RFR: 8261710: SA DSO objects have sizes that are too large [v4]

[Serguei Spitsyn]

On Wed, 17 Feb 2021 06:28:09 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

>> This PR relates to [JDK-8261702](https://bugs.openjdk.java.net/browse/JDK-8261702) ( #2562 )
>> When SA creates a DSO object, which is used to represent a shared object file (.so), it initializes the "size" to be the size of the shared object file. This usually results in the size being too big. This can cause SA to get confused about whether or not an address is in the shared object. SA should instead set the DSO's size to the amount of the file that is actually mapped for executable code.
>
> Yasumasa Suenaga has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Use p_filesz instead of p_memsz

Hi Yasumasa,

Just some comments.

src/jdk.hotspot.agent/linux/native/libsaproc/libproc_impl.c
+static inline uintptr_t align_down(uintptr_t ptr, size_t size) {
+  return (ptr & ~(size - 1));
+}
+
+static inline uintptr_t align_up(uintptr_t ptr, size_t size) {
+  return ((ptr + size - 1) & ~(size - 1));
+}

The name of 'size' parameter is confusing. Should it be renamed to something like page_size of psize?

+  lib->end = (uintptr_t)-1L;
. . .
+      if ((lib->end == (uintptr_t)-1L) || (lib->end < aligned_end)) {
+        lib->end = aligned_end;
       }
 
The condition  `(lib->end == (uintptr_t)-1L)` is a subset of `(lib->end < aligned_end)`, and so, can be removed. The same is true for the condition:
+        if ((lib->exec_end == (uintptr_t)-1L) || (lib->exec_end < aligned_end)) {
+          lib->exec_end = aligned_end;
+        }

`+      print_debug("%s [%d] 0x%lx-0x%lx: base = 0x%lx, vaddr = 0x%lx, memsz = 0x%lx, filesz = 0x%lx\n", lib->name, cnt, aligned_start, aligned_end, lib->base, ph->p_vaddr, ph->p_memsz, ph->p_filesz);`

It is better to split this long line.

Thanks,
Serguei

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PR: https://git.openjdk.java.net/jdk/pull/2563