Private stack is allocated in function bpf_int_jit_compile() with
alignment 16. The x86 register 9 (X86_REG_R9) is used to replace
bpf frame register (BPF_REG_10). The private stack is used per
subprog per cpu. The X86_REG_R9 is saved and restored around every
func call (not including tailcall) to maintain correctness of
X86_REG_R9.
Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
---
arch/x86/net/bpf_jit_comp.c | 77 +++++++++++++++++++++++++++++++++++++
include/linux/bpf.h | 1 +
2 files changed, 78 insertions(+)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 3ff638c37999..55556a64f776 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -325,6 +325,22 @@ struct jit_context {
/* Number of bytes that will be skipped on tailcall */
#define X86_TAIL_CALL_OFFSET (12 + ENDBR_INSN_SIZE)
+static void push_r9(u8 **pprog)
+{
+ u8 *prog = *pprog;
+
+ EMIT2(0x41, 0x51); /* push r9 */
+ *pprog = prog;
+}
+
+static void pop_r9(u8 **pprog)
+{
+ u8 *prog = *pprog;
+
+ EMIT2(0x41, 0x59); /* pop r9 */
+ *pprog = prog;
+}
+
static void push_r12(u8 **pprog)
{
u8 *prog = *pprog;
@@ -1404,6 +1420,24 @@ static void emit_shiftx(u8 **pprog, u32 dst_reg, u8 src_reg, bool is64, u8 op)
*pprog = prog;
}
+static void emit_priv_frame_ptr(u8 **pprog, void __percpu *priv_frame_ptr)
+{
+ u8 *prog = *pprog;
+
+ /* movabs r9, priv_frame_ptr */
+ emit_mov_imm64(&prog, X86_REG_R9, (__force long) priv_frame_ptr >> 32,
+ (u32) (__force long) priv_frame_ptr);
+
+#ifdef CONFIG_SMP
+ /* add <r9>, gs:[<off>] */
+ EMIT2(0x65, 0x4c);
+ EMIT3(0x03, 0x0c, 0x25);
+ EMIT((u32)(unsigned long)&this_cpu_off, 4);
+#endif
+
+ *pprog = prog;
+}
+
#define INSN_SZ_DIFF (((addrs[i] - addrs[i - 1]) - (prog - temp)))
#define __LOAD_TCC_PTR(off) \
@@ -1421,6 +1455,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image
int insn_cnt = bpf_prog->len;
bool seen_exit = false;
u8 temp[BPF_MAX_INSN_SIZE + BPF_INSN_SAFETY];
+ void __percpu *priv_frame_ptr = NULL;
u64 arena_vm_start, user_vm_start;
int i, excnt = 0;
int ilen, proglen = 0;
@@ -1429,6 +1464,10 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image
int err;
stack_depth = bpf_prog->aux->stack_depth;
+ if (bpf_prog->aux->priv_stack_ptr) {
+ priv_frame_ptr = bpf_prog->aux->priv_stack_ptr + round_up(stack_depth, 16);
+ stack_depth = 0;
+ }
arena_vm_start = bpf_arena_get_kern_vm_start(bpf_prog->aux->arena);
user_vm_start = bpf_arena_get_user_vm_start(bpf_prog->aux->arena);
@@ -1457,6 +1496,9 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image
emit_mov_imm64(&prog, X86_REG_R12,
arena_vm_start >> 32, (u32) arena_vm_start);
+ if (priv_frame_ptr)
+ emit_priv_frame_ptr(&prog, priv_frame_ptr);
+
ilen = prog - temp;
if (rw_image)
memcpy(rw_image + proglen, temp, ilen);
@@ -1476,6 +1518,14 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image
u8 *func;
int nops;
+ if (priv_frame_ptr) {
+ if (src_reg == BPF_REG_FP)
+ src_reg = X86_REG_R9;
+
+ if (dst_reg == BPF_REG_FP)
+ dst_reg = X86_REG_R9;
+ }
+
switch (insn->code) {
/* ALU */
case BPF_ALU | BPF_ADD | BPF_X:
@@ -2136,9 +2186,15 @@ st: if (is_imm8(insn->off))
}
if (!imm32)
return -EINVAL;
+ if (priv_frame_ptr) {
+ push_r9(&prog);
+ ip += 2;
+ }
ip += x86_call_depth_emit_accounting(&prog, func, ip);
if (emit_call(&prog, func, ip))
return -EINVAL;
+ if (priv_frame_ptr)
+ pop_r9(&prog);
break;
}
@@ -3323,6 +3379,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
struct bpf_binary_header *rw_header = NULL;
struct bpf_binary_header *header = NULL;
struct bpf_prog *tmp, *orig_prog = prog;
+ void __percpu *priv_stack_ptr = NULL;
struct x64_jit_data *jit_data;
int proglen, oldproglen = 0;
struct jit_context ctx = {};
@@ -3359,6 +3416,15 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
}
prog->aux->jit_data = jit_data;
}
+ priv_stack_ptr = prog->aux->priv_stack_ptr;
+ if (!priv_stack_ptr && prog->aux->jits_use_priv_stack) {
+ priv_stack_ptr = __alloc_percpu_gfp(prog->aux->stack_depth, 16, GFP_KERNEL);
+ if (!priv_stack_ptr) {
+ prog = orig_prog;
+ goto out_priv_stack;
+ }
+ prog->aux->priv_stack_ptr = priv_stack_ptr;
+ }
addrs = jit_data->addrs;
if (addrs) {
ctx = jit_data->ctx;
@@ -3494,6 +3560,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
bpf_prog_fill_jited_linfo(prog, addrs + 1);
out_addrs:
kvfree(addrs);
+ if (!image && priv_stack_ptr) {
+ free_percpu(priv_stack_ptr);
+ prog->aux->priv_stack_ptr = NULL;
+ }
+out_priv_stack:
kfree(jit_data);
prog->aux->jit_data = NULL;
}
@@ -3547,6 +3618,7 @@ void bpf_jit_free(struct bpf_prog *prog)
prog->bpf_func = (void *)prog->bpf_func - cfi_get_offset();
hdr = bpf_jit_binary_pack_hdr(prog);
bpf_jit_binary_pack_free(hdr, NULL);
+ free_percpu(prog->aux->priv_stack_ptr);
WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(prog));
}
@@ -3562,6 +3634,11 @@ bool bpf_jit_supports_exceptions(void)
return IS_ENABLED(CONFIG_UNWINDER_ORC);
}
+bool bpf_jit_supports_private_stack(void)
+{
+ return true;
+}
+
void arch_bpf_stack_walk(bool (*consume_fn)(void *cookie, u64 ip, u64 sp, u64 bp), void *cookie)
{
#if defined(CONFIG_UNWINDER_ORC)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 15f20d508174..9cfb8f55d691 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1507,6 +1507,7 @@ struct bpf_prog_aux {
u32 max_rdwr_access;
struct btf *attach_btf;
const struct bpf_ctx_arg_aux *ctx_arg_info;
+ void __percpu *priv_stack_ptr;
struct mutex dst_mutex; /* protects dst_* pointers below, *after* prog becomes visible */
struct bpf_prog *dst_prog;
struct bpf_trampoline *dst_trampoline;
--
2.43.5
