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s390/bpf: Change seen_reg to a mask

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Using a mask instead of an array saves a small amount of memory and
allows marking multiple registers as seen with a simple "or". Another
positive side-effect is that it speeds up verification with jitterbug.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20240703005047.40915-2-iii@linux.ibm.com
This commit is contained in:
Ilya Leoshkevich 2024-07-03 02:48:47 +02:00 committed by Daniel Borkmann
parent bc239eb271
commit 7ba4f43e16
1 changed files with 16 additions and 16 deletions
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32
arch/s390/net/bpf_jit_comp.c
View file

@ -35,7 +35,7 @@
struct bpf_jit {
u32 seen; /* Flags to remember seen eBPF instructions */
u32 seen_reg[16]; /* Array to remember which registers are used */
u16 seen_regs; /* Mask to remember which registers are used */
u32 *addrs; /* Array with relative instruction addresses */
u8 *prg_buf; /* Start of program */
int size; /* Size of program and literal pool */
@ -120,8 +120,8 @@ static inline void reg_set_seen(struct bpf_jit *jit, u32 b1)
{
u32 r1 = reg2hex[b1];
if (r1 >= 6 && r1 <= 15 && !jit->seen_reg[r1])
jit->seen_reg[r1] = 1;
if (r1 >= 6 && r1 <= 15)
jit->seen_regs |= (1 << r1);
}
#define REG_SET_SEEN(b1) \
@ -129,8 +129,6 @@ static inline void reg_set_seen(struct bpf_jit *jit, u32 b1)
reg_set_seen(jit, b1); \
})
#define REG_SEEN(b1) jit->seen_reg[reg2hex[(b1)]]
/*
* EMIT macros for code generation
*/
@ -438,12 +436,12 @@ static void restore_regs(struct bpf_jit *jit, u32 rs, u32 re, u32 stack_depth)
/*
* Return first seen register (from start)
*/
static int get_start(struct bpf_jit *jit, int start)
static int get_start(u16 seen_regs, int start)
{
int i;
for (i = start; i <= 15; i++) {
if (jit->seen_reg[i])
if (seen_regs & (1 << i))
return i;
}
return 0;
@ -452,15 +450,15 @@ static int get_start(struct bpf_jit *jit, int start)
/*
* Return last seen register (from start) (gap >= 2)
*/
static int get_end(struct bpf_jit *jit, int start)
static int get_end(u16 seen_regs, int start)
{
int i;
for (i = start; i < 15; i++) {
if (!jit->seen_reg[i] && !jit->seen_reg[i + 1])
if (!(seen_regs & (3 << i)))
return i - 1;
}
return jit->seen_reg[15] ? 15 : 14;
return (seen_regs & (1 << 15)) ? 15 : 14;
}
#define REGS_SAVE 1
@ -469,8 +467,10 @@ 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, u32 stack_depth)
static void save_restore_regs(struct bpf_jit *jit, int op, u32 stack_depth,
u16 extra_regs)
{
u16 seen_regs = jit->seen_regs | extra_regs;
const int last = 15, save_restore_size = 6;
int re = 6, rs;
@ -484,10 +484,10 @@ static void save_restore_regs(struct bpf_jit *jit, int op, u32 stack_depth)
}
do {
rs = get_start(jit, re);
rs = get_start(seen_regs, re);
if (!rs)
break;
re = get_end(jit, rs + 1);
re = get_end(seen_regs, rs + 1);
if (op == REGS_SAVE)
save_regs(jit, rs, re);
else
@ -573,7 +573,7 @@ static void bpf_jit_prologue(struct bpf_jit *jit, struct bpf_prog *fp,
/* Tail calls have to skip above initialization */
jit->tail_call_start = jit->prg;
/* Save registers */
save_restore_regs(jit, REGS_SAVE, stack_depth);
save_restore_regs(jit, REGS_SAVE, stack_depth, 0);
/* Setup literal pool */
if (is_first_pass(jit) || (jit->seen & SEEN_LITERAL)) {
if (!is_first_pass(jit) &&
@ -649,7 +649,7 @@ static void bpf_jit_epilogue(struct bpf_jit *jit, u32 stack_depth)
/* Load exit code: lgr %r2,%b0 */
EMIT4(0xb9040000, REG_2, BPF_REG_0);
/* Restore registers */
save_restore_regs(jit, REGS_RESTORE, stack_depth);
save_restore_regs(jit, REGS_RESTORE, stack_depth, 0);
if (nospec_uses_trampoline()) {
jit->r14_thunk_ip = jit->prg;
/* Generate __s390_indirect_jump_r14 thunk */
@ -1847,7 +1847,7 @@ 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);
save_restore_regs(jit, REGS_RESTORE, stack_depth, 0);
/*
* goto *(prog->bpf_func + tail_call_start);