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[PATCH 9/9] tracing: MIPS: cleanup of the address space checking

To: Ralf Baechle <ralf@linux-mips.org>
Subject: [PATCH 9/9] tracing: MIPS: cleanup of the address space checking
From: Wu Zhangjin <wuzhangjin@gmail.com>
Date: Fri, 14 May 2010 19:08:34 +0800
Cc: linux-mips <linux-mips@linux-mips.org>, David Daney <david.s.daney@gmail.com>, Wu Zhangjin <wuzhangjin@gmail.com>
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In-reply-to: <cover.1273834561.git.wuzhangjin@gmail.com>
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Original-recipient: rfc822;linux-mips@linux-mips.org
References: <cover.1273834561.git.wuzhangjin@gmail.com>
References: <cover.1273834561.git.wuzhangjin@gmail.com>
Sender: linux-mips-bounce@linux-mips.org
From: Wu Zhangjin <wuzhangjin@gmail.com>

This patch adds an inline function in_module() to check which space the
instruction pointer in, kernel space or module space.

Note:  This will not work when the kernel space and module space are the
same. If they are the same, we need to modify scripts/recordmcount.pl,
ftrace_make_nop/call() and the other related parts to ensure the
enabling/disabling of the calling site to _mcount is right for both
kernel and module.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
---
 arch/mips/kernel/ftrace.c |   22 +++++++++++++++++++---
 1 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index 628e90b..5a84a1f 100644
--- a/arch/mips/kernel/ftrace.c
+++ b/arch/mips/kernel/ftrace.c
@@ -17,6 +17,22 @@
 #include <asm/cacheflush.h>
 #include <asm/uasm.h>
 
+/*
+ * If the Instruction Pointer is in module space (0xc0000000), return true;
+ * otherwise, it is in kernel space (0x80000000), return false.
+ *
+ * FIXME: This will not work when the kernel space and module space are the
+ * same. If they are the same, we need to modify scripts/recordmcount.pl,
+ * ftrace_make_nop/call() and the other related parts to ensure the
+ * enabling/disabling of the calling site to _mcount is right for both kernel
+ * and module.
+ */
+
+static inline int in_module(unsigned long ip)
+{
+       return ip & 0x40000000;
+}
+
 #ifdef CONFIG_DYNAMIC_FTRACE
 
 #define JAL 0x0c000000         /* jump & link: ip --> ra, jump to target */
@@ -78,7 +94,7 @@ int ftrace_make_nop(struct module *mod,
         * We have compiled module with -mlong-calls, but compiled the kernel
         * without it, we need to cope with them respectively.
         */
-       if (ip & 0x40000000) {
+       if (in_module(ip)) {
 #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
                /*
                 * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
@@ -117,7 +133,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long 
addr)
        unsigned long ip = rec->ip;
 
        /* ip, module: 0xc0000000, kernel: 0x80000000 */
-       new = (ip & 0x40000000) ? insn_lui_v1_hi16_mcount : 
insn_jal_ftrace_caller;
+       new = in_module(ip) ? insn_lui_v1_hi16_mcount : insn_jal_ftrace_caller;
 
        return ftrace_modify_code(ip, new);
 }
@@ -188,7 +204,7 @@ unsigned long ftrace_get_parent_addr(unsigned long 
self_addr,
         * instruction "lui v1, hi_16bit_of_mcount"(offset is 20), but for
         * kernel, move to the instruction "move ra, at"(offset is 12)
         */
-       ip = self_addr - ((self_addr & 0x40000000) ? 20 : 12);
+       ip = self_addr - (in_module(self_addr) ? 20 : 12);
 
        /*
         * search the text until finding the non-store instruction or "s{d,w}
-- 
1.7.0.4


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