MIPS: mcount: Adjust stack pointer for static trace in MIPS32

Every mcount() call in the MIPS 32-bit kernel is done as follows:

[...]
move at, ra
jal _mcount
addiu sp, sp, -8
[...]

but upon returning from the mcount() function, the stack pointer
is not adjusted properly. This is explained in details in 58b69401c797
(MIPS: Function tracer: Fix broken function tracing).

Commit ad8c396936e3 ("MIPS: Unbreak function tracer for 64-bit kernel.)
fixed the stack manipulation for 64-bit but it didn't fix it completely
for MIPS32.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: <stable@vger.kernel.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7792/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
index 5d25462..2f7c734 100644 (file)
--- a/arch/mips/kernel/mcount.S
+++ b/arch/mips/kernel/mcount.S
@@ -129,7 +129,11 @@ NESTED(_mcount, PT_SIZE, ra)
         nop
 #endif
        b       ftrace_stub
+#ifdef CONFIG_32BIT
+        addiu sp, sp, 8
+#else
         nop
+#endif
 
 static_trace:
        MCOUNT_SAVE_REGS
@@ -139,6 +143,9 @@ static_trace:
         move   a1, AT          /* arg2: parent's return address */
 
        MCOUNT_RESTORE_REGS
+#ifdef CONFIG_32BIT
+       addiu sp, sp, 8
+#endif
        .globl ftrace_stub
 ftrace_stub:
        RETURN_BACK
@@ -183,6 +190,11 @@ NESTED(ftrace_graph_caller, PT_SIZE, ra)
        jal     prepare_ftrace_return
         nop
        MCOUNT_RESTORE_REGS
+#ifndef CONFIG_DYNAMIC_FTRACE
+#ifdef CONFIG_32BIT
+       addiu sp, sp, 8
+#endif
+#endif
        RETURN_BACK
        END(ftrace_graph_caller)