s390/bpf: Centralize frame offset calculations

The calculation of the distance from %r15 to the caller-allocated
portion of the stack frame is copy-pasted into multiple places in the
JIT code.

Move it to bpf_jit_prog() and save the result into bpf_jit::frame_off,
so that the other parts of the JIT can use it.

Signed-off-by: Ilya Leoshkevich <[email protected]>

Author: iii-i

arch/s390/net/bpf_jit_comp.c

@@ -54,6 +54,7 @@ struct bpf_jit {
 	int prologue_plt;	/* Start of prologue hotpatch PLT */
 	int kern_arena;		/* Pool offset of kernel arena address */
 	u64 user_arena;		/* User arena address */
+	u32 frame_off;		/* Offset of frame from %r15 */
 };
 
 #define SEEN_MEM	BIT(0)		/* use mem[] for temporary storage */
@@ -443,12 +444,9 @@ static void save_regs(struct bpf_jit *jit, u32 rs, u32 re)
 /*
  * Restore registers from "rs" (register start) to "re" (register end) on stack
  */
-static void restore_regs(struct bpf_jit *jit, u32 rs, u32 re, u32 stack_depth)
+static void restore_regs(struct bpf_jit *jit, u32 rs, u32 re)
 {
-	u32 off = STK_OFF_R6 + (rs - 6) * 8;
-
-	if (jit->seen & SEEN_STACK)
-		off += STK_OFF + stack_depth;
+	u32 off = jit->frame_off + STK_OFF_R6 + (rs - 6) * 8;
 
 	if (rs == re)
 		/* lg %rs,off(%r15) */
@@ -492,8 +490,7 @@ static int get_end(u16 seen_regs, int start)
  * Save and restore clobbered registers (6-15) on stack.
  * We save/restore registers in chunks with gap >= 2 registers.
  */
-static void save_restore_regs(struct bpf_jit *jit, int op, u32 stack_depth,
-			      u16 extra_regs)
+static void save_restore_regs(struct bpf_jit *jit, int op, u16 extra_regs)
 {
 	u16 seen_regs = jit->seen_regs | extra_regs;
 	const int last = 15, save_restore_size = 6;
@@ -516,7 +513,7 @@ static void save_restore_regs(struct bpf_jit *jit, int op, u32 stack_depth,
 		if (op == REGS_SAVE)
 			save_regs(jit, rs, re);
 		else
-			restore_regs(jit, rs, re, stack_depth);
+			restore_regs(jit, rs, re);
 		re++;
 	} while (re <= last);
 }
@@ -575,8 +572,7 @@ static void bpf_jit_plt(struct bpf_plt *plt, void *ret, void *target)
  * Save registers and create stack frame if necessary.
  * See stack frame layout description in "bpf_jit.h"!
  */
-static void bpf_jit_prologue(struct bpf_jit *jit, struct bpf_prog *fp,
-			     u32 stack_depth)
+static void bpf_jit_prologue(struct bpf_jit *jit, struct bpf_prog *fp)
 {
 	/* No-op for hotpatching */
 	/* brcl 0,prologue_plt */
@@ -609,7 +605,7 @@ static void bpf_jit_prologue(struct bpf_jit *jit, struct bpf_prog *fp,
 		jit->seen_regs |= NVREGS;
 	} else {
 		/* Save registers */
-		save_restore_regs(jit, REGS_SAVE, stack_depth,
+		save_restore_regs(jit, REGS_SAVE,
 				  fp->aux->exception_boundary ? NVREGS : 0);
 	}
 	/* Setup literal pool */
@@ -631,8 +627,8 @@ static void bpf_jit_prologue(struct bpf_jit *jit, struct bpf_prog *fp,
 		EMIT4(0xb9040000, REG_W1, REG_15);
 		/* la %bfp,STK_160_UNUSED(%r15) (BPF frame pointer) */
 		EMIT4_DISP(0x41000000, BPF_REG_FP, REG_15, STK_160_UNUSED);
-		/* aghi %r15,-STK_OFF */
-		EMIT4_IMM(0xa70b0000, REG_15, -(STK_OFF + stack_depth));
+		/* aghi %r15,-frame_off */
+		EMIT4_IMM(0xa70b0000, REG_15, -jit->frame_off);
 		/* stg %w1,152(%r15) (backchain) */
 		EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W1, REG_0,
 			      REG_15, 152);
@@ -669,13 +665,13 @@ static void call_r1(struct bpf_jit *jit)
 /*
  * Function epilogue
  */
-static void bpf_jit_epilogue(struct bpf_jit *jit, u32 stack_depth)
+static void bpf_jit_epilogue(struct bpf_jit *jit)
 {
 	jit->exit_ip = jit->prg;
 	/* Load exit code: lgr %r2,%b0 */
 	EMIT4(0xb9040000, REG_2, BPF_REG_0);
 	/* Restore registers */
-	save_restore_regs(jit, REGS_RESTORE, stack_depth, 0);
+	save_restore_regs(jit, REGS_RESTORE, 0);
 	EMIT_JUMP_REG(14);
 
 	jit->prg = ALIGN(jit->prg, 8);
@@ -857,7 +853,7 @@ static int sign_extend(struct bpf_jit *jit, int r, u8 size, u8 flags)
  * stack space for the large switch statement.
  */
 static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
-				 int i, bool extra_pass, u32 stack_depth)
+				 int i, bool extra_pass)
 {
 	struct bpf_insn *insn = &fp->insnsi[i];
 	s32 branch_oc_off = insn->off;
@@ -1778,9 +1774,9 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
 		 * Note 2: We assume that the verifier does not let us call the
 		 * main program, which clears the tail call counter on entry.
 		 */
-		/* mvc STK_OFF_TCCNT(4,%r15),N(%r15) */
+		/* mvc STK_OFF_TCCNT(4,%r15),frame_off+STK_OFF_TCCNT(%r15) */
 		_EMIT6(0xd203f000 | STK_OFF_TCCNT,
-		       0xf000 | (STK_OFF_TCCNT + STK_OFF + stack_depth));
+		       0xf000 | (jit->frame_off + STK_OFF_TCCNT));
 
 		/* Sign-extend the kfunc arguments. */
 		if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) {
@@ -1831,10 +1827,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
 		 *         goto out;
 		 */
 
-		if (jit->seen & SEEN_STACK)
-			off = STK_OFF_TCCNT + STK_OFF + stack_depth;
-		else
-			off = STK_OFF_TCCNT;
+		off = jit->frame_off + STK_OFF_TCCNT;
 		/* lhi %w0,1 */
 		EMIT4_IMM(0xa7080000, REG_W0, 1);
 		/* laal %w1,%w0,off(%r15) */
@@ -1864,7 +1857,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
 		/*
 		 * Restore registers before calling function
 		 */
-		save_restore_regs(jit, REGS_RESTORE, stack_depth, 0);
+		save_restore_regs(jit, REGS_RESTORE, 0);
 
 		/*
 		 * goto *(prog->bpf_func + tail_call_start);
@@ -2157,7 +2150,7 @@ static int bpf_set_addr(struct bpf_jit *jit, int i)
  * Compile eBPF program into s390x code
  */
 static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp,
-			bool extra_pass, u32 stack_depth)
+			bool extra_pass)
 {
 	int i, insn_count, lit32_size, lit64_size;
 	u64 kern_arena;
@@ -2166,24 +2159,28 @@ static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp,
 	jit->lit64 = jit->lit64_start;
 	jit->prg = 0;
 	jit->excnt = 0;
+	if (is_first_pass(jit) || (jit->seen & SEEN_STACK))
+		jit->frame_off = STK_OFF + round_up(fp->aux->stack_depth, 8);
+	else
+		jit->frame_off = 0;
 
 	kern_arena = bpf_arena_get_kern_vm_start(fp->aux->arena);
 	if (kern_arena)
 		jit->kern_arena = _EMIT_CONST_U64(kern_arena);
 	jit->user_arena = bpf_arena_get_user_vm_start(fp->aux->arena);
 
-	bpf_jit_prologue(jit, fp, stack_depth);
+	bpf_jit_prologue(jit, fp);
 	if (bpf_set_addr(jit, 0) < 0)
 		return -1;
 	for (i = 0; i < fp->len; i += insn_count) {
-		insn_count = bpf_jit_insn(jit, fp, i, extra_pass, stack_depth);
+		insn_count = bpf_jit_insn(jit, fp, i, extra_pass);
 		if (insn_count < 0)
 			return -1;
 		/* Next instruction address */
 		if (bpf_set_addr(jit, i + insn_count) < 0)
 			return -1;
 	}
-	bpf_jit_epilogue(jit, stack_depth);
+	bpf_jit_epilogue(jit);
 
 	lit32_size = jit->lit32 - jit->lit32_start;
 	lit64_size = jit->lit64 - jit->lit64_start;
@@ -2259,7 +2256,6 @@ static struct bpf_binary_header *bpf_jit_alloc(struct bpf_jit *jit,
  */
 struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
 {
-	u32 stack_depth = round_up(fp->aux->stack_depth, 8);
 	struct bpf_prog *tmp, *orig_fp = fp;
 	struct bpf_binary_header *header;
 	struct s390_jit_data *jit_data;
@@ -2312,7 +2308,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
 	 *   - 3:   Calculate program size and addrs array
 	 */
 	for (pass = 1; pass <= 3; pass++) {
-		if (bpf_jit_prog(&jit, fp, extra_pass, stack_depth)) {
+		if (bpf_jit_prog(&jit, fp, extra_pass)) {
 			fp = orig_fp;
 			goto free_addrs;
 		}
@@ -2326,7 +2322,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
 		goto free_addrs;
 	}
 skip_init_ctx:
-	if (bpf_jit_prog(&jit, fp, extra_pass, stack_depth)) {
+	if (bpf_jit_prog(&jit, fp, extra_pass)) {
 		bpf_jit_binary_free(header);
 		fp = orig_fp;
 		goto free_addrs;