Re: arch/ia64/ia32/binfmt_elf32.c: elf32_map() broken ia64 build

[John Reiser]

Paul Jackson wrote:
> Not sure how (no lkml thread that I can see), but it seems from Andrew's
> broken out patch "bssprot.patch" in 2.6.6-rc2-mm2 that John Reiser
> and/or others on the To list above conspired to break the build of
> arch/ia64/ia32/binfmt_elf32.c: elf32_map().

There was no conspiracy.  The patch was compiled and linked on three archs,
and ia64 was not one of them.  The #define of elf32_map contributed to
the obfuscation.

> Would someone care to recommend a proper fix?

A proper fix might require help from an ia64 maintainer to define macros
IA32_ELF_PAGESTART, IA32_ELF_PAGEALIGN, IA32_ELF_PAGEOFFSET
and will require ia32_do_munmap().  Below is partial progress,
"completing the parallelogram" from fs/binfmt_elf.c via
arch/x86_64/ia32/ia32_binfmt.c and arch/s390/kernel/binfmt_elf32.c.
This patch requires an ia32_do_munmap().  Until then, Paul's change
is sufficient, and loses no functionality except when PT_LOADs from the
same file designate non-adjacent regions, which was part of the reason
for the bssprot* patch(es) anyway.

When applied after 2.6.6-rc2-mm2, this compiles with warning (no prototype
for ia32_do_munmap), does not link (ia32_do_munmap is undefined), and
has not been executed.

--- ./arch/ia64/ia32/binfmt_elf32.c.orig	2004-04-26 19:17:14.000000000 -0700
+++ ./arch/ia64/ia32/binfmt_elf32.c	2004-04-26 19:57:19.000000000 -0700
@@ -220,10 +220,33 @@
 }

 static unsigned long
-elf32_map (struct file *filep, unsigned long addr, struct elf_phdr *eppnt, int prot, int type)
+elf32_map (struct file *filep, unsigned long addr, struct elf_phdr const *eppnt,
+	 int prot, int type, unsigned long total_size)
 {
-	unsigned long pgoff = (eppnt->p_vaddr) & ~IA32_PAGE_MASK;
+		/* IA32_ELF_PAGEOFFSET ? */
+	unsigned long const pgoff = eppnt->p_vaddr & ~IA32_PAGE_MASK;

-	return ia32_do_mmap(filep, (addr & IA32_PAGE_MASK), eppnt->p_filesz + pgoff, prot, type,
-			    eppnt->p_offset - pgoff);
+	unsigned long size = eppnt->p_filesz + pgoff;
+	unsigned long off  = eppnt->p_offset - pgoff;
+
+	addr = addr & IA32_PAGE_MASK;  /* IA32_ELF_PAGESTART ? */
+	size = IA32_PAGE_ALIGN(size);  /* IA32_ELF_PAGEALIGN ? */
+
+	/*
+	 * total_size is the size of the ELF (interpreter) image.
+	 * The _first_ mmap needs to know the full size, otherwise
+	 * randomization might put this image into an overlapping
+	 * position with the ELF binary image. (since size < total_size)
+	 * So we first map the 'big' image - and unmap the remainder at
+	 * the end. (which unmap is needed for ELF images with holes.)
+	 */
+	if (total_size) {
+		unsigned long map_addr;
+		total_size = IA32_PAGE_ALIGN(total_size);  /* IA32_ELF_PAGEALIGN ? */
+		map_addr = ia32_do_mmap(filep, addr, total_size, prot, type, off);
+		if (!BAD_ADDR(map_addr))
+			ia32_do_munmap(current->mm, map_addr+size, total_size-size);
+		return map_addr;
+	} else
+		return ia32_do_mmap(filep, addr, size, prot, type, off);
 }

--



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