From: Pu Lehui <pulehui@xxxxxxxxxx>
Implement bpf_arch_text_poke for RV64. For call scenario,
to make bpf trampoline compatible with the kernel and bpf
context, we follow the framework of RV64 ftrace to reserve
4 nops for bpf programs as function entry, and use auipc+jalr
instructions for function call. However, since auipc+jalr
call instruction is non-atomic operation, we need to use
stop-machine to make sure instructions patching in atomic
context. Also, we use auipc+jalr pair and need to patch
in stop-machine context for jump scenario.
Signed-off-by: Pu Lehui <pulehui@xxxxxxxxxx>
---
arch/riscv/net/bpf_jit.h | 5 ++
arch/riscv/net/bpf_jit_comp64.c | 88 ++++++++++++++++++++++++++++++++-
2 files changed, 91 insertions(+), 2 deletions(-)
diff --git a/arch/riscv/net/bpf_jit.h b/arch/riscv/net/bpf_jit.h
index d926e0f7ef57..bf9802a63061 100644
--- a/arch/riscv/net/bpf_jit.h
+++ b/arch/riscv/net/bpf_jit.h
@@ -573,6 +573,11 @@ static inline u32 rv_fence(u8 pred, u8 succ)
return rv_i_insn(imm11_0, 0, 0, 0, 0xf);
}
+static inline u32 rv_nop(void)
+{
+ return rv_i_insn(0, 0, 0, 0, 0x13);
+}
+
/* RVC instrutions. */
static inline u16 rvc_addi4spn(u8 rd, u32 imm10)
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 69ebab81d935..b6b9bbcc977a 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -8,6 +8,8 @@
#include <linux/bitfield.h>
#include <linux/bpf.h>
#include <linux/filter.h>
+#include <linux/memory.h>
+#include <linux/stop_machine.h>
#include "bpf_jit.h"
#define RV_REG_TCC RV_REG_A6
@@ -238,7 +240,7 @@ static void __build_epilogue(bool is_tail_call, struct rv_jit_context *ctx)
if (!is_tail_call)
emit_mv(RV_REG_A0, RV_REG_A5, ctx);
emit_jalr(RV_REG_ZERO, is_tail_call ? RV_REG_T3 : RV_REG_RA,
- is_tail_call ? 4 : 0, /* skip TCC init */
+ is_tail_call ? 20 : 0, /* skip reserved nops and TCC init */
ctx);
}
@@ -615,6 +617,84 @@ static int add_exception_handler(const struct bpf_insn *insn,
return 0;
}
+static int gen_call_or_nops(void *target, void *ip, u32 *insns)
+{
+ s64 rvoff;
+ int i, ret;
+ struct rv_jit_context ctx;
+
+ ctx.ninsns = 0;
+ ctx.insns = (u16 *)insns;
+
+ if (!target) {
+ for (i = 0; i < 4; i++)
+ emit(rv_nop(), &ctx);
+ return 0;
+ }
+
+ rvoff = (s64)(target - (ip + 4));
+ emit(rv_sd(RV_REG_SP, -8, RV_REG_RA), &ctx);
+ ret = emit_jump_and_link(RV_REG_RA, rvoff, false, &ctx);
+ if (ret)
+ return ret;
+ emit(rv_ld(RV_REG_RA, -8, RV_REG_SP), &ctx);
+
+ return 0;
+}
+
+static int gen_jump_or_nops(void *target, void *ip, u32 *insns)
+{
+ s64 rvoff;
+ struct rv_jit_context ctx;
+
+ ctx.ninsns = 0;
+ ctx.insns = (u16 *)insns;
+
+ if (!target) {
+ emit(rv_nop(), &ctx);
+ emit(rv_nop(), &ctx);
+ return 0;
+ }
+
+ rvoff = (s64)(target - ip);
+ return emit_jump_and_link(RV_REG_ZERO, rvoff, false, &ctx);
+}
+
+int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
+ void *old_addr, void *new_addr)
+{
+ u32 old_insns[4], new_insns[4];
+ bool is_call = poke_type == BPF_MOD_CALL;
+ int (*gen_insns)(void *target, void *ip, u32 *insns);
+ int ninsns = is_call ? 4 : 2;
+ int ret;
+
+ if (!is_bpf_text_address((unsigned long)ip))
+ return -ENOTSUPP;
+
+ gen_insns = is_call ? gen_call_or_nops : gen_jump_or_nops;
+
+ ret = gen_insns(old_addr, ip, old_insns);
+ if (ret)
+ return ret;
+
+ if (memcmp(ip, old_insns, ninsns * 4))
+ return -EFAULT;
+
+ ret = gen_insns(new_addr, ip, new_insns);
+ if (ret)
+ return ret;
+
+ cpus_read_lock();
+ mutex_lock(&text_mutex);
+ if (memcmp(ip, new_insns, ninsns * 4))
+ ret = patch_text(ip, new_insns, ninsns);
+ mutex_unlock(&text_mutex);
+ cpus_read_unlock();
+
+ return ret;
+}
+
int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
bool extra_pass)
{
@@ -1266,7 +1346,7 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
void bpf_jit_build_prologue(struct rv_jit_context *ctx)
{
- int stack_adjust = 0, store_offset, bpf_stack_adjust;
+ int i, stack_adjust = 0, store_offset, bpf_stack_adjust;
bpf_stack_adjust = round_up(ctx->prog->aux->stack_depth, 16);
if (bpf_stack_adjust)
@@ -1293,6 +1373,10 @@ void bpf_jit_build_prologue(struct rv_jit_context *ctx)
store_offset = stack_adjust - 8;
+ /* reserve 4 nop insns */
+ for (i = 0; i < 4; i++)
+ emit(rv_nop(), ctx);
+
/* First instruction is always setting the tail-call-counter
* (TCC) register. This instruction is skipped for tail calls.
* Force using a 4-byte (non-compressed) instruction.
--
2.25.1
