iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

s390/bpf: Factor out emitting probe nops

Browse Source 
The upcoming arena support for the loop-based BPF_XCHG implementation
requires emitting nop and extable entries separately. Move nop handling
into a separate function, and keep track of the nop offset.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20240701234304.14336-3-iii@linux.ibm.com
This commit is contained in:
Ilya Leoshkevich
2024-07-02 01:40:20 +02:00
committed by Daniel Borkmann
parent df34ec9db6
commit d0736d8c49
1 changed files with 40 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

62
arch/s390/net/bpf_jit_comp.c
View File

@ -693,24 +693,52 @@ bool ex_handler_bpf(const struct exception_table_entry *x, struct pt_regs *regs)
return true;
}
/*
* A single BPF probe instruction
*/
struct bpf_jit_probe {
int prg; /* JITed instruction offset */
int nop_prg; /* JITed nop offset */
};
static void bpf_jit_probe_init(struct bpf_jit_probe *probe)
{
probe->prg = -1;
probe->nop_prg = -1;
}
/*
* Handlers of certain exceptions leave psw.addr pointing to the instruction
* directly after the failing one. Therefore, create two exception table
* entries and also add a nop in case two probing instructions come directly
* after each other.
*/
static void bpf_jit_probe_emit_nop(struct bpf_jit *jit,
struct bpf_jit_probe *probe)
{
probe->nop_prg = jit->prg;
/* bcr 0,%0 */
_EMIT2(0x0700);
}
static int bpf_jit_probe_mem(struct bpf_jit *jit, struct bpf_prog *fp,
int probe_prg, int nop_prg)
struct bpf_jit_probe *probe)
{
struct exception_table_entry *ex;
int reg, prg;
int i, prg, reg;
s64 delta;
u8 *insn;
int i;
bpf_jit_probe_emit_nop(jit, probe);
if (!fp->aux->extable)
/* Do nothing during early JIT passes. */
return 0;
insn = jit->prg_buf + probe_prg;
insn = jit->prg_buf + probe->prg;
reg = get_probe_mem_regno(insn);
if (WARN_ON_ONCE(reg < 0))
/* JIT bug - unexpected probe instruction. */
return -1;
if (WARN_ON_ONCE(probe_prg + insn_length(*insn) != nop_prg))
if (WARN_ON_ONCE(probe->prg + insn_length(*insn) != probe->nop_prg))
/* JIT bug - gap between probe and nop instructions. */
return -1;
for (i = 0; i < 2; i++) {
@ -719,7 +747,7 @@ static int bpf_jit_probe_mem(struct bpf_jit *jit, struct bpf_prog *fp,
return -1;
ex = &fp->aux->extable[jit->excnt];
/* Add extable entries for probe and nop instructions. */
prg = i == 0 ? probe_prg : nop_prg;
prg = i == 0 ? probe->prg : probe->nop_prg;
delta = jit->prg_buf + prg - (u8 *)&ex->insn;
if (WARN_ON_ONCE(delta < INT_MIN || delta > INT_MAX))
/* JIT bug - code and extable must be close. */
@ -729,7 +757,7 @@ static int bpf_jit_probe_mem(struct bpf_jit *jit, struct bpf_prog *fp,
* Always land on the nop. Note that extable infrastructure
* ignores fixup field, it is handled by ex_handler_bpf().
*/
delta = jit->prg_buf + nop_prg - (u8 *)&ex->fixup;
delta = jit->prg_buf + probe->nop_prg - (u8 *)&ex->fixup;
if (WARN_ON_ONCE(delta < INT_MIN || delta > INT_MAX))
/* JIT bug - landing pad and extable must be close. */
return -1;
@ -782,19 +810,19 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
s32 branch_oc_off = insn->off;
u32 dst_reg = insn->dst_reg;
u32 src_reg = insn->src_reg;
struct bpf_jit_probe probe;
int last, insn_count = 1;
u32 *addrs = jit->addrs;
s32 imm = insn->imm;
s16 off = insn->off;
int probe_prg = -1;
unsigned int mask;
int nop_prg;
int err;
bpf_jit_probe_init(&probe);
if (BPF_CLASS(insn->code) == BPF_LDX &&
(BPF_MODE(insn->code) == BPF_PROBE_MEM ||
BPF_MODE(insn->code) == BPF_PROBE_MEMSX))
probe_prg = jit->prg;
probe.prg = jit->prg;
switch (insn->code) {
/*
@ -1897,18 +1925,8 @@ branch_oc:
return -1;
}
if (probe_prg != -1) {
/*
* Handlers of certain exceptions leave psw.addr pointing to
* the instruction directly after the failing one. Therefore,
* create two exception table entries and also add a nop in
* case two probing instructions come directly after each
* other.
*/
nop_prg = jit->prg;
/* bcr 0,%0 */
_EMIT2(0x0700);
err = bpf_jit_probe_mem(jit, fp, probe_prg, nop_prg);
if (probe.prg != -1) {
err = bpf_jit_probe_mem(jit, fp, &probe);
if (err < 0)
return err;
}