Commit 6e179d64 authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

s390: add automatic detection of the spectre defense 



Automatically decide between nobp vs. expolines if the spectre_v2=auto
kernel parameter is specified or CONFIG_EXPOLINE_AUTO=y is set.

The decision made at boot time due to CONFIG_EXPOLINE_AUTO=y being set
can be overruled with the nobp, nospec and spectre_v2 kernel parameters.

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent b2e2f43a

arch/s390/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -576,7 +576,7 @@ choice 
config EXPOLINE_OFF

	bool "spectre_v2=off"



config EXPOLINE_MEDIUM

config EXPOLINE_AUTO

	bool "spectre_v2=auto"



config EXPOLINE_FULL

arch/s390/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -81,7 +81,7 @@ ifdef CONFIG_EXPOLINE 
    CC_FLAGS_EXPOLINE += -mfunction-return=thunk

    CC_FLAGS_EXPOLINE += -mindirect-branch-table

    export CC_FLAGS_EXPOLINE

    cflags-y += $(CC_FLAGS_EXPOLINE)

    cflags-y += $(CC_FLAGS_EXPOLINE) -DCC_USING_EXPOLINE

  endif

endif

arch/s390/include/asm/nospec-branch.h

+2 −4
Original line number Diff line number Diff line
@@ -6,12 +6,10 @@ 


#include <linux/types.h>



extern int nospec_call_disable;

extern int nospec_return_disable;

extern int nospec_disable;



void nospec_init_branches(void);

void nospec_call_revert(s32 *start, s32 *end);

void nospec_return_revert(s32 *start, s32 *end);

void nospec_revert(s32 *start, s32 *end);



#endif /* __ASSEMBLY__ */

arch/s390/kernel/alternative.c

+1 −0
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 
#include <linux/module.h>

#include <asm/alternative.h>

#include <asm/facility.h>

#include <asm/nospec-branch.h>



#define MAX_PATCH_LEN (255 - 1)

arch/s390/kernel/module.c

+5 −6
Original line number Diff line number Diff line
@@ -159,7 +159,7 @@ int module_frob_arch_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs, 
	me->core_layout.size += me->arch.got_size;

	me->arch.plt_offset = me->core_layout.size;

	if (me->arch.plt_size) {

		if (IS_ENABLED(CONFIG_EXPOLINE) && !nospec_call_disable)

		if (IS_ENABLED(CONFIG_EXPOLINE) && !nospec_disable)

			me->arch.plt_size += PLT_ENTRY_SIZE;

		me->core_layout.size += me->arch.plt_size;

	}
@@ -318,8 +318,7 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab, 
				info->plt_offset;

			ip[0] = 0x0d10e310;	/* basr 1,0  */

			ip[1] = 0x100a0004;	/* lg	1,10(1) */

			if (IS_ENABLED(CONFIG_EXPOLINE) &&

			    !nospec_call_disable) {

			if (IS_ENABLED(CONFIG_EXPOLINE) && !nospec_disable) {

				unsigned int *ij;

				ij = me->core_layout.base +

					me->arch.plt_offset +
@@ -440,7 +439,7 @@ int module_finalize(const Elf_Ehdr *hdr, 
	void *aseg;



	if (IS_ENABLED(CONFIG_EXPOLINE) &&

	    !nospec_call_disable && me->arch.plt_size) {

	    !nospec_disable && me->arch.plt_size) {

		unsigned int *ij;



		ij = me->core_layout.base + me->arch.plt_offset +
@@ -467,11 +466,11 @@ int module_finalize(const Elf_Ehdr *hdr, 


		if (IS_ENABLED(CONFIG_EXPOLINE) &&

		    (!strcmp(".nospec_call_table", secname)))

			nospec_call_revert(aseg, aseg + s->sh_size);

			nospec_revert(aseg, aseg + s->sh_size);



		if (IS_ENABLED(CONFIG_EXPOLINE) &&

		    (!strcmp(".nospec_return_table", secname)))

			nospec_return_revert(aseg, aseg + s->sh_size);

			nospec_revert(aseg, aseg + s->sh_size);

	}



	jump_label_apply_nops(me);

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