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Subject[PATCH v1 1/4] trace_events: Add trace_print_register to print register fields
Date
This is a hybrid method that combines the functionality of
trace_print_flags_seq and trace_print_symbols_seq. It supports printing
bit fields, enum fields, and numeric fields.

Given the following register definition:
* 0 - Enabled
* 1 - Width, 0 = 1-bits, 1 = 4-bits
* 2:3 - DMA, 0 = None, 1 = SDMA, 2 = ADMA, 3 = ADMA2
* 4:7 - Timeout Counter

The register fields could be defined as follows:

const struct trace_print_field reg[] = {
{1<<0, "ENABLED"},
{
.mask = 1<<1,
.name = "WIDTH",
.symbols = (const struct trace_print_flags[]) {
{0, "1-BIT"},
{1, "4-BIT"},
{}
}
}, {
.mask = 3<<2,
.symbols = (const struct trace_print_flags[]) {
{0, "NONE"},
{1, "SDMA"},
{2, "ADMA"},
{3, "ADMA2"},
{}
}
},
{0xF<<4, "TIMEOUT"}
}

This would print out the following given value 0xAB:

ENABLED: 1 | WIDTH: 4-BIT | ADMA | TIMEOUT: 0xA

See https://pastebin.com/x73d5cvL for this in action.

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
---

include/linux/trace_events.h | 4 ++
include/linux/tracepoint-defs.h | 6 ++
include/trace/trace_events.h | 9 +++
kernel/trace/trace_output.c | 121 ++++++++++++++++++++++++++++++++
4 files changed, 140 insertions(+)

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 8a62731673f7..3c44909ce8b3 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -23,6 +23,10 @@ const char *trace_print_flags_seq(struct trace_seq *p, const char *delim,
const char *trace_print_symbols_seq(struct trace_seq *p, unsigned long val,
const struct trace_print_flags *symbol_array);

+const char *trace_print_register(struct trace_seq *p,
+ const struct trace_print_field fields[],
+ unsigned long val, unsigned long mask);
+
#if BITS_PER_LONG == 32
const char *trace_print_flags_seq_u64(struct trace_seq *p, const char *delim,
unsigned long long flags,
diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
index 49ba9cde7e4b..c3dc27c192f4 100644
--- a/include/linux/tracepoint-defs.h
+++ b/include/linux/tracepoint-defs.h
@@ -16,6 +16,12 @@ struct trace_print_flags {
const char *name;
};

+struct trace_print_field {
+ unsigned long mask;
+ const char *name;
+ const struct trace_print_flags *symbols;
+};
+
struct trace_print_flags_u64 {
unsigned long long mask;
const char *name;
diff --git a/include/trace/trace_events.h b/include/trace/trace_events.h
index 4ecdfe2e3580..6adc32fcb1c3 100644
--- a/include/trace/trace_events.h
+++ b/include/trace/trace_events.h
@@ -300,6 +300,14 @@ TRACE_MAKE_SYSTEM_STR();
trace_print_symbols_seq(p, value, symbols); \
})

+#undef __print_register
+#define __print_register(value, mask, field_array...) \
+ ({ \
+ static const struct trace_print_field fields[] = \
+ { field_array, {} }; \
+ trace_print_register(p, value, mask, fields); \
+ })
+
#undef __print_flags_u64
#undef __print_symbolic_u64
#if BITS_PER_LONG == 32
@@ -744,6 +752,7 @@ static inline void ftrace_test_probe_##call(void) \

#undef __print_flags
#undef __print_symbolic
+#undef __print_register
#undef __print_hex
#undef __print_hex_str
#undef __get_dynamic_array
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 54373d93e251..cd5727ad54c3 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -124,6 +124,127 @@ trace_print_symbols_seq(struct trace_seq *p, unsigned long val,
}
EXPORT_SYMBOL(trace_print_symbols_seq);

+/**
+ * trace_print_register - Prints all the fields of a register.
+ *
+ * This is a hybrid method that combines the functionality of
+ * trace_print_flags_seq and trace_print_symbols_seq. It supports printing
+ * bit fields, enum fields, and numeric fields.
+ *
+ * Given the following register definition:
+ * * 0 - Enabled
+ * * 1 - Width, 0 = 1-bits, 1 = 4-bits
+ * * 2:3 - DMA, 0 = None, 1 = SDMA, 2 = ADMA, 3 = ADMA2
+ * * 4:7 - Timeout Counter
+ *
+ * The register fields could be defined as follows:
+ *
+ * const struct trace_print_field reg[] = {
+ * {1<<0, "ENABLED"},
+ * {
+ * .mask = 1<<1,
+ * .name = "WIDTH",
+ * .symbols = (const struct trace_print_flags[]) {
+ * {0, "1-BIT"},
+ * {1, "4-BIT"},
+ * {}
+ * }
+ * }, {
+ * .mask = 3<<2,
+ * .symbols = (const struct trace_print_flags[]) {
+ * {0, "NONE"},
+ * {1, "SDMA"},
+ * {2, "ADMA"},
+ * {3, "ADMA2"},
+ * {}
+ * }
+ * },
+ * {0xF<<4, "TIMEOUT"}
+ * }
+ *
+ * This would print out the following given value 0xAB:
+ *
+ * ENABLED: 1 | WIDTH: 4-BIT | ADMA | TIMEOUT: 0xA
+ *
+ * @p: trace buffer
+ * @fields: Array of fields that describe the register. Must be terminated with
+ * an empty value.
+ * @val: register value
+ * @mask: Mask that defines the bits present in @val. Useful if only a subset
+ * of the register was read. Any fields that fall outside of the mask
+ * will not be printed.
+ */
+const char *trace_print_register(struct trace_seq *p,
+ const struct trace_print_field fields[],
+ unsigned long val, unsigned long mask)
+{
+ const char *ret = trace_seq_buffer_ptr(p);
+ char *tail;
+ unsigned long fval;
+ int first = 1, symbol_found;
+ const struct trace_print_field *field;
+ const struct trace_print_flags *symbol;
+
+ for (field = fields; field->mask; field++) {
+ /* Make sure the field mask is within the accessed bits */
+ if ((mask & field->mask) != field->mask)
+ continue;
+
+ if (!first)
+ trace_seq_puts(p, " | ");
+
+ first = 0;
+
+ if (field->name) {
+ trace_seq_puts(p, field->name);
+ trace_seq_puts(p, ": ");
+ }
+
+ fval = val & field->mask;
+ fval >>= ffs(field->mask) - 1;
+
+ val &= ~field->mask;
+
+ symbol_found = 0;
+ for (symbol = field->symbols; symbol && symbol->name;
+ symbol++) {
+ if (symbol->mask != fval)
+ continue;
+ trace_seq_puts(p, symbol->name);
+ symbol_found = 1;
+ break;
+ }
+
+ if (!symbol_found) {
+ if (fval == 0) {
+ trace_seq_puts(p, "0");
+ } else if (fval == 1) {
+ trace_seq_puts(p, "1");
+ } else {
+ trace_seq_printf(p, "%#x", fval);
+
+ /* Strip off the null terminator */
+ for (tail = trace_seq_buffer_ptr(p) - 1;
+ tail > ret && !*tail; tail--) {
+ p->seq.len--;
+ }
+ }
+ }
+ }
+
+ /* Print any left over bits */
+ if (val) {
+ if (!first)
+ trace_seq_puts(p, " | ");
+ trace_seq_printf(p, "%#x", val);
+ }
+
+ trace_seq_putc(p, 0);
+
+ return ret;
+}
+EXPORT_SYMBOL(trace_print_register);
+
#if BITS_PER_LONG == 32
const char *
trace_print_flags_seq_u64(struct trace_seq *p, const char *delim,
--
2.21.0.392.gf8f6787159e-goog
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