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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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6651ee070b
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>
67 lines
1.9 KiB
C
67 lines
1.9 KiB
C
/*
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* BPF Jit compiler defines
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*
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* Copyright IBM Corp. 2012,2015
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*
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* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
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* Michael Holzheu <holzheu@linux.vnet.ibm.com>
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*/
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#ifndef __ARCH_S390_NET_BPF_JIT_H
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#define __ARCH_S390_NET_BPF_JIT_H
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#ifndef __ASSEMBLY__
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#include <linux/filter.h>
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#include <linux/types.h>
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extern u8 sk_load_word_pos[], sk_load_half_pos[], sk_load_byte_pos[];
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extern u8 sk_load_word[], sk_load_half[], sk_load_byte[];
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#endif /* __ASSEMBLY__ */
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/*
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* Stackframe layout (packed stack):
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*
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* ^ high
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* +---------------+ |
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* | old backchain | |
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* +---------------+ |
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* | r15 - r6 | |
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* +---------------+ |
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* | 4 byte align | |
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* | tail_call_cnt | |
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* BFP -> +===============+ |
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* | | |
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* | BPF stack | |
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* | | |
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* +---------------+ |
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* | 8 byte hlen | |
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* R15+168 -> +---------------+ |
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* | 4 byte align | |
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* +---------------+ |
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* | 4 byte temp | |
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* | for bpf_jit.S | |
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* R15+160 -> +---------------+ |
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* | new backchain | |
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* R15+152 -> +---------------+ |
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* | + 152 byte SA | |
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* R15 -> +---------------+ + low
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*
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* We get 160 bytes stack space from calling function, but only use
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* 12 * 8 byte for old backchain, r15..r6, and tail_call_cnt.
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*/
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#define STK_SPACE (MAX_BPF_STACK + 8 + 4 + 4 + 160)
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#define STK_160_UNUSED (160 - 12 * 8)
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#define STK_OFF (STK_SPACE - STK_160_UNUSED)
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#define STK_OFF_TMP 160 /* Offset of tmp buffer on stack */
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#define STK_OFF_HLEN 168 /* Offset of SKB header length on stack */
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#define STK_OFF_R6 (160 - 11 * 8) /* Offset of r6 on stack */
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#define STK_OFF_TCCNT (160 - 12 * 8) /* Offset of tail_call_cnt on stack */
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/* Offset to skip condition code check */
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#define OFF_OK 4
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#endif /* __ARCH_S390_NET_BPF_JIT_H */
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