[PATCH 6.4 465/800] powerpc/signal32: Force inlining of __unsafe_save_user_regs() and save_tm_user_regs_unsafe()

Greg Kroah-Hartman
2023-07-16T20:16:05Z

From: Christophe Leroy <christophe.leroy@csgroup.eu>

[ 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@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/7e469c8f01860a69c1ada3ca6a5e2aa65f0f74b2.1685955220.git.christophe.leroy@csgroup.eu
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/powerpc/kernel/signal_32.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index c114c7f25645c..7a718ed32b277 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -264,8 +264,9 @@ 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;

@@ -364,8 +365,9 @@ 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);
@@ -444,8 +446,9 @@ 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;
}
--
2.39.2