diff options
Diffstat (limited to 'tools/lib/bpf/bpf_core_read.h')
| -rw-r--r-- | tools/lib/bpf/bpf_core_read.h | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/tools/lib/bpf/bpf_core_read.h b/tools/lib/bpf/bpf_core_read.h index a273df3784f4..11461b2623b0 100644 --- a/tools/lib/bpf/bpf_core_read.h +++ b/tools/lib/bpf/bpf_core_read.h @@ -12,9 +12,81 @@ */ enum bpf_field_info_kind { BPF_FIELD_BYTE_OFFSET = 0, /* field byte offset */ + BPF_FIELD_BYTE_SIZE = 1, BPF_FIELD_EXISTS = 2, /* field existence in target kernel */ + BPF_FIELD_SIGNED = 3, + BPF_FIELD_LSHIFT_U64 = 4, + BPF_FIELD_RSHIFT_U64 = 5, }; +#define __CORE_RELO(src, field, info) \ + __builtin_preserve_field_info((src)->field, BPF_FIELD_##info) + +#if __BYTE_ORDER == __LITTLE_ENDIAN +#define __CORE_BITFIELD_PROBE_READ(dst, src, fld) \ + bpf_probe_read((void *)dst, \ + __CORE_RELO(src, fld, BYTE_SIZE), \ + (const void *)src + __CORE_RELO(src, fld, BYTE_OFFSET)) +#else +/* semantics of LSHIFT_64 assumes loading values into low-ordered bytes, so + * for big-endian we need to adjust destination pointer accordingly, based on + * field byte size + */ +#define __CORE_BITFIELD_PROBE_READ(dst, src, fld) \ + bpf_probe_read((void *)dst + (8 - __CORE_RELO(src, fld, BYTE_SIZE)), \ + __CORE_RELO(src, fld, BYTE_SIZE), \ + (const void *)src + __CORE_RELO(src, fld, BYTE_OFFSET)) +#endif + +/* + * Extract bitfield, identified by src->field, and put its value into u64 + * *res. All this is done in relocatable manner, so bitfield changes such as + * signedness, bit size, offset changes, this will be handled automatically. + * This version of macro is using bpf_probe_read() to read underlying integer + * storage. Macro functions as an expression and its return type is + * bpf_probe_read()'s return value: 0, on success, <0 on error. + */ +#define BPF_CORE_READ_BITFIELD_PROBED(src, field, res) ({ \ + unsigned long long val; \ + \ + *res = 0; \ + val = __CORE_BITFIELD_PROBE_READ(res, src, field); \ + if (!val) { \ + *res <<= __CORE_RELO(src, field, LSHIFT_U64); \ + val = __CORE_RELO(src, field, RSHIFT_U64); \ + if (__CORE_RELO(src, field, SIGNED)) \ + *res = ((long long)*res) >> val; \ + else \ + *res = ((unsigned long long)*res) >> val; \ + val = 0; \ + } \ + val; \ +}) + +/* + * Extract bitfield, identified by src->field, and return its value as u64. + * This version of macro is using direct memory reads and should be used from + * BPF program types that support such functionality (e.g., typed raw + * tracepoints). + */ +#define BPF_CORE_READ_BITFIELD(s, field) ({ \ + const void *p = (const void *)s + __CORE_RELO(s, field, BYTE_OFFSET); \ + unsigned long long val; \ + \ + switch (__CORE_RELO(s, field, BYTE_SIZE)) { \ + case 1: val = *(const unsigned char *)p; \ + case 2: val = *(const unsigned short *)p; \ + case 4: val = *(const unsigned int *)p; \ + case 8: val = *(const unsigned long long *)p; \ + } \ + val <<= __CORE_RELO(s, field, LSHIFT_U64); \ + if (__CORE_RELO(s, field, SIGNED)) \ + val = ((long long)val) >> __CORE_RELO(s, field, RSHIFT_U64); \ + else \ + val = val >> __CORE_RELO(s, field, RSHIFT_U64); \ + val; \ +}) + /* * Convenience macro to check that field actually exists in target kernel's. * Returns: @@ -25,6 +97,13 @@ enum bpf_field_info_kind { __builtin_preserve_field_info(field, BPF_FIELD_EXISTS) /* + * Convenience macro to get byte size of a field. Works for integers, + * struct/unions, pointers, arrays, and enums. + */ +#define bpf_core_field_size(field) \ + __builtin_preserve_field_info(field, BPF_FIELD_BYTE_SIZE) + +/* * bpf_core_read() abstracts away bpf_probe_read() call and captures offset * relocation for source address using __builtin_preserve_access_index() * built-in, provided by Clang. |