Patch "powerpc/signal32: Force inlining of __unsafe_save_user_regs() and save_tm_user_regs_unsafe()" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    powerpc/signal32: Force inlining of __unsafe_save_user_regs() and save_tm_user_regs_unsafe()

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     powerpc-signal32-force-inlining-of-__unsafe_save_use.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit b2e0bbb63a1e36b6d7771d71ae2fb2dcad45b3ce
Author: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Date:   Mon Jun 5 10:58:35 2023 +0200

    powerpc/signal32: Force inlining of __unsafe_save_user_regs() and save_tm_user_regs_unsafe()
    
    [ Upstream commit a03b1a0b19398a47489fdcef02ec19c2ba05a15d ]
    
    Looking at generated code for handle_signal32() shows calls to a
    function called __unsafe_save_user_regs.constprop.0 while user access
    is open.
    
    And that __unsafe_save_user_regs.constprop.0 function has two nops at
    the begining, allowing it to be traced, which is unexpected during
    user access open window.
    
    The solution could be to mark __unsafe_save_user_regs() no trace, but
    to be on the safe side the most efficient is to flag it __always_inline
    as already done for function __unsafe_restore_general_regs(). The
    function is relatively small and only called twice, so the size
    increase will remain in the noise.
    
    Do the same with save_tm_user_regs_unsafe() as it may suffer the
    same issue.
    
    Fixes: ef75e7318294 ("powerpc/signal32: Transform save_user_regs() and save_tm_user_regs() in 'unsafe' version")
    Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
    Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
    Link: https://msgid.link/7e469c8f01860a69c1ada3ca6a5e2aa65f0f74b2.1685955220.git.christophe.leroy@xxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index 3e053e2fd6b69..68ed8ecf64fcc 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -258,8 +258,9 @@ static void prepare_save_user_regs(int ctx_has_vsx_region)
 #endif
 }
 
-static int __unsafe_save_user_regs(struct pt_regs *regs, struct mcontext __user *frame,
-				   struct mcontext __user *tm_frame, int ctx_has_vsx_region)
+static __always_inline int
+__unsafe_save_user_regs(struct pt_regs *regs, struct mcontext __user *frame,
+			struct mcontext __user *tm_frame, int ctx_has_vsx_region)
 {
 	unsigned long msr = regs->msr;
 
@@ -358,8 +359,9 @@ static void prepare_save_tm_user_regs(void)
 		current->thread.ckvrsave = mfspr(SPRN_VRSAVE);
 }
 
-static int save_tm_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user *frame,
-				    struct mcontext __user *tm_frame, unsigned long msr)
+static __always_inline int
+save_tm_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user *frame,
+			 struct mcontext __user *tm_frame, unsigned long msr)
 {
 	/* Save both sets of general registers */
 	unsafe_save_general_regs(&current->thread.ckpt_regs, frame, failed);
@@ -438,8 +440,9 @@ static int save_tm_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user
 #else
 static void prepare_save_tm_user_regs(void) { }
 
-static int save_tm_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user *frame,
-				    struct mcontext __user *tm_frame, unsigned long msr)
+static __always_inline int
+save_tm_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user *frame,
+			 struct mcontext __user *tm_frame, unsigned long msr)
 {
 	return 0;
 }