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powerpc/bpf: Reallocate BPF registers to volatile registers when poss…
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…ible on PPC64

Implement commit 4027203 ("powerpc/bpf: Reallocate BPF registers to
volatile registers when possible on PPC32") for PPC64.

When the BPF routine doesn't call any function, the non volatile
registers can be reallocated to volatile registers in order to avoid
having to save them/restore on the stack. To keep track of which
registers can be reallocated to make sure registers are set seen when
used.

Before this patch, the test torvalds#359 ADD default X is:
   0:   nop
   4:   nop
   8:   std     r27,-40(r1)
   c:   std     r28,-32(r1)
  10:   xor     r8,r8,r8
  14:   rotlwi  r8,r8,0
  18:   xor     r28,r28,r28
  1c:   rotlwi  r28,r28,0
  20:   mr      r27,r3
  24:   li      r8,66
  28:   add     r8,r8,r28
  2c:   rotlwi  r8,r8,0
  30:   ld      r27,-40(r1)
  34:   ld      r28,-32(r1)
  38:   mr      r3,r8
  3c:   blr

After this patch, the same test has become:
   0:   nop
   4:   nop
   8:   xor     r8,r8,r8
   c:   rotlwi  r8,r8,0
  10:   xor     r5,r5,r5
  14:   rotlwi  r5,r5,0
  18:   mr      r4,r3
  1c:   li      r8,66
  20:   add     r8,r8,r5
  24:   rotlwi  r8,r8,0
  28:   mr      r3,r8
  2c:   blr

Signed-off-by: Jordan Niethe <[email protected]>
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@iamjpn @intel-lab-lkp
iamjpn authored and intel-lab-lkp committed Jul 27, 2021
1 parent 283acec commit 8e40280
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Showing 2 changed files with 52 additions and 10 deletions.
2 changes: 2 additions & 0 deletions arch/powerpc/net/bpf_jit64.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -70,6 +70,7 @@ const int b2p[MAX_BPF_JIT_REG + 2] = {
*/
#define PPC_BPF_LL(ctx, r, base, i) do { \
if ((i) % 4) { \
bpf_set_seen_register(ctx, bpf_to_ppc(ctx, TMP_REG_2));\
EMIT(PPC_RAW_LI(bpf_to_ppc(ctx, TMP_REG_2), (i)));\
EMIT(PPC_RAW_LDX(r, base, \
bpf_to_ppc(ctx, TMP_REG_2))); \
Expand All @@ -78,6 +79,7 @@ const int b2p[MAX_BPF_JIT_REG + 2] = {
} while(0)
#define PPC_BPF_STL(ctx, r, base, i) do { \
if ((i) % 4) { \
bpf_set_seen_register(ctx, bpf_to_ppc(ctx, TMP_REG_2));\
EMIT(PPC_RAW_LI(bpf_to_ppc(ctx, TMP_REG_2), (i)));\
EMIT(PPC_RAW_STDX(r, base, \
bpf_to_ppc(ctx, TMP_REG_2))); \
Expand Down
60 changes: 50 additions & 10 deletions arch/powerpc/net/bpf_jit_comp64.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,24 @@ static int bpf_jit_stack_offsetof(struct codegen_context *ctx, int reg)

void bpf_jit_realloc_regs(struct codegen_context *ctx)
{
if (ctx->seen & SEEN_FUNC)
return;

while (ctx->seen & SEEN_NVREG_MASK &&
(ctx->seen & SEEN_VREG_MASK) != SEEN_VREG_MASK) {
int old = 32 - fls(ctx->seen & SEEN_NVREG_MASK);
int new = 32 - fls(~ctx->seen & SEEN_VREG_MASK);
int i;

for (i = BPF_REG_0; i <= TMP_REG_2; i++) {
if (ctx->b2p[i] != old)
continue;
ctx->b2p[i] = new;
bpf_set_seen_register(ctx, new);
bpf_clear_seen_register(ctx, old);
break;
}
}
}

void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
Expand Down Expand Up @@ -106,10 +124,9 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
* If we haven't created our own stack frame, we save these
* in the protected zone below the previous stack frame
*/
for (i = BPF_REG_6; i <= BPF_REG_10; i++)
if (bpf_is_seen_register(ctx, bpf_to_ppc(ctx, i)))
PPC_BPF_STL(ctx, bpf_to_ppc(ctx, i), 1,
bpf_jit_stack_offsetof(ctx, bpf_to_ppc(ctx, i)));
for (i = BPF_PPC_NVR_MIN; i <= 31; i++)
if (bpf_is_seen_register(ctx, i))
PPC_BPF_STL(ctx, i, 1, bpf_jit_stack_offsetof(ctx, i));

/* Setup frame pointer to point to the bpf stack area */
if (bpf_is_seen_register(ctx, bpf_to_ppc(ctx, BPF_REG_FP)))
Expand All @@ -122,10 +139,9 @@ static void bpf_jit_emit_common_epilogue(u32 *image, struct codegen_context *ctx
int i;

/* Restore NVRs */
for (i = BPF_REG_6; i <= BPF_REG_10; i++)
if (bpf_is_seen_register(ctx, bpf_to_ppc(ctx, i)))
PPC_BPF_LL(ctx, bpf_to_ppc(ctx, i), 1,
bpf_jit_stack_offsetof(ctx, bpf_to_ppc(ctx, i)));
for (i = BPF_PPC_NVR_MIN; i <= 31; i++)
if (bpf_is_seen_register(ctx, i))
PPC_BPF_LL(ctx, i, 1, bpf_jit_stack_offsetof(ctx, i));

/* Tear down our stack frame */
if (bpf_has_stack_frame(ctx)) {
Expand Down Expand Up @@ -223,6 +239,7 @@ static void bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32
* if (index >= array->map.max_entries)
* goto out;
*/
bpf_set_seen_register(ctx, bpf_to_ppc(ctx, TMP_REG_1));
EMIT(PPC_RAW_LWZ(bpf_to_ppc(ctx, TMP_REG_1), b2p_bpf_array,
offsetof(struct bpf_array, map.max_entries)));
EMIT(PPC_RAW_RLWINM(b2p_index, b2p_index, 0, 0, 31));
Expand Down Expand Up @@ -318,9 +335,9 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
* optimization but everything else should work without
* any issues.
*/
if (dst_reg >= BPF_PPC_NVR_MIN && dst_reg < 32)
if (dst_reg >= 3 && dst_reg < 32)
bpf_set_seen_register(ctx, dst_reg);
if (src_reg >= BPF_PPC_NVR_MIN && src_reg < 32)
if (src_reg >= 3 && src_reg < 32)
bpf_set_seen_register(ctx, src_reg);

switch (code) {
Expand All @@ -345,6 +362,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
if (imm >= -32768 && imm < 32768)
EMIT(PPC_RAW_ADDI(dst_reg, dst_reg, IMM_L(imm)));
else {
bpf_set_seen_register(ctx, tmp1_reg);
PPC_LI32(tmp1_reg, imm);
EMIT(PPC_RAW_ADD(dst_reg, dst_reg, tmp1_reg));
}
Expand All @@ -362,6 +380,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
if (imm >= -32768 && imm < 32768)
EMIT(PPC_RAW_MULI(dst_reg, dst_reg, IMM_L(imm)));
else {
bpf_set_seen_register(ctx, tmp1_reg);
PPC_LI32(tmp1_reg, imm);
if (BPF_CLASS(code) == BPF_ALU)
EMIT(PPC_RAW_MULW(dst_reg, dst_reg, tmp1_reg));
Expand All @@ -372,6 +391,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
case BPF_ALU | BPF_DIV | BPF_X: /* (u32) dst /= (u32) src */
case BPF_ALU | BPF_MOD | BPF_X: /* (u32) dst %= (u32) src */
if (BPF_OP(code) == BPF_MOD) {
bpf_set_seen_register(ctx, tmp1_reg);
EMIT(PPC_RAW_DIVWU(tmp1_reg, dst_reg, src_reg));
EMIT(PPC_RAW_MULW(tmp1_reg, src_reg, tmp1_reg));
EMIT(PPC_RAW_SUB(dst_reg, dst_reg, tmp1_reg));
Expand All @@ -381,6 +401,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
case BPF_ALU64 | BPF_DIV | BPF_X: /* dst /= src */
case BPF_ALU64 | BPF_MOD | BPF_X: /* dst %= src */
if (BPF_OP(code) == BPF_MOD) {
bpf_set_seen_register(ctx, tmp1_reg);
EMIT(PPC_RAW_DIVDU(tmp1_reg, dst_reg, src_reg));
EMIT(PPC_RAW_MULD(tmp1_reg, src_reg, tmp1_reg));
EMIT(PPC_RAW_SUB(dst_reg, dst_reg, tmp1_reg));
Expand All @@ -396,10 +417,12 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
else if (imm == 1)
goto bpf_alu32_trunc;

bpf_set_seen_register(ctx, tmp1_reg);
PPC_LI32(tmp1_reg, imm);
switch (BPF_CLASS(code)) {
case BPF_ALU:
if (BPF_OP(code) == BPF_MOD) {
bpf_set_seen_register(ctx, tmp2_reg);
EMIT(PPC_RAW_DIVWU(tmp2_reg, dst_reg, tmp1_reg));
EMIT(PPC_RAW_MULW(tmp1_reg, tmp1_reg, tmp2_reg));
EMIT(PPC_RAW_SUB(dst_reg, dst_reg, tmp1_reg));
Expand All @@ -408,6 +431,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
break;
case BPF_ALU64:
if (BPF_OP(code) == BPF_MOD) {
bpf_set_seen_register(ctx, tmp2_reg);
EMIT(PPC_RAW_DIVDU(tmp2_reg, dst_reg, tmp1_reg));
EMIT(PPC_RAW_MULD(tmp1_reg, tmp1_reg, tmp2_reg));
EMIT(PPC_RAW_SUB(dst_reg, dst_reg, tmp1_reg));
Expand All @@ -434,6 +458,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
EMIT(PPC_RAW_ANDI(dst_reg, dst_reg, IMM_L(imm)));
else {
/* Sign-extended */
bpf_set_seen_register(ctx, tmp1_reg);
PPC_LI32(tmp1_reg, imm);
EMIT(PPC_RAW_AND(dst_reg, dst_reg, tmp1_reg));
}
Expand All @@ -446,6 +471,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
case BPF_ALU64 | BPF_OR | BPF_K:/* dst = dst | imm */
if (imm < 0 && BPF_CLASS(code) == BPF_ALU64) {
/* Sign-extended */
bpf_set_seen_register(ctx, tmp1_reg);
PPC_LI32(tmp1_reg, imm);
EMIT(PPC_RAW_OR(dst_reg, dst_reg, tmp1_reg));
} else {
Expand All @@ -463,6 +489,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
case BPF_ALU64 | BPF_XOR | BPF_K: /* dst ^= imm */
if (imm < 0 && BPF_CLASS(code) == BPF_ALU64) {
/* Sign-extended */
bpf_set_seen_register(ctx, tmp1_reg);
PPC_LI32(tmp1_reg, imm);
EMIT(PPC_RAW_XOR(dst_reg, dst_reg, tmp1_reg));
} else {
Expand Down Expand Up @@ -562,6 +589,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
if (BPF_SRC(code) == BPF_FROM_LE)
goto emit_clear;
#endif
bpf_set_seen_register(ctx, tmp1_reg);
switch (imm) {
case 16:
/* Rotate 8 bits left & mask with 0x0000ff00 */
Expand Down Expand Up @@ -625,6 +653,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
case BPF_STX | BPF_MEM | BPF_B: /* *(u8 *)(dst + off) = src */
case BPF_ST | BPF_MEM | BPF_B: /* *(u8 *)(dst + off) = imm */
if (BPF_CLASS(code) == BPF_ST) {
bpf_set_seen_register(ctx, tmp1_reg);
EMIT(PPC_RAW_LI(tmp1_reg, imm));
src_reg = tmp1_reg;
}
Expand All @@ -633,6 +662,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
case BPF_STX | BPF_MEM | BPF_H: /* (u16 *)(dst + off) = src */
case BPF_ST | BPF_MEM | BPF_H: /* (u16 *)(dst + off) = imm */
if (BPF_CLASS(code) == BPF_ST) {
bpf_set_seen_register(ctx, tmp1_reg);
EMIT(PPC_RAW_LI(tmp1_reg, imm));
src_reg = tmp1_reg;
}
Expand All @@ -641,6 +671,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
case BPF_STX | BPF_MEM | BPF_W: /* *(u32 *)(dst + off) = src */
case BPF_ST | BPF_MEM | BPF_W: /* *(u32 *)(dst + off) = imm */
if (BPF_CLASS(code) == BPF_ST) {
bpf_set_seen_register(ctx, tmp1_reg);
PPC_LI32(tmp1_reg, imm);
src_reg = tmp1_reg;
}
Expand All @@ -649,6 +680,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
case BPF_STX | BPF_MEM | BPF_DW: /* (u64 *)(dst + off) = src */
case BPF_ST | BPF_MEM | BPF_DW: /* *(u64 *)(dst + off) = imm */
if (BPF_CLASS(code) == BPF_ST) {
bpf_set_seen_register(ctx, tmp1_reg);
PPC_LI32(tmp1_reg, imm);
src_reg = tmp1_reg;
}
Expand All @@ -669,6 +701,8 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
/* *(u32 *)(dst + off) += src */

/* Get EA into TMP_REG_1 */
bpf_set_seen_register(ctx, tmp1_reg);
bpf_set_seen_register(ctx, tmp2_reg);
EMIT(PPC_RAW_ADDI(tmp1_reg, dst_reg, off));
tmp_idx = ctx->idx * 4;
/* load value from memory into TMP_REG_2 */
Expand All @@ -689,6 +723,8 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
}
/* *(u64 *)(dst + off) += src */

bpf_set_seen_register(ctx, tmp1_reg);
bpf_set_seen_register(ctx, tmp2_reg);
EMIT(PPC_RAW_ADDI(tmp1_reg, dst_reg, off));
tmp_idx = ctx->idx * 4;
EMIT(PPC_RAW_LDARX(tmp2_reg, 0, tmp1_reg, 0));
Expand Down Expand Up @@ -870,6 +906,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
break;
case BPF_JMP | BPF_JSET | BPF_X:
case BPF_JMP32 | BPF_JSET | BPF_X:
bpf_set_seen_register(ctx, tmp1_reg);
if (BPF_CLASS(code) == BPF_JMP) {
EMIT(PPC_RAW_AND_DOT(tmp1_reg, dst_reg, src_reg));
} else {
Expand Down Expand Up @@ -903,6 +940,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
EMIT(PPC_RAW_CMPLDI(dst_reg, imm));
} else {
/* sign-extending load */
bpf_set_seen_register(ctx, tmp1_reg);
PPC_LI32(tmp1_reg, imm);
/* ... but unsigned comparison */
if (is_jmp32)
Expand Down Expand Up @@ -933,6 +971,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
else
EMIT(PPC_RAW_CMPDI(dst_reg, imm));
} else {
bpf_set_seen_register(ctx, tmp1_reg);
PPC_LI32(tmp1_reg, imm);
if (is_jmp32)
EMIT(PPC_RAW_CMPW(dst_reg, tmp1_reg));
Expand All @@ -944,6 +983,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
case BPF_JMP | BPF_JSET | BPF_K:
case BPF_JMP32 | BPF_JSET | BPF_K:
/* andi does not sign-extend the immediate */
bpf_set_seen_register(ctx, tmp1_reg);
if (imm >= 0 && imm < 32768)
/* PPC_ANDI is _only/always_ dot-form */
EMIT(PPC_RAW_ANDI(tmp1_reg, dst_reg, imm));
Expand Down

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