Hi Yasumasa,
Thanks for the review. I tried the following for line 188:
if ((phdr->p_type == PT_LOAD || phdr->p_type == PT_INTERP) &&
phdr->p_vaddr < baseaddr) {
However, "base" still ended up being 0. I added some printfs. For the
exec file there is both a PT_INTER with p_vaddr of 0x238 and a PT_LOAD
with p_vaddr 0. I'm not sure which to use, but in either case that won't
be the proper base when added to 0:
if (add_lib_info_fd(ph, exec_file, ph->core->exec_fd,
(uintptr_t)0 +
find_base_address(ph->core->exec_fd, &exec_ehdr)) == NULL) {
goto err;
}
So maybe it's the (uintptr_t)0 that is the problem here. For shared libs
instead of 0 it computes the value to add:
if (lib_base_diff == ZERO_LOAD_ADDRESS ) {
lib_base_diff = calc_prelinked_load_address(ph,
lib_fd, &elf_ehdr, link_map_addr);
if (lib_base_diff == INVALID_LOAD_ADDRESS) {
close(lib_fd);
return false;
}
}
lib_base = lib_base_diff + find_base_address(lib_fd,
&elf_ehdr);
So in this case we've actually computed lib_base_diff rather than just
assumed 0.
Chris
On 7/6/20 10:46 PM, Yasumasa Suenaga wrote:
Hi Chris,
Your change looks good.
BTW I saw JDK-8248876. I'm not sure, but I guess we can fix this issue
if we allow PT_INTERP in L118:
```
105 uintptr_t find_base_address(int fd, ELF_EHDR* ehdr) {
:
115 // the base address of a shared object is the lowest vaddr of
116 // its loadable segments (PT_LOAD)
117 for (phdr = phbuf, cnt = 0; cnt < ehdr->e_phnum; cnt++, phdr++) {
118 if (phdr->p_type == PT_LOAD && phdr->p_vaddr < baseaddr) {
119 baseaddr = phdr->p_vaddr;
120 }
121 }
```
/proc/<PID>/maps shows top of `java` is 0x56543b9df000:
56543b9df000-56543b9e0000 r--p 00000000 08:10 55770
/usr/lib/jvm/java-11-openjdk-amd64/bin/java
`i target` on GDB shows 0x56543b9df000 is .interp section:
Local exec file:
`/usr/lib/jvm/java-11-openjdk-amd64/bin/java', file type
elf64-x86-64.
Entry point: 0x56543b9e0330
0x000056543b9df318 - 0x000056543b9df334 is .interp
Thanks,
Yasumasa
On 2020/07/07 13:18, Chris Plummer wrote:
Hello,
Please help review the following:
http://cr.openjdk.java.net/~cjplummer/8248878/webrev.00/index.html
https://bugs.openjdk.java.net/browse/JDK-8248878
The explanation of the fix is in the CR. The parent CR, JDK-8248876
[1], explains the issue being addressed.
There's no test for this fix yet. It requires the changes I'm making
for JDK-8247514 [2], which include changes to "findpc" support and
the ClhsdbFindPC.java test that trigger this issue.
[1] https://bugs.openjdk.java.net/browse/JDK-8248876
[2] https://bugs.openjdk.java.net/browse/JDK-8247514
thanks,
Chris
