Commit 2268169c authored by Vasily Gorbik's avatar Vasily Gorbik
Browse files

s390: remove unused expoline to BC instructions 



This reverts commit 6deaa3bb ("s390: extend expoline to BC
instructions"). Expolines to BC instructions were added to be utilized
by commit de5cb6eb ("s390: use expoline thunks in the BPF JIT"). But
corresponding code has been removed by commit e1cf4bef ("bpf, s390x:
remove ld_abs/ld_ind"). And compiler does not generate such expolines as
well.

Compared to regular expolines, expolines to BC instructions contain
displacement and all possible variations cannot be generated in advance,
making kpatch support more complicated. So, remove those to avoid
future usages.

Acked-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Acked-by: default avatarSumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 7d8484c4

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

+0 −57
Original line number Diff line number Diff line
@@ -35,18 +35,10 @@ _LC_BR_R1 = __LC_BR_R1 
	__THUNK_PROLOG_NAME __s390_indirect_jump_r\r2\()use_r\r1

	.endm



	.macro __THUNK_PROLOG_BC d0,r1,r2

	__THUNK_PROLOG_NAME __s390_indirect_branch_\d0\()_\r2\()use_\r1

	.endm



	.macro __THUNK_BR r1,r2

	jg	__s390_indirect_jump_r\r2\()use_r\r1

	.endm



	.macro __THUNK_BC d0,r1,r2

	jg	__s390_indirect_branch_\d0\()_\r2\()use_\r1

	.endm



	.macro __THUNK_BRASL r1,r2,r3

	brasl	\r1,__s390_indirect_jump_r\r3\()use_r\r2

	.endm
@@ -89,23 +81,6 @@ _LC_BR_R1 = __LC_BR_R1 
	.endif

	.endm



	.macro	__DECODE_DRR expand,disp,reg,ruse

	.set __decode_fail,1

	.irp r1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15

	.ifc \reg,%r\r1

	.irp r2,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15

	.ifc \ruse,%r\r2

	\expand \disp,\r1,\r2

	.set __decode_fail,0

	.endif

	.endr

	.endif

	.endr

	.if __decode_fail == 1

	.error "__DECODE_DRR failed"

	.endif

	.endm



	.macro __THUNK_EX_BR reg,ruse

	# Be very careful when adding instructions to this macro!

	# The ALTERNATIVE replacement code has a .+10 which targets
@@ -126,42 +101,17 @@ _LC_BR_R1 = __LC_BR_R1 
555:	br	\reg

	.endm



	.macro __THUNK_EX_BC disp,reg,ruse

#ifdef CONFIG_HAVE_MARCH_Z10_FEATURES

	exrl	0,556f

	j	.

#else

	larl	\ruse,556f

	ex	0,0(\ruse)

	j	.

#endif

556:	b	\disp(\reg)

	.endm



	.macro GEN_BR_THUNK reg,ruse=%r1

	__DECODE_RR __THUNK_PROLOG_BR,\reg,\ruse

	__THUNK_EX_BR \reg,\ruse

	__THUNK_EPILOG

	.endm



	.macro GEN_B_THUNK disp,reg,ruse=%r1

	__DECODE_DRR __THUNK_PROLOG_BC,\disp,\reg,\ruse

	__THUNK_EX_BC \disp,\reg,\ruse

	__THUNK_EPILOG

	.endm



	.macro BR_EX reg,ruse=%r1

557:	__DECODE_RR __THUNK_BR,\reg,\ruse

	.pushsection .s390_indirect_branches,"a",@progbits

	.long	557b-.

	.popsection

	.endm



	 .macro B_EX disp,reg,ruse=%r1

558:	__DECODE_DRR __THUNK_BC,\disp,\reg,\ruse

	.pushsection .s390_indirect_branches,"a",@progbits

	.long	558b-.

	.popsection

	.endm



	.macro BASR_EX rsave,rtarget,ruse=%r1
@@ -173,17 +123,10 @@ _LC_BR_R1 = __LC_BR_R1 


#else

	.macro GEN_BR_THUNK reg,ruse=%r1

	.endm



	.macro GEN_B_THUNK disp,reg,ruse=%r1

	.endm



	 .macro BR_EX reg,ruse=%r1

	br	\reg

	.endm



	 .macro B_EX disp,reg,ruse=%r1

	b	\disp(\reg)

	.endm



	.macro BASR_EX rsave,rtarget,ruse=%r1

arch/s390/kernel/nospec-branch.c

+5 −20
Original line number Diff line number Diff line
@@ -105,6 +105,7 @@ static void __init_or_module __nospec_revert(s32 *start, s32 *end) 
	s32 *epo;



	/* Second part of the instruction replace is always a nop */

	memcpy(insnbuf + 2, branch, sizeof(branch));

	for (epo = start; epo < end; epo++) {

		instr = (u8 *) epo + *epo;

		if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x04)
@@ -125,34 +126,18 @@ static void __init_or_module __nospec_revert(s32 *start, s32 *end) 
			br = thunk + (*(int *)(thunk + 2)) * 2;

		else

			continue;

		/* Check for unconditional branch 0x07f? or 0x47f???? */

		if ((br[0] & 0xbf) != 0x07 || (br[1] & 0xf0) != 0xf0)

		if (br[0] != 0x07 || (br[1] & 0xf0) != 0xf0)

			continue;



		memcpy(insnbuf + 2, branch, sizeof(branch));

		switch (type) {

		case BRCL_EXPOLINE:

			/* brcl to thunk, replace with br + nop */

			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 */

			/* brasl to thunk, replace with basr + nop */

			insnbuf[0] = 0x0d;

			}

			insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f);

			break;

		}