From aea2f7b8911617d7a8c23fb73d69e78764f91b58 Mon Sep 17 00:00:00 2001 From: Martin KaFai Lau Date: Tue, 22 May 2018 14:57:20 -0700 Subject: bpf: btf: Remove unused bits from uapi/linux/btf.h This patch does the followings: 1. Limit BTF_MAX_TYPES and BTF_MAX_NAME_OFFSET to 64k. We can raise it later. 2. Remove the BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID. They are currently encoded at the highest bit of a u32. It is because the current use case does not require supporting parent type (i.e type_id referring to a type in another BTF file). It also does not support referring to a string in ELF. The BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID checks are replaced by BTF_TYPE_ID_CHECK and BTF_STR_OFFSET_CHECK which are defined in btf.c instead of uapi/linux/btf.h. 3. Limit the BTF_INFO_KIND from 5 bits to 4 bits which is enough. There is unused bits headroom if we ever needed it later. 4. The root bit in BTF_INFO is also removed because it is not used in the current use case. 5. Remove BTF_INT_VARARGS since func type is not supported now. The BTF_INT_ENCODING is limited to 4 bits instead of 8 bits. The above can be added back later because the verifier ensures the unused bits are zeros. Signed-off-by: Martin KaFai Lau Acked-by: Yonghong Song Signed-off-by: Daniel Borkmann --- include/uapi/linux/btf.h | 29 +++++++++-------------------- 1 file changed, 9 insertions(+), 20 deletions(-) (limited to 'include/uapi') diff --git a/include/uapi/linux/btf.h b/include/uapi/linux/btf.h index 4fa479741a02..0b5ddbe135a4 100644 --- a/include/uapi/linux/btf.h +++ b/include/uapi/linux/btf.h @@ -22,28 +22,19 @@ struct btf_header { }; /* Max # of type identifier */ -#define BTF_MAX_TYPE 0x7fffffff +#define BTF_MAX_TYPE 0x0000ffff /* Max offset into the string section */ -#define BTF_MAX_NAME_OFFSET 0x7fffffff +#define BTF_MAX_NAME_OFFSET 0x0000ffff /* Max # of struct/union/enum members or func args */ #define BTF_MAX_VLEN 0xffff -/* The type id is referring to a parent BTF */ -#define BTF_TYPE_PARENT(id) (((id) >> 31) & 0x1) -#define BTF_TYPE_ID(id) ((id) & BTF_MAX_TYPE) - -/* String is in the ELF string section */ -#define BTF_STR_TBL_ELF_ID(ref) (((ref) >> 31) & 0x1) -#define BTF_STR_OFFSET(ref) ((ref) & BTF_MAX_NAME_OFFSET) - struct btf_type { __u32 name_off; /* "info" bits arrangement * bits 0-15: vlen (e.g. # of struct's members) * bits 16-23: unused - * bits 24-28: kind (e.g. int, ptr, array...etc) - * bits 29-30: unused - * bits 31: root + * bits 24-27: kind (e.g. int, ptr, array...etc) + * bits 28-31: unused */ __u32 info; /* "size" is used by INT, ENUM, STRUCT and UNION. @@ -58,8 +49,7 @@ struct btf_type { }; }; -#define BTF_INFO_KIND(info) (((info) >> 24) & 0x1f) -#define BTF_INFO_ISROOT(info) (!!(((info) >> 24) & 0x80)) +#define BTF_INFO_KIND(info) (((info) >> 24) & 0x0f) #define BTF_INFO_VLEN(info) ((info) & 0xffff) #define BTF_KIND_UNKN 0 /* Unknown */ @@ -84,15 +74,14 @@ struct btf_type { /* BTF_KIND_INT is followed by a u32 and the following * is the 32 bits arrangement: */ -#define BTF_INT_ENCODING(VAL) (((VAL) & 0xff000000) >> 24) +#define BTF_INT_ENCODING(VAL) (((VAL) & 0x0f000000) >> 24) #define BTF_INT_OFFSET(VAL) (((VAL & 0x00ff0000)) >> 16) #define BTF_INT_BITS(VAL) ((VAL) & 0x0000ffff) /* Attributes stored in the BTF_INT_ENCODING */ -#define BTF_INT_SIGNED 0x1 -#define BTF_INT_CHAR 0x2 -#define BTF_INT_BOOL 0x4 -#define BTF_INT_VARARGS 0x8 +#define BTF_INT_SIGNED (1 << 0) +#define BTF_INT_CHAR (1 << 1) +#define BTF_INT_BOOL (1 << 2) /* BTF_KIND_ENUM is followed by multiple "struct btf_enum". * The exact number of btf_enum is stored in the vlen (of the -- cgit v1.2.3-55-g7522