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btf: Extend UAPI to support BTF location (inline site) info
Add BTF_KIND_LOC_PARAM, BTF_KIND_LOC_PROTO and BTF_KIND_LOCSEC to help represent location information for functions. BTF_KIND_LOC_PARAM is used to represent how we retrieve data at a location; either via register(s), or register+offset, a dereference of a register+offset or a constant value. BTF_KIND_LOC_PROTO represents location information about a location with multiple BTF_KIND_LOC_PARAMs. And finally BTF_KIND_LOCSEC is a set of location sites, each of which has - a BTF_KIND_FUNC function associated with the inline site - a location prototype specifying where to find the function parameters - an address offset relative to the kernel base address This can be used to support representing - a fully-inlined function at potentially multiple inline sites with potentially different parameter availability - a partially-inlined function where some _LOC_PROTOs represent inlined sites as above and others have normal _FUNC representations Also BTF_KIND_LOCSEC struct btf_loc will have two type id references; one for the associated func, the other for the loc_proto. Accordingly increase the number of m_offs references in btf_field_desc to 2. Signed-off-by: Alan Maguire <alan.maguire@oracle.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://patch.msgid.link/20260924111428.75957-2-alan.maguire@oracle.com
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Alan Maguire authored and 
Andrii Nakryiko committed
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8608f22d05
commit
d09ea52795
1 file changed
+80
-3
@@ -54,8 +54,8 @@ struct btf_type {
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* decl_tag and type_tag
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*/
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__u32 info;
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/* "size" is used by INT, ENUM, STRUCT, UNION, DATASEC and ENUM64.
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* "size" tells the size of the type it is describing.
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/* "size" is used by INT, ENUM, STRUCT, UNION, DATASEC, ENUM64
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* and LOC_PARAM. "size" tells the size of the type it is describing.
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*
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* "type" is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT,
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* FUNC, FUNC_PROTO, VAR, DECL_TAG and TYPE_TAG.
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@@ -92,7 +92,9 @@ enum {
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BTF_KIND_DECL_TAG = 17, /* Decl Tag */
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BTF_KIND_TYPE_TAG = 18, /* Type Tag */
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BTF_KIND_ENUM64 = 19, /* Enumeration up to 64-bit values */
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BTF_KIND_LOC_PARAM = 20, /* Location parameter information */
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BTF_KIND_LOC_PROTO = 21, /* Location prototype for site */
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BTF_KIND_LOCSEC = 22, /* Location section */
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NR_BTF_KINDS,
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BTF_KIND_MAX = NR_BTF_KINDS - 1,
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};
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@@ -212,4 +214,79 @@ struct btf_enum64 {
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__u32 val_hi32;
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};
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/*
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* BTF_KIND_LOC_PARAM is followed by a single "struct btf_loc_param"
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* that contains flags specifying the contents of the vlen-specified
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* number of 4-byte values that follow.
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*/
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struct btf_loc_param {
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__u32 flags;
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__u32 values[];
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};
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/*
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* The combination of size, vlen and flags gives us the means to interpret
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* the following vlen-specified set of 4-byte values:
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*
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* - a BTF_LOC_PARAM_CONST is a constant value; combination
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* of size, vlen and _SIGNED flag determines it. If the value requires
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* 64 bits it is stored in {lo,hi} order.
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* - a BTF_LOC_PARAM_ADDR|BTF_LOC_PARAM_CONST is an address that should be
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* normalized with respect to kernel/module base address.
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* - a BTF_LOC_PARAM_REG with vlen 1 is a simple register number;
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* with vlen 2 it is a multi-register parameter. Register numbers are
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* numbers derived from DW_OP_reg values, i.e. 0 is DW_OP_reg0; since
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* DW_OP_fbreg has its own special DW_OP_value and DW_OP_regx can refer
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* to an arbitrary register number, we reserve BTF_LOC_PARAM_FBREG for
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* the frame base register to avoid collisions.
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* - a _REG | OFFSET describes an address without dereferencing it.
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* - a _REG | DEREF with vlen 1 dereferences the value in the register
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* number specified.
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* - a REG | DEREF | OFFSET with vlen > 1 specifies the register number
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* in the first 4-byte value and the offset in the remainder.
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* In the case of REG and OFFSET combinations, the OFFSET has the width
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* of the value words while the type size describes the represented parameter,
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* so for example a REG | DEREF | OFFSET with size 8 and vlen 2 would be
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* an 8-byte register dereference with signed 4-byte offset, since the vlen 2
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* values consist of a register value and the signed value.
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*/
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enum btf_loc_param_flags {
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BTF_LOC_PARAM_SIGNED = 0x1,
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BTF_LOC_PARAM_CONST = 0x2,
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BTF_LOC_PARAM_ADDR = 0x4,
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BTF_LOC_PARAM_REG = 0x8,
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BTF_LOC_PARAM_DEREF = 0x10,
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BTF_LOC_PARAM_OFFSET = 0x20,
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};
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enum {
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BTF_LOC_PARAM_FBREG = 0xffffffff
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};
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/*
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* BTF_KIND_LOC_PROTO specifies location prototypes; i.e. how locations relate
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* to parameters; a struct btf_type of BTF_KIND_LOC_PROTO is followed by a
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* vlen-specified number of __u32 BTF type ids which specify the associated
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* BTF_KIND_LOC_PARAM for each function parameter associated with the
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* location. The type should either be 0 (no location info) or point at
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* a BTF_KIND_LOC_PARAM.
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*/
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/*
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* BTF_KIND_LOCSEC consists of vlen-specified number of "struct btf_loc"
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* containing location site-specific information for a specific ELF section;
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* for example locations in ".text" are in a LOCSEC named "inline.text".
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*
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* - function (func)
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* - location prototype type id (loc_proto)
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* - address offset (offset) relative to the runtime base address of the
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* ELF section associated with the LOCSEC
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*/
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struct btf_loc {
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__u32 func;
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__u32 loc_proto;
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__u32 offset;
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};
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#endif /* __LINUX_BTF_H__ */
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