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tracing/probes: Support BTF based data structure field access
Using BTF to access the fields of a data structure. You can use this
for accessing the field with '->' or '.' operation with BTF argument.
# echo 't sched_switch next=next->pid vruntime=next->se.vruntime' \
> dynamic_events
# echo 1 > events/tracepoints/sched_switch/enable
# head -n 40 trace | tail
<idle>-0 [000] d..3. 272.565382: sched_switch: (__probestub_sched_switch+0x4/0x10) next=26 vruntime=956533179
kcompactd0-26 [000] d..3. 272.565406: sched_switch: (__probestub_sched_switch+0x4/0x10) next=0 vruntime=0
<idle>-0 [000] d..3. 273.069441: sched_switch: (__probestub_sched_switch+0x4/0x10) next=9 vruntime=956533179
kworker/0:1-9 [000] d..3. 273.069464: sched_switch: (__probestub_sched_switch+0x4/0x10) next=26 vruntime=956579181
kcompactd0-26 [000] d..3. 273.069480: sched_switch: (__probestub_sched_switch+0x4/0x10) next=0 vruntime=0
<idle>-0 [000] d..3. 273.141434: sched_switch: (__probestub_sched_switch+0x4/0x10) next=22 vruntime=956533179
kworker/u2:1-22 [000] d..3. 273.141461: sched_switch: (__probestub_sched_switch+0x4/0x10) next=0 vruntime=0
<idle>-0 [000] d..3. 273.480872: sched_switch: (__probestub_sched_switch+0x4/0x10) next=22 vruntime=956585857
kworker/u2:1-22 [000] d..3. 273.480905: sched_switch: (__probestub_sched_switch+0x4/0x10) next=70 vruntime=959533179
sh-70 [000] d..3. 273.481102: sched_switch: (__probestub_sched_switch+0x4/0x10) next=0 vruntime=0
Link: https://lore.kernel.org/all/169272157251.160970.9318175874130965571.stgit@devnote2/
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Masami Hiramatsu (Google)
parent
302db0f5b3
commit
c440adfbe3
@ -5717,7 +5717,8 @@ static const char readme_msg[] =
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"\t fetcharg: (%<register>|$<efield>), @<address>, @<symbol>[+|-<offset>],\n"
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#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
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#ifdef CONFIG_PROBE_EVENTS_BTF_ARGS
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"\t $stack<index>, $stack, $retval, $comm, $arg<N>, <argname>\n"
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"\t $stack<index>, $stack, $retval, $comm, $arg<N>,\n"
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"\t <argname>[->field[->field|.field...]],\n"
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#else
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"\t $stack<index>, $stack, $retval, $comm, $arg<N>,\n"
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#endif
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@ -310,16 +310,14 @@ static u32 btf_type_int(const struct btf_type *t)
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return *(u32 *)(t + 1);
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}
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static const char *type_from_btf_id(struct btf *btf, s32 id)
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static const char *fetch_type_from_btf_type(struct btf *btf,
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const struct btf_type *type,
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struct traceprobe_parse_context *ctx)
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{
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const struct btf_type *t;
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u32 intdata;
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s32 tid;
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/* TODO: const char * could be converted as a string */
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t = btf_type_skip_modifiers(btf, id, &tid);
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switch (BTF_INFO_KIND(t->info)) {
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switch (BTF_INFO_KIND(type->info)) {
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case BTF_KIND_ENUM:
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/* enum is "int", so convert to "s32" */
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return "s32";
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@ -332,7 +330,7 @@ static const char *type_from_btf_id(struct btf *btf, s32 id)
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else
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return "x32";
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case BTF_KIND_INT:
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intdata = btf_type_int(t);
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intdata = btf_type_int(type);
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if (BTF_INT_ENCODING(intdata) & BTF_INT_SIGNED) {
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switch (BTF_INT_BITS(intdata)) {
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case 8:
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@ -355,6 +353,10 @@ static const char *type_from_btf_id(struct btf *btf, s32 id)
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case 64:
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return "u64";
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}
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/* bitfield, size is encoded in the type */
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ctx->last_bitsize = BTF_INT_BITS(intdata);
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ctx->last_bitoffs += BTF_INT_OFFSET(intdata);
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return "u64";
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}
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}
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/* TODO: support other types */
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@ -406,15 +408,136 @@ static void clear_btf_context(struct traceprobe_parse_context *ctx)
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}
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}
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static int parse_btf_arg(const char *varname, struct fetch_insn *code,
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/* Return 1 if the field separater is arrow operator ('->') */
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static int split_next_field(char *varname, char **next_field,
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struct traceprobe_parse_context *ctx)
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{
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char *field;
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int ret = 0;
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field = strpbrk(varname, ".-");
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if (field) {
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if (field[0] == '-' && field[1] == '>') {
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field[0] = '\0';
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field += 2;
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ret = 1;
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} else if (field[0] == '.') {
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field[0] = '\0';
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field += 1;
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} else {
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trace_probe_log_err(ctx->offset + field - varname, BAD_HYPHEN);
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return -EINVAL;
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}
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*next_field = field;
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}
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return ret;
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}
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/*
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* Parse the field of data structure. The @type must be a pointer type
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* pointing the target data structure type.
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*/
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static int parse_btf_field(char *fieldname, const struct btf_type *type,
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struct fetch_insn **pcode, struct fetch_insn *end,
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struct traceprobe_parse_context *ctx)
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{
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struct fetch_insn *code = *pcode;
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const struct btf_member *field;
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u32 bitoffs, anon_offs;
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char *next;
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int is_ptr;
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s32 tid;
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do {
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/* Outer loop for solving arrow operator ('->') */
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if (BTF_INFO_KIND(type->info) != BTF_KIND_PTR) {
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trace_probe_log_err(ctx->offset, NO_PTR_STRCT);
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return -EINVAL;
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}
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/* Convert a struct pointer type to a struct type */
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type = btf_type_skip_modifiers(ctx->btf, type->type, &tid);
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if (!type) {
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trace_probe_log_err(ctx->offset, BAD_BTF_TID);
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return -EINVAL;
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}
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bitoffs = 0;
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do {
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/* Inner loop for solving dot operator ('.') */
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next = NULL;
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is_ptr = split_next_field(fieldname, &next, ctx);
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if (is_ptr < 0)
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return is_ptr;
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anon_offs = 0;
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field = btf_find_struct_member(ctx->btf, type, fieldname,
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&anon_offs);
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if (!field) {
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trace_probe_log_err(ctx->offset, NO_BTF_FIELD);
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return -ENOENT;
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}
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/* Add anonymous structure/union offset */
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bitoffs += anon_offs;
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/* Accumulate the bit-offsets of the dot-connected fields */
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if (btf_type_kflag(type)) {
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bitoffs += BTF_MEMBER_BIT_OFFSET(field->offset);
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ctx->last_bitsize = BTF_MEMBER_BITFIELD_SIZE(field->offset);
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} else {
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bitoffs += field->offset;
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ctx->last_bitsize = 0;
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}
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type = btf_type_skip_modifiers(ctx->btf, field->type, &tid);
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if (!type) {
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trace_probe_log_err(ctx->offset, BAD_BTF_TID);
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return -EINVAL;
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}
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ctx->offset += next - fieldname;
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fieldname = next;
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} while (!is_ptr && fieldname);
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if (++code == end) {
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trace_probe_log_err(ctx->offset, TOO_MANY_OPS);
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return -EINVAL;
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}
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code->op = FETCH_OP_DEREF; /* TODO: user deref support */
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code->offset = bitoffs / 8;
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*pcode = code;
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ctx->last_bitoffs = bitoffs % 8;
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ctx->last_type = type;
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} while (fieldname);
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return 0;
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}
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static int parse_btf_arg(char *varname,
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struct fetch_insn **pcode, struct fetch_insn *end,
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struct traceprobe_parse_context *ctx)
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{
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struct fetch_insn *code = *pcode;
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const struct btf_param *params;
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int i;
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const struct btf_type *type;
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char *field = NULL;
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int i, is_ptr;
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u32 tid;
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if (WARN_ON_ONCE(!ctx->funcname))
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return -EINVAL;
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is_ptr = split_next_field(varname, &field, ctx);
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if (is_ptr < 0)
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return is_ptr;
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if (!is_ptr && field) {
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/* dot-connected field on an argument is not supported. */
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trace_probe_log_err(ctx->offset + field - varname,
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NOSUP_DAT_ARG);
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return -EOPNOTSUPP;
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}
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if (!ctx->params) {
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params = find_btf_func_param(ctx->funcname,
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&ctx->nr_params, &ctx->btf,
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@ -436,24 +559,39 @@ static int parse_btf_arg(const char *varname, struct fetch_insn *code,
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code->param = i + 1;
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else
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code->param = i;
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return 0;
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tid = params[i].type;
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goto found;
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}
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}
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trace_probe_log_err(ctx->offset, NO_BTFARG);
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return -ENOENT;
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found:
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type = btf_type_skip_modifiers(ctx->btf, tid, &tid);
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if (!type) {
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trace_probe_log_err(ctx->offset, BAD_BTF_TID);
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return -EINVAL;
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}
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/* Initialize the last type information */
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ctx->last_type = type;
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ctx->last_bitoffs = 0;
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ctx->last_bitsize = 0;
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if (field) {
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ctx->offset += field - varname;
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return parse_btf_field(field, type, pcode, end, ctx);
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}
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return 0;
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}
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static const struct fetch_type *parse_btf_arg_type(int arg_idx,
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static const struct fetch_type *parse_btf_arg_type(
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struct traceprobe_parse_context *ctx)
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{
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struct btf *btf = ctx->btf;
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const char *typestr = NULL;
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if (btf && ctx->params) {
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if (ctx->flags & TPARG_FL_TPOINT)
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arg_idx--;
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typestr = type_from_btf_id(btf, ctx->params[arg_idx].type);
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}
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if (btf && ctx->last_type)
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typestr = fetch_type_from_btf_type(btf, ctx->last_type, ctx);
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return find_fetch_type(typestr, ctx->flags);
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}
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@ -462,14 +600,16 @@ static const struct fetch_type *parse_btf_retval_type(
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struct traceprobe_parse_context *ctx)
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{
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const char *typestr = NULL;
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const struct btf_type *t;
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const struct btf_type *type;
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struct btf *btf;
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if (ctx->funcname) {
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/* Do not use ctx->btf, because it must be used with ctx->param */
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t = btf_find_func_proto(ctx->funcname, &btf);
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if (t) {
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typestr = type_from_btf_id(btf, t->type);
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type = btf_find_func_proto(ctx->funcname, &btf);
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if (type) {
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type = btf_type_skip_modifiers(btf, type->type, NULL);
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if (!IS_ERR_OR_NULL(type))
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typestr = fetch_type_from_btf_type(btf, type, ctx);
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btf_put(btf);
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}
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}
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@ -477,6 +617,28 @@ static const struct fetch_type *parse_btf_retval_type(
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return find_fetch_type(typestr, ctx->flags);
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}
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static int parse_btf_bitfield(struct fetch_insn **pcode,
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struct traceprobe_parse_context *ctx)
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{
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struct fetch_insn *code = *pcode;
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if ((ctx->last_bitsize % 8 == 0) && ctx->last_bitoffs == 0)
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return 0;
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code++;
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if (code->op != FETCH_OP_NOP) {
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trace_probe_log_err(ctx->offset, TOO_MANY_OPS);
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return -EINVAL;
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}
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*pcode = code;
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code->op = FETCH_OP_MOD_BF;
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code->lshift = 64 - (ctx->last_bitsize + ctx->last_bitoffs);
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code->rshift = 64 - ctx->last_bitsize;
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code->basesize = 64 / 8;
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return 0;
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}
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static bool is_btf_retval_void(const char *funcname)
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{
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const struct btf_type *t;
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@ -503,14 +665,22 @@ static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr
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return ERR_PTR(-EOPNOTSUPP);
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}
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static int parse_btf_arg(const char *varname, struct fetch_insn *code,
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static int parse_btf_arg(char *varname,
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struct fetch_insn **pcode, struct fetch_insn *end,
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struct traceprobe_parse_context *ctx)
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{
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trace_probe_log_err(ctx->offset, NOSUP_BTFARG);
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return -EOPNOTSUPP;
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}
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#define parse_btf_arg_type(idx, ctx) \
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static int parse_btf_bitfield(struct fetch_insn **pcode,
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struct traceprobe_parse_context *ctx)
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{
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trace_probe_log_err(ctx->offset, NOSUP_BTFARG);
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return -EOPNOTSUPP;
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}
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#define parse_btf_arg_type(ctx) \
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find_fetch_type(NULL, ctx->flags)
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#define parse_btf_retval_type(ctx) \
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@ -778,6 +948,8 @@ parse_probe_arg(char *arg, const struct fetch_type *type,
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code->op = deref;
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code->offset = offset;
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/* Reset the last type if used */
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ctx->last_type = NULL;
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}
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break;
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case '\\': /* Immediate value */
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@ -801,7 +973,7 @@ parse_probe_arg(char *arg, const struct fetch_type *type,
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trace_probe_log_err(ctx->offset, NOSUP_BTFARG);
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return -EINVAL;
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}
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ret = parse_btf_arg(arg, code, ctx);
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ret = parse_btf_arg(arg, pcode, end, ctx);
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break;
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}
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}
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@ -947,6 +1119,7 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size,
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goto out;
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code[FETCH_INSN_MAX - 1].op = FETCH_OP_END;
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ctx->last_type = NULL;
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ret = parse_probe_arg(arg, parg->type, &code, &code[FETCH_INSN_MAX - 1],
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ctx);
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if (ret)
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@ -954,9 +1127,9 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size,
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/* Update storing type if BTF is available */
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if (IS_ENABLED(CONFIG_PROBE_EVENTS_BTF_ARGS) && !t) {
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if (code->op == FETCH_OP_ARG)
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parg->type = parse_btf_arg_type(code->param, ctx);
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else if (code->op == FETCH_OP_RETVAL)
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if (ctx->last_type)
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parg->type = parse_btf_arg_type(ctx);
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else if (ctx->flags & TPARG_FL_RETURN)
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parg->type = parse_btf_retval_type(ctx);
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}
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@ -1031,6 +1204,11 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size,
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trace_probe_log_err(ctx->offset + t - arg, BAD_BITFIELD);
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goto fail;
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}
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} else if (IS_ENABLED(CONFIG_PROBE_EVENTS_BTF_ARGS) &&
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ctx->last_type) {
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ret = parse_btf_bitfield(&code, ctx);
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if (ret)
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goto fail;
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}
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ret = -EINVAL;
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/* Loop(Array) operation */
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@ -388,6 +388,9 @@ struct traceprobe_parse_context {
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const struct btf_param *params; /* Parameter of the function */
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s32 nr_params; /* The number of the parameters */
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struct btf *btf; /* The BTF to be used */
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const struct btf_type *last_type; /* Saved type */
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u32 last_bitoffs; /* Saved bitoffs */
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u32 last_bitsize; /* Saved bitsize */
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unsigned int flags;
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int offset;
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};
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@ -503,7 +506,13 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call,
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C(BAD_VAR_ARGS, "$arg* must be an independent parameter without name etc."),\
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C(NOFENTRY_ARGS, "$arg* can be used only on function entry"), \
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C(DOUBLE_ARGS, "$arg* can be used only once in the parameters"), \
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C(ARGS_2LONG, "$arg* failed because the argument list is too long"),
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C(ARGS_2LONG, "$arg* failed because the argument list is too long"), \
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C(ARGIDX_2BIG, "$argN index is too big"), \
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C(NO_PTR_STRCT, "This is not a pointer to union/structure."), \
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C(NOSUP_DAT_ARG, "Non pointer structure/union argument is not supported."),\
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C(BAD_HYPHEN, "Failed to parse single hyphen. Forgot '>'?"), \
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C(NO_BTF_FIELD, "This field is not found."), \
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C(BAD_BTF_TID, "Failed to get BTF type info."),
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#undef C
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#define C(a, b) TP_ERR_##a
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