github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-28 09:04:39 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

s390/bpf: Use kernel's expoline thunks

Browse Source 
Simplify the JIT code by replacing the custom expolines with the ones
defined in the kernel text.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20250519223646.66382-4-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Ilya Leoshkevich 2025-05-19 23:30:06 +01:00 committed by Alexei Starovoitov
parent 9053ba042f
commit 7f332f9fe9
1 changed files with 17 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

61
arch/s390/net/bpf_jit_comp.c
View File

@ -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;
}