From: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Date: Tue, 12 Oct 2021 18:00:53 +0530
Subject: bpf ppc64: Add BPF_PROBE_MEM support for JIT
Patch-mainline: v5.17-rc1
Git-commit: 983bdc0245a29cdefcd30d9d484d3edbc4b6d787
References: jsc#PED-1368
BPF load instruction with BPF_PROBE_MEM mode can cause a fault
inside kernel. Append exception table for such instructions
within BPF program.
Unlike other archs which uses extable 'fixup' field to pass dest_reg
and nip, BPF exception table on PowerPC follows the generic PowerPC
exception table design, where it populates both fixup and extable
sections within BPF program. fixup section contains two instructions,
first instruction clears dest_reg and 2nd jumps to next instruction
in the BPF code. extable 'insn' field contains relative offset of
the instruction and 'fixup' field contains relative offset of the
fixup entry. Example layout of BPF program with extable present:
+------------------+
| |
| |
0x4020 -->| ld r27,4(r3) |
| |
| |
0x40ac -->| lwz r3,0(r4) |
| |
| |
|------------------|
0x4280 -->| li r27,0 | \ fixup entry
| b 0x4024 | /
0x4288 -->| li r3,0 |
| b 0x40b0 |
|------------------|
0x4290 -->| insn=0xfffffd90 | \ extable entry
| fixup=0xffffffec | /
0x4298 -->| insn=0xfffffe14 |
| fixup=0xffffffec |
+------------------+
(Addresses shown here are chosen random, not real)
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211012123056.485795-6-hbathini@linux.ibm.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
arch/powerpc/net/bpf_jit.h | 8 ++++
arch/powerpc/net/bpf_jit_comp.c | 66 ++++++++++++++++++++++++++++++++++----
arch/powerpc/net/bpf_jit_comp32.c | 2 -
arch/powerpc/net/bpf_jit_comp64.c | 13 ++++++-
4 files changed, 80 insertions(+), 9 deletions(-)
--- a/arch/powerpc/net/bpf_jit.h
+++ b/arch/powerpc/net/bpf_jit.h
@@ -150,8 +150,11 @@ struct codegen_context {
unsigned int idx;
unsigned int stack_size;
int b2p[ARRAY_SIZE(b2p)];
+ unsigned int exentry_idx;
};
+#define BPF_FIXUP_LEN 2 /* Two instructions => 8 bytes */
+
static inline void bpf_flush_icache(void *start, void *end)
{
smp_wmb(); /* smp write barrier */
@@ -175,11 +178,14 @@ static inline void bpf_clear_seen_regist
void bpf_jit_emit_func_call_rel(u32 *image, struct codegen_context *ctx, u64 func);
int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *ctx,
- u32 *addrs);
+ u32 *addrs, int pass);
void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx);
void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx);
void bpf_jit_realloc_regs(struct codegen_context *ctx);
+int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, int pass, struct codegen_context *ctx,
+ int insn_idx, int jmp_off, int dst_reg);
+
#endif
#endif
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -101,6 +101,8 @@ struct bpf_prog *bpf_int_jit_compile(str
struct bpf_prog *tmp_fp;
bool bpf_blinded = false;
bool extra_pass = false;
+ u32 extable_len;
+ u32 fixup_len;
if (!fp->jit_requested)
return org_fp;
@@ -131,7 +133,6 @@ struct bpf_prog *bpf_int_jit_compile(str
image = jit_data->image;
bpf_hdr = jit_data->header;
proglen = jit_data->proglen;
- alloclen = proglen + FUNCTION_DESCR_SIZE;
extra_pass = true;
goto skip_init_ctx;
}
@@ -149,7 +150,7 @@ struct bpf_prog *bpf_int_jit_compile(str
cgctx.stack_size = round_up(fp->aux->stack_depth, 16);
/* Scouting faux-generate pass 0 */
- if (bpf_jit_build_body(fp, 0, &cgctx, addrs)) {
+ if (bpf_jit_build_body(fp, 0, &cgctx, addrs, 0)) {
/* We hit something illegal or unsupported. */
fp = org_fp;
goto out_addrs;
@@ -162,7 +163,7 @@ struct bpf_prog *bpf_int_jit_compile(str
*/
if (cgctx.seen & SEEN_TAILCALL) {
cgctx.idx = 0;
- if (bpf_jit_build_body(fp, 0, &cgctx, addrs)) {
+ if (bpf_jit_build_body(fp, 0, &cgctx, addrs, 0)) {
fp = org_fp;
goto out_addrs;
}
@@ -177,8 +178,11 @@ struct bpf_prog *bpf_int_jit_compile(str
bpf_jit_build_prologue(0, &cgctx);
bpf_jit_build_epilogue(0, &cgctx);
+ fixup_len = fp->aux->num_exentries * BPF_FIXUP_LEN * 4;
+ extable_len = fp->aux->num_exentries * sizeof(struct exception_table_entry);
+
proglen = cgctx.idx * 4;
- alloclen = proglen + FUNCTION_DESCR_SIZE;
+ alloclen = proglen + FUNCTION_DESCR_SIZE + fixup_len + extable_len;
bpf_hdr = bpf_jit_binary_alloc(alloclen, &image, 4, bpf_jit_fill_ill_insns);
if (!bpf_hdr) {
@@ -186,6 +190,9 @@ struct bpf_prog *bpf_int_jit_compile(str
goto out_addrs;
}
+ if (extable_len)
+ fp->aux->extable = (void *)image + FUNCTION_DESCR_SIZE + proglen + fixup_len;
+
skip_init_ctx:
code_base = (u32 *)(image + FUNCTION_DESCR_SIZE);
@@ -210,7 +217,7 @@ skip_init_ctx:
/* Now build the prologue, body code & epilogue for real. */
cgctx.idx = 0;
bpf_jit_build_prologue(code_base, &cgctx);
- if (bpf_jit_build_body(fp, code_base, &cgctx, addrs)) {
+ if (bpf_jit_build_body(fp, code_base, &cgctx, addrs, pass)) {
bpf_jit_binary_free(bpf_hdr);
fp = org_fp;
goto out_addrs;
@@ -238,7 +245,7 @@ skip_codegen_passes:
fp->bpf_func = (void *)image;
fp->jited = 1;
- fp->jited_len = alloclen;
+ fp->jited_len = proglen + FUNCTION_DESCR_SIZE;
bpf_flush_icache(bpf_hdr, (u8 *)bpf_hdr + (bpf_hdr->pages * PAGE_SIZE));
if (!fp->is_func || extra_pass) {
@@ -262,3 +269,50 @@ out:
return fp;
}
+
+/*
+ * The caller should check for (BPF_MODE(code) == BPF_PROBE_MEM) before calling
+ * this function, as this only applies to BPF_PROBE_MEM, for now.
+ */
+int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, int pass, struct codegen_context *ctx,
+ int insn_idx, int jmp_off, int dst_reg)
+{
+ off_t offset;
+ unsigned long pc;
+ struct exception_table_entry *ex;
+ u32 *fixup;
+
+ /* Populate extable entries only in the last pass */
+ if (pass != 2)
+ return 0;
+
+ if (!fp->aux->extable ||
+ WARN_ON_ONCE(ctx->exentry_idx >= fp->aux->num_exentries))
+ return -EINVAL;
+
+ pc = (unsigned long)&image[insn_idx];
+
+ fixup = (void *)fp->aux->extable -
+ (fp->aux->num_exentries * BPF_FIXUP_LEN * 4) +
+ (ctx->exentry_idx * BPF_FIXUP_LEN * 4);
+
+ fixup[0] = PPC_RAW_LI(dst_reg, 0);
+
+ fixup[BPF_FIXUP_LEN - 1] =
+ PPC_RAW_BRANCH((long)(pc + jmp_off) - (long)&fixup[BPF_FIXUP_LEN - 1]);
+
+ ex = &fp->aux->extable[ctx->exentry_idx];
+
+ offset = pc - (long)&ex->insn;
+ if (WARN_ON_ONCE(offset >= 0 || offset < INT_MIN))
+ return -ERANGE;
+ ex->insn = offset;
+
+ offset = (long)fixup - (long)&ex->fixup;
+ if (WARN_ON_ONCE(offset >= 0 || offset < INT_MIN))
+ return -ERANGE;
+ ex->fixup = offset;
+
+ ctx->exentry_idx++;
+ return 0;
+}
--- a/arch/powerpc/net/bpf_jit_comp32.c
+++ b/arch/powerpc/net/bpf_jit_comp32.c
@@ -268,7 +268,7 @@ static int bpf_jit_emit_tail_call(u32 *i
/* Assemble the body code between the prologue & epilogue */
int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *ctx,
- u32 *addrs)
+ u32 *addrs, int pass)
{
const struct bpf_insn *insn = fp->insnsi;
int flen = fp->len;
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -297,7 +297,7 @@ asm (
/* Assemble the body code between the prologue & epilogue */
int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *ctx,
- u32 *addrs)
+ u32 *addrs, int pass)
{
enum stf_barrier_type stf_barrier = stf_barrier_type_get();
const struct bpf_insn *insn = fp->insnsi;
@@ -779,12 +779,16 @@ emit_clear:
*/
/* dst = *(u8 *)(ul) (src + off) */
case BPF_LDX | BPF_MEM | BPF_B:
+ case BPF_LDX | BPF_PROBE_MEM | BPF_B:
/* dst = *(u16 *)(ul) (src + off) */
case BPF_LDX | BPF_MEM | BPF_H:
+ case BPF_LDX | BPF_PROBE_MEM | BPF_H:
/* dst = *(u32 *)(ul) (src + off) */
case BPF_LDX | BPF_MEM | BPF_W:
+ case BPF_LDX | BPF_PROBE_MEM | BPF_W:
/* dst = *(u64 *)(ul) (src + off) */
case BPF_LDX | BPF_MEM | BPF_DW:
+ case BPF_LDX | BPF_PROBE_MEM | BPF_DW:
switch (size) {
case BPF_B:
EMIT(PPC_RAW_LBZ(dst_reg, src_reg, off));
@@ -802,6 +806,13 @@ emit_clear:
if (size != BPF_DW && insn_is_zext(&insn[i + 1]))
addrs[++i] = ctx->idx * 4;
+
+ if (BPF_MODE(code) == BPF_PROBE_MEM) {
+ ret = bpf_add_extable_entry(fp, image, pass, ctx, ctx->idx - 1,
+ 4, dst_reg);
+ if (ret)
+ return ret;
+ }
break;
/*