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| author | Michael Holzheu <holzheu@linux.vnet.ibm.com> | 2015-06-09 06:51:06 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-06-09 20:47:10 +0200 |
| commit | 6651ee070b3124fe9b9db383e3a895a0e4aded65 (patch) | |
| tree | cd1662179dd84ff08d76eb85037900538540c3fc /arch/s390/net/bpf_jit.h | |
| parent | Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net (diff) | |
| download | linux-6651ee070b3124fe9b9db383e3a895a0e4aded65.tar.xz linux-6651ee070b3124fe9b9db383e3a895a0e4aded65.zip | |
s390/bpf: implement bpf_tail_call() helper
bpf_tail_call() arguments:
- ctx......: Context pointer
- jmp_table: One of BPF_MAP_TYPE_PROG_ARRAY maps used as the jump table
- index....: Index in the jump table
In this implementation s390x JIT does stack unwinding and jumps into the
callee program prologue. Caller and callee use the same stack.
With this patch a tail call generates the following code on s390x:
if (index >= array->map.max_entries)
goto out
000003ff8001c7e4: e31030100016 llgf %r1,16(%r3)
000003ff8001c7ea: ec41001fa065 clgrj %r4,%r1,10,3ff8001c828
if (tail_call_cnt++ > MAX_TAIL_CALL_CNT)
goto out;
000003ff8001c7f0: a7080001 lhi %r0,1
000003ff8001c7f4: eb10f25000fa laal %r1,%r0,592(%r15)
000003ff8001c7fa: ec120017207f clij %r1,32,2,3ff8001c828
prog = array->prog[index];
if (prog == NULL)
goto out;
000003ff8001c800: eb140003000d sllg %r1,%r4,3
000003ff8001c806: e31310800004 lg %r1,128(%r3,%r1)
000003ff8001c80c: ec18000e007d clgij %r1,0,8,3ff8001c828
Restore registers before calling function
000003ff8001c812: eb68f2980004 lmg %r6,%r8,664(%r15)
000003ff8001c818: ebbff2c00004 lmg %r11,%r15,704(%r15)
goto *(prog->bpf_func + tail_call_start);
000003ff8001c81e: e31100200004 lg %r1,32(%r1,%r0)
000003ff8001c824: 47f01006 bc 15,6(%r1)
Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch/s390/net/bpf_jit.h')
| -rw-r--r-- | arch/s390/net/bpf_jit.h | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/arch/s390/net/bpf_jit.h b/arch/s390/net/bpf_jit.h index de156ba3bd71..f6498eec9ee1 100644 --- a/arch/s390/net/bpf_jit.h +++ b/arch/s390/net/bpf_jit.h @@ -28,6 +28,9 @@ extern u8 sk_load_word[], sk_load_half[], sk_load_byte[]; * | old backchain | | * +---------------+ | * | r15 - r6 | | + * +---------------+ | + * | 4 byte align | | + * | tail_call_cnt | | * BFP -> +===============+ | * | | | * | BPF stack | | @@ -46,14 +49,17 @@ extern u8 sk_load_word[], sk_load_half[], sk_load_byte[]; * R15 -> +---------------+ + low * * We get 160 bytes stack space from calling function, but only use - * 11 * 8 byte (old backchain + r15 - r6) for storing registers. + * 12 * 8 byte for old backchain, r15..r6, and tail_call_cnt. */ #define STK_SPACE (MAX_BPF_STACK + 8 + 4 + 4 + 160) -#define STK_160_UNUSED (160 - 11 * 8) +#define STK_160_UNUSED (160 - 12 * 8) #define STK_OFF (STK_SPACE - STK_160_UNUSED) #define STK_OFF_TMP 160 /* Offset of tmp buffer on stack */ #define STK_OFF_HLEN 168 /* Offset of SKB header length on stack */ +#define STK_OFF_R6 (160 - 11 * 8) /* Offset of r6 on stack */ +#define STK_OFF_TCCNT (160 - 12 * 8) /* Offset of tail_call_cnt on stack */ + /* Offset to skip condition code check */ #define OFF_OK 4 |