We need to dig deeper in some emit cases, but for now lets make this
a bit more robust by checking if the types are unnamed.
Things like:
struct b {
struct {
int a;
};
}
This is well handled in the main fprintf routines, but its interaction
with the emit routines need more work, lets at least remove the segfault
and leave fixing this for good for v1.14.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Since we don't have something like DW_AT_alignment for
__attribute__((__packed__)), we need to use whatever hints that are
there in the alignments to figure out if a naturally packed struct has
the __attribute__((packed)) in the original sources, because that is
needed to waiver its natural alignment requisites.
For instance,
/* Used at: btrfs.c */
/* <1e7b> /home/acme/git/pahole/btrfs.c:199 */
struct btrfs_block_group_cache {
struct btrfs_key key; /* 0 17 */
struct btrfs_block_group_item item; /* 17 24 */
/* XXX 7 bytes hole, try to pack */
struct btrfs_fs_info * fs_info; /* 48 8 */
struct inode * inode; /* 56 8 */
In the original source code, btrfs_block_group_item is marked
__packed__, and being so, even seemingly unnecessarily, makes it, when
embedded in another struct, like the above, forfeit its natural
alingment, that would be 8 bytes, and instead appear right at the 17th
byte offset...
struct btrfs_block_group_item {
__le64 used; /* 0 8 */
__le64 chunk_objectid; /* 8 8 */
__le64 flags; /* 16 8 */
/* size: 24, cachelines: 1, members: 3 */
/* last cacheline: 24 bytes */
} __attribute__((__packed__));
So we need to, seeing its use at a unnatural offset, go backwards to the
btrfs_block_group_item pahole internal data structure, 'struct type' and
mark is_packed field as 'true', despite it not looking like a packed
struct.
Same thing with:
struct ieee80211_mcs_info {
u8 rx_mask[10]; /* 0 10 */
__le16 rx_highest; /* 10 2 */
u8 tx_params; /* 12 1 */
u8 reserved[3]; /* 13 3 */
/* size: 16, cachelines: 1, members: 4 */
/* last cacheline: 16 bytes */
};
That is naturally aligned and as 16 bytes, a power of two, then when it appears at the end of:
$ pahole -IC ieee80211_sta_ht_cap vht.o
/* Used at: vht.c */
/* <31ea> /home/acme/git/pahole/vht.c:1769 */
struct ieee80211_sta_ht_cap {
u16 cap; /* 0 2 */
bool ht_supported; /* 2 1 */
u8 ampdu_factor; /* 3 1 */
u8 ampdu_density; /* 4 1 */
/* XXX 1 byte hole, try to pack */
struct ieee80211_mcs_info mcs; /* 6 16 */
/* size: 22, cachelines: 1, members: 5 */
/* sum members: 21, holes: 1, sum holes: 1 */
/* last cacheline: 22 bytes */
};
$
We get that one byte hole if ieee80211_mcs_info isn't marked __packed__, as soon as we mark it:
$ pahole -IC ieee80211_sta_ht_cap vht.o
/* Used at: vht.c */
/* <31ea> /home/acme/git/pahole/vht.c:1769 */
struct ieee80211_sta_ht_cap {
u16 cap; /* 0 2 */
bool ht_supported; /* 2 1 */
u8 ampdu_factor; /* 3 1 */
u8 ampdu_density; /* 4 1 */
struct ieee80211_mcs_info mcs; /* 5 16 */
/* size: 22, cachelines: 1, members: 5 */
/* padding: 1 */
/* last cacheline: 22 bytes */
};
[acme@quaco pahole]$
It works, so __packed__ in this case just says: trow away the natural
alignment, make it 1 in whatever container structs.
So, before emitting the types for some struct, we go back looking at
each of its members and checking for such unnatural offsets, marking the
types as __packed__. Now:
$ pfunct --compile /home/acme/git/build/v5.1-rc4+/net/mac80211/vht.o | grep "^struct ieee80211_mcs_info" -A8
struct ieee80211_mcs_info {
u8 rx_mask[10]; /* 0 10 */
__le16 rx_highest; /* 10 2 */
u8 tx_params; /* 12 1 */
u8 reserved[3]; /* 13 3 */
/* size: 16, cachelines: 1, members: 4 */
/* last cacheline: 16 bytes */
} __attribute__((__packed__));
$
$ pfunct --compile /home/acme/git/build/v5.1-rc4+/fs/btrfs/free-space-tree.o | grep "^struct btrfs_block_group_item" -A7
struct btrfs_block_group_item {
__le64 used; /* 0 8 */
__le64 chunk_objectid; /* 8 8 */
__le64 flags; /* 16 8 */
/* size: 24, cachelines: 1, members: 3 */
/* last cacheline: 24 bytes */
} __attribute__((__packed__));
$
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Like in:
static int
cifs_setlease(struct file *file, long arg, struct file_lock **lease, void **priv)
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
For instance, with the existing code we ended up with:
typedef __kernel_size_t size_t;
size_t tcp_opt_stats_get_size(void)
{
}
Which lacks unwinding what a __kernel_size_t is, i.e.
type__emit_definitions() was only emitting definitions for the members
of structs and unions, do it for typedefs too, and then we end up what
we need, which is:
typedef long unsigned int __kernel_ulong_t;
typedef __kernel_ulong_t __kernel_size_t;
typedef __kernel_size_t size_t;
size_t tcp_opt_stats_get_size(void)
{
}
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
As Thomas Gleixner wisely pointed out, using 'self' is stupid, it
doesn't convey useful information, so use sensible names.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Instead pass thru cu__strings(cu, i) so that we can figure out if the
underlying debugging format handler can do that more efficiently, such as by
looking up directly the ELF section ".strtab".
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
To shorten the name and to reflect the fact that we're no longer
"finding" a type, but merely accessing an array with a bounds check in
this function.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Amazing how many crept up over time, should have set the
execute bit of .git/hooks/pre-commit already, duh.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
To take advantage of cache effects and to avoid calling cu__find_holes
more than once on the same struct.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
So that one can get an skeleton from where a function can be
reimplemented, or a probe can be written to attach to a tracepoint.
Right now it will only expand the types for
struct/union/typedef/enumeration types, but it is a good start.
[acme@doppio pahole]$ pfunct --expand_types --function inet6_ioctl ipv6.ko > a.c
[acme@doppio pahole]$ echo "int main(void) { return 0; }" >> a.c
[acme@doppio pahole]$ gcc -Wall -g a.c -o a
[acme@doppio pahole]$ grep ^#include a.c
[acme@doppio pahole]$
No errors, no includes.
This is present in ctracer, where we don't want to _require_ any header
files, just the object file with the function we want to probe. From
there we get the function signature, and reconstruct the types needed to
access members of structs passed as parameters.
We still need to add padding to reconstruct __attribute__ alignment
effects.
Also, if we can detect what are the exact members accessed in the probe,
we can reconstruct just what is needed to access those members,
hopefully reducing the time needed for gcc to digest the resulting
source code. And also reducing the size of the output, which can
hopefully be interesting to help focus on what the probe is doing.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
For correctly created and completely parsed debugging information the type will
always be found, but as we still need to parse more tags and expecting
debugging information to be always correctly built is not sane... sprinkle some
asserts.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
At that point we are emitting the definitions for the member types,
so we have to print a newline after each.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
To indicate wheter the semicolon should be supressed. Useful for
prototype/function emission, etc.
Also move the struct stats to be inside its body, to simplify tag__fprintf,
that now looks at conf.no_semicolon after calling the tag type specific
__fprintf method.
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
C++ uses this, and to cache the result of the lookup at type__name time we need
to pass the cu to class__name and type__name. Big fallout because of that :-\
But now the output is mucho embelished by the humongous strings representing
C++ templates.
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
For now its just the direct ancestor of struct type. But it will exists by
itself, to represent the DW_TAG_namespace DWARF tag, that is how the C++
'namespace' (and other languages too, heck, I'd love to get my hands on a
binary with DWARF info built from, say, ADA source code, objectiveC... COBOL!
:-P).
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
This is in preparation for the introduction of struct namespace, that will be
struct type ancestor.
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Will be useful to show that the intent is to traverse just the DW_TAG_member
entries in the type list. Right now there are both DW_TAG_inheritance and
DW_TAG_member entries in the ->members type list. But there will be many more
tags, like enumerations, classes, etc, that are defined inside classes, a C++
feature. This will also help with DW_TAG_namespace support.
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Arnaldo Carvalho de Melo
Domenico Andreoli
Arnaldo Carvalho de Melo