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Subject[PATCH] Thread core dumps for 2.4.4
The attached patch allows core dumps from thread processes in the 2.4.4
kernel. This patch is the same as the last one I sent out except it fixes
the same bug that `kernel/fork.c' had with duplicate info in the `mm'
structure, plus this patch has had more extensive testing.

--
Don Dugger
"Censeo Toto nos in Kansa esse decisse." - D. Gale
n0ano@valinux.com
Ph: 303/938-9838



diff -aur linux-2.4.4-ref/fs/binfmt_aout.c linux/fs/binfmt_aout.c
--- linux-2.4.4-ref/fs/binfmt_aout.c Mon Mar 19 13:34:56 2001
+++ linux/fs/binfmt_aout.c Wed May 2 15:50:42 2001
@@ -31,7 +31,8 @@

static int load_aout_binary(struct linux_binprm *, struct pt_regs * regs);
static int load_aout_library(struct file*);
-static int aout_core_dump(long signr, struct pt_regs * regs, struct file *file);
+static int aout_core_dump(long signr, struct pt_regs * regs,
+ struct file *file, struct mm_struct * mm);

extern void dump_thread(struct pt_regs *, struct user *);

@@ -78,7 +79,8 @@
* dumping of the process results in another error..
*/

-static int aout_core_dump(long signr, struct pt_regs * regs, struct file *file)
+static int aout_core_dump(long signr, struct pt_regs * regs,
+ struct file * file, struct mm_struct * mm)
{
mm_segment_t fs;
int has_dumped = 0;
diff -aur linux-2.4.4-ref/fs/binfmt_elf.c linux/fs/binfmt_elf.c
--- linux-2.4.4-ref/fs/binfmt_elf.c Thu Apr 5 18:13:23 2001
+++ linux/fs/binfmt_elf.c Wed May 2 15:50:42 2001
@@ -56,7 +56,8 @@
* don't even try.
*/
#ifdef USE_ELF_CORE_DUMP
-static int elf_core_dump(long signr, struct pt_regs * regs, struct file * file);
+static int elf_core_dump(long signr, struct pt_regs * regs,
+ struct file * file, struct mm_struct * mm);
#else
#define elf_core_dump NULL
#endif
@@ -976,7 +977,8 @@
* and then they are actually written out. If we run out of core limit
* we just truncate.
*/
-static int elf_core_dump(long signr, struct pt_regs * regs, struct file * file)
+static int elf_core_dump(long signr, struct pt_regs * regs,
+ struct file * file, struct mm_struct * mm)
{
int has_dumped = 0;
mm_segment_t fs;
@@ -993,7 +995,7 @@
elf_fpregset_t fpu; /* NT_PRFPREG */
struct elf_prpsinfo psinfo; /* NT_PRPSINFO */

- segs = current->mm->map_count;
+ segs = mm->map_count;

#ifdef DEBUG
printk("elf_core_dump: %d segs %lu limit\n", segs, limit);
@@ -1153,7 +1155,7 @@
dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);

/* Write program headers for segments dump */
- for(vma = current->mm->mmap; vma != NULL; vma = vma->vm_next) {
+ for(vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
struct elf_phdr phdr;
size_t sz;

@@ -1182,7 +1184,7 @@

DUMP_SEEK(dataoff);

- for(vma = current->mm->mmap; vma != NULL; vma = vma->vm_next) {
+ for(vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
unsigned long addr;

if (!maydump(vma))
diff -aur linux-2.4.4-ref/fs/exec.c linux/fs/exec.c
--- linux-2.4.4-ref/fs/exec.c Thu Apr 26 15:11:29 2001
+++ linux/fs/exec.c Thu May 3 08:18:54 2001
@@ -923,16 +923,18 @@

int do_coredump(long signr, struct pt_regs * regs)
{
+ struct mm_struct *mm;
struct linux_binfmt * binfmt;
- char corename[6+sizeof(current->comm)];
+ char corename[6+sizeof(current->comm)+10];
struct file * file;
struct inode * inode;
+ int r;

lock_kernel();
binfmt = current->binfmt;
if (!binfmt || !binfmt->core_dump)
goto fail;
- if (!current->dumpable || atomic_read(&current->mm->mm_users) != 1)
+ if (!current->dumpable)
goto fail;
current->dumpable = 0;
if (current->rlim[RLIMIT_CORE].rlim_cur < binfmt->min_coredump)
@@ -944,6 +946,8 @@
#else
corename[4] = '\0';
#endif
+ if (atomic_read(&current->mm->mm_users) != 1)
+ sprintf(&corename[4], ".%d", current->pid);
file = filp_open(corename, O_CREAT | 2 | O_NOFOLLOW, 0600);
if (IS_ERR(file))
goto fail;
@@ -961,11 +965,42 @@
goto close_fail;
if (do_truncate(file->f_dentry, 0) != 0)
goto close_fail;
- if (!binfmt->core_dump(signr, regs, file))
+ /*
+ * Copy the mm structure to avoid potential races with
+ * other threads
+ */
+ if ((mm = kmem_cache_alloc(mm_cachep, SLAB_KERNEL)) == NULL)
goto close_fail;
+ memcpy(mm, current->mm, sizeof(*mm));
+
+ /* Clear new context for now */
+ memset(&mm->context, 0, sizeof(mm->context));
+
+ if (!mm_init(mm)) {
+ kmem_cache_free(mm_cachep, mm);
+ goto close_fail;
+ }
+ down_write(&current->mm->mmap_sem);
+ r = dup_mmap(mm);
+ up_write(&current->mm->mmap_sem);
+
+ /*
+ * Add it to the mmlist after the parent.
+ */
+ spin_lock(&mmlist_lock);
+ list_add(&mm->mmlist, &current->mm->mmlist);
+ mmlist_nr++;
+ spin_unlock(&mmlist_lock);
+
+ if (r) {
+ mmput(mm);
+ goto close_fail;
+ }
+ r = binfmt->core_dump(signr, regs, file, mm);
unlock_kernel();
+ mmput(mm);
filp_close(file, NULL);
- return 1;
+ return r;

close_fail:
filp_close(file, NULL);
diff -aur linux-2.4.4-ref/include/linux/binfmts.h linux/include/linux/binfmts.h
--- linux-2.4.4-ref/include/linux/binfmts.h Wed May 2 14:49:42 2001
+++ linux/include/linux/binfmts.h Wed May 2 15:50:42 2001
@@ -41,7 +41,8 @@
struct module *module;
int (*load_binary)(struct linux_binprm *, struct pt_regs * regs);
int (*load_shlib)(struct file *);
- int (*core_dump)(long signr, struct pt_regs * regs, struct file * file);
+ int (*core_dump)(long signr, struct pt_regs * regs,
+ struct file * file, struct mm_struct *mm);
unsigned long min_coredump; /* minimal dump size */
};

diff -aur linux-2.4.4-ref/include/linux/sched.h linux/include/linux/sched.h
--- linux-2.4.4-ref/include/linux/sched.h Wed May 2 15:57:14 2001
+++ linux/include/linux/sched.h Wed May 2 16:10:30 2001
@@ -710,6 +710,8 @@
/*
* Routines for handling mm_structs
*/
+extern struct mm_struct * mm_init(struct mm_struct * mm);
+extern int dup_mmap(struct mm_struct * mm);
extern struct mm_struct * mm_alloc(void);

extern struct mm_struct * start_lazy_tlb(void);
diff -aur linux-2.4.4-ref/kernel/fork.c linux/kernel/fork.c
--- linux-2.4.4-ref/kernel/fork.c Thu Apr 26 07:11:17 2001
+++ linux/kernel/fork.c Wed May 2 15:50:42 2001
@@ -122,7 +122,7 @@
return last_pid;
}

-static inline int dup_mmap(struct mm_struct * mm)
+int dup_mmap(struct mm_struct * mm)
{
struct vm_area_struct * mpnt, *tmp, **pprev;
int retval;
@@ -197,7 +197,7 @@
#define allocate_mm() (kmem_cache_alloc(mm_cachep, SLAB_KERNEL))
#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))

-static struct mm_struct * mm_init(struct mm_struct * mm)
+struct mm_struct * mm_init(struct mm_struct * mm)
{
atomic_set(&mm->mm_users, 1);
atomic_set(&mm->mm_count, 1);
-
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