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LoongArch: BPF: Add fsession support for trampolines

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Implement BPF_TRACE_FSESSION support in LoongArch BPF JIT. The logic
here is almost identical to what has been done in RISC-V JIT.

The key changes are:
  - Allocate stack space for function meta and session cookies
  - Introduce invoke_bpf() as a wrapper around invoke_bpf_prog() that
    populates session cookies before each invocation
  - Implement bpf_jit_supports_fsession() callback

Tested-by: Vincent Li <vincent.mc.li@gmail.com>
Reviewed-by: Menglong Dong <menglong8.dong@gmail.com>
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Hengqi Chen
2026-04-23 12:49:36 +08:00
committed by Huacai Chen
parent 6ef04707e8
commit e815df29b6
1 changed files with 66 additions and 10 deletions
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76
arch/loongarch/net/bpf_jit.c
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@@ -1737,6 +1737,29 @@ static int invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l,
return ret;
}
static int invoke_bpf(struct jit_ctx *ctx, struct bpf_tramp_links *tl,
int args_off, int retval_off, int run_ctx_off,
int func_meta_off, bool save_ret, u64 func_meta, int cookie_off)
{
int i, cur_cookie = (cookie_off - args_off) / 8;
for (i = 0; i < tl->nr_links; i++) {
int err;
if (bpf_prog_calls_session_cookie(tl->links[i])) {
u64 meta = func_meta | ((u64)cur_cookie << BPF_TRAMP_COOKIE_INDEX_SHIFT);
emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -func_meta_off, meta);
cur_cookie--;
}
err = invoke_bpf_prog(ctx, tl->links[i], args_off, retval_off, run_ctx_off, save_ret);
if (err)
return err;
}
return 0;
}
void *arch_alloc_bpf_trampoline(unsigned int size)
{
return bpf_prog_pack_alloc(size, jit_fill_hole);
@@ -1788,8 +1811,10 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
void *func_addr, u32 flags)
{
int i, ret, save_ret;
int cookie_cnt, cookie_off;
int stack_size, args_off, stk_args_off, nr_arg_slots = 0;
int retval_off, nregs_off, ip_off, run_ctx_off, sreg_off, tcc_ptr_off;
int retval_off, func_meta_off, ip_off, run_ctx_off, sreg_off, tcc_ptr_off;
unsigned long long func_meta;
bool is_struct_ops = flags & BPF_TRAMP_F_INDIRECT;
void *orig_call = func_addr;
struct bpf_tramp_links *fentry = &tlinks[BPF_TRAMP_FENTRY];
@@ -1813,10 +1838,14 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
* [ ... ]
* FP - args_off [ arg reg1 ]
*
* FP - nregs_off [ arg regs count ]
* FP - func_meta_off [ regs count, etc ]
*
* FP - ip_off [ traced func ] BPF_TRAMP_F_IP_ARG
*
* [ stack cookie N ]
* [ ... ]
* FP - cookie_off [ stack cookie 1 ]
*
* FP - run_ctx_off [ bpf_tramp_run_ctx ]
*
* FP - sreg_off [ callee saved reg ]
@@ -1859,9 +1888,9 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
stack_size += nr_arg_slots * 8;
args_off = stack_size;
/* Room of trampoline frame to store args number */
/* Room of function metadata, such as regs count */
stack_size += 8;
nregs_off = stack_size;
func_meta_off = stack_size;
/* Room of trampoline frame to store ip address */
if (flags & BPF_TRAMP_F_IP_ARG) {
@@ -1869,6 +1898,12 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
ip_off = stack_size;
}
cookie_cnt = bpf_fsession_cookie_cnt(tlinks);
/* Room for session cookies */
stack_size += cookie_cnt * 8;
cookie_off = stack_size;
/* Room of trampoline frame to store struct bpf_tramp_run_ctx */
stack_size += round_up(sizeof(struct bpf_tramp_run_ctx), 8);
run_ctx_off = stack_size;
@@ -1929,10 +1964,20 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -ip_off, (u64)func_addr);
/* store arg regs count */
emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -nregs_off, nr_arg_slots);
func_meta = nr_arg_slots;
emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -func_meta_off, func_meta);
store_args(ctx, nr_arg_slots, args_off);
if (bpf_fsession_cnt(tlinks)) {
/* clear all session cookies' value */
for (i = 0; i < cookie_cnt; i++)
emit_insn(ctx, std, LOONGARCH_GPR_ZERO, LOONGARCH_GPR_FP, -cookie_off + 8 * i);
/* clear return value to make sure fentry always get 0 */
emit_insn(ctx, std, LOONGARCH_GPR_ZERO, LOONGARCH_GPR_FP, -retval_off);
}
/* To traced function */
/* Ftrace jump skips 2 NOP instructions */
if (is_kernel_text((unsigned long)orig_call) ||
@@ -1949,9 +1994,9 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
return ret;
}
for (i = 0; i < fentry->nr_links; i++) {
ret = invoke_bpf_prog(ctx, fentry->links[i], args_off, retval_off,
run_ctx_off, flags & BPF_TRAMP_F_RET_FENTRY_RET);
if (fentry->nr_links) {
ret = invoke_bpf(ctx, fentry, args_off, retval_off, run_ctx_off, func_meta_off,
flags & BPF_TRAMP_F_RET_FENTRY_RET, func_meta, cookie_off);
if (ret)
return ret;
}
@@ -1995,8 +2040,14 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
*branches[i] = larch_insn_gen_bne(LOONGARCH_GPR_T1, LOONGARCH_GPR_ZERO, offset);
}
for (i = 0; i < fexit->nr_links; i++) {
ret = invoke_bpf_prog(ctx, fexit->links[i], args_off, retval_off, run_ctx_off, false);
/* Set "is_return" flag for fsession */
func_meta |= (1ULL << BPF_TRAMP_IS_RETURN_SHIFT);
if (bpf_fsession_cnt(tlinks))
emit_store_stack_imm64(ctx, LOONGARCH_GPR_T1, -func_meta_off, func_meta);
if (fexit->nr_links) {
ret = invoke_bpf(ctx, fexit, args_off, retval_off, run_ctx_off,
func_meta_off, false, func_meta, cookie_off);
if (ret)
goto out;
}
@@ -2331,6 +2382,11 @@ bool bpf_jit_supports_arena(void)
return true;
}
bool bpf_jit_supports_fsession(void)
{
return true;
}
/* Indicate the JIT backend supports mixing bpf2bpf and tailcalls. */
bool bpf_jit_supports_subprog_tailcalls(void)
{