4.4-stable review patch. If anyone has any objections, please let me know.
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From: Martin Schwidefsky schwidefsky@de.ibm.com
[ 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@de.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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; }