linux-user/elfload: Write process memory to core file in larger chunks

We do not need to copy pages from guest memory before writing
them out.  Because vmas are contiguous in host memory, we can
write them in one go.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

linux-user/elfload.c

@@ -4551,32 +4551,13 @@ static int elf_core_dump(int signr, const CPUArchState *env)
     }
 
     /*
-     * Finally we can dump process memory into corefile as well.
+     * Finally write process memory into the corefile as well.
      */
     for (vma = vma_first(&mm); vma != NULL; vma = vma_next(vma)) {
-        abi_ulong addr;
-        abi_ulong end;
+        size_t size = vma_dump_size(vma);
 
-        end = vma->vma_start + vma_dump_size(vma);
-
-        for (addr = vma->vma_start; addr < end;
-             addr += TARGET_PAGE_SIZE) {
-            char page[TARGET_PAGE_SIZE];
-            int error;
-
-            /*
-             *  Read in page from target process memory and
-             *  write it to coredump file.
-             */
-            error = copy_from_user(page, addr, sizeof (page));
-            if (error != 0) {
-                (void) fprintf(stderr, "unable to dump " TARGET_ABI_FMT_lx "\n",
-                               addr);
-                errno = -error;
-                goto out;
-            }
-            if (dump_write(fd, page, TARGET_PAGE_SIZE) < 0)
-                goto out;
+        if (size && dump_write(fd, g2h_untagged(vma->vma_start), size) < 0) {
+            goto out;
         }
     }
     errno = 0;