Commit 78372709 authored by Michael Holzheu's avatar Michael Holzheu Committed by Heiko Carstens
Browse files

s390/bpf: take advantage of stack_depth tracking 



Make use of the "stack_depth" tracking feature introduced with
commit 8726679a ("bpf: teach verifier to track stack depth") for the
s390 JIT, so that stack usage can be reduced.

Signed-off-by: default avatarMichael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
parent 22841cea

arch/s390/net/bpf_jit.h

+5 −2
Original line number Diff line number Diff line
@@ -52,10 +52,13 @@ extern u8 sk_load_word[], sk_load_half[], sk_load_byte[]; 
 *

 * We get 160 bytes stack space from calling function, but only use

 * 12 * 8 byte for old backchain, r15..r6, and tail_call_cnt.

 *

 * The stack size used by the BPF program ("BPF stack" above) is passed

 * via "aux->stack_depth".

 */

#define STK_SPACE	(MAX_BPF_STACK + 8 + 8 + 4 + 4 + 160)

#define STK_SPACE_ADD (8 + 8 + 4 + 4 + 160)

#define STK_160_UNUSED	(160 - 12 * 8)

#define STK_OFF		(STK_SPACE - STK_160_UNUSED)

#define STK_OFF		(STK_SPACE_ADD - STK_160_UNUSED)

#define STK_OFF_TMP	160	/* Offset of tmp buffer on stack */

#define STK_OFF_HLEN	168	/* Offset of SKB header length on stack */

#define STK_OFF_SKBP	176	/* Offset of SKB pointer on stack */

arch/s390/net/bpf_jit_comp.c

+13 −13
Original line number Diff line number Diff line
@@ -319,12 +319,12 @@ 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)

static void restore_regs(struct bpf_jit *jit, u32 rs, u32 re, u32 stack_depth)

{

	u32 off = STK_OFF_R6 + (rs - 6) * 8;



	if (jit->seen & SEEN_STACK)

		off += STK_OFF;

		off += STK_OFF + stack_depth;



	if (rs == re)

		/* lg %rs,off(%r15) */
@@ -368,7 +368,7 @@ static int get_end(struct bpf_jit *jit, 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)

static void save_restore_regs(struct bpf_jit *jit, int op, u32 stack_depth)

{



	int re = 6, rs;
@@ -381,7 +381,7 @@ static void save_restore_regs(struct bpf_jit *jit, int op) 
		if (op == REGS_SAVE)

			save_regs(jit, rs, re);

		else

			restore_regs(jit, rs, re);

			restore_regs(jit, rs, re, stack_depth);

		re++;

	} while (re <= 15);

}
@@ -413,7 +413,7 @@ static void emit_load_skb_data_hlen(struct bpf_jit *jit) 
 * Save registers and create stack frame if necessary.

 * See stack frame layout desription in "bpf_jit.h"!

 */

static void bpf_jit_prologue(struct bpf_jit *jit)

static void bpf_jit_prologue(struct bpf_jit *jit, u32 stack_depth)

{

	if (jit->seen & SEEN_TAIL_CALL) {

		/* xc STK_OFF_TCCNT(4,%r15),STK_OFF_TCCNT(%r15) */
@@ -426,7 +426,7 @@ static void bpf_jit_prologue(struct bpf_jit *jit) 
	/* Tail calls have to skip above initialization */

	jit->tail_call_start = jit->prg;

	/* Save registers */

	save_restore_regs(jit, REGS_SAVE);

	save_restore_regs(jit, REGS_SAVE, stack_depth);

	/* Setup literal pool */

	if (jit->seen & SEEN_LITERAL) {

		/* basr %r13,0 */
@@ -441,7 +441,7 @@ static void bpf_jit_prologue(struct bpf_jit *jit) 
		/* 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);

		EMIT4_IMM(0xa70b0000, REG_15, -(STK_OFF + stack_depth));

		if (jit->seen & SEEN_FUNC)

			/* stg %w1,152(%r15) (backchain) */

			EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W1, REG_0,
@@ -458,7 +458,7 @@ static void bpf_jit_prologue(struct bpf_jit *jit) 
/*

 * Function epilogue

 */

static void bpf_jit_epilogue(struct bpf_jit *jit)

static void bpf_jit_epilogue(struct bpf_jit *jit, u32 stack_depth)

{

	/* Return 0 */

	if (jit->seen & SEEN_RET0) {
@@ -470,7 +470,7 @@ static void bpf_jit_epilogue(struct bpf_jit *jit) 
	/* Load exit code: lgr %r2,%b0 */

	EMIT4(0xb9040000, REG_2, BPF_REG_0);

	/* Restore registers */

	save_restore_regs(jit, REGS_RESTORE);

	save_restore_regs(jit, REGS_RESTORE, stack_depth);

	/* br %r14 */

	_EMIT2(0x07fe);

}
@@ -1018,7 +1018,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i 
		 */



		if (jit->seen & SEEN_STACK)

			off = STK_OFF_TCCNT + STK_OFF;

			off = STK_OFF_TCCNT + STK_OFF + fp->aux->stack_depth;

		else

			off = STK_OFF_TCCNT;

		/* lhi %w0,1 */
@@ -1046,7 +1046,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i 
		/*

		 * Restore registers before calling function

		 */

		save_restore_regs(jit, REGS_RESTORE);

		save_restore_regs(jit, REGS_RESTORE, fp->aux->stack_depth);



		/*

		 * goto *(prog->bpf_func + tail_call_start);
@@ -1272,7 +1272,7 @@ static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp) 
	jit->lit = jit->lit_start;

	jit->prg = 0;



	bpf_jit_prologue(jit);

	bpf_jit_prologue(jit, fp->aux->stack_depth);

	for (i = 0; i < fp->len; i += insn_count) {

		insn_count = bpf_jit_insn(jit, fp, i);

		if (insn_count < 0)
@@ -1280,7 +1280,7 @@ static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp) 
		/* Next instruction address */

		jit->addrs[i + insn_count] = jit->prg;

	}

	bpf_jit_epilogue(jit);

	bpf_jit_epilogue(jit, fp->aux->stack_depth);



	jit->lit_start = jit->prg;

	jit->size = jit->lit;

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