From: Jiri Olsa <jolsa@redhat.com>
Date: Mon, 4 Oct 2010 13:17:45 -0400
Subject: [misc] oprofile: add backtraces for compat mode processes
Message-id: <1286198265-6220-1-git-send-email-jolsa@redhat.com>
Patchwork-id: 28571
O-Subject: [PATCH RHEL5] BZ 622024 oprofile,
	x86: adding backtrace dump for 32bit process in compat mode
Bugzilla: 622024
RH-Acked-by: Don Zickus <dzickus@redhat.com>

Bugzilla: 622024
https://bugzilla.redhat.com/show_bug.cgi?id=622024

Description:
============
This patch implements the oprofile backtrace  generation for 32 bit
applications running in the 64bit environment (compat mode).

With this change it's possible to get backtrace for 32bits applications
under the 64bits environment using oprofile's callgraph options.

Upstream status:
================
patch was accepted upstream, it's in oprofile tree
git://git.kernel.org/pub/scm/linux/kernel/git/rric/oprofile.git

- oprofile, x86: Using struct stack_frame for 64bit processes dump
  commit f6dedecc37164a58bb80ae2ed9d204669ffc4850
  Author: Jiri Olsa <jolsa@redhat.com>

Brew:
=====
https://brewweb.devel.redhat.com/taskinfo?taskID=2794979

Tested:
=======
verified on 32-bit binary, oprofile generated stack report

wbr,
jirka

diff --git a/arch/i386/oprofile/backtrace.c b/arch/i386/oprofile/backtrace.c
index c049ce4..ea6c0a8 100644
--- a/arch/i386/oprofile/backtrace.c
+++ b/arch/i386/oprofile/backtrace.c
@@ -13,6 +13,7 @@
 #include <linux/mm.h>
 #include <asm/ptrace.h>
 #include <asm/uaccess.h>
+#include <linux/compat.h>
 
 struct frame_head {
 	struct frame_head * ebp;
@@ -32,6 +33,60 @@ dump_kernel_backtrace(struct frame_head * head)
 	return head->ebp;
 }
 
+#ifdef CONFIG_COMPAT
+struct stack_frame_ia32 {
+	u32 next_frame;
+	u32 return_address;
+};
+
+static struct stack_frame_ia32 *
+dump_user_backtrace_32(struct stack_frame_ia32 *head)
+{
+	struct stack_frame_ia32 bufhead[2];
+	struct stack_frame_ia32 *fp;
+
+	/* Also check accessibility of one struct frame_head beyond */
+	if (!access_ok(VERIFY_READ, head, sizeof(bufhead)))
+		return NULL;
+	if (__copy_from_user_inatomic(bufhead, head, sizeof(bufhead)))
+		return NULL;
+
+	fp = (struct stack_frame_ia32 *) compat_ptr(bufhead[0].next_frame);
+
+	oprofile_add_trace(bufhead[0].return_address);
+
+	/* frame pointers should strictly progress back up the stack
+	* (towards higher addresses) */
+	if (head >= fp)
+		return NULL;
+
+	return fp;
+}
+
+static inline int
+x86_backtrace_32(struct pt_regs * const regs, unsigned int depth)
+{
+	struct stack_frame_ia32 *head;
+
+	/* User process is 32-bit */
+	if (!current || !test_thread_flag(TIF_IA32))
+		return 0;
+
+	head = (struct stack_frame_ia32 *) regs->rbp;
+	while (depth-- && head)
+		head = dump_user_backtrace_32(head);
+
+	return 1;
+}
+
+#else
+static inline int
+x86_backtrace_32(struct pt_regs * const regs, unsigned int depth)
+{
+	return 0;
+}
+#endif /* CONFIG_COMPAT */
+
 static struct frame_head *
 dump_user_backtrace(struct frame_head * head)
 {
@@ -122,6 +177,9 @@ x86_backtrace(struct pt_regs * const regs, unsigned int depth)
 		return;
 	}
 
+	if (x86_backtrace_32(regs, depth))
+		return;
+
 	while (depth-- && head)
 		head = dump_user_backtrace(head);
 }