[PATCH bpf-next v2 1/2] riscv, bpf: Add 12-argument support for RV64 bpf trampoline
Pu Lehui
pulehui at huaweicloud.com
Tue Apr 2 21:17:09 PDT 2024
From: Pu Lehui <pulehui at huawei.com>
This patch adds 12 function arguments support for riscv64 bpf
trampoline. The current bpf trampoline supports <= sizeof(u64) bytes
scalar arguments [0] and <= 16 bytes struct arguments [1]. Therefore, we
focus on the situation where scalars are at most XLEN bits and
aggregates whose total size does not exceed 2×XLEN bits in the riscv
calling convention [2].
Link: https://elixir.bootlin.com/linux/v6.8/source/kernel/bpf/btf.c#L6184 [0]
Link: https://elixir.bootlin.com/linux/v6.8/source/kernel/bpf/btf.c#L6769 [1]
Link: https://github.com/riscv-non-isa/riscv-elf-psabi-doc/releases/download/draft-20230929-e5c800e661a53efe3c2678d71a306323b60eb13b/riscv-abi.pdf [2]
Signed-off-by: Pu Lehui <pulehui at huawei.com>
Acked-by: Björn Töpel <bjorn at kernel.org>
Reviewed-by: Björn Töpel <bjorn at rivosinc.com>
---
arch/riscv/net/bpf_jit_comp64.c | 65 +++++++++++++++++++++++----------
1 file changed, 46 insertions(+), 19 deletions(-)
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 77ea306452d4..7e2d6e8c60c2 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -14,6 +14,7 @@
#include <asm/cfi.h>
#include "bpf_jit.h"
+#define RV_MAX_ARGS_REG 8
#define RV_FENTRY_NINSNS 2
#define RV_REG_TCC RV_REG_A6
@@ -688,26 +689,44 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
return ret;
}
-static void store_args(int nregs, int args_off, struct rv_jit_context *ctx)
+static void store_args(int nr_arg_slots, int args_off, struct rv_jit_context *ctx)
{
int i;
- for (i = 0; i < nregs; i++) {
- emit_sd(RV_REG_FP, -args_off, RV_REG_A0 + i, ctx);
+ for (i = 0; i < nr_arg_slots; i++) {
+ if (i < RV_MAX_ARGS_REG) {
+ emit_sd(RV_REG_FP, -args_off, RV_REG_A0 + i, ctx);
+ } else {
+ /* skip slots for T0 and FP of traced function */
+ emit_ld(RV_REG_T1, 16 + (i - RV_MAX_ARGS_REG) * 8, RV_REG_FP, ctx);
+ emit_sd(RV_REG_FP, -args_off, RV_REG_T1, ctx);
+ }
args_off -= 8;
}
}
-static void restore_args(int nregs, int args_off, struct rv_jit_context *ctx)
+static void restore_args(int nr_args_reg, int args_off, struct rv_jit_context *ctx)
{
int i;
- for (i = 0; i < nregs; i++) {
+ for (i = 0; i < nr_args_reg; i++) {
emit_ld(RV_REG_A0 + i, -args_off, RV_REG_FP, ctx);
args_off -= 8;
}
}
+static void restore_stack_args(int nr_args_stack, int args_off, int stk_arg_off, struct rv_jit_context *ctx)
+{
+ int i;
+
+ for (i = 0; i < nr_args_stack; i++) {
+ emit_ld(RV_REG_T1, -(args_off - RV_MAX_ARGS_REG * 8), RV_REG_FP, ctx);
+ emit_sd(RV_REG_FP, -stk_arg_off, RV_REG_T1, ctx);
+ args_off -= 8;
+ stk_arg_off -= 8;
+ }
+}
+
static int invoke_bpf_prog(struct bpf_tramp_link *l, int args_off, int retval_off,
int run_ctx_off, bool save_ret, struct rv_jit_context *ctx)
{
@@ -780,8 +799,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
{
int i, ret, offset;
int *branches_off = NULL;
- int stack_size = 0, nregs = m->nr_args;
- int retval_off, args_off, nregs_off, ip_off, run_ctx_off, sreg_off;
+ int stack_size = 0, nr_arg_slots = 0;
+ int retval_off, args_off, nregs_off, ip_off, run_ctx_off, sreg_off, stk_arg_off;
struct bpf_tramp_links *fentry = &tlinks[BPF_TRAMP_FENTRY];
struct bpf_tramp_links *fexit = &tlinks[BPF_TRAMP_FEXIT];
struct bpf_tramp_links *fmod_ret = &tlinks[BPF_TRAMP_MODIFY_RETURN];
@@ -827,20 +846,21 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
* FP - sreg_off [ callee saved reg ]
*
* [ pads ] pads for 16 bytes alignment
+ *
+ * [ stack_argN ]
+ * [ ... ]
+ * FP - stk_arg_off [ stack_arg1 ] BPF_TRAMP_F_CALL_ORIG
*/
if (flags & (BPF_TRAMP_F_ORIG_STACK | BPF_TRAMP_F_SHARE_IPMODIFY))
return -ENOTSUPP;
- /* extra regiters for struct arguments */
- for (i = 0; i < m->nr_args; i++)
- if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG)
- nregs += round_up(m->arg_size[i], 8) / 8 - 1;
-
- /* 8 arguments passed by registers */
- if (nregs > 8)
+ if (m->nr_args > MAX_BPF_FUNC_ARGS)
return -ENOTSUPP;
+ for (i = 0; i < m->nr_args; i++)
+ nr_arg_slots += round_up(m->arg_size[i], 8) / 8;
+
/* room of trampoline frame to store return address and frame pointer */
stack_size += 16;
@@ -850,7 +870,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
retval_off = stack_size;
}
- stack_size += nregs * 8;
+ stack_size += nr_arg_slots * 8;
args_off = stack_size;
stack_size += 8;
@@ -867,8 +887,14 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
stack_size += 8;
sreg_off = stack_size;
+ if (nr_arg_slots - RV_MAX_ARGS_REG > 0)
+ stack_size += (nr_arg_slots - RV_MAX_ARGS_REG) * 8;
+
stack_size = round_up(stack_size, 16);
+ /* room for args on stack must be at the top of stack*/
+ stk_arg_off = stack_size;
+
if (!is_struct_ops) {
/* For the trampoline called from function entry,
* the frame of traced function and the frame of
@@ -904,10 +930,10 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
emit_sd(RV_REG_FP, -ip_off, RV_REG_T1, ctx);
}
- emit_li(RV_REG_T1, nregs, ctx);
+ emit_li(RV_REG_T1, nr_arg_slots, ctx);
emit_sd(RV_REG_FP, -nregs_off, RV_REG_T1, ctx);
- store_args(nregs, args_off, ctx);
+ store_args(nr_arg_slots, args_off, ctx);
/* skip to actual body of traced function */
if (flags & BPF_TRAMP_F_SKIP_FRAME)
@@ -947,7 +973,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
}
if (flags & BPF_TRAMP_F_CALL_ORIG) {
- restore_args(nregs, args_off, ctx);
+ restore_args(min_t(int, nr_arg_slots, RV_MAX_ARGS_REG), args_off, ctx);
+ restore_stack_args(nr_arg_slots - RV_MAX_ARGS_REG, args_off, stk_arg_off, ctx);
ret = emit_call((const u64)orig_call, true, ctx);
if (ret)
goto out;
@@ -982,7 +1009,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
}
if (flags & BPF_TRAMP_F_RESTORE_REGS)
- restore_args(nregs, args_off, ctx);
+ restore_args(min_t(int, nr_arg_slots, RV_MAX_ARGS_REG), args_off, ctx);
if (save_ret) {
emit_ld(RV_REG_A0, -retval_off, RV_REG_FP, ctx);
--
2.34.1
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