From d87b3215a7dcd5ff97c7da984283e5330ee6b4c7 Mon Sep 17 00:00:00 2001
From: Jason Hiser <jdhiser@gmail.com>
Date: Sat, 9 Feb 2019 16:35:20 -0500
Subject: [PATCH] fixed filesz setting in phdr
---
include/elfwrite.h | 2 +
src/elfwrite.cpp | 101 ++++++++++++++++++++++++++++-----------------
2 files changed, 66 insertions(+), 37 deletions(-)
diff --git a/include/elfwrite.h b/include/elfwrite.h
index 5fae1ad33..b3d176d89 100644
--- a/include/elfwrite.h
+++ b/include/elfwrite.h
@@ -173,6 +173,8 @@ class ElfWriterImpl : public ElfWriter
IRDB_SDK::DataScoop_t* find_scoop_by_name(const std::string& name, IRDB_SDK::FileIR_t* );
void AddSections(FILE* fout);
void update_phdr_for_scoop_sections(IRDB_SDK::FileIR_t* );
+ void trim_last_segment_filesz(IRDB_SDK::FileIR_t* firp);
+
void WriteElf(FILE* fout);
private:
unsigned int DetermineMaxPhdrSize();
diff --git a/src/elfwrite.cpp b/src/elfwrite.cpp
index da648b577..b870ebcbd 100644
--- a/src/elfwrite.cpp
+++ b/src/elfwrite.cpp
@@ -23,6 +23,10 @@ using namespace zipr;
using namespace ELFIO;
+static inline uintptr_t page_round_down(uintptr_t x)
+{
+ return x & (~(PAGE_SIZE-1));
+}
static inline uintptr_t page_round_up(uintptr_t x)
{
return ( (((uintptr_t)(x)) + PAGE_SIZE-1) & (~(PAGE_SIZE-1)) );
@@ -187,13 +191,6 @@ void ElfWriter::CreateSegmap(const ELFIO::elfio *elfiop, FileIR_t* firp, const s
// if we switch perms, or skip a page
if( (perms.m_perms!=segperms.m_perms) || (segend!=pagestart))
{
-/*
- LoadSegment_t *seg=new LoadSegment_t;
- seg->memsz=segend-segstart;
- seg->filesz=initend-segstart;
- seg->start_page=segstart;
- seg->m_perms=segperms.m_perms;
-*/
const auto seg=new LoadSegment_t(initend-segstart, segend-segstart, 0, segstart,segperms.m_perms);
segvec.push_back(seg);
@@ -204,32 +201,19 @@ void ElfWriter::CreateSegmap(const ELFIO::elfio *elfiop, FileIR_t* firp, const s
segend=segstart+PAGE_SIZE;
update_initend(perms);
-/*
- if( should_bss_optimize(perms) ) // perms.is_zero_initialized() && m_bss_opts)
- initend=segstart;
- else
- initend=segend;
-*/
}
else
{
// else, same permission and next page, extend segment.
segend=pagestart+PAGE_SIZE;
- if(! should_bss_optimize(perms) ) // !perms.is_zero_initialized() || ! m_bss_opts)
+ if(! should_bss_optimize(perms) )
initend=pagestart+PAGE_SIZE;
}
}
// make sure we print the last one
-/*
- LoadSegment_t *seg=new LoadSegment_t;
- seg->memsz=segend-segstart;
- seg->filesz=initend-segstart;
- seg->start_page=segstart;
- seg->m_perms=segperms.m_perms;
-*/
const auto seg=new LoadSegment_t(initend-segstart, segend-segstart, 0, segstart,segperms.m_perms);
segvec.push_back(seg);
@@ -553,6 +537,53 @@ void ElfWriterImpl<T_Elf_Ehdr,T_Elf_Phdr,T_Elf_Addr,T_Elf_Shdr,T_Elf_Sym, T_Elf
}
return;
}
+template <class T_Elf_Ehdr, class T_Elf_Phdr, class T_Elf_Addr, class T_Elf_Shdr, class T_Elf_Sym, class T_Elf_Rel, class T_Elf_Rela, class T_Elf_Dyn>
+void ElfWriterImpl<T_Elf_Ehdr,T_Elf_Phdr,T_Elf_Addr,T_Elf_Shdr,T_Elf_Sym, T_Elf_Rel, T_Elf_Rela, T_Elf_Dyn>::trim_last_segment_filesz(FileIR_t* firp)
+{
+ // skip trimming if we aren't doing bss optimization.
+ if(!m_bss_opts) return;
+
+
+ // find the last pt load segment header.
+ auto seg_to_trim=-1;
+ for(auto i=0u;i<new_phdrs.size(); i++)
+ {
+ if(new_phdrs[i].p_type==PT_LOAD)
+ {
+ seg_to_trim=i;
+ }
+
+ }
+ assert(seg_to_trim!=-1);
+
+
+
+
+ const auto seg_start_addr=new_phdrs[seg_to_trim].p_vaddr;
+ const auto seg_filesz=new_phdrs[seg_to_trim].p_filesz;
+ const auto seg_end_addr=seg_start_addr+seg_filesz-1;
+ const auto seg_end_page_start=page_round_down(seg_end_addr);
+ const auto &page=pagemap[seg_end_page_start];
+
+ // don't write 0's at end of last page
+ auto k=PAGE_SIZE-1;
+ for (/* above */; k>=0; k--)
+ {
+ if(page.data[k]!=0)
+ break;
+ }
+ const auto last_nonzero_byte_in_seg = k;
+ const auto bytes_to_trim = (PAGE_SIZE - 1) - last_nonzero_byte_in_seg;
+
+ // lastly, update the filesz so we don't need the reste of those bytes.
+ // memsz is allowed to be bigger than filesz.
+ new_phdrs[seg_to_trim].p_filesz -= bytes_to_trim;
+
+ return;
+
+}
+
+
template <class T_Elf_Ehdr, class T_Elf_Phdr, class T_Elf_Addr, class T_Elf_Shdr, class T_Elf_Sym, class T_Elf_Rel, class T_Elf_Rela, class T_Elf_Dyn>
@@ -693,30 +724,16 @@ bool ElfWriterImpl<T_Elf_Ehdr,T_Elf_Phdr,T_Elf_Addr,T_Elf_Shdr,T_Elf_Sym, T_Elf_
std::vector<T_Elf_Phdr> relro_phdrs;
new_phdrs.insert(new_phdrs.end(), relro_phdrs.begin(), relro_phdrs.end());
-#ifdef CGC
-//
-// Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
-// LOAD 0x000f20 0x00000000 0x00000000 0x00000 0x00000 0x1000 (edited)
- // create 0-size headre
- std::cout<<"New phdrs at: "<<std::hex<<new_phdr_addr<<std::endl;
- T_Elf_Phdr aqphdr;
- memset(&aqphdr,0,sizeof(aqphdr));
- aqphdr.p_type = PT_LOAD;
- aqphdr.p_offset =phdr_map_offset;
- aqphdr.p_align =0x1000;
- new_phdrs.insert(new_phdrs.begin(),aqphdr);
-#endif
-
// record the new ehdr.
new_ehdr=ehdr;
new_ehdr.e_phoff=phdr_map_offset;
new_ehdr.e_shoff=0;
new_ehdr.e_shnum=0;
new_ehdr.e_phnum=new_phdrs.size();
- // new_ehdr.e_phoff=sizeof(new_ehdr);
new_ehdr.e_shstrndx=0;
update_phdr_for_scoop_sections(m_firp);
+ trim_last_segment_filesz(m_firp);
return true;
@@ -751,6 +768,11 @@ void ElfWriterImpl<T_Elf_Ehdr,T_Elf_Phdr,T_Elf_Addr,T_Elf_Shdr,T_Elf_Sym, T_Elf_
}
else
{
+#if 0
+note: this does not work on centos as it leaves the segments
+start address + filesize to be a number greater than the entire files size.
+This causes the loader to complain. The "right" way to do this is to update the
+filesz before we start writing out the elf. See "trim_last_seg_filesz"
// don't write 0's at end of last page
int k=0;
for (k=PAGE_SIZE-1;k>=0;k--)
@@ -759,7 +781,12 @@ void ElfWriterImpl<T_Elf_Ehdr,T_Elf_Phdr,T_Elf_Addr,T_Elf_Shdr,T_Elf_Sym, T_Elf_
break;
}
std::cout<<"phdr["<<std::dec<<loadcnt<<"] optimizing last page write to size k="<<std::hex<<k<<std::endl;
- fwrite(page.data.data(), k+1, 1, fout);
+#endif
+ const auto end_offset=new_phdrs[i].p_filesz;
+ const auto current_offset = j;
+ const auto bytes_to_write = end_offset - current_offset;
+ assert(bytes_to_write <= PAGE_SIZE);
+ fwrite(page.data.data(), bytes_to_write, 1, fout);
}
}
--
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