[Draft] - Align key components to the nearest 8-bit size #30
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Signed-off-by: Komal, Jain <[email protected]>
komaljai
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I found some small issues, but the general idea of storePrimitive* and getPrimitive* makes sense
However, I have a question.
In cases where you have something like a bit<22>.
Is getPrimitive32's first parameter guaranteed to be zeroed out?
Analogously, is the second parameter of storePrimitive32 (u32 value) guaranteed to have the remaining 10 bits zeroed out?
If it is, I think there is no issue, otherwise masking or shifting should be necessary
| a[2] = (u8)(value >> 16); | ||
| a[3] = (u8)(value >> 24); | ||
| a[4] = (u8)(value >> 32); | ||
| if (size < 48) { |
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Maybe I'm misunderstanding, but shouldn't it be:
| if (size < 48) { | |
| if (size >= 48) { |
You'd want to get the sixth byte if the size is bigger >= 48
| if (size < 48) { | ||
| a[5] = (u8)(value >> 40); | ||
| } | ||
| if (size < 56){ |
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The same thing would apply for the seventh byte
| @@ -65,6 +65,39 @@ REGISTER_TABLE(hdr_md_cpumap, BPF_MAP_TYPE_PERCPU_ARRAY, u32, struct hdr_md, 2) | |||
| BPF_ANNOTATE_KV_PAIR(hdr_md_cpumap, u32, struct hdr_md) | |||
| REGISTER_END() | |||
|
|
|||
| u32 getPrimitive32(u8 *a, int size) { | |||
| u64 getPrimitive64(u8 *a, int size) { | ||
| if(size < 40) { | ||
| return ((a[4] << 32) | (a[3] << 24) | (a[2] << 16) | (a[1] << 8) | a[0]); | ||
| } else { | ||
| if(size < 48) { | ||
| return ((a[5] << 40) | (a[4] << 32) | (a[3] << 24) | (a[2] << 16) | (a[1] << 8) | a[0]); | ||
| } else { | ||
| return ((a[6] << 48) | (a[5] << 40) | (a[4] << 32) | (a[3] << 24) | (a[2] << 16) | (a[1] << 8) | a[0]); | ||
| } | ||
| } | ||
| } |
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Just to avoid the warnings
| u64 getPrimitive64(u8 *a, int size) { | |
| if(size < 40) { | |
| return ((a[4] << 32) | (a[3] << 24) | (a[2] << 16) | (a[1] << 8) | a[0]); | |
| } else { | |
| if(size < 48) { | |
| return ((a[5] << 40) | (a[4] << 32) | (a[3] << 24) | (a[2] << 16) | (a[1] << 8) | a[0]); | |
| } else { | |
| return ((a[6] << 48) | (a[5] << 40) | (a[4] << 32) | (a[3] << 24) | (a[2] << 16) | (a[1] << 8) | a[0]); | |
| } | |
| } | |
| } | |
| u64 getPrimitive64(u8 *a, int size) { | |
| if(size < 40) { | |
| return (((((u64)a[4]) << 32)) | (((u64)a[3]) << 24) | (((u64)a[2]) << 16) | (((u64)a[1]) << 8) | a[0]); | |
| } else { | |
| if(size < 48) { | |
| return ((((u64)a[5]) << 40) | (((u64)a[4]) << 32) | (((u64)a[3]) << 24) | (((u64)a[2]) << 16) | (((u64)a[1]) << 8) | a[0]); | |
| } else { | |
| return ((((u64)a[6]) << 48) | (((u64)a[5]) << 40) | (((u64)a[4]) << 32) | (((u64)a[3]) << 24) | (((u64)a[2]) << 16) | (((u64)a[1]) << 8) | a[0]); | |
| } | |
| } | |
| } |
| u32 getPrimitive32(u8 *a, int size) { | ||
| return ((a[2]<<16) | (a[1] << 8) | a[0]); | ||
| } |
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Just to avoid the warnings
| u32 getPrimitive32(u8 *a, int size) { | |
| return ((a[2]<<16) | (a[1] << 8) | a[0]); | |
| } | |
| u32 getPrimitive32(u8 *a) { | |
| return ((((u32)a[2]) << 16) | (((u32)a[1]) << 8) | a[0]); | |
| } |
| @@ -114,8 +114,8 @@ if (/* hdr->ipv4.isValid() */ | |||
| break; | |||
| case MAINCONTROLIMPL_IPV4_TBL_1_ACT_MAINCONTROLIMPL_SEND_NH: | |||
| { | |||
| hdr->ethernet.srcAddr = bpf_cpu_to_be64(value->u.MainControlImpl_send_nh.smac); | |||
| hdr->ethernet.dstAddr = ntohll(value->u.MainControlImpl_send_nh.dmac << 16); | |||
| storePrimitive64(&hdr->ethernet.srcAddr, 48, (bpf_cpu_to_be64(value->u.MainControlImpl_send_nh.smac))); | |||
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I think I accidentally found a bug
Was testing changing EthernetAddress' typecast[1] to a bit<39> and saw that the generated code was outputing this line as:
storePrimitive64(&hdr->ethernet.srcAddr, 40, (bpf_cpu_to_be64((u64)(u64)value->u.MainControlImpl_send_nh.smac)));
From what I understood, the second argument should be 39, not 40
[1] https://github.com/p4lang/p4c/blob/main/testdata/p4tc_samples/add_entry_1_example.p4#L4
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