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linux/arch/parisc/net/bpf_jit_core.c
Mikulas Patocka 1fd2c10acb parisc: fix unaligned accesses in BPF
There were spurious unaligned access warnings when calling BPF code.
Sometimes, the warnings were triggered with any incoming packet, making
the machine hard to use.

The reason for the warnings is this: on parisc64, pointers to functions
are not really pointers to functions, they are pointers to 16-byte
descriptor. The first 8 bytes of the descriptor is a pointer to the
function and the next 8 bytes of the descriptor is the content of the
"dp" register. This descriptor is generated in the function
bpf_jit_build_prologue.

The problem is that the function bpf_int_jit_compile advertises 4-byte
alignment when calling bpf_jit_binary_alloc, bpf_jit_binary_alloc
randomizes the returned array and if the array happens to be not aligned
on 8-byte boundary, the descriptor generated in bpf_jit_build_prologue is
also not aligned and this triggers the unaligned access warning.

Fix this by advertising 8-byte alignment on parisc64 when calling
bpf_jit_binary_alloc.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Helge Deller <deller@gmx.de>
2024-07-29 16:19:07 +02:00

208 lines
4.6 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Common functionality for HPPA32 and HPPA64 BPF JIT compilers
*
* Copyright (c) 2023 Helge Deller <deller@gmx.de>
*
*/
#include <linux/bpf.h>
#include <linux/filter.h>
#include "bpf_jit.h"
/* Number of iterations to try until offsets converge. */
#define NR_JIT_ITERATIONS 35
static int build_body(struct hppa_jit_context *ctx, bool extra_pass, int *offset)
{
const struct bpf_prog *prog = ctx->prog;
int i;
ctx->reg_seen_collect = true;
for (i = 0; i < prog->len; i++) {
const struct bpf_insn *insn = &prog->insnsi[i];
int ret;
ret = bpf_jit_emit_insn(insn, ctx, extra_pass);
/* BPF_LD | BPF_IMM | BPF_DW: skip the next instruction. */
if (ret > 0)
i++;
if (offset)
offset[i] = ctx->ninsns;
if (ret < 0)
return ret;
}
ctx->reg_seen_collect = false;
return 0;
}
bool bpf_jit_needs_zext(void)
{
return true;
}
struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
{
unsigned int prog_size = 0, extable_size = 0;
bool tmp_blinded = false, extra_pass = false;
struct bpf_prog *tmp, *orig_prog = prog;
int pass = 0, prev_ninsns = 0, prologue_len, i;
struct hppa_jit_data *jit_data;
struct hppa_jit_context *ctx;
if (!prog->jit_requested)
return orig_prog;
tmp = bpf_jit_blind_constants(prog);
if (IS_ERR(tmp))
return orig_prog;
if (tmp != prog) {
tmp_blinded = true;
prog = tmp;
}
jit_data = prog->aux->jit_data;
if (!jit_data) {
jit_data = kzalloc(sizeof(*jit_data), GFP_KERNEL);
if (!jit_data) {
prog = orig_prog;
goto out;
}
prog->aux->jit_data = jit_data;
}
ctx = &jit_data->ctx;
if (ctx->offset) {
extra_pass = true;
prog_size = sizeof(*ctx->insns) * ctx->ninsns;
goto skip_init_ctx;
}
ctx->prog = prog;
ctx->offset = kcalloc(prog->len, sizeof(int), GFP_KERNEL);
if (!ctx->offset) {
prog = orig_prog;
goto out_offset;
}
for (i = 0; i < prog->len; i++) {
prev_ninsns += 20;
ctx->offset[i] = prev_ninsns;
}
for (i = 0; i < NR_JIT_ITERATIONS; i++) {
pass++;
ctx->ninsns = 0;
if (build_body(ctx, extra_pass, ctx->offset)) {
prog = orig_prog;
goto out_offset;
}
ctx->body_len = ctx->ninsns;
bpf_jit_build_prologue(ctx);
ctx->prologue_len = ctx->ninsns - ctx->body_len;
ctx->epilogue_offset = ctx->ninsns;
bpf_jit_build_epilogue(ctx);
if (ctx->ninsns == prev_ninsns) {
if (jit_data->header)
break;
/* obtain the actual image size */
extable_size = prog->aux->num_exentries *
sizeof(struct exception_table_entry);
prog_size = sizeof(*ctx->insns) * ctx->ninsns;
jit_data->header =
bpf_jit_binary_alloc(prog_size + extable_size,
&jit_data->image,
sizeof(long),
bpf_fill_ill_insns);
if (!jit_data->header) {
prog = orig_prog;
goto out_offset;
}
ctx->insns = (u32 *)jit_data->image;
/*
* Now, when the image is allocated, the image can
* potentially shrink more (auipc/jalr -> jal).
*/
}
prev_ninsns = ctx->ninsns;
}
if (i == NR_JIT_ITERATIONS) {
pr_err("bpf-jit: image did not converge in <%d passes!\n", i);
if (jit_data->header)
bpf_jit_binary_free(jit_data->header);
prog = orig_prog;
goto out_offset;
}
if (extable_size)
prog->aux->extable = (void *)ctx->insns + prog_size;
skip_init_ctx:
pass++;
ctx->ninsns = 0;
bpf_jit_build_prologue(ctx);
if (build_body(ctx, extra_pass, NULL)) {
bpf_jit_binary_free(jit_data->header);
prog = orig_prog;
goto out_offset;
}
bpf_jit_build_epilogue(ctx);
if (HPPA_JIT_DEBUG || bpf_jit_enable > 1) {
if (HPPA_JIT_DUMP)
bpf_jit_dump(prog->len, prog_size, pass, ctx->insns);
if (HPPA_JIT_REBOOT)
{ extern int machine_restart(char *); machine_restart(""); }
}
prog->bpf_func = (void *)ctx->insns;
prog->jited = 1;
prog->jited_len = prog_size;
bpf_flush_icache(jit_data->header, ctx->insns + ctx->ninsns);
if (!prog->is_func || extra_pass) {
if (bpf_jit_binary_lock_ro(jit_data->header)) {
bpf_jit_binary_free(jit_data->header);
prog->bpf_func = NULL;
prog->jited = 0;
prog->jited_len = 0;
goto out_offset;
}
prologue_len = ctx->epilogue_offset - ctx->body_len;
for (i = 0; i < prog->len; i++)
ctx->offset[i] += prologue_len;
bpf_prog_fill_jited_linfo(prog, ctx->offset);
out_offset:
kfree(ctx->offset);
kfree(jit_data);
prog->aux->jit_data = NULL;
}
out:
if (HPPA_JIT_REBOOT)
{ extern int machine_restart(char *); machine_restart(""); }
if (tmp_blinded)
bpf_jit_prog_release_other(prog, prog == orig_prog ?
tmp : orig_prog);
return prog;
}
u64 hppa_div64(u64 div, u64 divisor)
{
div = div64_u64(div, divisor);
return div;
}
u64 hppa_div64_rem(u64 div, u64 divisor)
{
u64 rem;
div64_u64_rem(div, divisor, &rem);
return rem;
}