Add jit support for private stack. For a particular subtree, e.g.,
subtree_root <== stack depth 120
subprog1 <== stack depth 80
subprog2 <== stack depth 40
subprog3 <== stack depth 160
Let us say that private_stack_ptr is the memory address allocated for
private stack. The frame pointer for each above is calculated like below:
subtree_root <== subtree_root_fp = private_stack_ptr + 120
subprog1 <== subtree_subprog1_fp = subtree_root_fp + 80
subprog2 <== subtree_subprog2_fp = subtree_subprog1_fp + 40
subprog3 <== subtree_subprog1_fp = subtree_root_fp + 160
For any function call to helper/kfunc, push/pop prog frame pointer
is needed in order to preserve frame pointer value.
To deal with exception handling, push/pop frame pointer is also used
surrounding call to subsequent subprog. For example,
subtree_root
subprog1
...
insn: call bpf_throw
...
After jit, we will have
subtree_root
insn: push r9
subprog1
...
insn: push r9
insn: call bpf_throw
insn: pop r9
...
insn: pop r9
exception_handler
pop r9
...
where r9 represents the fp for each subprog.
Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
---
arch/x86/net/bpf_jit_comp.c | 87 ++++++++++++++++++++++++++++++++++---
1 file changed, 81 insertions(+), 6 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 06b080b61aa5..c264822c926b 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;
@@ -491,7 +507,7 @@ static void emit_prologue_tail_call(u8 **pprog, bool is_subprog)
*/
static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf,
bool tail_call_reachable, bool is_subprog,
- bool is_exception_cb)
+ bool is_exception_cb, enum bpf_pstack_state pstack)
{
u8 *prog = *pprog;
@@ -518,6 +534,8 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf,
* first restore those callee-saved regs from stack, before
* reusing the stack frame.
*/
+ if (pstack)
+ pop_r9(&prog);
pop_callee_regs(&prog, all_callee_regs_used);
pop_r12(&prog);
/* Reset the stack frame. */
@@ -1404,6 +1422,22 @@ static void emit_shiftx(u8 **pprog, u32 dst_reg, u8 src_reg, bool is64, u8 op)
*pprog = prog;
}
+static void emit_private_frame_ptr(u8 **pprog, void *private_frame_ptr)
+{
+ u8 *prog = *pprog;
+
+ /* movabs r9, private_frame_ptr */
+ emit_mov_imm64(&prog, X86_REG_R9, (long) private_frame_ptr >> 32,
+ (u32) (long) private_frame_ptr);
+
+ /* add <r9>, gs:[<off>] */
+ EMIT2(0x65, 0x4c);
+ EMIT3(0x03, 0x0c, 0x25);
+ EMIT((u32)(unsigned long)&this_cpu_off, 4);
+
+ *pprog = prog;
+}
+
#define INSN_SZ_DIFF (((addrs[i] - addrs[i - 1]) - (prog - temp)))
#define __LOAD_TCC_PTR(off) \
@@ -1421,20 +1455,31 @@ 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 *private_frame_ptr = NULL;
u64 arena_vm_start, user_vm_start;
+ u32 orig_stack_depth, stack_depth;
int i, excnt = 0;
int ilen, proglen = 0;
u8 *prog = temp;
int err;
+ stack_depth = bpf_prog->aux->stack_depth;
+ orig_stack_depth = round_up(stack_depth, 8);
+ if (bpf_prog->pstack) {
+ stack_depth = 0;
+ if (bpf_prog->pstack == PSTACK_TREE_ROOT)
+ private_frame_ptr = bpf_prog->private_stack_ptr + orig_stack_depth;
+ }
+
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);
detect_reg_usage(insn, insn_cnt, callee_regs_used);
- emit_prologue(&prog, bpf_prog->aux->stack_depth,
+ emit_prologue(&prog, stack_depth,
bpf_prog_was_classic(bpf_prog), tail_call_reachable,
- bpf_is_subprog(bpf_prog), bpf_prog->aux->exception_cb);
+ bpf_is_subprog(bpf_prog), bpf_prog->aux->exception_cb,
+ bpf_prog->pstack);
/* Exception callback will clobber callee regs for its own use, and
* restore the original callee regs from main prog's stack frame.
*/
@@ -1454,6 +1499,17 @@ 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 (bpf_prog->pstack == PSTACK_TREE_ROOT) {
+ emit_private_frame_ptr(&prog, private_frame_ptr);
+ } else if (bpf_prog->pstack == PSTACK_TREE_INTERNAL && orig_stack_depth) {
+ /* r9 += orig_stack_depth */
+ maybe_emit_1mod(&prog, X86_REG_R9, true);
+ if (is_imm8(orig_stack_depth))
+ EMIT3(0x83, add_1reg(0xC0, X86_REG_R9), orig_stack_depth);
+ else
+ EMIT2_off32(0x81, add_1reg(0xC0, X86_REG_R9), orig_stack_depth);
+ }
+
ilen = prog - temp;
if (rw_image)
memcpy(rw_image + proglen, temp, ilen);
@@ -1473,6 +1529,14 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image
u8 *func;
int nops;
+ if (bpf_prog->pstack) {
+ 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:
@@ -2128,14 +2192,20 @@ st: if (is_imm8(insn->off))
func = (u8 *) __bpf_call_base + imm32;
if (tail_call_reachable) {
- LOAD_TAIL_CALL_CNT_PTR(bpf_prog->aux->stack_depth);
+ LOAD_TAIL_CALL_CNT_PTR(stack_depth);
ip += 7;
}
if (!imm32)
return -EINVAL;
+ if (bpf_prog->pstack) {
+ push_r9(&prog);
+ ip += 2;
+ }
ip += x86_call_depth_emit_accounting(&prog, func, ip);
if (emit_call(&prog, func, ip))
return -EINVAL;
+ if (bpf_prog->pstack)
+ pop_r9(&prog);
break;
}
@@ -2145,13 +2215,13 @@ st: if (is_imm8(insn->off))
&bpf_prog->aux->poke_tab[imm32 - 1],
&prog, image + addrs[i - 1],
callee_regs_used,
- bpf_prog->aux->stack_depth,
+ stack_depth,
ctx);
else
emit_bpf_tail_call_indirect(bpf_prog,
&prog,
callee_regs_used,
- bpf_prog->aux->stack_depth,
+ stack_depth,
image + addrs[i - 1],
ctx);
break;
@@ -3559,6 +3629,11 @@ 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)
--
2.43.5
