libbpf: Switch tracing and CO-RE helper macros to bpf_probe_read_kernel() (70785cfb) · Commits · 戴 / test

tools/lib/bpf/bpf_core_read.h

+22 −18

Original line number	Diff line number	Diff line
		@@ -24,7 +24,8 @@ enum bpf_field_info_kind {

		#if __BYTE_ORDER == __LITTLE_ENDIAN
		#define __CORE_BITFIELD_PROBE_READ(dst, src, fld) \
		bpf_probe_read((void *)dst, \
		bpf_probe_read_kernel( \
		(void *)dst, \
		__CORE_RELO(src, fld, BYTE_SIZE), \
		(const void *)src + __CORE_RELO(src, fld, BYTE_OFFSET))
		#else
		@@ -33,7 +34,8 @@ enum bpf_field_info_kind {
		* field byte size
		*/
		#define __CORE_BITFIELD_PROBE_READ(dst, src, fld) \
		bpf_probe_read((void *)dst + (8 - __CORE_RELO(src, fld, BYTE_SIZE)), \
		bpf_probe_read_kernel( \
		(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
		@@ -42,9 +44,9 @@ enum bpf_field_info_kind {
		* Extract bitfield, identified by s->field, and return its value as u64.
		* 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.
		* This version of macro is using bpf_probe_read_kernel() to read underlying
		* integer storage. Macro functions as an expression and its return type is
		* bpf_probe_read_kernel()'s return value: 0, on success, <0 on error.
		*/
		#define BPF_CORE_READ_BITFIELD_PROBED(s, field) ({ \
		unsigned long long val = 0; \
		@@ -99,8 +101,8 @@ enum bpf_field_info_kind {
		__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()
		* bpf_core_read() abstracts away bpf_probe_read_kernel() call and captures
		* offset relocation for source address using __builtin_preserve_access_index()
		* built-in, provided by Clang.
		*
		* __builtin_preserve_access_index() takes as an argument an expression of
		@@ -115,7 +117,7 @@ enum bpf_field_info_kind {
		* (local) BTF, used to record relocation.
		*/
		#define bpf_core_read(dst, sz, src) \
		bpf_probe_read(dst, sz, \
		bpf_probe_read_kernel(dst, sz, \
		(const void *)__builtin_preserve_access_index(src))

		/*
		@@ -124,7 +126,7 @@ enum bpf_field_info_kind {
		* argument.
		*/
		#define bpf_core_read_str(dst, sz, src) \
		bpf_probe_read_str(dst, sz, \
		bpf_probe_read_kernel_str(dst, sz, \
		(const void *)__builtin_preserve_access_index(src))

		#define ___concat(a, b) a ## b
		@@ -239,15 +241,17 @@ enum bpf_field_info_kind {
		* int x = BPF_CORE_READ(s, a.b.c, d.e, f, g);
		*
		* BPF_CORE_READ will decompose above statement into 4 bpf_core_read (BPF
		* CO-RE relocatable bpf_probe_read() wrapper) calls, logically equivalent to:
		* CO-RE relocatable bpf_probe_read_kernel() wrapper) calls, logically
		* equivalent to:
		* 1. const void *__t = s->a.b.c;
		* 2. __t = __t->d.e;
		* 3. __t = __t->f;
		* 4. return __t->g;
		*
		* Equivalence is logical, because there is a heavy type casting/preservation
		* involved, as well as all the reads are happening through bpf_probe_read()
		* calls using __builtin_preserve_access_index() to emit CO-RE relocations.
		* involved, as well as all the reads are happening through
		* bpf_probe_read_kernel() calls using __builtin_preserve_access_index() to
		* emit CO-RE relocations.
		*
		* N.B. Only up to 9 "field accessors" are supported, which should be more
		* than enough for any practical purpose.

tools/lib/bpf/bpf_tracing.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -289,9 +289,9 @@ struct pt_regs;
		#define BPF_KRETPROBE_READ_RET_IP BPF_KPROBE_READ_RET_IP
		#else
		#define BPF_KPROBE_READ_RET_IP(ip, ctx) \
		({ bpf_probe_read(&(ip), sizeof(ip), (void *)PT_REGS_RET(ctx)); })
		({ bpf_probe_read_kernel(&(ip), sizeof(ip), (void *)PT_REGS_RET(ctx)); })
		#define BPF_KRETPROBE_READ_RET_IP(ip, ctx) \
		({ bpf_probe_read(&(ip), sizeof(ip), \
		({ bpf_probe_read_kernel(&(ip), sizeof(ip), \
		(void *)(PT_REGS_FP(ctx) + sizeof(ip))); })
		#endif

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