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s390/bpf: take advantage of stack_depth tracking 

Make use of the "stack_depth" tracking feature introduced with
commit 8726679a0f ("bpf: teach verifier to track stack depth") for the
s390 JIT, so that stack usage can be reduced.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
This commit is contained in:
Michael Holzheu 2017-11-07 19:16:25 +01:00 committed by Heiko Carstens
parent 22841cea1a
commit 78372709bf
2 changed files with 18 additions and 15 deletions
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7
arch/s390/net/bpf_jit.h
View File

@ -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 * We get 160 bytes stack space from calling function, but only use
* 12 * 8 byte for old backchain, r15..r6, and tail_call_cnt. * 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_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_TMP 160 /* Offset of tmp buffer on stack */
#define STK_OFF_HLEN 168 /* Offset of SKB header length 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 */ #define STK_OFF_SKBP 176 /* Offset of SKB pointer on stack */

26
arch/s390/net/bpf_jit_comp.c
View File

@ -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 * 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; u32 off = STK_OFF_R6 + (rs - 6) * 8;
if (jit->seen & SEEN_STACK) if (jit->seen & SEEN_STACK)
off += STK_OFF; off += STK_OFF + stack_depth;
if (rs == re) if (rs == re)
/* lg %rs,off(%r15) */ /* 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. * Save and restore clobbered registers (6-15) on stack.
* We save/restore registers in chunks with gap >= 2 registers. * 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; int re = 6, rs;
@ -381,7 +381,7 @@ static void save_restore_regs(struct bpf_jit *jit, int op)
if (op == REGS_SAVE) if (op == REGS_SAVE)
save_regs(jit, rs, re); save_regs(jit, rs, re);
else else
restore_regs(jit, rs, re); restore_regs(jit, rs, re, stack_depth);
re++; re++;
} while (re <= 15); } 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. * Save registers and create stack frame if necessary.
* See stack frame layout desription in "bpf_jit.h"! * 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) { if (jit->seen & SEEN_TAIL_CALL) {
/* xc STK_OFF_TCCNT(4,%r15),STK_OFF_TCCNT(%r15) */ /* 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 */ /* Tail calls have to skip above initialization */
jit->tail_call_start = jit->prg; jit->tail_call_start = jit->prg;
/* Save registers */ /* Save registers */
save_restore_regs(jit, REGS_SAVE); save_restore_regs(jit, REGS_SAVE, stack_depth);
/* Setup literal pool */ /* Setup literal pool */
if (jit->seen & SEEN_LITERAL) { if (jit->seen & SEEN_LITERAL) {
/* basr %r13,0 */ /* 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) */ /* la %bfp,STK_160_UNUSED(%r15) (BPF frame pointer) */
EMIT4_DISP(0x41000000, BPF_REG_FP, REG_15, STK_160_UNUSED); EMIT4_DISP(0x41000000, BPF_REG_FP, REG_15, STK_160_UNUSED);
/* aghi %r15,-STK_OFF */ /* 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) if (jit->seen & SEEN_FUNC)
/* stg %w1,152(%r15) (backchain) */ /* stg %w1,152(%r15) (backchain) */
EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W1, REG_0, EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W1, REG_0,
@ -458,7 +458,7 @@ static void bpf_jit_prologue(struct bpf_jit *jit)
/* /*
* Function epilogue * 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 */ /* Return 0 */
if (jit->seen & SEEN_RET0) { if (jit->seen & SEEN_RET0) {
@ -470,7 +470,7 @@ static void bpf_jit_epilogue(struct bpf_jit *jit)
/* Load exit code: lgr %r2,%b0 */ /* Load exit code: lgr %r2,%b0 */
EMIT4(0xb9040000, REG_2, BPF_REG_0); EMIT4(0xb9040000, REG_2, BPF_REG_0);
/* Restore registers */ /* Restore registers */
save_restore_regs(jit, REGS_RESTORE); save_restore_regs(jit, REGS_RESTORE, stack_depth);
/* br %r14 */ /* br %r14 */
_EMIT2(0x07fe); _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) if (jit->seen & SEEN_STACK)
off = STK_OFF_TCCNT + STK_OFF; off = STK_OFF_TCCNT + STK_OFF + fp->aux->stack_depth;
else else
off = STK_OFF_TCCNT; off = STK_OFF_TCCNT;
/* lhi %w0,1 */ /* 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 * 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); * 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->lit = jit->lit_start;
jit->prg = 0; jit->prg = 0;
bpf_jit_prologue(jit); bpf_jit_prologue(jit, fp->aux->stack_depth);
for (i = 0; i < fp->len; i += insn_count) { for (i = 0; i < fp->len; i += insn_count) {
insn_count = bpf_jit_insn(jit, fp, i); insn_count = bpf_jit_insn(jit, fp, i);
if (insn_count < 0) if (insn_count < 0)
@ -1280,7 +1280,7 @@ static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp)
/* Next instruction address */ /* Next instruction address */
jit->addrs[i + insn_count] = jit->prg; 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->lit_start = jit->prg;
jit->size = jit->lit; jit->size = jit->lit;