diff options
| author | Hari Bathini <hbathini@linux.ibm.com> | 2021-10-12 15:30:55 +0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2021-11-25 03:25:32 +0300 |
| commit | 23b51916ee129833453d8a3d6bde0ff392f82fce (patch) | |
| tree | 3bdf36e2581dc645c35036836352ce8ceea254c5 /arch/powerpc/net/bpf_jit.h | |
| parent | 9c70c7147ffec31de67d33243570a533b29f9759 (diff) | |
| download | linux-23b51916ee129833453d8a3d6bde0ff392f82fce.tar.xz | |
bpf ppc32: Add BPF_PROBE_MEM support for JIT
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 3 instructions,
first 2 instructions clear dest_reg (lower & higher 32-bit registers)
and last instruction 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 -->| lwz r28,4(r4) |
| |
| |
0x40ac -->| lwz r3,0(r24) |
| lwz r4,4(r24) |
| |
| |
|------------------|
0x4278 -->| li r28,0 | \
| li r27,0 | | fixup entry
| b 0x4024 | /
0x4284 -->| li r4,0 |
| li r3,0 |
| b 0x40b4 |
|------------------|
0x4290 -->| insn=0xfffffd90 | \ extable entry
| fixup=0xffffffe4 | /
0x4298 -->| insn=0xfffffe14 |
| fixup=0xffffffe8 |
+------------------+
(Addresses shown here are chosen random, not real)
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/20211012123056.485795-8-hbathini@linux.ibm.com
Diffstat (limited to 'arch/powerpc/net/bpf_jit.h')
| -rw-r--r-- | arch/powerpc/net/bpf_jit.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h index 444c9debce91..b20a2a83a6e7 100644 --- a/arch/powerpc/net/bpf_jit.h +++ b/arch/powerpc/net/bpf_jit.h @@ -153,7 +153,11 @@ struct codegen_context { unsigned int exentry_idx; }; +#ifdef CONFIG_PPC32 +#define BPF_FIXUP_LEN 3 /* Three instructions => 12 bytes */ +#else #define BPF_FIXUP_LEN 2 /* Two instructions => 8 bytes */ +#endif static inline void bpf_flush_icache(void *start, void *end) { |