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Message-ID: <20250805062747.3479221-3-skb99@linux.ibm.com>
Date: Tue, 5 Aug 2025 11:57:43 +0530
From: Saket Kumar Bhaskar <skb99@...ux.ibm.com>
To: bpf@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: hbathini@...ux.ibm.com, sachinpb@...ux.ibm.com, venkat88@...ux.ibm.com,
andrii@...nel.org, eddyz87@...il.com, mykolal@...com, ast@...nel.org,
daniel@...earbox.net, martin.lau@...ux.dev, song@...nel.org,
yonghong.song@...ux.dev, john.fastabend@...il.com, kpsingh@...nel.org,
sdf@...ichev.me, haoluo@...gle.com, jolsa@...nel.org,
christophe.leroy@...roup.eu, naveen@...nel.org, maddy@...ux.ibm.com,
mpe@...erman.id.au, npiggin@...il.com, memxor@...il.com,
iii@...ux.ibm.com, shuah@...nel.org
Subject: [bpf-next 2/6] bpf,powerpc: Implement PROBE_MEM32 pseudo instructions
Add support for [LDX | STX | ST], PROBE_MEM32, [B | H | W | DW]
instructions. They are similar to PROBE_MEM instructions with the
following differences:
- PROBE_MEM32 supports store.
- PROBE_MEM32 relies on the verifier to clear upper 32-bit of the
src/dst register
- PROBE_MEM32 adds 64-bit kern_vm_start address (which is stored in _R26
in the prologue). Due to bpf_arena constructions such _R26 + reg +
off16 access is guaranteed to be within arena virtual range, so no
address check at run-time.
- PROBE_MEM32 allows STX and ST. If they fault the store is a nop. When
LDX faults the destination register is zeroed.
To support these on powerpc, we do tmp1 = _R26 + src/dst reg and then use
tmp1 as the new src/dst register. This allows us to reuse most of the
code for normal [LDX | STX | ST].
Signed-off-by: Saket Kumar Bhaskar <skb99@...ux.ibm.com>
---
arch/powerpc/net/bpf_jit.h | 5 +-
arch/powerpc/net/bpf_jit_comp.c | 10 ++-
arch/powerpc/net/bpf_jit_comp32.c | 2 +-
arch/powerpc/net/bpf_jit_comp64.c | 108 ++++++++++++++++++++++++++++--
4 files changed, 114 insertions(+), 11 deletions(-)
diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
index 4c26912c2e3c..2d095a873305 100644
--- a/arch/powerpc/net/bpf_jit.h
+++ b/arch/powerpc/net/bpf_jit.h
@@ -161,9 +161,10 @@ struct codegen_context {
unsigned int seen;
unsigned int idx;
unsigned int stack_size;
- int b2p[MAX_BPF_JIT_REG + 2];
+ int b2p[MAX_BPF_JIT_REG + 3];
unsigned int exentry_idx;
unsigned int alt_exit_addr;
+ u64 arena_vm_start;
};
#define bpf_to_ppc(r) (ctx->b2p[r])
@@ -201,7 +202,7 @@ int bpf_jit_emit_exit_insn(u32 *image, struct codegen_context *ctx, int tmp_reg,
int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, u32 *fimage, int pass,
struct codegen_context *ctx, int insn_idx,
- int jmp_off, int dst_reg);
+ int jmp_off, int dst_reg, u32 code);
#endif
diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index c0684733e9d6..35bfdf4d8785 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -204,6 +204,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
/* Make sure that the stack is quadword aligned. */
cgctx.stack_size = round_up(fp->aux->stack_depth, 16);
+ cgctx.arena_vm_start = bpf_arena_get_kern_vm_start(fp->aux->arena);
/* Scouting faux-generate pass 0 */
if (bpf_jit_build_body(fp, NULL, NULL, &cgctx, addrs, 0, false)) {
@@ -326,7 +327,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
*/
int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, u32 *fimage, int pass,
struct codegen_context *ctx, int insn_idx, int jmp_off,
- int dst_reg)
+ int dst_reg, u32 code)
{
off_t offset;
unsigned long pc;
@@ -354,7 +355,12 @@ int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, u32 *fimage, int pass
(fp->aux->num_exentries * BPF_FIXUP_LEN * 4) +
(ctx->exentry_idx * BPF_FIXUP_LEN * 4);
- fixup[0] = PPC_RAW_LI(dst_reg, 0);
+ if ((BPF_CLASS(code) == BPF_LDX && BPF_MODE(code) == BPF_PROBE_MEM32) ||
+ (BPF_CLASS(code) == BPF_LDX && BPF_MODE(code) == BPF_PROBE_MEM))
+ fixup[0] = PPC_RAW_LI(dst_reg, 0);
+ else if (BPF_CLASS(code) == BPF_ST || BPF_CLASS(code) == BPF_STX)
+ fixup[0] = PPC_RAW_NOP();
+
if (IS_ENABLED(CONFIG_PPC32))
fixup[1] = PPC_RAW_LI(dst_reg - 1, 0); /* clear higher 32-bit register too */
diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
index 0aace304dfe1..3087e744fb25 100644
--- a/arch/powerpc/net/bpf_jit_comp32.c
+++ b/arch/powerpc/net/bpf_jit_comp32.c
@@ -1087,7 +1087,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
}
ret = bpf_add_extable_entry(fp, image, fimage, pass, ctx, insn_idx,
- jmp_off, dst_reg);
+ jmp_off, dst_reg, code);
if (ret)
return ret;
}
diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index 489de21fe3d6..16e62766c757 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -44,6 +44,7 @@
/* BPF register usage */
#define TMP_REG_1 (MAX_BPF_JIT_REG + 0)
#define TMP_REG_2 (MAX_BPF_JIT_REG + 1)
+#define ARENA_VM_START (MAX_BPF_JIT_REG + 2)
/* BPF to ppc register mappings */
void bpf_jit_init_reg_mapping(struct codegen_context *ctx)
@@ -61,6 +62,8 @@ void bpf_jit_init_reg_mapping(struct codegen_context *ctx)
ctx->b2p[BPF_REG_7] = _R28;
ctx->b2p[BPF_REG_8] = _R29;
ctx->b2p[BPF_REG_9] = _R30;
+ /* non volatile register for kern_vm_start address */
+ ctx->b2p[ARENA_VM_START] = _R26;
/* frame pointer aka BPF_REG_10 */
ctx->b2p[BPF_REG_FP] = _R31;
/* eBPF jit internal registers */
@@ -69,8 +72,8 @@ void bpf_jit_init_reg_mapping(struct codegen_context *ctx)
ctx->b2p[TMP_REG_2] = _R10;
}
-/* PPC NVR range -- update this if we ever use NVRs below r27 */
-#define BPF_PPC_NVR_MIN _R27
+/* PPC NVR range -- update this if we ever use NVRs below r26 */
+#define BPF_PPC_NVR_MIN _R26
static inline bool bpf_has_stack_frame(struct codegen_context *ctx)
{
@@ -170,10 +173,17 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
if (bpf_is_seen_register(ctx, bpf_to_ppc(i)))
EMIT(PPC_RAW_STD(bpf_to_ppc(i), _R1, bpf_jit_stack_offsetof(ctx, bpf_to_ppc(i))));
+ if (ctx->arena_vm_start)
+ EMIT(PPC_RAW_STD(bpf_to_ppc(ARENA_VM_START), _R1,
+ bpf_jit_stack_offsetof(ctx, bpf_to_ppc(ARENA_VM_START))));
+
/* Setup frame pointer to point to the bpf stack area */
if (bpf_is_seen_register(ctx, bpf_to_ppc(BPF_REG_FP)))
EMIT(PPC_RAW_ADDI(bpf_to_ppc(BPF_REG_FP), _R1,
STACK_FRAME_MIN_SIZE + ctx->stack_size));
+
+ if (ctx->arena_vm_start)
+ PPC_LI64(bpf_to_ppc(ARENA_VM_START), ctx->arena_vm_start);
}
static void bpf_jit_emit_common_epilogue(u32 *image, struct codegen_context *ctx)
@@ -185,6 +195,10 @@ static void bpf_jit_emit_common_epilogue(u32 *image, struct codegen_context *ctx
if (bpf_is_seen_register(ctx, bpf_to_ppc(i)))
EMIT(PPC_RAW_LD(bpf_to_ppc(i), _R1, bpf_jit_stack_offsetof(ctx, bpf_to_ppc(i))));
+ if (ctx->arena_vm_start)
+ EMIT(PPC_RAW_LD(bpf_to_ppc(ARENA_VM_START), _R1,
+ bpf_jit_stack_offsetof(ctx, bpf_to_ppc(ARENA_VM_START))));
+
/* Tear down our stack frame */
if (bpf_has_stack_frame(ctx)) {
EMIT(PPC_RAW_ADDI(_R1, _R1, BPF_PPC_STACKFRAME + ctx->stack_size));
@@ -990,6 +1004,50 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
}
break;
+ case BPF_STX | BPF_PROBE_MEM32 | BPF_B:
+ case BPF_STX | BPF_PROBE_MEM32 | BPF_H:
+ case BPF_STX | BPF_PROBE_MEM32 | BPF_W:
+ case BPF_STX | BPF_PROBE_MEM32 | BPF_DW:
+
+ EMIT(PPC_RAW_ADD(tmp1_reg, dst_reg, bpf_to_ppc(ARENA_VM_START)));
+
+ ret = bpf_jit_emit_probe_mem_store(ctx, src_reg, off, code, image);
+ if (ret)
+ return ret;
+
+ ret = bpf_add_extable_entry(fp, image, fimage, pass, ctx,
+ ctx->idx - 1, 4, -1, code);
+ if (ret)
+ return ret;
+
+ break;
+
+ case BPF_ST | BPF_PROBE_MEM32 | BPF_B:
+ case BPF_ST | BPF_PROBE_MEM32 | BPF_H:
+ case BPF_ST | BPF_PROBE_MEM32 | BPF_W:
+ case BPF_ST | BPF_PROBE_MEM32 | BPF_DW:
+
+ EMIT(PPC_RAW_ADD(tmp1_reg, dst_reg, bpf_to_ppc(ARENA_VM_START)));
+
+ if (BPF_SIZE(code) == BPF_W || BPF_SIZE(code) == BPF_DW) {
+ PPC_LI32(tmp2_reg, imm);
+ src_reg = tmp2_reg;
+ } else {
+ EMIT(PPC_RAW_LI(tmp2_reg, imm));
+ src_reg = tmp2_reg;
+ }
+
+ ret = bpf_jit_emit_probe_mem_store(ctx, src_reg, off, code, image);
+ if (ret)
+ return ret;
+
+ ret = bpf_add_extable_entry(fp, image, fimage, pass, ctx,
+ ctx->idx - 1, 4, -1, code);
+ if (ret)
+ return ret;
+
+ break;
+
/*
* BPF_STX ATOMIC (atomic ops)
*/
@@ -1142,9 +1200,10 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
* Check if 'off' is word aligned for BPF_DW, because
* we might generate two instructions.
*/
- if ((BPF_SIZE(code) == BPF_DW ||
- (BPF_SIZE(code) == BPF_B && BPF_MODE(code) == BPF_PROBE_MEMSX)) &&
- (off & 3))
+ if ((BPF_SIZE(code) == BPF_DW && (off & 3)) ||
+ (BPF_SIZE(code) == BPF_B &&
+ BPF_MODE(code) == BPF_PROBE_MEMSX) ||
+ (BPF_SIZE(code) == BPF_B && BPF_MODE(code) == BPF_MEMSX))
PPC_JMP((ctx->idx + 3) * 4);
else
PPC_JMP((ctx->idx + 2) * 4);
@@ -1190,12 +1249,49 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
if (BPF_MODE(code) == BPF_PROBE_MEM) {
ret = bpf_add_extable_entry(fp, image, fimage, pass, ctx,
- ctx->idx - 1, 4, dst_reg);
+ ctx->idx - 1, 4, dst_reg, code);
if (ret)
return ret;
}
break;
+ /* dst = *(u64 *)(ul) (src + ARENA_VM_START + off) */
+ case BPF_LDX | BPF_PROBE_MEM32 | BPF_B:
+ case BPF_LDX | BPF_PROBE_MEM32 | BPF_H:
+ case BPF_LDX | BPF_PROBE_MEM32 | BPF_W:
+ case BPF_LDX | BPF_PROBE_MEM32 | BPF_DW:
+
+ EMIT(PPC_RAW_ADD(tmp1_reg, src_reg, bpf_to_ppc(ARENA_VM_START)));
+
+ switch (size) {
+ case BPF_B:
+ EMIT(PPC_RAW_LBZ(dst_reg, tmp1_reg, off));
+ break;
+ case BPF_H:
+ EMIT(PPC_RAW_LHZ(dst_reg, tmp1_reg, off));
+ break;
+ case BPF_W:
+ EMIT(PPC_RAW_LWZ(dst_reg, tmp1_reg, off));
+ break;
+ case BPF_DW:
+ if (off % 4) {
+ EMIT(PPC_RAW_LI(tmp2_reg, off));
+ EMIT(PPC_RAW_LDX(dst_reg, tmp1_reg, tmp2_reg));
+ } else {
+ EMIT(PPC_RAW_LD(dst_reg, tmp1_reg, off));
+ }
+ break;
+ }
+
+ if (size != BPF_DW && insn_is_zext(&insn[i + 1]))
+ addrs[++i] = ctx->idx * 4;
+
+ ret = bpf_add_extable_entry(fp, image, fimage, pass, ctx,
+ ctx->idx - 1, 4, dst_reg, code);
+ if (ret)
+ return ret;
+ break;
+
/*
* Doubleword load
* 16 byte instruction that uses two 'struct bpf_insn'
--
2.43.5
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