Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

Alexei Starovoitov says:

====================
pull-request: bpf-next 2020-09-23

The following pull-request contains BPF updates for your *net-next* tree.

We've added 95 non-merge commits during the last 22 day(s) which contain
a total of 124 files changed, 4211 insertions(+), 2040 deletions(-).

The main changes are:

1) Full multi function support in libbpf, from Andrii.

2) Refactoring of function argument checks, from Lorenz.

3) Make bpf_tail_call compatible with functions (subprograms), from Maciej.

4) Program metadata support, from YiFei.

5) bpf iterator optimizations, from Yonghong.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 239 insertions, 103 deletions

diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index be4b8532dd3c..0a4182792876 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -50,7 +50,6 @@ struct bpf_jit {
 	int r14_thunk_ip;	/* Address of expoline thunk for 'br %r14' */
 	int tail_call_start;	/* Tail call start offset */
 	int excnt;		/* Number of exception table entries */
-	int labels[1];		/* Labels for local jumps */
 };
 
 #define SEEN_MEM	BIT(0)		/* use mem[] for temporary storage */
@@ -229,18 +228,18 @@ static inline void reg_set_seen(struct bpf_jit *jit, u32 b1)
 	REG_SET_SEEN(b3);					\
 })
 
-#define EMIT6_PCREL_LABEL(op1, op2, b1, b2, label, mask)	\
+#define EMIT6_PCREL_RIEB(op1, op2, b1, b2, mask, target)	\
 ({								\
-	int rel = (jit->labels[label] - jit->prg) >> 1;		\
+	unsigned int rel = (int)((target) - jit->prg) / 2;	\
 	_EMIT6((op1) | reg(b1, b2) << 16 | (rel & 0xffff),	\
 	       (op2) | (mask) << 12);				\
 	REG_SET_SEEN(b1);					\
 	REG_SET_SEEN(b2);					\
 })
 
-#define EMIT6_PCREL_IMM_LABEL(op1, op2, b1, imm, label, mask)	\
+#define EMIT6_PCREL_RIEC(op1, op2, b1, imm, mask, target)	\
 ({								\
-	int rel = (jit->labels[label] - jit->prg) >> 1;		\
+	unsigned int rel = (int)((target) - jit->prg) / 2;	\
 	_EMIT6((op1) | (reg_high(b1) | (mask)) << 16 |		\
 		(rel & 0xffff), (op2) | ((imm) & 0xff) << 8);	\
 	REG_SET_SEEN(b1);					\
@@ -1282,7 +1281,9 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
 		EMIT4(0xb9040000, BPF_REG_0, REG_2);
 		break;
 	}
-	case BPF_JMP | BPF_TAIL_CALL:
+	case BPF_JMP | BPF_TAIL_CALL: {
+		int patch_1_clrj, patch_2_clij, patch_3_brc;
+
 		/*
 		 * Implicit input:
 		 *  B1: pointer to ctx
@@ -1300,16 +1301,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
 		EMIT6_DISP_LH(0xe3000000, 0x0016, REG_W1, REG_0, BPF_REG_2,
 			      offsetof(struct bpf_array, map.max_entries));
 		/* if ((u32)%b3 >= (u32)%w1) goto out; */
-		if (!is_first_pass(jit) && can_use_rel(jit, jit->labels[0])) {
-			/* clrj %b3,%w1,0xa,label0 */
-			EMIT6_PCREL_LABEL(0xec000000, 0x0077, BPF_REG_3,
-					  REG_W1, 0, 0xa);
-		} else {
-			/* clr %b3,%w1 */
-			EMIT2(0x1500, BPF_REG_3, REG_W1);
-			/* brcl 0xa,label0 */
-			EMIT6_PCREL_RILC(0xc0040000, 0xa, jit->labels[0]);
-		}
+		/* clrj %b3,%w1,0xa,out */
+		patch_1_clrj = jit->prg;
+		EMIT6_PCREL_RIEB(0xec000000, 0x0077, BPF_REG_3, REG_W1, 0xa,
+				 jit->prg);
 
 		/*
 		 * if (tail_call_cnt++ > MAX_TAIL_CALL_CNT)
@@ -1324,16 +1319,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
 		EMIT4_IMM(0xa7080000, REG_W0, 1);
 		/* laal %w1,%w0,off(%r15) */
 		EMIT6_DISP_LH(0xeb000000, 0x00fa, REG_W1, REG_W0, REG_15, off);
-		if (!is_first_pass(jit) && can_use_rel(jit, jit->labels[0])) {
-			/* clij %w1,MAX_TAIL_CALL_CNT,0x2,label0 */
-			EMIT6_PCREL_IMM_LABEL(0xec000000, 0x007f, REG_W1,
-					      MAX_TAIL_CALL_CNT, 0, 0x2);
-		} else {
-			/* clfi %w1,MAX_TAIL_CALL_CNT */
-			EMIT6_IMM(0xc20f0000, REG_W1, MAX_TAIL_CALL_CNT);
-			/* brcl 0x2,label0 */
-			EMIT6_PCREL_RILC(0xc0040000, 0x2, jit->labels[0]);
-		}
+		/* clij %w1,MAX_TAIL_CALL_CNT,0x2,out */
+		patch_2_clij = jit->prg;
+		EMIT6_PCREL_RIEC(0xec000000, 0x007f, REG_W1, MAX_TAIL_CALL_CNT,
+				 2, jit->prg);
 
 		/*
 		 * prog = array->ptrs[index];
@@ -1348,13 +1337,9 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
 		/* ltg %r1,prog(%b2,%r1) */
 		EMIT6_DISP_LH(0xe3000000, 0x0002, REG_1, BPF_REG_2,
 			      REG_1, offsetof(struct bpf_array, ptrs));
-		if (!is_first_pass(jit) && can_use_rel(jit, jit->labels[0])) {
-			/* brc 0x8,label0 */
-			EMIT4_PCREL_RIC(0xa7040000, 0x8, jit->labels[0]);
-		} else {
-			/* brcl 0x8,label0 */
-			EMIT6_PCREL_RILC(0xc0040000, 0x8, jit->labels[0]);
-		}
+		/* brc 0x8,out */
+		patch_3_brc = jit->prg;
+		EMIT4_PCREL_RIC(0xa7040000, 8, jit->prg);
 
 		/*
 		 * Restore registers before calling function
@@ -1371,8 +1356,16 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
 		/* bc 0xf,tail_call_start(%r1) */
 		_EMIT4(0x47f01000 + jit->tail_call_start);
 		/* out: */
-		jit->labels[0] = jit->prg;
+		if (jit->prg_buf) {
+			*(u16 *)(jit->prg_buf + patch_1_clrj + 2) =
+				(jit->prg - patch_1_clrj) >> 1;
+			*(u16 *)(jit->prg_buf + patch_2_clij + 2) =
+				(jit->prg - patch_2_clij) >> 1;
+			*(u16 *)(jit->prg_buf + patch_3_brc + 2) =
+				(jit->prg - patch_3_brc) >> 1;
+		}
 		break;
+	}
 	case BPF_JMP | BPF_EXIT: /* return b0 */
 		last = (i == fp->len - 1) ? 1 : 0;
 		if (last)
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index e7752b4038ff..e491c3d9f227 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -314,19 +314,19 @@ static inline void mds_idle_clear_cpu_buffers(void)
  *    lfence
  *    jmp spec_trap
  *  do_rop:
- *    mov %rax,(%rsp) for x86_64
+ *    mov %rcx,(%rsp) for x86_64
  *    mov %edx,(%esp) for x86_32
  *    retq
  *
  * Without retpolines configured:
  *
- *    jmp *%rax for x86_64
+ *    jmp *%rcx for x86_64
  *    jmp *%edx for x86_32
  */
 #ifdef CONFIG_RETPOLINE
 # ifdef CONFIG_X86_64
-#  define RETPOLINE_RAX_BPF_JIT_SIZE	17
-#  define RETPOLINE_RAX_BPF_JIT()				\
+#  define RETPOLINE_RCX_BPF_JIT_SIZE	17
+#  define RETPOLINE_RCX_BPF_JIT()				\
 do {								\
 	EMIT1_off32(0xE8, 7);	 /* callq do_rop */		\
 	/* spec_trap: */					\
@@ -334,7 +334,7 @@ do {								\
 	EMIT3(0x0F, 0xAE, 0xE8); /* lfence */			\
 	EMIT2(0xEB, 0xF9);       /* jmp spec_trap */		\
 	/* do_rop: */						\
-	EMIT4(0x48, 0x89, 0x04, 0x24); /* mov %rax,(%rsp) */	\
+	EMIT4(0x48, 0x89, 0x0C, 0x24); /* mov %rcx,(%rsp) */	\
 	EMIT1(0xC3);             /* retq */			\
 } while (0)
 # else /* !CONFIG_X86_64 */
@@ -352,9 +352,9 @@ do {								\
 # endif
 #else /* !CONFIG_RETPOLINE */
 # ifdef CONFIG_X86_64
-#  define RETPOLINE_RAX_BPF_JIT_SIZE	2
-#  define RETPOLINE_RAX_BPF_JIT()				\
-	EMIT2(0xFF, 0xE0);       /* jmp *%rax */
+#  define RETPOLINE_RCX_BPF_JIT_SIZE	2
+#  define RETPOLINE_RCX_BPF_JIT()				\
+	EMIT2(0xFF, 0xE1);       /* jmp *%rcx */
 # else /* !CONFIG_X86_64 */
 #  define RETPOLINE_EDX_BPF_JIT()				\
 	EMIT2(0xFF, 0xE2)        /* jmp *%edx */
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 7d9ea7b41c71..26f43279b78b 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -221,14 +221,48 @@ struct jit_context {
 
 /* Number of bytes emit_patch() needs to generate instructions */
 #define X86_PATCH_SIZE		5
+/* Number of bytes that will be skipped on tailcall */
+#define X86_TAIL_CALL_OFFSET	11
 
-#define PROLOGUE_SIZE		25
+static void push_callee_regs(u8 **pprog, bool *callee_regs_used)
+{
+	u8 *prog = *pprog;
+	int cnt = 0;
+
+	if (callee_regs_used[0])
+		EMIT1(0x53);         /* push rbx */
+	if (callee_regs_used[1])
+		EMIT2(0x41, 0x55);   /* push r13 */
+	if (callee_regs_used[2])
+		EMIT2(0x41, 0x56);   /* push r14 */
+	if (callee_regs_used[3])
+		EMIT2(0x41, 0x57);   /* push r15 */
+	*pprog = prog;
+}
+
+static void pop_callee_regs(u8 **pprog, bool *callee_regs_used)
+{
+	u8 *prog = *pprog;
+	int cnt = 0;
+
+	if (callee_regs_used[3])
+		EMIT2(0x41, 0x5F);   /* pop r15 */
+	if (callee_regs_used[2])
+		EMIT2(0x41, 0x5E);   /* pop r14 */
+	if (callee_regs_used[1])
+		EMIT2(0x41, 0x5D);   /* pop r13 */
+	if (callee_regs_used[0])
+		EMIT1(0x5B);         /* pop rbx */
+	*pprog = prog;
+}
 
 /*
- * Emit x86-64 prologue code for BPF program and check its size.
- * bpf_tail_call helper will skip it while jumping into another program
+ * Emit x86-64 prologue code for BPF program.
+ * bpf_tail_call helper will skip the first X86_TAIL_CALL_OFFSET bytes
+ * while jumping to another program
  */
-static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf)
+static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf,
+			  bool tail_call_reachable, bool is_subprog)
 {
 	u8 *prog = *pprog;
 	int cnt = X86_PATCH_SIZE;
@@ -238,19 +272,18 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf)
 	 */
 	memcpy(prog, ideal_nops[NOP_ATOMIC5], cnt);
 	prog += cnt;
+	if (!ebpf_from_cbpf) {
+		if (tail_call_reachable && !is_subprog)
+			EMIT2(0x31, 0xC0); /* xor eax, eax */
+		else
+			EMIT2(0x66, 0x90); /* nop2 */
+	}
 	EMIT1(0x55);             /* push rbp */
 	EMIT3(0x48, 0x89, 0xE5); /* mov rbp, rsp */
 	/* sub rsp, rounded_stack_depth */
 	EMIT3_off32(0x48, 0x81, 0xEC, round_up(stack_depth, 8));
-	EMIT1(0x53);             /* push rbx */
-	EMIT2(0x41, 0x55);       /* push r13 */
-	EMIT2(0x41, 0x56);       /* push r14 */
-	EMIT2(0x41, 0x57);       /* push r15 */
-	if (!ebpf_from_cbpf) {
-		/* zero init tail_call_cnt */
-		EMIT2(0x6a, 0x00);
-		BUILD_BUG_ON(cnt != PROLOGUE_SIZE);
-	}
+	if (tail_call_reachable)
+		EMIT1(0x50);         /* push rax */
 	*pprog = prog;
 }
 
@@ -314,13 +347,14 @@ static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
 	mutex_lock(&text_mutex);
 	if (memcmp(ip, old_insn, X86_PATCH_SIZE))
 		goto out;
+	ret = 1;
 	if (memcmp(ip, new_insn, X86_PATCH_SIZE)) {
 		if (text_live)
 			text_poke_bp(ip, new_insn, X86_PATCH_SIZE, NULL);
 		else
 			memcpy(ip, new_insn, X86_PATCH_SIZE);
+		ret = 0;
 	}
-	ret = 0;
 out:
 	mutex_unlock(&text_mutex);
 	return ret;
@@ -337,6 +371,22 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
 	return __bpf_arch_text_poke(ip, t, old_addr, new_addr, true);
 }
 
+static int get_pop_bytes(bool *callee_regs_used)
+{
+	int bytes = 0;
+
+	if (callee_regs_used[3])
+		bytes += 2;
+	if (callee_regs_used[2])
+		bytes += 2;
+	if (callee_regs_used[1])
+		bytes += 2;
+	if (callee_regs_used[0])
+		bytes += 1;
+
+	return bytes;
+}
+
 /*
  * Generate the following code:
  *
@@ -351,12 +401,26 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
  *   goto *(prog->bpf_func + prologue_size);
  * out:
  */
-static void emit_bpf_tail_call_indirect(u8 **pprog)
+static void emit_bpf_tail_call_indirect(u8 **pprog, bool *callee_regs_used,
+					u32 stack_depth)
 {
+	int tcc_off = -4 - round_up(stack_depth, 8);
 	u8 *prog = *pprog;
-	int label1, label2, label3;
+	int pop_bytes = 0;
+	int off1 = 49;
+	int off2 = 38;
+	int off3 = 16;
 	int cnt = 0;
 
+	/* count the additional bytes used for popping callee regs from stack
+	 * that need to be taken into account for each of the offsets that
+	 * are used for bailing out of the tail call
+	 */
+	pop_bytes = get_pop_bytes(callee_regs_used);
+	off1 += pop_bytes;
+	off2 += pop_bytes;
+	off3 += pop_bytes;
+
 	/*
 	 * rdi - pointer to ctx
 	 * rsi - pointer to bpf_array
@@ -370,72 +434,106 @@ static void emit_bpf_tail_call_indirect(u8 **pprog)
 	EMIT2(0x89, 0xD2);                        /* mov edx, edx */
 	EMIT3(0x39, 0x56,                         /* cmp dword ptr [rsi + 16], edx */
 	      offsetof(struct bpf_array, map.max_entries));
-#define OFFSET1 (41 + RETPOLINE_RAX_BPF_JIT_SIZE) /* Number of bytes to jump */
+#define OFFSET1 (off1 + RETPOLINE_RCX_BPF_JIT_SIZE) /* Number of bytes to jump */
 	EMIT2(X86_JBE, OFFSET1);                  /* jbe out */
-	label1 = cnt;
 
 	/*
 	 * if (tail_call_cnt > MAX_TAIL_CALL_CNT)
 	 *	goto out;
 	 */
-	EMIT2_off32(0x8B, 0x85, -36 - MAX_BPF_STACK); /* mov eax, dword ptr [rbp - 548] */
+	EMIT2_off32(0x8B, 0x85, tcc_off);         /* mov eax, dword ptr [rbp - tcc_off] */
 	EMIT3(0x83, 0xF8, MAX_TAIL_CALL_CNT);     /* cmp eax, MAX_TAIL_CALL_CNT */
-#define OFFSET2 (30 + RETPOLINE_RAX_BPF_JIT_SIZE)
+#define OFFSET2 (off2 + RETPOLINE_RCX_BPF_JIT_SIZE)
 	EMIT2(X86_JA, OFFSET2);                   /* ja out */
-	label2 = cnt;
 	EMIT3(0x83, 0xC0, 0x01);                  /* add eax, 1 */
-	EMIT2_off32(0x89, 0x85, -36 - MAX_BPF_STACK); /* mov dword ptr [rbp -548], eax */
+	EMIT2_off32(0x89, 0x85, tcc_off);         /* mov dword ptr [rbp - tcc_off], eax */
 
 	/* prog = array->ptrs[index]; */
-	EMIT4_off32(0x48, 0x8B, 0x84, 0xD6,       /* mov rax, [rsi + rdx * 8 + offsetof(...)] */
+	EMIT4_off32(0x48, 0x8B, 0x8C, 0xD6,       /* mov rcx, [rsi + rdx * 8 + offsetof(...)] */
 		    offsetof(struct bpf_array, ptrs));
 
 	/*
 	 * if (prog == NULL)
 	 *	goto out;
 	 */
-	EMIT3(0x48, 0x85, 0xC0);		  /* test rax,rax */
-#define OFFSET3 (8 + RETPOLINE_RAX_BPF_JIT_SIZE)
+	EMIT3(0x48, 0x85, 0xC9);                  /* test rcx,rcx */
+#define OFFSET3 (off3 + RETPOLINE_RCX_BPF_JIT_SIZE)
 	EMIT2(X86_JE, OFFSET3);                   /* je out */
-	label3 = cnt;
 
-	/* goto *(prog->bpf_func + prologue_size); */
-	EMIT4(0x48, 0x8B, 0x40,                   /* mov rax, qword ptr [rax + 32] */
-	      offsetof(struct bpf_prog, bpf_func));
-	EMIT4(0x48, 0x83, 0xC0, PROLOGUE_SIZE);   /* add rax, prologue_size */
+	*pprog = prog;
+	pop_callee_regs(pprog, callee_regs_used);
+	prog = *pprog;
+
+	EMIT1(0x58);                              /* pop rax */
+	EMIT3_off32(0x48, 0x81, 0xC4,             /* add rsp, sd */
+		    round_up(stack_depth, 8));
 
+	/* goto *(prog->bpf_func + X86_TAIL_CALL_OFFSET); */
+	EMIT4(0x48, 0x8B, 0x49,                   /* mov rcx, qword ptr [rcx + 32] */
+	      offsetof(struct bpf_prog, bpf_func));
+	EMIT4(0x48, 0x83, 0xC1,                   /* add rcx, X86_TAIL_CALL_OFFSET */
+	      X86_TAIL_CALL_OFFSET);
 	/*
-	 * Wow we're ready to jump into next BPF program
+	 * Now we're ready to jump into next BPF program
 	 * rdi == ctx (1st arg)
-	 * rax == prog->bpf_func + prologue_size
+	 * rcx == prog->bpf_func + X86_TAIL_CALL_OFFSET
 	 */
-	RETPOLINE_RAX_BPF_JIT();
+	RETPOLINE_RCX_BPF_JIT();
 
 	/* out: */
-	BUILD_BUG_ON(cnt - label1 != OFFSET1);
-	BUILD_BUG_ON(cnt - label2 != OFFSET2);
-	BUILD_BUG_ON(cnt - label3 != OFFSET3);
 	*pprog = prog;
 }
 
 static void emit_bpf_tail_call_direct(struct bpf_jit_poke_descriptor *poke,
-				      u8 **pprog, int addr, u8 *image)
+				      u8 **pprog, int addr, u8 *image,
+				      bool *callee_regs_used, u32 stack_depth)
 {
+	int tcc_off = -4 - round_up(stack_depth, 8);
 	u8 *prog = *pprog;
+	int pop_bytes = 0;
+	int off1 = 27;
+	int poke_off;
 	int cnt = 0;
 
+	/* count the additional bytes used for popping callee regs to stack
+	 * that need to be taken into account for jump offset that is used for
+	 * bailing out from of the tail call when limit is reached
+	 */
+	pop_bytes = get_pop_bytes(callee_regs_used);
+	off1 += pop_bytes;
+
+	/*
+	 * total bytes for:
+	 * - nop5/ jmpq $off
+	 * - pop callee regs
+	 * - sub rsp, $val
+	 * - pop rax
+	 */
+	poke_off = X86_PATCH_SIZE + pop_bytes + 7 + 1;
+
 	/*
 	 * if (tail_call_cnt > MAX_TAIL_CALL_CNT)
 	 *	goto out;
 	 */
-	EMIT2_off32(0x8B, 0x85, -36 - MAX_BPF_STACK); /* mov eax, dword ptr [rbp - 548] */
+	EMIT2_off32(0x8B, 0x85, tcc_off);             /* mov eax, dword ptr [rbp - tcc_off] */
 	EMIT3(0x83, 0xF8, MAX_TAIL_CALL_CNT);         /* cmp eax, MAX_TAIL_CALL_CNT */
-	EMIT2(X86_JA, 14);                            /* ja out */
+	EMIT2(X86_JA, off1);                          /* ja out */
 	EMIT3(0x83, 0xC0, 0x01);                      /* add eax, 1 */
-	EMIT2_off32(0x89, 0x85, -36 - MAX_BPF_STACK); /* mov dword ptr [rbp -548], eax */
+	EMIT2_off32(0x89, 0x85, tcc_off);             /* mov dword ptr [rbp - tcc_off], eax */
+
+	poke->tailcall_bypass = image + (addr - poke_off - X86_PATCH_SIZE);
+	poke->adj_off = X86_TAIL_CALL_OFFSET;
+	poke->tailcall_target = image + (addr - X86_PATCH_SIZE);
+	poke->bypass_addr = (u8 *)poke->tailcall_target + X86_PATCH_SIZE;
 
-	poke->ip = image + (addr - X86_PATCH_SIZE);
-	poke->adj_off = PROLOGUE_SIZE;
+	emit_jump(&prog, (u8 *)poke->tailcall_target + X86_PATCH_SIZE,
+		  poke->tailcall_bypass);
+
+	*pprog = prog;
+	pop_callee_regs(pprog, callee_regs_used);
+	prog = *pprog;
+	EMIT1(0x58);                                  /* pop rax */
+	EMIT3_off32(0x48, 0x81, 0xC4, round_up(stack_depth, 8));
 
 	memcpy(prog, ideal_nops[NOP_ATOMIC5], X86_PATCH_SIZE);
 	prog += X86_PATCH_SIZE;
@@ -453,7 +551,7 @@ static void bpf_tail_call_direct_fixup(struct bpf_prog *prog)
 
 	for (i = 0; i < prog->aux->size_poke_tab; i++) {
 		poke = &prog->aux->poke_tab[i];
-		WARN_ON_ONCE(READ_ONCE(poke->ip_stable));
+		WARN_ON_ONCE(READ_ONCE(poke->tailcall_target_stable));
 
 		if (poke->reason != BPF_POKE_REASON_TAIL_CALL)
 			continue;
@@ -464,18 +562,25 @@ static void bpf_tail_call_direct_fixup(struct bpf_prog *prog)
 		if (target) {
 			/* Plain memcpy is used when image is not live yet
 			 * and still not locked as read-only. Once poke
-			 * location is active (poke->ip_stable), any parallel
-			 * bpf_arch_text_poke() might occur still on the
-			 * read-write image until we finally locked it as
-			 * read-only. Both modifications on the given image
-			 * are under text_mutex to avoid interference.
+			 * location is active (poke->tailcall_target_stable),
+			 * any parallel bpf_arch_text_poke() might occur
+			 * still on the read-write image until we finally
+			 * locked it as read-only. Both modifications on
+			 * the given image are under text_mutex to avoid
+			 * interference.
 			 */
-			ret = __bpf_arch_text_poke(poke->ip, BPF_MOD_JUMP, NULL,
+			ret = __bpf_arch_text_poke(poke->tailcall_target,
+						   BPF_MOD_JUMP, NULL,
 						   (u8 *)target->bpf_func +
 						   poke->adj_off, false);
 			BUG_ON(ret < 0);
+			ret = __bpf_arch_text_poke(poke->tailcall_bypass,
+						   BPF_MOD_JUMP,
+						   (u8 *)poke->tailcall_target +
+						   X86_PATCH_SIZE, NULL, false);
+			BUG_ON(ret < 0);
 		}
-		WRITE_ONCE(poke->ip_stable, true);
+		WRITE_ONCE(poke->tailcall_target_stable, true);
 		mutex_unlock(&array->aux->poke_mutex);
 	}
 }
@@ -652,19 +757,49 @@ static bool ex_handler_bpf(const struct exception_table_entry *x,
 	return true;
 }
 
+static void detect_reg_usage(struct bpf_insn *insn, int insn_cnt,
+			     bool *regs_used, bool *tail_call_seen)
+{
+	int i;
+
+	for (i = 1; i <= insn_cnt; i++, insn++) {
+		if (insn->code == (BPF_JMP | BPF_TAIL_CALL))
+			*tail_call_seen = true;
+		if (insn->dst_reg == BPF_REG_6 || insn->src_reg == BPF_REG_6)
+			regs_used[0] = true;
+		if (insn->dst_reg == BPF_REG_7 || insn->src_reg == BPF_REG_7)
+			regs_used[1] = true;
+		if (insn->dst_reg == BPF_REG_8 || insn->src_reg == BPF_REG_8)
+			regs_used[2] = true;
+		if (insn->dst_reg == BPF_REG_9 || insn->src_reg == BPF_REG_9)
+			regs_used[3] = true;
+	}
+}
+
 static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
 		  int oldproglen, struct jit_context *ctx)
 {
+	bool tail_call_reachable = bpf_prog->aux->tail_call_reachable;
 	struct bpf_insn *insn = bpf_prog->insnsi;
+	bool callee_regs_used[4] = {};
 	int insn_cnt = bpf_prog->len;
+	bool tail_call_seen = false;
 	bool seen_exit = false;
 	u8 temp[BPF_MAX_INSN_SIZE + BPF_INSN_SAFETY];
 	int i, cnt = 0, excnt = 0;
 	int proglen = 0;
 	u8 *prog = temp;
 
+	detect_reg_usage(insn, insn_cnt, callee_regs_used,
+			 &tail_call_seen);
+
+	/* tail call's presence in current prog implies it is reachable */
+	tail_call_reachable |= tail_call_seen;
+
 	emit_prologue(&prog, bpf_prog->aux->stack_depth,
-		      bpf_prog_was_classic(bpf_prog));
+		      bpf_prog_was_classic(bpf_prog), tail_call_reachable,
+		      bpf_prog->aux->func_idx != 0);
+	push_callee_regs(&prog, callee_regs_used);
 	addrs[0] = prog - temp;
 
 	for (i = 1; i <= insn_cnt; i++, insn++) {
@@ -1102,16 +1237,27 @@ xadd:			if (is_imm8(insn->off))
 			/* call */
 		case BPF_JMP | BPF_CALL:
 			func = (u8 *) __bpf_call_base + imm32;
-			if (!imm32 || emit_call(&prog, func, image + addrs[i - 1]))
-				return -EINVAL;
+			if (tail_call_reachable) {
+				EMIT3_off32(0x48, 0x8B, 0x85,
+					    -(bpf_prog->aux->stack_depth + 8));
+				if (!imm32 || emit_call(&prog, func, image + addrs[i - 1] + 7))
+					return -EINVAL;
+			} else {
+				if (!imm32 || emit_call(&prog, func, image + addrs[i - 1]))
+					return -EINVAL;
+			}
 			break;
 
 		case BPF_JMP | BPF_TAIL_CALL:
 			if (imm32)
 				emit_bpf_tail_call_direct(&bpf_prog->aux->poke_tab[imm32 - 1],
-							  &prog, addrs[i], image);
+							  &prog, addrs[i], image,
+							  callee_regs_used,
+							  bpf_prog->aux->stack_depth);
 			else
-				emit_bpf_tail_call_indirect(&prog);
+				emit_bpf_tail_call_indirect(&prog,
+							    callee_regs_used,
+							    bpf_prog->aux->stack_depth);
 			break;
 
 			/* cond jump */
@@ -1294,12 +1440,9 @@ emit_jmp:
 			seen_exit = true;
 			/* Update cleanup_addr */
 			ctx->cleanup_addr = proglen;
-			if (!bpf_prog_was_classic(bpf_prog))
-				EMIT1(0x5B); /* get rid of tail_call_cnt */
-			EMIT2(0x41, 0x5F);   /* pop r15 */
-			EMIT2(0x41, 0x5E);   /* pop r14 */
-			EMIT2(0x41, 0x5D);   /* pop r13 */
-			EMIT1(0x5B);         /* pop rbx */
+			pop_callee_regs(&prog, callee_regs_used);
+			if (tail_call_reachable)
+				EMIT1(0x59); /* pop rcx, get rid of tail_call_cnt */
 			EMIT1(0xC9);         /* leave */
 			EMIT1(0xC3);         /* ret */
 			break;