On 4/2/21 7:57 AM, Arnaldo Carvalho de Melo wrote:
Em Fri, Apr 02, 2021 at 11:04:18AM -0300, Arnaldo Carvalho de Melo escreveu:
Em Thu, Apr 01, 2021 at 05:00:46PM -0700, David Blaikie escreveu:
On Thu, Apr 1, 2021 at 4:41 PM Yonghong Song <yhs@xxxxxx> wrote:
On 4/1/21 3:27 PM, David Blaikie wrote:
Though people may come up with novel uses of DWARF features. What would
happen if this constraint were violated/what's your motivation for
asking (I don't quite understand the connection between test_progs
failure description, and this question)
I have some codes to check the tag associated with abstract_origin
for a subprogram must be a subprogram. Through experiment, I didn't
see a violation, so I wonder that I can get confirmation from you
and then I may delete that code.
The test_progs failure exposed the bug, that is all.
pahole cannot handle all weird usages of dwarf, so I think pahole
is fine only to support well-formed dwarf.
Sounds good. Thanks for the context!
David, since you took the time to go thru the changes and to agree that
Yonghong's fix is good, can I add a:
Acked-by: David Blaikie <dblaikie@xxxxxxxxx>
to this patch?
Maybe even a:
Reviewed-by: David Blaikie <dblaikie@xxxxxxxxx>
What I have is at tmp.master, please take a look and check that
everything is ok, the only think I wished to fix but I think can be left
for later is in the tmp.master branch at:
git://git.kernel.org/pub/scm/devel/pahole/pahole.git tmp.master
Thanks. I checked out the branch and did some testing with latest clang
trunk (just pulled in).
With kernel LTO note support, I tested gcc non-lto, and llvm-lto mode,
it works fine.
Without kernel LTO note support, I tested
gcc non-lto <=== ok
llvm non-lto <=== not ok
llvm lto <=== ok
Surprisingly llvm non-lto vmlinux had the same "tcp_slow_start" issue.
Some previous version of clang does not have this issue.
I double checked the dwarfdump and it is indeed has the same reason
for lto vmlinux. I checked abbrev section and there is no cross-cu
references.
That means we need to adapt this patch
dwarf_loader: Handle subprogram ret type with abstract_origin properly
for non merging case as well.
The previous patch fixed lto subprogram abstract_origin issue,
I will submit a followup patch for this.
I did some testing for this ret type fix:
https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?h=tmp.master
And for the LTO ELF notes:
https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?h=tmp.master&id=7a79d2d7a573a863aa36fd06f540fe9fa824db4e
The only remaining thing, which I think can be left for 1.22 is:
[acme@five pahole]$ btfdiff vmlinux.clang.thin.LTO
vmlinux.clang.thin.LTO vmlinux.clang.thin.LTO+ELF_note
[acme@five pahole]$ btfdiff vmlinux.clang.thin.LTO+ELF_note
--- /tmp/btfdiff.dwarf.CtLJpQ 2021-04-02 11:55:09.658433186 -0300
+++ /tmp/btfdiff.btf.d3L3vy 2021-04-02 11:55:09.925439277 -0300
@@ -67255,7 +67255,7 @@ struct cpu_rmap {
struct {
u16 index; /* 16 2 */
u16 dist; /* 18 2 */
- } near[0]; /* 16 0 */
+ } near[]; /* 16 0 */
/* size: 16, cachelines: 1, members: 5 */
/* last cacheline: 16 bytes */
@@ -101181,7 +101181,7 @@ struct linux_efi_memreserve {
struct {
phys_addr_t base; /* 16 8 */
phys_addr_t size; /* 24 8 */
- } entry[0]; /* 16 0 */
+ } entry[]; /* 16 0 */
/* size: 16, cachelines: 1, members: 4 */
/* last cacheline: 16 bytes */
@@ -113516,7 +113516,7 @@ struct netlink_policy_dump_state {
struct {
const struct nla_policy * policy; /* 16 8 */
unsigned int maxtype; /* 24 4 */
- } policies[0]; /* 16 0 */
+ } policies[]; /* 16 0 */
/* size: 16, cachelines: 1, members: 4 */
/* sum members: 12, holes: 1, sum holes: 4 */
[acme@five pahole]$
- Arnaldo
