Global variables are accessed using PC-relative address so it needs to
be handled separately. The PC-rel addressing is detected by using
DWARF_REG_PC. On x86, %rip register would be used.
The address can be calculated using the ip and offset in the
instruction. But it should start from the next instruction so add
calculate_pcrel_addr() to do it properly.
But global variables defined in a different file would only have a
declaration which doesn't include a location list. So it first tries
to get the type info using the address, and then looks up the variable
declarations using name. The name of global variables should be get
from the symbol table. The declaration would have the type info.
So extend find_var_type() to take both address and name for global
variables.
The stat is now looks like:
Annotate data type stats:
total 294, ok 153 (52.0%), bad 141 (48.0%)
-----------------------------------------------------------
30 : no_sym
32 : no_mem_ops
61 : no_var
10 : no_typeinfo
8 : bad_offset
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20240117062657.985479-7-namhyung@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
A typical function prologue and epilogue include multiple stack
operations to save and restore the current value of registers.
On x86, it looks like below:
push r15
push r14
push r13
push r12
...
pop r12
pop r13
pop r14
pop r15
ret
As these all touches the stack memory region, chances are high that they
appear in a memory profile data. But these are not used for any real
purpose yet so it'd return no types.
One of my profile type shows that non neglible portion of data came from
the stack operations. It also seems GCC generates more stack operations
than clang.
Annotate Instruction stats
total 264, ok 169 (64.0%), bad 95 (36.0%)
Name : Good Bad
-----------------------------------------------------------
movq : 49 27
movl : 24 9
popq : 0 19 <-- here
cmpl : 17 2
addq : 14 1
cmpq : 12 2
cmpxchgl : 3 7
Instead of dealing them as unknown, let's create a seperate pseudo type
to represent those stack operations separately.
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20240117062657.985479-5-namhyung@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
On x86, instructions for array access often looks like below.
mov 0x1234(%rax,%rbx,8), %rcx
Usually the first register holds the type information and the second one
has the index. And the current code only looks up a variable for the
first register. But it's possible to be in the other way around so it
needs to check the second register if the first one failed.
The stat changed like this.
Annotate data type stats:
total 294, ok 148 (50.3%), bad 146 (49.7%)
-----------------------------------------------------------
30 : no_sym
32 : no_mem_ops
66 : no_var
10 : no_typeinfo
8 : bad_offset
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20240117062657.985479-4-namhyung@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
The --type-stat option is to be used with --data-type and to print
detailed failure reasons for the data type annotation.
$ perf annotate --data-type --type-stat
Annotate data type stats:
total 294, ok 116 (39.5%), bad 178 (60.5%)
-----------------------------------------------------------
30 : no_sym
40 : no_insn_ops
33 : no_mem_ops
63 : no_var
4 : no_typeinfo
8 : bad_offset
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: linux-toolchains@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Link: https://lore.kernel.org/r/20231213001323.718046-17-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The annotated_data_type__update_samples() to get histogram for data type
access.
It'll be called by perf annotate to show which fields in the data type
are accessed frequently.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: linux-toolchains@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Link: https://lore.kernel.org/r/20231213001323.718046-12-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Add child member field if the current type is a composite type like a
struct or union. The member fields are linked in the children list and
do the same recursively if the child itself is a composite type.
Add 'self' member to the annotated_data_type to handle the members in
the same way.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: linux-toolchains@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Link: https://lore.kernel.org/r/20231213001323.718046-11-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
To aggregate accesses to the same data type, add 'data_types' tree in
DSO to maintain data types and find it by name and size.
It might have different data types that happen to have the same name,
so it also compares the size of the type.
Even if it doesn't 100% guarantee, it reduces the possibility of
mis-handling of such conflicts.
And I don't think it's common to have different types with the same
name.
Committer notes:
Very few cases on the Linux kernel, but there are some different types
with the same name, unsure if there is a debug mode in libbpf dedup that
warns about such cases, but there are provisions in pahole for that,
see:
"emit: Notice type shadowing, i.e. multiple types with the same name (enum, struct, union, etc)"
https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=4f332dbfd02072e4f410db7bdcda8d6e3422974b
$ pahole --compile > vmlinux.h
$ rm -f a ; make a
cc a.c -o a
$ grep __[0-9] vmlinux.h
union irte__1 {
struct map_info__1;
struct map_info__1 {
struct map_info__1 * next; /* 0 8 */
$
drivers/iommu/amd/amd_iommu_types.h 'union irte'
include/linux/dmar.h 'struct irte'
include/linux/device-mapper.h:
union map_info {
void *ptr;
};
include/linux/mtd/map.h:
struct map_info {
const char *name;
unsigned long size;
resource_size_t phys;
<SNIP>
kernel/events/uprobes.c:
struct map_info {
struct map_info *next;
struct mm_struct *mm;
unsigned long vaddr;
};
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: linux-toolchains@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Link: https://lore.kernel.org/r/20231213001323.718046-5-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The find_data_type() is to get a data type from the memory access at the
given address (IP) using a register and an offset.
It requires DWARF debug info in the DSO and searches the list of
variables and function parameters in the scope.
In a pseudo code, it does basically the following:
find_data_type(dso, ip, reg, offset)
{
pc = map__rip_2objdump(ip);
CU = dwarf_addrdie(dso->dwarf, pc);
scopes = die_get_scopes(CU, pc);
for_each_scope(S, scopes) {
V = die_find_variable_by_reg(S, pc, reg);
if (V && V.type == pointer_type) {
T = die_get_real_type(V);
if (offset < T.size)
return T;
}
}
return NULL;
}
Committer notes:
The 'size' variable in check_variable() is 64-bit, so use PRIu64 and
inttypes.h to debug it.
Ditto at find_data_type_die().
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: linux-toolchains@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Link: https://lore.kernel.org/r/20231213001323.718046-4-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
