4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
[ Upstream commit 6deaa3bbca804b2a3627fd685f75de64da7be535 ]
The BPF JIT uses a 'b <disp>(%r<x>)' instruction in the definition
of the sk_load_word and sk_load_half functions.
Add support for branch-on-condition instructions contained in the
thunk code of an expoline.
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/s390/include/asm/nospec-insn.h | 57 ++++++++++++++++++++++++++++++++++++
arch/s390/kernel/nospec-branch.c | 25 ++++++++++++---
2 files changed, 77 insertions(+), 5 deletions(-)
--- a/arch/s390/include/asm/nospec-insn.h
+++ b/arch/s390/include/asm/nospec-insn.h
@@ -32,10 +32,18 @@
__THUNK_PROLOG_NAME __s390x_indirect_jump_r\r2\()use_r\r1
.endm
+ .macro __THUNK_PROLOG_BC d0,r1,r2
+ __THUNK_PROLOG_NAME __s390x_indirect_branch_\d0\()_\r2\()use_\r1
+ .endm
+
.macro __THUNK_BR r1,r2
jg __s390x_indirect_jump_r\r2\()use_r\r1
.endm
+ .macro __THUNK_BC d0,r1,r2
+ jg __s390x_indirect_branch_\d0\()_\r2\()use_\r1
+ .endm
+
.macro __THUNK_BRASL r1,r2,r3
brasl \r1,__s390x_indirect_jump_r\r3\()use_r\r2
.endm
@@ -78,6 +86,23 @@
.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
@@ -98,12 +123,30 @@
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
@@ -111,6 +154,13 @@
.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
559: __DECODE_RRR __THUNK_BRASL,\rsave,\rtarget,\ruse
.pushsection .s390_indirect_branches,"a",@progbits
@@ -122,10 +172,17 @@
.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
basr \rsave,\rtarget
.endm
--- a/arch/s390/kernel/nospec-branch.c
+++ b/arch/s390/kernel/nospec-branch.c
@@ -94,7 +94,6 @@ static void __init_or_module __nospec_re
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)
@@ -115,18 +114,34 @@ static void __init_or_module __nospec_re
br = thunk + (*(int *)(thunk + 2)) * 2;
else
continue;
- if (br[0] != 0x07 || (br[1] & 0xf0) != 0xf0)
+ /* Check for unconditional branch 0x07f? or 0x47f???? */
+ if ((br[0] & 0xbf) != 0x07 || (br[1] & 0xf0) != 0xf0)
continue;
+
+ memcpy(insnbuf + 2, (char[]) { 0x47, 0x00, 0x07, 0x00 }, 4);
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:
- /* brasl to thunk, replace with basr + nop */
- insnbuf[0] = 0x0d;
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 */
+ insnbuf[0] = 0x0d;
+ }
break;
}
