7 +136,11 @@ struct lowcore {
__u64 vdso_per_cpu_data; /* 0x03b8 */
__u64 machine_flags; /* 0x03c0 */
__u64 gmap; /* 0x03c8 */
- __u8 pad_0x03d0[0x0e00-0x03d0]; /* 0x03d0 */
+ __u8 pad_0x03d0[0x0400-0x03d0]; /* 0x03d0 */
+
+ /* br %r1 trampoline */
+ __u16 br_r1_trampoline; /* 0x0400 */
+ __u8 pad_0x0402[0x0e00-0x0402]; /* 0x0402 */
/*
* 0xe00 contains the address of the IPL Parameter Information
diff --git a/arch/s390/include/asm/nospec-branch.h b/arch/s390/include/asm/nospec-branch.h
new file mode 100644
index 000000000000..7df48e5cf36f
--- /dev/null
+++ b/arch/s390/include/asm/nospec-branch.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_S390_EXPOLINE_H
+#define _ASM_S390_EXPOLINE_H
+
+#ifndef __ASSEMBLY__
+
+#include <linux/types.h>
+
+extern int nospec_call_disable;
+extern int nospec_return_disable;
+
+void nospec_init_branches(void);
+void nospec_call_revert(s32 *start, s32 *end);
+void nospec_return_revert(s32 *start, s32 *end);
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ASM_S390_EXPOLINE_H */
diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile
index 909bce65cb2b..7f27e3da9709 100644
--- a/arch/s390/kernel/Makefile
+++ b/arch/s390/kernel/Makefile
@@ -29,6 +29,7 @@ UBSAN_SANITIZE_early.o := n
#
ifneq ($(CC_FLAGS_MARCH),-march=z900)
CFLAGS_REMOVE_als.o += $(CC_FLAGS_MARCH)
+CFLAGS_REMOVE_als.o += $(CC_FLAGS_EXPOLINE)
CFLAGS_als.o += -march=z900
AFLAGS_REMOVE_head.o += $(CC_FLAGS_MARCH)
AFLAGS_head.o += -march=z900
@@ -63,6 +64,9 @@ obj-y += entry.o reipl.o relocate_kernel.o kdebugfs.o alternative.o
extra-y += head.o head64.o vmlinux.lds
+obj-$(CONFIG_EXPOLINE) += nospec-branch.o
+CFLAGS_REMOVE_expoline.o += $(CC_FLAGS_EXPOLINE)
+
obj-$(CONFIG_MODULES) += module.o
obj-$(CONFIG_SMP) += smp.o
obj-$(CONFIG_SCHED_TOPOLOGY) += topology.o
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 53145b5d987d..13a133a6015c 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -222,6 +222,68 @@ _PIF_WORK = (_PIF_PER_TRAP | _PIF_SYSCALL_RESTART)
.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"
.Ldummy:
/*
@@ -237,7 +299,7 @@ _PIF_WORK = (_PIF_PER_TRAP | _PIF_SYSCALL_RESTART)
ENTRY(__bpon)
.globl __bpon
BPON
- br %r14
+ BR_R1USE_R14
/*
* Scheduler resume function, called by switch_to
@@ -261,9 +323,9 @@ ENTRY(__switch_to)
mvc __LC_CURRENT_PID(4,%r0),0(%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:
@@ -330,7 +392,7 @@ 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
@@ -389,7 +451,7 @@ 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:
@@ -574,7 +636,7 @@ 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
@@ -598,7 +660,7 @@ 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
/*
@@ -678,9 +740,9 @@ 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 ?
@@ -998,7 +1060,7 @@ ENTRY(psw_idle)
stpt __TIMER_IDLE_ENTER(%r2)
.Lpsw_idle_lpsw:
lpswe __SF_EMPTY(%r15)
- br %r14
+ BR_R1USE_R14
.Lpsw_idle_end:
/*
@@ -1012,7 +1074,7 @@ 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)
lg %r3,__THREAD_FPU_regs(%r2)
TSTMSK __LC_MACHINE_FLAGS,MACHINE_FLAG_VX
@@ -1039,7 +1101,8 @@ 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:
EXPORT_SYMBOL(save_fpu_regs)
@@ -1057,7 +1120,7 @@ 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
@@ -1084,7 +1147,8 @@ 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:
@@ -1301,7 +1365,7 @@ 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:
@@ -1337,7 +1401,7 @@ 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:
@@ -1390,7 +1454,7 @@ 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
@@ -1402,7 +1466,7 @@ cleanup_critical:
.Lcleanup_sysc_tif:
larl %r9,.Lsysc_tif
- br %r14
+ BR_R11USE_R14
.Lcleanup_sysc_restore:
# check if stpt has been executed
@@ -1419,14 +1483,14 @@ 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
@@ -1440,7 +1504,7 @@ 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
@@ -1493,17 +1557,17 @@ 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
@@ -1523,7 +1587,6 @@ cleanup_critical:
.Lsie_crit_mcck_length:
.quad .Lsie_skip - .Lsie_entry
#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 b7abfad4fd7d..1fc6d1ff92d3 100644
--- a/arch/s390/kernel/module.c
+++ b/arch/s390/kernel/module.c
@@ -19,6 +19,8 @@
#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
@@ -156,7 +158,11 @@ int module_frob_arch_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
me->arch.got_offset = me->core_layout.size;
me->core_layout.size += me->arch.got_size;
me->arch.plt_offset = me->core_layout.size;
- me->core_layout.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_layout.size += me->arch.plt_size;
+ }
return 0;
}
@@ -310,9 +316,21 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
unsigned int *ip;
ip = me->core_layout.base + 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->core_layout.base +
+ 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;
@@ -418,16 +436,42 @@ 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->core_layout.base + 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..69d7fcf48158
--- /dev/null
+++ b/arch/s390/kernel/nospec-branch.c
@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/module.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 bcd2a4a3937e..a6a91f01a17a 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -68,6 +68,7 @@
#include <asm/sysinfo.h>
#include <asm/numa.h>
#include <asm/alternative.h>
+#include <asm/nospec-branch.h>
#include "entry.h"
/*
@@ -379,6 +380,7 @@ static void __init setup_lowcore(void)
lc->spinlock_index = 0;
arch_spin_lock_setup(0);
#endif
+ lc->br_r1_trampoline = 0x07f1; /* br %r1 */
set_prefix((u32)(unsigned long) lc);
lowcore_ptr[0] = lc;
@@ -954,6 +956,8 @@ 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 2fd7d609dae0..a4a9fe1934e9 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -214,6 +214,7 @@ static int pcpu_alloc_lowcore(struct pcpu *pcpu, int cpu)
lc->cpu_nr = cpu;
lc->spinlock_lockval = arch_spin_lockval(cpu);
lc->spinlock_index = 0;
+ lc->br_r1_trampoline = 0x07f1; /* br %r1 */
if (nmi_alloc_per_cpu(lc))
goto out;
if (vdso_alloc_per_cpu(lc))
diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
index 608cf2987d19..08d12cfaf091 100644
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -123,6 +123,20 @@ 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 614b44e70a28..a2b33a22c82a 100644
--- a/drivers/s390/char/Makefile
+++ b/drivers/s390/char/Makefile
@@ -19,6 +19,8 @@ endif
CFLAGS_sclp_early_core.o += -D__NO_FORTIFY
+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 sclp_early_core.o
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.