vmlinux/386 check for __ksymtab; fix unpack

src/p_vmlinx.cpp

@@ -46,12 +46,13 @@ static const
 **************************************************************************/
 
 PackVmlinuxI386::PackVmlinuxI386(InputFile *f) :
-    super(f), n_ptload(0), phdri(NULL), shdri(NULL)
+    super(f), n_ptload(0), phdri(NULL), shdri(NULL), shstrtab(NULL)
 {
 }
 
 PackVmlinuxI386::~PackVmlinuxI386()
 {
+    delete [] shstrtab;
     delete [] phdri;
     delete [] shdri;
 }
@@ -81,6 +82,34 @@ int PackVmlinuxI386::getStrategy(Filter &/*ft*/)
     return (opt->no_filter ? -3 : ((opt->filter > 0) ? -2 : 2));
 }
 
+
+Elf_LE32_Shdr const *
+PackVmlinuxI386::getElfSections()
+{
+    Elf_LE32_Shdr const *p, *shstrsec=0;
+    shdri = new Elf_LE32_Shdr[(unsigned) ehdri.e_shnum];
+    fi->seek(ehdri.e_shoff, SEEK_SET);
+    fi->readx(shdri, ehdri.e_shnum * sizeof(*shdri));
+    int j;
+    for (p = shdri, j= ehdri.e_shnum; --j>=0; ++p) {
+        if (Elf32_Shdr::SHT_STRTAB==p->sh_type
+        &&  (p->sh_size + p->sh_offset) <= (unsigned) file_size
+        &&  (10+ p->sh_name) <= p->sh_size  // 1+ strlen(".shstrtab")
+        ) {
+            delete [] shstrtab;
+            shstrtab = new char[1+ p->sh_size];
+            fi->seek(p->sh_offset, SEEK_SET);
+            fi->readx(shstrtab, p->sh_size);
+            shstrtab[p->sh_size] = '\0';
+            if (0==strcmp(".shstrtab", shstrtab + p->sh_name)) {
+                shstrsec = p;
+                break;
+            }
+        }
+    }
+    return shstrsec;
+}
+
 static int __acc_cdecl_qsort
 compare_Phdr(void const *aa, void const *bb)
 {
@@ -143,6 +172,22 @@ bool PackVmlinuxI386::canPack()
         return false;
     }
 
+    // A Linux kernel must have a __ksymtab section. [??]
+    Elf_LE32_Shdr const *p, *const shstrsec = getElfSections();
+    if (0==shstrsec) {
+        return false;
+    }
+    int j;
+    for (p = shdri, j= ehdri.e_shnum; --j>=0; ++p) {
+        if (Elf32_Shdr::SHT_PROGBITS==p->sh_type
+        && 0==strcmp("__ksymtab", p->sh_name + shstrtab)) {
+            break;
+        }
+    }
+    if (j < 0) {
+        return false;
+    }
+
     phdri = new Elf_LE32_Phdr[(unsigned) ehdri.e_phnum];
     fi->seek(ehdri.e_phoff, SEEK_SET);
     fi->readx(phdri, ehdri.e_phnum * sizeof(*phdri));
@@ -220,6 +265,8 @@ static bool defineFilterSymbols(Linker *linker, const Filter *ft)
     return true;
 }
 
+static const
+#include "stub/i386-linux.kernel.head-vmlinux.h"
 
 void PackVmlinuxI386::pack(OutputFile *fo)
 {
@@ -284,13 +331,9 @@ void PackVmlinuxI386::pack(OutputFile *fo)
     shdro[1].sh_type = Elf32_Shdr::SHT_PROGBITS;
     shdro[1].sh_flags = Elf32_Shdr::SHF_ALLOC | Elf32_Shdr::SHF_EXECINSTR;
     shdro[1].sh_offset = fo_off;
-    shdro[1].sh_size = 1+ 4+ ph.c_len + lsize;
+    shdro[1].sh_size = sizeof(head_stack) + ph.c_len + lsize;
     shdro[1].sh_addralign = 1;
 
-    {
-        static const
-#include "stub/i386-linux.kernel.head-vmlinux.h"
-
     // ENTRY_POINT
     fo->write(&head_stack[0], sizeof(head_stack)-2*(1+ 4) +1);
     tmp_le32 = ehdri.e_entry; fo->write(&tmp_le32, 4);
@@ -303,7 +346,6 @@ void PackVmlinuxI386::pack(OutputFile *fo)
 
     fo->write(obuf, ph.c_len); fo_off += ph.c_len;
     fo->write(loader, lsize); fo_off += lsize;
-    }
 
 #if 0
     printf("%-13s: compressed   : %8u bytes\n", getName(), ph.c_len);
@@ -416,35 +458,18 @@ int PackVmlinuxI386::canUnpack()
         return false;
 
     // find the .shstrtab section
-    char shstrtab[40];
+    Elf_LE32_Shdr const *const shstrsec = getElfSections();
-    Elf_LE32_Shdr *p, *p_shstrtab=0;
+    if (0==shstrsec) {
-    shdri = new Elf_LE32_Shdr[(unsigned) ehdri.e_shnum];
-    fi->seek(ehdri.e_shoff, SEEK_SET);
-    fi->readx(shdri, ehdri.e_shnum * sizeof(*shdri));
-    int j;
-    for (p = shdri, j= ehdri.e_shnum; --j>=0; ++p) {
-        if (Elf32_Shdr::SHT_STRTAB==p->sh_type
-        &&  p->sh_size <= sizeof(shstrtab)
-        &&  (p->sh_size + p->sh_offset) <= (unsigned) file_size
-        &&  (10+ p->sh_name) <= p->sh_size  // 1+ strlen(".shstrtab")
-        ) {
-            fi->seek(p->sh_offset, SEEK_SET);
-            fi->readx(shstrtab, p->sh_size);
-            if (0==strcmp(".shstrtab", shstrtab + p->sh_name)) {
-                p_shstrtab = p;
-                break;
-            }
-        }
-    }
-    if (0==p_shstrtab) {
         return false;
     }
 
     // check for .text .note .note  and sane (.sh_size + .sh_offset)
     p_note0 = p_note1 = p_text = 0;
+    int j;
+    Elf_LE32_Shdr *p;
     for (p= shdri, j= ehdri.e_shnum; --j>=0; ++p) {
         if ((unsigned)file_size < (p->sh_size + p->sh_offset)
-        ||  p_shstrtab->sh_size < (5+ p->sh_name) ) {
+        ||  shstrsec->sh_size < (5+ p->sh_name) ) {
             continue;
         }
         if (0==strcmp(".text", shstrtab + p->sh_name)) {
@@ -491,7 +516,7 @@ void PackVmlinuxI386::unpack(OutputFile *fo)
     ibuf.dealloc();
 
     ph = ph_tmp;
-    fi->seek(p_text->sh_offset, SEEK_SET);
+    fi->seek(p_text->sh_offset + sizeof(head_stack) -5, SEEK_SET);
     fi->readx(&buf[0], 5);
     if (0xE8!=buf[0] ||  get_le32(&buf[1]) != ph.c_len)
     {

src/p_vmlinx.h

@@ -55,6 +55,7 @@ public:
     virtual int canUnpack();
 
 protected:
+    virtual Elf_LE32_Shdr const *getElfSections();
     virtual int buildLoader(const Filter *ft);
     virtual Linker* newLinker() const;
 //    virtual const upx_byte *getLoader() const;
@@ -64,6 +65,7 @@ protected:
     unsigned sz_ptload;
     Elf_LE32_Phdr *phdri; // from input file
     Elf_LE32_Shdr *shdri; // from input file
+    char *shstrtab; // from input file
     Elf_LE32_Shdr *p_text;
     Elf_LE32_Shdr *p_note0;
     Elf_LE32_Shdr *p_note1;