linux-kernel - Re: [PATCH 4/11] i386 vDSO: use VM

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Date:	Tue, 23 Jan 2007 11:48:25 -0800
From:	Andrew Morton <akpm@...l.org>
To:	Roland McGrath <roland@...hat.com>
Cc:	Linus Torvalds <torvalds@...l.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/11] i386 vDSO: use VM_ALWAYSDUMP

On Sat, 13 Jan 2007 21:34:28 -0800 (PST)
Roland McGrath <roland@...hat.com> wrote:

> +	     vma = vma->vm_next ?: vma == gate_vma ? NULL : gate_vma) {

Painful.   Can we do this?


diff -puN fs/binfmt_elf.c~i386-vdso-use-vm_alwaysdump-tidy fs/binfmt_elf.c
--- a/fs/binfmt_elf.c~i386-vdso-use-vm_alwaysdump-tidy
+++ a/fs/binfmt_elf.c
@@ -1429,6 +1429,23 @@ static int elf_dump_thread_status(long s
 }
 
 /*
+ * Helper function for iterating across a vma list.  It ensures that the caller
+ * will visit `gate_vma' prior to terminating the search.
+ */
+static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
+					struct vm_area_struct *gate_vma)
+{
+	struct vm_area_struct *ret;
+
+	ret = this_vma->vm_next;
+	if (ret)
+		return ret;
+	if (this_vma == gate_vma)
+		return NULL;
+	return gate_vma;
+}
+
+/*
  * Actual dumper
  *
  * This is a two-pass process; first we find the offsets of the bits,
@@ -1600,8 +1617,7 @@ static int elf_core_dump(long signr, str
 	dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);
 
 	/* Write program headers for segments dump */
-	for (vma = current->mm->mmap; vma != NULL;
-	     vma = vma->vm_next ?: vma == gate_vma ? NULL : gate_vma) {
+	for (vma = current->mm->mmap; vma; vma = next_vma(vma, gate_vma)) {
 		struct elf_phdr phdr;
 		size_t sz;
 
@@ -1650,8 +1666,7 @@ static int elf_core_dump(long signr, str
 	/* Align to page */
 	DUMP_SEEK(dataoff - foffset);
 
-	for (vma = current->mm->mmap; vma != NULL;
-	     vma = vma->vm_next ?: vma == gate_vma ? NULL : gate_vma) {
+	for (vma = current->mm->mmap; vma; vma = next_vma(vma, gate_vma)) {
 		unsigned long addr;
 
 		if (!maydump(vma))
_

-
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