RFR: 8367609: serviceability/sa/ClhsdbPmap.java fails when built with Clang [v5]

[Francesco Andreuzzi]

On Tue, 23 Sep 2025 14:24:47 GMT, Kevin Walls <kevinw at openjdk.org> wrote:

>> Francesco Andreuzzi has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - nn
>>  - comment and rename
>
> Thanks for the additional info.
> 
> If I ignore what's said so far and start again, I see the following...  (anyone should feel free to correct, we aren't in this
> area every day!...)
> 
> hsdb> ERROR: address conflict @ 0x7fa9ff0e4440 (existing map size = 102400, size = 97328, flags = 5)
> 
>           print_error("address conflict @ 0x%lx (existing map size = %ld, size = %ld, flags = %d)\n",
>                         target_vaddr, existing_map->memsz, lib_php->p_memsz, lib_php->p_flags);
> 
> core has no mapping at exactly 0x7fa9ff0e4440 but has:
> 
>   Start                 End               Page Offset
>   0x00007fa9ff0db000  0x00007fa9ff0e4000  0x0000000000000000 /home/fandreuz/code/jdk/build/clang/images/jdk/lib/libjimage.so  (0x9000 size) 0x841c rounded up
>   0x00007fa9ff0e4000  0x00007fa9ff0fd000  0x0000000000000008 /home/fandreuz/code/jdk/build/clang/images/jdk/lib/libjimage.so (0x19000 size) the existing map size from the error
>   
> 
> The error is having a size 0x17c30 mapping that should go at 0x00007fa9ff0e4000
> That is the second LOAD phdr from libjimage.
> 
> The check which has been working for gcc builds:
> ROUNDUP(existing_map->memsz, page_size) != ROUNDUP(lib_php->p_memsz, page_size)
> 
> 102400 	= 0x19000 is mem size, page size aligned. The core has a mapping of this size.
> 97328	= 0x17c30 libjimage has this, which rounds up to only 0x18000
> 
> libjimage is providing too little data? 
> But target vaddr 0x7fa9ff0e4440 is offset into the actual segment 0x00007fa9ff0e4000 by  0x440  (1088 bytes)
> 
> 0x17c30 + 0x440 = 0x18070 which rounds up to the wanted 0x19000
> 
> 
> src/jdk.hotspot.agent/linux/native/libsaproc/ps_core.c
> 
> 399       uintptr_t target_vaddr = lib_php->p_vaddr + lib_base;
> 400       map_info *existing_map = core_lookup(ph, target_vaddr);
> 
> (Existing code expects target_vaddr and existing_map->vaddr to be exactly equal, not to see target_vaddr being
> anything other than 0x1000 aligned.)
> 
> Maybe we:
> check if target_vaddr > existing_map->vaddr and add any difference to the library mem size we compare?
> 
> 
> 429             (ROUNDUP(existing_map->memsz, page_size) != ROUNDUP(lib_php->p_memsz, page_size))) {
> 
> +        uint64_t lib_memsz = lib_php->p_memsz; // check type
> +        if (target_vaddr > existing_map->vaddr) {
> +            lib_memsz += (target_vaddr - existing_map->vaddr);
> +        }
> +        lib_memsz = ROUNDUP(lib_memsz, page_size);
> +
>          if ((existing_map->memsz != page_size) &&
>              (existing_map->fd != lib_fd) &&
> -            (ROUNDUP(existing_map->memsz, page_s...

Hi @kevinjwalls, what you say makes sense to me. I tried the updated check on my environment and it fixed the problem as well as what I initially proposed in this PR. 

I updated the PR too, the new check looks cleaner than what I had.

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PR Comment: https://git.openjdk.org/jdk/pull/27274#issuecomment-3344262943