[PATCH 03/19] Make fill_psinfo generic

[Janani Venkataraman <jananive@in.ibm.com>]

From:Suzuki K. Poulose <suzuki@in.ibm.com>

fill_psinfo() fills the NT_PRPSINFO note for the core. NT_PRPSINFO stores the
command line of the process, which is stored at from mm->arg_start. Make
fill_psinfo reusable by supporting other tasks. Use access_process_vm() to read
the command line args for non-current task.

Signed-off-by: Suzuki K. Poulose <suzuki@in.ibm.com>
---
 fs/binfmt_elf.c |   18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 107bbd3..4eee017 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1222,9 +1222,21 @@ static int fill_psinfo(struct elf_prpsinfo *psinfo, struct task_struct *p,
 	len = mm->arg_end - mm->arg_start;
 	if (len >= ELF_PRARGSZ)
 		len = ELF_PRARGSZ-1;
-	if (copy_from_user(&psinfo->pr_psargs,
-		           (const char __user *)mm->arg_start, len))
-		return -EFAULT;
+	/*
+	* If we are dumping core for "another task"
+	* we can't use copy_from_user().
+	*/
+	if (p->mm == current->mm) {
+		if (copy_from_user(&psinfo->pr_psargs,
+				(const char __user *)mm->arg_start, len))
+			return -EFAULT;
+	} else {
+		int bytes = access_process_vm(p, mm->arg_start,
+						&psinfo->pr_psargs, len, 0);
+		if (bytes != len)
+			return -EFAULT;
+	}
+
 	for(i = 0; i < len; i++)
 		if (psinfo->pr_psargs[i] == 0)
 			psinfo->pr_psargs[i] = ' ';