From 7f332f9fe9d854c1680fea223b6cb04530859a1a Mon Sep 17 00:00:00 2001 From: Ilya Leoshkevich Date: Mon, 19 May 2025 23:30:06 +0100 Subject: [PATCH] s390/bpf: Use kernel's expoline thunks Simplify the JIT code by replacing the custom expolines with the ones defined in the kernel text. Signed-off-by: Ilya Leoshkevich Link: https://lore.kernel.org/r/20250519223646.66382-4-iii@linux.ibm.com Signed-off-by: Alexei Starovoitov --- arch/s390/net/bpf_jit_comp.c | 61 ++++++++++-------------------------- 1 file changed, 17 insertions(+), 44 deletions(-) diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c index 70a93e03bfb3..c7f8313ba449 100644 --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -48,8 +48,6 @@ struct bpf_jit { int lit64; /* Current position in 64-bit literal pool */ int base_ip; /* Base address for literal pool */ int exit_ip; /* Address of exit */ - int r1_thunk_ip; /* Address of expoline thunk for 'br %r1' */ - int r14_thunk_ip; /* Address of expoline thunk for 'br %r14' */ int tail_call_start; /* Tail call start offset */ int excnt; /* Number of exception table entries */ int prologue_plt_ret; /* Return address for prologue hotpatch PLT */ @@ -642,28 +640,17 @@ static void bpf_jit_prologue(struct bpf_jit *jit, struct bpf_prog *fp, } /* - * Emit an expoline for a jump that follows + * Jump using a register either directly or via an expoline thunk */ -static void emit_expoline(struct bpf_jit *jit) -{ - /* exrl %r0,.+10 */ - EMIT6_PCREL_RIL(0xc6000000, jit->prg + 10); - /* j . */ - EMIT4_PCREL(0xa7f40000, 0); -} - -/* - * Emit __s390_indirect_jump_r1 thunk if necessary - */ -static void emit_r1_thunk(struct bpf_jit *jit) -{ - if (nospec_uses_trampoline()) { - jit->r1_thunk_ip = jit->prg; - emit_expoline(jit); - /* br %r1 */ - _EMIT2(0x07f1); - } -} +#define EMIT_JUMP_REG(reg) do { \ + if (nospec_uses_trampoline()) \ + /* brcl 0xf,__s390_indirect_jump_rN */ \ + EMIT6_PCREL_RILC_PTR(0xc0040000, 0x0f, \ + __s390_indirect_jump_r ## reg); \ + else \ + /* br %rN */ \ + _EMIT2(0x07f0 | reg); \ +} while (0) /* * Call r1 either directly or via __s390_indirect_jump_r1 thunk @@ -672,7 +659,8 @@ static void call_r1(struct bpf_jit *jit) { if (nospec_uses_trampoline()) /* brasl %r14,__s390_indirect_jump_r1 */ - EMIT6_PCREL_RILB(0xc0050000, REG_14, jit->r1_thunk_ip); + EMIT6_PCREL_RILB_PTR(0xc0050000, REG_14, + __s390_indirect_jump_r1); else /* basr %r14,%r1 */ EMIT2(0x0d00, REG_14, REG_1); @@ -688,16 +676,7 @@ static void bpf_jit_epilogue(struct bpf_jit *jit, u32 stack_depth) EMIT4(0xb9040000, REG_2, BPF_REG_0); /* Restore registers */ save_restore_regs(jit, REGS_RESTORE, stack_depth, 0); - if (nospec_uses_trampoline()) { - jit->r14_thunk_ip = jit->prg; - /* Generate __s390_indirect_jump_r14 thunk */ - emit_expoline(jit); - } - /* br %r14 */ - _EMIT2(0x07fe); - - if (is_first_pass(jit) || (jit->seen & SEEN_FUNC)) - emit_r1_thunk(jit); + EMIT_JUMP_REG(14); jit->prg = ALIGN(jit->prg, 8); jit->prologue_plt = jit->prg; @@ -1899,7 +1878,8 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, /* aghi %r1,tail_call_start */ EMIT4_IMM(0xa70b0000, REG_1, jit->tail_call_start); /* brcl 0xf,__s390_indirect_jump_r1 */ - EMIT6_PCREL_RILC(0xc0040000, 0xf, jit->r1_thunk_ip); + EMIT6_PCREL_RILC_PTR(0xc0040000, 0xf, + __s390_indirect_jump_r1); } else { /* bc 0xf,tail_call_start(%r1) */ _EMIT4(0x47f01000 + jit->tail_call_start); @@ -2868,17 +2848,10 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, 0xf000 | tjit->tccnt_off); /* aghi %r15,stack_size */ EMIT4_IMM(0xa70b0000, REG_15, tjit->stack_size); - /* Emit an expoline for the following indirect jump. */ - if (nospec_uses_trampoline()) - emit_expoline(jit); if (flags & BPF_TRAMP_F_SKIP_FRAME) - /* br %r14 */ - _EMIT2(0x07fe); + EMIT_JUMP_REG(14); else - /* br %r1 */ - _EMIT2(0x07f1); - - emit_r1_thunk(jit); + EMIT_JUMP_REG(1); return 0; } -- 2.50.1