Em Thu, Jan 10, 2019 at 02:50:32PM -0300, Arnaldo Carvalho de Melo escreveu:
> So, the size for an enumeration in BTF is in bytes, not in bits, as in
> CTF, fixed with the patch below, looking at the other cases now.
We're down to packed data structs, probably in the BTF encoder, see
below.
$ diff -u /tmp/tcp.o.dwarf.c /tmp/tcp.o.btf.c
--- /tmp/tcp.o.dwarf.c 2019-01-10 12:10:26.890521322 -0300
+++ /tmp/tcp.o.btf.c 2019-01-10 14:46:04.584743337 -0300
@@ -585,11 +585,17 @@
__u16 vesapm_off; /* 48 2 */
__u16 pages; /* 50 2 */
__u16 vesa_attributes; /* 52 2 */
- __u32 capabilities; /* 54 4 */
- __u32 ext_lfb_base; /* 58 4 */
+ __u32 capabilities; /* 52 4 */
+ __u32 ext_lfb_base; /* 56 4 */
+
+ /* XXX 2 bytes hole, try to pack */
+
__u8 _reserved[2]; /* 62 2 */
Were these 4 extra bytes came from? The original struct is:
/*
* These are set up by the setup-routine at boot-time:
*/
struct screen_info {
__u8 orig_x; /* 0x00 */
__u8 orig_y; /* 0x01 */
__u16 ext_mem_k; /* 0x02 */
__u16 orig_video_page; /* 0x04 */
__u8 orig_video_mode; /* 0x06 */
__u8 orig_video_cols; /* 0x07 */
__u8 flags; /* 0x08 */
__u8 unused2; /* 0x09 */
__u16 orig_video_ega_bx;/* 0x0a */
__u16 unused3; /* 0x0c */
__u8 orig_video_lines; /* 0x0e */
__u8 orig_video_isVGA; /* 0x0f */
__u16 orig_video_points;/* 0x10 */
/* VESA graphic mode -- linear frame buffer */
__u16 lfb_width; /* 0x12 */
__u16 lfb_height; /* 0x14 */
__u16 lfb_depth; /* 0x16 */
__u32 lfb_base; /* 0x18 */
__u32 lfb_size; /* 0x1c */
__u16 cl_magic, cl_offset; /* 0x20 */
__u16 lfb_linelength; /* 0x24 */
__u8 red_size; /* 0x26 */
__u8 red_pos; /* 0x27 */
__u8 green_size; /* 0x28 */
__u8 green_pos; /* 0x29 */
__u8 blue_size; /* 0x2a */
__u8 blue_pos; /* 0x2b */
__u8 rsvd_size; /* 0x2c */
__u8 rsvd_pos; /* 0x2d */
__u16 vesapm_seg; /* 0x2e */
__u16 vesapm_off; /* 0x30 */
__u16 pages; /* 0x32 */
__u16 vesa_attributes; /* 0x34 */
__u32 capabilities; /* 0x36 */
__u32 ext_lfb_base; /* 0x3a */
__u8 _reserved[2]; /* 0x3e */
} __attribute__((packed));
$ pahole --hex -F dwarf -C screen_info ~/git/build/v4.20-rc5/net/ipv4/tcp.o
struct screen_info {
__u8 orig_x; /* 0 0x1 */
__u8 orig_y; /* 0x1 0x1 */
__u16 ext_mem_k; /* 0x2 0x2 */
__u16 orig_video_page; /* 0x4 0x2 */
__u8 orig_video_mode; /* 0x6 0x1 */
__u8 orig_video_cols; /* 0x7 0x1 */
__u8 flags; /* 0x8 0x1 */
__u8 unused2; /* 0x9 0x1 */
__u16 orig_video_ega_bx; /* 0xa 0x2 */
__u16 unused3; /* 0xc 0x2 */
__u8 orig_video_lines; /* 0xe 0x1 */
__u8 orig_video_isVGA; /* 0xf 0x1 */
__u16 orig_video_points; /* 0x10 0x2 */
__u16 lfb_width; /* 0x12 0x2 */
__u16 lfb_height; /* 0x14 0x2 */
__u16 lfb_depth; /* 0x16 0x2 */
__u32 lfb_base; /* 0x18 0x4 */
__u32 lfb_size; /* 0x1c 0x4 */
__u16 cl_magic; /* 0x20 0x2 */
__u16 cl_offset; /* 0x22 0x2 */
__u16 lfb_linelength; /* 0x24 0x2 */
__u8 red_size; /* 0x26 0x1 */
__u8 red_pos; /* 0x27 0x1 */
__u8 green_size; /* 0x28 0x1 */
__u8 green_pos; /* 0x29 0x1 */
__u8 blue_size; /* 0x2a 0x1 */
__u8 blue_pos; /* 0x2b 0x1 */
__u8 rsvd_size; /* 0x2c 0x1 */
__u8 rsvd_pos; /* 0x2d 0x1 */
__u16 vesapm_seg; /* 0x2e 0x2 */
__u16 vesapm_off; /* 0x30 0x2 */
__u16 pages; /* 0x32 0x2 */
__u16 vesa_attributes; /* 0x34 0x2 */
__u32 capabilities; /* 0x36 0x4 */
__u32 ext_lfb_base; /* 0x3a 0x4 */
__u8 _reserved[2]; /* 0x3e 0x2 */
/* size: 64, cachelines: 1, members: 36 */
};
the dwarf loader/pahole printer seem to be doing the right thing, the
BTF encoder, it seems, has issues with attribute((packed)) structs, see
below.
[acme@quaco pahole]$ pahole --hex -F dwarf -C screen_info ~/git/build/v4.20-rc5/net/ipv4/tcp.o > /tmp/dwarf
[acme@quaco pahole]$ pahole --hex -F btf -C screen_info ~/git/build/v4.20-rc5/net/ipv4/tcp.o > /tmp/btf
[acme@quaco pahole]$ diff -u /tmp/dwarf /tmp/btf
--- /tmp/dwarf 2019-01-10 15:00:14.946723885 -0300
+++ /tmp/btf 2019-01-10 15:00:18.669757798 -0300
@@ -32,9 +32,15 @@
__u16 vesapm_off; /* 0x30 0x2 */
__u16 pages; /* 0x32 0x2 */
__u16 vesa_attributes; /* 0x34 0x2 */
- __u32 capabilities; /* 0x36 0x4 */
+ __u32 capabilities; /* 0x34 0x4 */
- __u32 ext_lfb_base; /* 0x3a 0x4 */
+ __u32 ext_lfb_base; /* 0x38 0x4 */
+
+ /* XXX 2 bytes hole, try to pack */
+
__u8 _reserved[2]; /* 0x3e 0x2 */
/* size: 64, cachelines: 1, members: 36 */
+ /* sum members: 60, holes: 1, sum holes: 2 */
+
+ /* BRAIN FART ALERT! 64 != 60 + 2(holes), diff = 2 */
};
[acme@quaco pahole]$
Why the BTF encoder or loader is getting this in the wrong place...
Debugging...
/* size: 64, cachelines: 1, members: 36 */
+ /* sum members: 60, holes: 1, sum holes: 2 */
+
+ /* BRAIN FART ALERT! 64 != 60 + 2(holes), diff = 2 */
};
struct apm_bios_info {
__u16 version; /* 0 2 */
@@ -630,7 +636,10 @@
__u32 sectors_per_track; /* 12 4 */
__u64 number_of_sectors; /* 16 8 */
__u16 bytes_per_sector; /* 24 2 */
- __u32 dpte_ptr; /* 26 4 */
+ __u32 dpte_ptr; /* 24 4 */
Looks like the same problem as with screen_info, 'dpte_ptr' got
"unionized" with 'bytes_per_sector'
+
+ /* XXX 2 bytes hole, try to pack */
+
__u16 key; /* 30 2 */
__u8 device_path_info_length; /* 32 1 */
__u8 reserved2; /* 33 1 */
@@ -683,7 +692,10 @@
} atapi; /* 56 16 */
struct {
__u16 id; /* 56 2 */
- __u64 lun; /* 58 8 */
+ __u64 lun; /* 56 8 */
Ditto, here it could be trying to put 'lun' in its natural alignment,
probably 'struct edd_device_params' is packed like screen_info? Yes...
include/uapi/linux/edd.h line 72
+
+ /* XXX 2 bytes hole, try to pack */
+
/* --- cacheline 1 boundary (64 bytes) was 2 bytes ago --- */
__u16 reserved1; /* 66 2 */
__u32 reserved2; /* 68 4 */
@@ -733,7 +745,10 @@
__u8 checksum; /* 73 1 */
/* size: 74, cachelines: 2, members: 18 */
+ /* sum members: 70, holes: 1, sum holes: 2 */
/* last cacheline: 10 bytes */
+
+ /* BRAIN FART ALERT! 74 != 70 + 2(holes), diff = 2 */
};
struct edd_info {
__u8 device; /* 0 1 */
@@ -849,10 +864,13 @@
};
struct desc_ptr {
short unsigned int size; /* 0 2 */
- long unsigned int address; /* 2 8 */
+ long unsigned int address; /* 0 8 */
One more packed struct:
struct desc_ptr {
unsigned short size;
unsigned long address;
} __attribute__((packed)) ;
/* size: 10, cachelines: 1, members: 2 */
+ /* padding: 2 */
/* last cacheline: 10 bytes */
+
+ /* BRAIN FART ALERT! 10 != 2 + 0(holes), diff = 8 */
};
struct pgprot {
pgprotval_t pgprot; /* 0 8 */
@@ -1467,10 +1485,13 @@
};
struct x86_hw_tss {
Also a packed struct
u32 reserved1; /* 0 4 */
- u64 sp0; /* 4 8 */
- u64 sp1; /* 12 8 */
- u64 sp2; /* 20 8 */
- u64 reserved2; /* 28 8 */
+ u64 sp0; /* 0 8 */
+ u64 sp1; /* 8 8 */
+ u64 sp2; /* 16 8 */
+ u64 reserved2; /* 24 8 */
+
+ /* XXX 4 bytes hole, try to pack */
+
u64 ist[7]; /* 36 56 */
/* --- cacheline 1 boundary (64 bytes) was 28 bytes ago --- */
u32 reserved3; /* 92 4 */
@@ -1479,7 +1500,10 @@
u16 io_bitmap_base; /* 102 2 */
/* size: 104, cachelines: 2, members: 10 */
+ /* sum members: 96, holes: 1, sum holes: 4 */
/* last cacheline: 40 bytes */
+
+ /* BRAIN FART ALERT! 104 != 96 + 4(holes), diff = 4 */
};
struct seq_operations {
void * (*start)(struct seq_file *, loff_t *); /* 0 8 */
This last one is interesting, was this done on purpose? I think one
level of indirection more and we would keep the original expressiveness.
@@ -8473,7 +8497,7 @@
struct lruvec_stat * lruvec_stat_cpu; /* 136 8 */
atomic_long_t lruvec_stat[30]; /* 144 240 */
/* --- cacheline 6 boundary (384 bytes) --- */
- long unsigned int lru_zone_size[5][5]; /* 384 200 */
+ long unsigned int lru_zone_size[25]; /* 384 200 */
/* --- cacheline 9 boundary (576 bytes) was 8 bytes ago --- */
struct mem_cgroup_reclaim_iter iter[13]; /* 584 208 */
/* --- cacheline 12 boundary (768 bytes) was 24 bytes ago --- */
- Arnaldo
