Commit b2268d55 authored by Ilya Leoshkevich's avatar Ilya Leoshkevich Committed by Alexei Starovoitov
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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: default avatarIlya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20250624121501.50536-2-iii@linux.ibm.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent c4b1be92

arch/s390/net/bpf_jit_comp.c

+26 −30
Original line number Diff line number Diff line
@@ -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;