Revert "bionic: loader: Extend LOAD segment VMAs"

Revert submission 2803156-loader_crt_pad_segment

Reason for revert: b/324952273

Reverted changes: /q/submissionid:2803156-loader_crt_pad_segment

Change-Id: I8af115c426c0113914abbf8fbd3e74c0d89408d1
diff --git a/linker/linker.cpp b/linker/linker.cpp
index 389e77d..724f821 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -3354,7 +3354,7 @@
                               "\"%s\" has text relocations",
                               get_realpath());
     add_dlwarning(get_realpath(), "text relocations");
-    if (phdr_table_unprotect_segments(phdr, phnum, load_bias, should_pad_segments_) < 0) {
+    if (phdr_table_unprotect_segments(phdr, phnum, load_bias) < 0) {
       DL_ERR("can't unprotect loadable segments for \"%s\": %s", get_realpath(), strerror(errno));
       return false;
     }
@@ -3370,7 +3370,7 @@
 #if !defined(__LP64__)
   if (has_text_relocations) {
     // All relocations are done, we can protect our segments back to read-only.
-    if (phdr_table_protect_segments(phdr, phnum, load_bias, should_pad_segments_) < 0) {
+    if (phdr_table_protect_segments(phdr, phnum, load_bias) < 0) {
       DL_ERR("can't protect segments for \"%s\": %s",
              get_realpath(), strerror(errno));
       return false;
diff --git a/linker/linker_main.cpp b/linker/linker_main.cpp
index 018a5eb..5f5eba4 100644
--- a/linker/linker_main.cpp
+++ b/linker/linker_main.cpp
@@ -201,7 +201,6 @@
   const ElfW(Phdr)* phdr;
   size_t phdr_count;
   ElfW(Addr) entry_point;
-  bool should_pad_segments;
 };
 
 static ExecutableInfo get_executable_info(const char* arg_path) {
@@ -294,7 +293,6 @@
   result.phdr = elf_reader.loaded_phdr();
   result.phdr_count = elf_reader.phdr_count();
   result.entry_point = elf_reader.entry_point();
-  result.should_pad_segments = elf_reader.should_pad_segments();
   return result;
 }
 
@@ -368,7 +366,6 @@
   somain = si;
   si->phdr = exe_info.phdr;
   si->phnum = exe_info.phdr_count;
-  si->set_should_pad_segments(exe_info.should_pad_segments);
   get_elf_base_from_phdr(si->phdr, si->phnum, &si->base, &si->load_bias);
   si->size = phdr_table_get_load_size(si->phdr, si->phnum);
   si->dynamic = nullptr;
@@ -402,7 +399,7 @@
     auto note_gnu_property = GnuPropertySection(somain);
     if (note_gnu_property.IsBTICompatible() &&
         (phdr_table_protect_segments(somain->phdr, somain->phnum, somain->load_bias,
-                                     somain->should_pad_segments(), &note_gnu_property) < 0)) {
+                                     &note_gnu_property) < 0)) {
       __linker_error("error: can't protect segments for \"%s\": %s", exe_info.path.c_str(),
                      strerror(errno));
     }
diff --git a/linker/linker_phdr.cpp b/linker/linker_phdr.cpp
index 1547cae..85cd949 100644
--- a/linker/linker_phdr.cpp
+++ b/linker/linker_phdr.cpp
@@ -196,7 +196,7 @@
     // For Armv8.5-A loaded executable segments may require PROT_BTI.
     if (note_gnu_property_.IsBTICompatible()) {
       did_load_ = (phdr_table_protect_segments(phdr_table_, phdr_num_, load_bias_,
-                                               should_pad_segments_, &note_gnu_property_) == 0);
+                                               &note_gnu_property_) == 0);
     }
 #endif
   }
@@ -747,36 +747,6 @@
   return true;
 }
 
-static inline void _extend_load_segment_vma(const ElfW(Phdr)* phdr_table, size_t phdr_count,
-                                             size_t phdr_idx, ElfW(Addr)* p_memsz,
-                                             ElfW(Addr)* p_filesz) {
-  const ElfW(Phdr)* phdr = &phdr_table[phdr_idx];
-  const ElfW(Phdr)* next = nullptr;
-  size_t next_idx = phdr_idx + 1;
-  if (next_idx < phdr_count && phdr_table[next_idx].p_type == PT_LOAD) {
-    next = &phdr_table[next_idx];
-  }
-
-  // If this is the last LOAD segment, no extension is needed
-  if (!next || *p_memsz != *p_filesz) {
-    return;
-  }
-
-  ElfW(Addr) next_start = page_start(next->p_vaddr);
-  ElfW(Addr) curr_end = page_end(phdr->p_vaddr + *p_memsz);
-
-  // If adjacent segment mappings overlap, no extension is needed.
-  if (curr_end >= next_start) {
-    return;
-  }
-
-  // Extend the LOAD segment mapping to be contiguous with that of
-  // the next LOAD segment.
-  ElfW(Addr) extend = next_start - curr_end;
-  *p_memsz += extend;
-  *p_filesz += extend;
-}
-
 bool ElfReader::LoadSegments() {
   for (size_t i = 0; i < phdr_num_; ++i) {
     const ElfW(Phdr)* phdr = &phdr_table_[i];
@@ -785,24 +755,18 @@
       continue;
     }
 
-    ElfW(Addr) p_memsz = phdr->p_memsz;
-    ElfW(Addr) p_filesz = phdr->p_filesz;
-    if (phdr->p_align > kPageSize && should_pad_segments_) {
-      _extend_load_segment_vma(phdr_table_, phdr_num_, i, &p_memsz, &p_filesz);
-    }
-
     // Segment addresses in memory.
     ElfW(Addr) seg_start = phdr->p_vaddr + load_bias_;
-    ElfW(Addr) seg_end = seg_start + p_memsz;
+    ElfW(Addr) seg_end   = seg_start + phdr->p_memsz;
 
     ElfW(Addr) seg_page_start = page_start(seg_start);
     ElfW(Addr) seg_page_end = page_end(seg_end);
 
-    ElfW(Addr) seg_file_end = seg_start + p_filesz;
+    ElfW(Addr) seg_file_end   = seg_start + phdr->p_filesz;
 
     // File offsets.
     ElfW(Addr) file_start = phdr->p_offset;
-    ElfW(Addr) file_end = file_start + p_filesz;
+    ElfW(Addr) file_end   = file_start + phdr->p_filesz;
 
     ElfW(Addr) file_page_start = page_start(file_start);
     ElfW(Addr) file_length = file_end - file_page_start;
@@ -812,12 +776,12 @@
       return false;
     }
 
-    if (file_start + phdr->p_filesz > static_cast<size_t>(file_size_)) {
+    if (file_end > static_cast<size_t>(file_size_)) {
       DL_ERR("invalid ELF file \"%s\" load segment[%zd]:"
           " p_offset (%p) + p_filesz (%p) ( = %p) past end of file (0x%" PRIx64 ")",
           name_.c_str(), i, reinterpret_cast<void*>(phdr->p_offset),
           reinterpret_cast<void*>(phdr->p_filesz),
-          reinterpret_cast<void*>(file_start + phdr->p_filesz), file_size_);
+          reinterpret_cast<void*>(file_end), file_size_);
       return false;
     }
 
@@ -857,18 +821,8 @@
 
     // if the segment is writable, and does not end on a page boundary,
     // zero-fill it until the page limit.
-    //
-    // The intention is to zero the partial page at that may exist at the
-    // end of a file backed mapping. With the extended seg_file_end, this
-    // file offset as calculated from the mapping start can overrun the end
-    // of the file. However pages in that range cannot be touched by userspace
-    // because the kernel will not be able to handle a file map fault past the
-    // extent of the file. No need to try zeroing this untouchable region.
-    // Zero the partial page at the end of the original unextended seg_file_end.
-    ElfW(Addr) seg_file_end_orig = seg_start + phdr->p_filesz;
-    if ((phdr->p_flags & PF_W) != 0 && page_offset(seg_file_end_orig) > 0) {
-      memset(reinterpret_cast<void*>(seg_file_end_orig), 0,
-             kPageSize - page_offset(seg_file_end_orig));
+    if ((phdr->p_flags & PF_W) != 0 && page_offset(seg_file_end) > 0) {
+      memset(reinterpret_cast<void*>(seg_file_end), 0, page_size() - page_offset(seg_file_end));
     }
 
     seg_file_end = page_end(seg_file_end);
@@ -901,23 +855,17 @@
  * phdr_table_protect_segments and phdr_table_unprotect_segments.
  */
 static int _phdr_table_set_load_prot(const ElfW(Phdr)* phdr_table, size_t phdr_count,
-                                     ElfW(Addr) load_bias, int extra_prot_flags,
-                                     bool should_pad_segments) {
-  for (size_t i = 0; i < phdr_count; ++i) {
-    const ElfW(Phdr)* phdr = &phdr_table[i];
+                                     ElfW(Addr) load_bias, int extra_prot_flags) {
+  const ElfW(Phdr)* phdr = phdr_table;
+  const ElfW(Phdr)* phdr_limit = phdr + phdr_count;
 
+  for (; phdr < phdr_limit; phdr++) {
     if (phdr->p_type != PT_LOAD || (phdr->p_flags & PF_W) != 0) {
       continue;
     }
 
-    ElfW(Addr) p_memsz = phdr->p_memsz;
-    ElfW(Addr) p_filesz = phdr->p_filesz;
-    if (phdr->p_align > kPageSize && should_pad_segments) {
-      _extend_load_segment_vma(phdr_table, phdr_count, i, &p_memsz, &p_filesz);
-    }
-
-    ElfW(Addr) seg_page_start = page_start(phdr->p_vaddr + load_bias);
-    ElfW(Addr) seg_page_end = page_end(phdr->p_vaddr + p_memsz + load_bias);
+    ElfW(Addr) seg_page_start = page_start(phdr->p_vaddr) + load_bias;
+    ElfW(Addr) seg_page_end = page_end(phdr->p_vaddr + phdr->p_memsz) + load_bias;
 
     int prot = PFLAGS_TO_PROT(phdr->p_flags) | extra_prot_flags;
     if ((prot & PROT_WRITE) != 0) {
@@ -952,21 +900,19 @@
  *   phdr_table  -> program header table
  *   phdr_count  -> number of entries in tables
  *   load_bias   -> load bias
- *   should_pad_segments -> Are segments extended to avoid gaps in the memory map
  *   prop        -> GnuPropertySection or nullptr
  * Return:
  *   0 on success, -1 on failure (error code in errno).
  */
 int phdr_table_protect_segments(const ElfW(Phdr)* phdr_table, size_t phdr_count,
-                                ElfW(Addr) load_bias, bool should_pad_segments,
-                                const GnuPropertySection* prop __unused) {
+                                ElfW(Addr) load_bias, const GnuPropertySection* prop __unused) {
   int prot = 0;
 #if defined(__aarch64__)
   if ((prop != nullptr) && prop->IsBTICompatible()) {
     prot |= PROT_BTI;
   }
 #endif
-  return _phdr_table_set_load_prot(phdr_table, phdr_count, load_bias, prot, should_pad_segments);
+  return _phdr_table_set_load_prot(phdr_table, phdr_count, load_bias, prot);
 }
 
 /* Change the protection of all loaded segments in memory to writable.
@@ -982,15 +928,12 @@
  *   phdr_table  -> program header table
  *   phdr_count  -> number of entries in tables
  *   load_bias   -> load bias
- *   should_pad_segments -> Are segments extended to avoid gaps in the memory map
  * Return:
  *   0 on success, -1 on failure (error code in errno).
  */
 int phdr_table_unprotect_segments(const ElfW(Phdr)* phdr_table,
-                                  size_t phdr_count, ElfW(Addr) load_bias,
-                                  bool should_pad_segments) {
-  return _phdr_table_set_load_prot(phdr_table, phdr_count, load_bias, PROT_WRITE,
-                                   should_pad_segments);
+                                  size_t phdr_count, ElfW(Addr) load_bias) {
+  return _phdr_table_set_load_prot(phdr_table, phdr_count, load_bias, PROT_WRITE);
 }
 
 /* Used internally by phdr_table_protect_gnu_relro and
diff --git a/linker/linker_phdr.h b/linker/linker_phdr.h
index 239ecb9..e5b87bb 100644
--- a/linker/linker_phdr.h
+++ b/linker/linker_phdr.h
@@ -128,11 +128,10 @@
 size_t phdr_table_get_maximum_alignment(const ElfW(Phdr)* phdr_table, size_t phdr_count);
 
 int phdr_table_protect_segments(const ElfW(Phdr)* phdr_table, size_t phdr_count,
-                                ElfW(Addr) load_bias, bool should_pad_segments,
-                                const GnuPropertySection* prop = nullptr);
+                                ElfW(Addr) load_bias, const GnuPropertySection* prop = nullptr);
 
 int phdr_table_unprotect_segments(const ElfW(Phdr)* phdr_table, size_t phdr_count,
-                                  ElfW(Addr) load_bias, bool should_pad_segments);
+                                  ElfW(Addr) load_bias);
 
 int phdr_table_protect_gnu_relro(const ElfW(Phdr)* phdr_table, size_t phdr_count,
                                  ElfW(Addr) load_bias);
diff --git a/linker/linker_relocate.cpp b/linker/linker_relocate.cpp
index 5b58895..952dade 100644
--- a/linker/linker_relocate.cpp
+++ b/linker/linker_relocate.cpp
@@ -187,8 +187,7 @@
   auto protect_segments = [&]() {
     // Make .text executable.
     if (phdr_table_protect_segments(relocator.si->phdr, relocator.si->phnum,
-                                    relocator.si->load_bias,
-                                    relocator.si->should_pad_segments()) < 0) {
+                                    relocator.si->load_bias) < 0) {
       DL_ERR("can't protect segments for \"%s\": %s",
              relocator.si->get_realpath(), strerror(errno));
       return false;
@@ -198,8 +197,7 @@
   auto unprotect_segments = [&]() {
     // Make .text writable.
     if (phdr_table_unprotect_segments(relocator.si->phdr, relocator.si->phnum,
-                                      relocator.si->load_bias,
-                                      relocator.si->should_pad_segments()) < 0) {
+                                      relocator.si->load_bias) < 0) {
       DL_ERR("can't unprotect loadable segments for \"%s\": %s",
              relocator.si->get_realpath(), strerror(errno));
       return false;