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linux/kernel/trace/trace_entries.h
Steven Rostedt (Google) e7186af7fb tracing: Add back FORTIFY_SOURCE logic to kernel_stack event structure 
For backward compatibility, older tooling expects to see the kernel_stack
event with a "caller" field that is a fixed size array of 8 addresses. The
code now supports more than 8 with an added "size" field that states the
real number of entries. But the "caller" field still just looks like a
fixed size to user space.

Since the tracing macros that create the user space format files also
creates the structures that those files represent, the kernel_stack event
structure had its "caller" field a fixed size of 8, but in reality, when
it is allocated on the ring buffer, it can hold more if the stack trace is
bigger that 8 functions. The copying of these entries was simply done with
a memcpy():

  size = nr_entries * sizeof(unsigned long);
  memcpy(entry->caller, fstack->calls, size);

The FORTIFY_SOURCE logic noticed at runtime that when the nr_entries was
larger than 8, that the memcpy() was writing more than what the structure
stated it can hold and it complained about it. This is because the
FORTIFY_SOURCE code is unaware that the amount allocated is actually
enough to hold the size. It does not expect that a fixed size field will
hold more than the fixed size.

This was originally solved by hiding the caller assignment with some
pointer arithmetic.

  ptr = ring_buffer_data();
  entry = ptr;

  ptr += offsetof(typeof(*entry), caller);
  memcpy(ptr, fstack->calls, size);

But it is considered bad form to hide from kernel hardening. Instead, make
it work nicely with FORTIFY_SOURCE by adding a new __stack_array() macro
that is specific for this one special use case. The macro will take 4
arguments: type, item, len, field (whereas the __array() macro takes just
the first three). This macro will act just like the __array() macro when
creating the code to deal with the format file that is exposed to user
space. But for the kernel, it will turn the caller field into:

  type item[] __counted_by(field);

or for this instance:

  unsigned long caller[] __counted_by(size);

Now the kernel code can expose the assignment of the caller to the
FORTIFY_SOURCE and everyone is happy!

Link: https://lore.kernel.org/linux-trace-kernel/20230712105235.5fc441aa@gandalf.local.home/
Link: https://lore.kernel.org/linux-trace-kernel/20230713092605.2ddb9788@rorschach.local.home

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
2023-07-30 18:11:44 -04:00

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// SPDX-License-Identifier: GPL-2.0
/*
* This file defines the trace event structures that go into the ring
* buffer directly. They are created via macros so that changes for them
* appear in the format file. Using macros will automate this process.
*
* The macro used to create a ftrace data structure is:
*
* FTRACE_ENTRY( name, struct_name, id, structure, print )
*
* @name: the name used the event name, as well as the name of
* the directory that holds the format file.
*
* @struct_name: the name of the structure that is created.
*
* @id: The event identifier that is used to detect what event
* this is from the ring buffer.
*
* @structure: the structure layout
*
* - __field( type, item )
* This is equivalent to declaring
* type item;
* in the structure.
* - __array( type, item, size )
* This is equivalent to declaring
* type item[size];
* in the structure.
*
* * for structures within structures, the format of the internal
* structure is laid out. This allows the internal structure
* to be deciphered for the format file. Although these macros
* may become out of sync with the internal structure, they
* will create a compile error if it happens. Since the
* internal structures are just tracing helpers, this is not
* an issue.
*
* When an internal structure is used, it should use:
*
* __field_struct( type, item )
*
* instead of __field. This will prevent it from being shown in
* the output file. The fields in the structure should use.
*
* __field_desc( type, container, item )
* __array_desc( type, container, item, len )
*
* type, item and len are the same as __field and __array, but
* container is added. This is the name of the item in
* __field_struct that this is describing.
*
*
* @print: the print format shown to users in the format file.
*/
/*
* Function trace entry - function address and parent function address:
*/
FTRACE_ENTRY_REG(function, ftrace_entry,
TRACE_FN,
F_STRUCT(
__field_fn( unsigned long, ip )
__field_fn( unsigned long, parent_ip )
),
F_printk(" %ps <-- %ps",
(void *)__entry->ip, (void *)__entry->parent_ip),
perf_ftrace_event_register
);
/* Function call entry */
FTRACE_ENTRY_PACKED(funcgraph_entry, ftrace_graph_ent_entry,
TRACE_GRAPH_ENT,
F_STRUCT(
__field_struct( struct ftrace_graph_ent, graph_ent )
__field_packed( unsigned long, graph_ent, func )
__field_packed( int, graph_ent, depth )
),
F_printk("--> %ps (%d)", (void *)__entry->func, __entry->depth)
);
/* Function return entry */
#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry,
TRACE_GRAPH_RET,
F_STRUCT(
__field_struct( struct ftrace_graph_ret, ret )
__field_packed( unsigned long, ret, func )
__field_packed( unsigned long, ret, retval )
__field_packed( int, ret, depth )
__field_packed( unsigned int, ret, overrun )
__field_packed( unsigned long long, ret, calltime)
__field_packed( unsigned long long, ret, rettime )
),
F_printk("<-- %ps (%d) (start: %llx end: %llx) over: %d retval: %lx",
(void *)__entry->func, __entry->depth,
__entry->calltime, __entry->rettime,
__entry->depth, __entry->retval)
);
#else
FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry,
TRACE_GRAPH_RET,
F_STRUCT(
__field_struct( struct ftrace_graph_ret, ret )
__field_packed( unsigned long, ret, func )
__field_packed( int, ret, depth )
__field_packed( unsigned int, ret, overrun )
__field_packed( unsigned long long, ret, calltime)
__field_packed( unsigned long long, ret, rettime )
),
F_printk("<-- %ps (%d) (start: %llx end: %llx) over: %d",
(void *)__entry->func, __entry->depth,
__entry->calltime, __entry->rettime,
__entry->depth)
);
#endif
/*
* Context switch trace entry - which task (and prio) we switched from/to:
*
* This is used for both wakeup and context switches. We only want
* to create one structure, but we need two outputs for it.
*/
#define FTRACE_CTX_FIELDS \
__field( unsigned int, prev_pid ) \
__field( unsigned int, next_pid ) \
__field( unsigned int, next_cpu ) \
__field( unsigned char, prev_prio ) \
__field( unsigned char, prev_state ) \
__field( unsigned char, next_prio ) \
__field( unsigned char, next_state )
FTRACE_ENTRY(context_switch, ctx_switch_entry,
TRACE_CTX,
F_STRUCT(
FTRACE_CTX_FIELDS
),
F_printk("%u:%u:%u ==> %u:%u:%u [%03u]",
__entry->prev_pid, __entry->prev_prio, __entry->prev_state,
__entry->next_pid, __entry->next_prio, __entry->next_state,
__entry->next_cpu)
);
/*
* FTRACE_ENTRY_DUP only creates the format file, it will not
* create another structure.
*/
FTRACE_ENTRY_DUP(wakeup, ctx_switch_entry,
TRACE_WAKE,
F_STRUCT(
FTRACE_CTX_FIELDS
),
F_printk("%u:%u:%u ==+ %u:%u:%u [%03u]",
__entry->prev_pid, __entry->prev_prio, __entry->prev_state,
__entry->next_pid, __entry->next_prio, __entry->next_state,
__entry->next_cpu)
);
/*
* Stack-trace entry:
*/
#define FTRACE_STACK_ENTRIES 8
FTRACE_ENTRY(kernel_stack, stack_entry,
TRACE_STACK,
F_STRUCT(
__field( int, size )
__stack_array( unsigned long, caller, FTRACE_STACK_ENTRIES, size)
),
F_printk("\t=> %ps\n\t=> %ps\n\t=> %ps\n"
"\t=> %ps\n\t=> %ps\n\t=> %ps\n"
"\t=> %ps\n\t=> %ps\n",
(void *)__entry->caller[0], (void *)__entry->caller[1],
(void *)__entry->caller[2], (void *)__entry->caller[3],
(void *)__entry->caller[4], (void *)__entry->caller[5],
(void *)__entry->caller[6], (void *)__entry->caller[7])
);
FTRACE_ENTRY(user_stack, userstack_entry,
TRACE_USER_STACK,
F_STRUCT(
__field( unsigned int, tgid )
__array( unsigned long, caller, FTRACE_STACK_ENTRIES )
),
F_printk("\t=> %ps\n\t=> %ps\n\t=> %ps\n"
"\t=> %ps\n\t=> %ps\n\t=> %ps\n"
"\t=> %ps\n\t=> %ps\n",
(void *)__entry->caller[0], (void *)__entry->caller[1],
(void *)__entry->caller[2], (void *)__entry->caller[3],
(void *)__entry->caller[4], (void *)__entry->caller[5],
(void *)__entry->caller[6], (void *)__entry->caller[7])
);
/*
* trace_printk entry:
*/
FTRACE_ENTRY(bprint, bprint_entry,
TRACE_BPRINT,
F_STRUCT(
__field( unsigned long, ip )
__field( const char *, fmt )
__dynamic_array( u32, buf )
),
F_printk("%ps: %s",
(void *)__entry->ip, __entry->fmt)
);
FTRACE_ENTRY_REG(print, print_entry,
TRACE_PRINT,
F_STRUCT(
__field( unsigned long, ip )
__dynamic_array( char, buf )
),
F_printk("%ps: %s",
(void *)__entry->ip, __entry->buf),
ftrace_event_register
);
FTRACE_ENTRY(raw_data, raw_data_entry,
TRACE_RAW_DATA,
F_STRUCT(
__field( unsigned int, id )
__dynamic_array( char, buf )
),
F_printk("id:%04x %08x",
__entry->id, (int)__entry->buf[0])
);
FTRACE_ENTRY(bputs, bputs_entry,
TRACE_BPUTS,
F_STRUCT(
__field( unsigned long, ip )
__field( const char *, str )
),
F_printk("%ps: %s",
(void *)__entry->ip, __entry->str)
);
FTRACE_ENTRY(mmiotrace_rw, trace_mmiotrace_rw,
TRACE_MMIO_RW,
F_STRUCT(
__field_struct( struct mmiotrace_rw, rw )
__field_desc( resource_size_t, rw, phys )
__field_desc( unsigned long, rw, value )
__field_desc( unsigned long, rw, pc )
__field_desc( int, rw, map_id )
__field_desc( unsigned char, rw, opcode )
__field_desc( unsigned char, rw, width )
),
F_printk("%lx %lx %lx %d %x %x",
(unsigned long)__entry->phys, __entry->value, __entry->pc,
__entry->map_id, __entry->opcode, __entry->width)
);
FTRACE_ENTRY(mmiotrace_map, trace_mmiotrace_map,
TRACE_MMIO_MAP,
F_STRUCT(
__field_struct( struct mmiotrace_map, map )
__field_desc( resource_size_t, map, phys )
__field_desc( unsigned long, map, virt )
__field_desc( unsigned long, map, len )
__field_desc( int, map, map_id )
__field_desc( unsigned char, map, opcode )
),
F_printk("%lx %lx %lx %d %x",
(unsigned long)__entry->phys, __entry->virt, __entry->len,
__entry->map_id, __entry->opcode)
);
#define TRACE_FUNC_SIZE 30
#define TRACE_FILE_SIZE 20
FTRACE_ENTRY(branch, trace_branch,
TRACE_BRANCH,
F_STRUCT(
__field( unsigned int, line )
__array( char, func, TRACE_FUNC_SIZE+1 )
__array( char, file, TRACE_FILE_SIZE+1 )
__field( char, correct )
__field( char, constant )
),
F_printk("%u:%s:%s (%u)%s",
__entry->line,
__entry->func, __entry->file, __entry->correct,
__entry->constant ? " CONSTANT" : "")
);
FTRACE_ENTRY(hwlat, hwlat_entry,
TRACE_HWLAT,
F_STRUCT(
__field( u64, duration )
__field( u64, outer_duration )
__field( u64, nmi_total_ts )
__field_struct( struct timespec64, timestamp )
__field_desc( s64, timestamp, tv_sec )
__field_desc( long, timestamp, tv_nsec )
__field( unsigned int, nmi_count )
__field( unsigned int, seqnum )
__field( unsigned int, count )
),
F_printk("cnt:%u\tts:%010llu.%010lu\tinner:%llu\touter:%llu\tcount:%d\tnmi-ts:%llu\tnmi-count:%u\n",
__entry->seqnum,
__entry->tv_sec,
__entry->tv_nsec,
__entry->duration,
__entry->outer_duration,
__entry->count,
__entry->nmi_total_ts,
__entry->nmi_count)
);
#define FUNC_REPEATS_GET_DELTA_TS(entry) \
(((u64)(entry)->top_delta_ts << 32) | (entry)->bottom_delta_ts) \
FTRACE_ENTRY(func_repeats, func_repeats_entry,
TRACE_FUNC_REPEATS,
F_STRUCT(
__field( unsigned long, ip )
__field( unsigned long, parent_ip )
__field( u16 , count )
__field( u16 , top_delta_ts )
__field( u32 , bottom_delta_ts )
),
F_printk(" %ps <-%ps\t(repeats:%u delta: -%llu)",
(void *)__entry->ip,
(void *)__entry->parent_ip,
__entry->count,
FUNC_REPEATS_GET_DELTA_TS(__entry))
);
FTRACE_ENTRY(osnoise, osnoise_entry,
TRACE_OSNOISE,
F_STRUCT(
__field( u64, noise )
__field( u64, runtime )
__field( u64, max_sample )
__field( unsigned int, hw_count )
__field( unsigned int, nmi_count )
__field( unsigned int, irq_count )
__field( unsigned int, softirq_count )
__field( unsigned int, thread_count )
),
F_printk("noise:%llu\tmax_sample:%llu\thw:%u\tnmi:%u\tirq:%u\tsoftirq:%u\tthread:%u\n",
__entry->noise,
__entry->max_sample,
__entry->hw_count,
__entry->nmi_count,
__entry->irq_count,
__entry->softirq_count,
__entry->thread_count)
);
FTRACE_ENTRY(timerlat, timerlat_entry,
TRACE_TIMERLAT,
F_STRUCT(
__field( unsigned int, seqnum )
__field( int, context )
__field( u64, timer_latency )
),
F_printk("seq:%u\tcontext:%d\ttimer_latency:%llu\n",
__entry->seqnum,
__entry->context,
__entry->timer_latency)
);
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