linux-kernel - [PATCH] openrisc: Revert adding fpcsr to sigcontext to unbreak userspace ABI

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Message-Id: <20230628171306.2608480-1-shorne@gmail.com>
Date:   Wed, 28 Jun 2023 18:13:04 +0100
From:   Stafford Horne <shorne@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Rich Felker <dalias@...c.org>, Stafford Horne <shorne@...il.com>,
        Szabolcs Nagy <nsz@...t70.net>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        linux-openrisc@...r.kernel.org
Subject: [PATCH] openrisc: Revert adding fpcsr to sigcontext to unbreak userspace ABI

With commit 27267655c531 ("openrisc: Support floating point user api") I
inproperly added an entry to the struct sigcontext which caused an
unwanted to chagne to the userspace ABI.

Revert this change to restore the ABI back to the pre kernel v6.4 ABI.

This means that fpcsr will not be accessible in signal handlers, but
that should be fine.

Fixes: 27267655c531 ("openrisc: Support floating point user api")
Reported-by: Szabolcs Nagy <nsz@...t70.net>
Closes: https://lore.kernel.org/openrisc/20230626213840.GA1236108@port70.net/
Signed-off-by: Stafford Horne <shorne@...il.com>
---
 arch/openrisc/include/uapi/asm/sigcontext.h | 1 -
 arch/openrisc/kernel/signal.c               | 2 --
 2 files changed, 3 deletions(-)

diff --git a/arch/openrisc/include/uapi/asm/sigcontext.h b/arch/openrisc/include/uapi/asm/sigcontext.h
index ca585e4af6b8..8ab775fc3450 100644
--- a/arch/openrisc/include/uapi/asm/sigcontext.h
+++ b/arch/openrisc/include/uapi/asm/sigcontext.h
@@ -28,7 +28,6 @@
 
 struct sigcontext {
 	struct user_regs_struct regs;  /* needs to be first */
-	struct __or1k_fpu_state fpu;
 	unsigned long oldmask;
 };
 
diff --git a/arch/openrisc/kernel/signal.c b/arch/openrisc/kernel/signal.c
index 4664a18f0787..80f69740c731 100644
--- a/arch/openrisc/kernel/signal.c
+++ b/arch/openrisc/kernel/signal.c
@@ -50,7 +50,6 @@ static int restore_sigcontext(struct pt_regs *regs,
 	err |= __copy_from_user(regs, sc->regs.gpr, 32 * sizeof(unsigned long));
 	err |= __copy_from_user(&regs->pc, &sc->regs.pc, sizeof(unsigned long));
 	err |= __copy_from_user(&regs->sr, &sc->regs.sr, sizeof(unsigned long));
-	err |= __copy_from_user(&regs->fpcsr, &sc->fpu.fpcsr, sizeof(unsigned long));
 
 	/* make sure the SM-bit is cleared so user-mode cannot fool us */
 	regs->sr &= ~SPR_SR_SM;
@@ -113,7 +112,6 @@ static int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
 	err |= __copy_to_user(sc->regs.gpr, regs, 32 * sizeof(unsigned long));
 	err |= __copy_to_user(&sc->regs.pc, &regs->pc, sizeof(unsigned long));
 	err |= __copy_to_user(&sc->regs.sr, &regs->sr, sizeof(unsigned long));
-	err |= __copy_to_user(&sc->fpu.fpcsr, &regs->fpcsr, sizeof(unsigned long));
 
 	return err;
 }
-- 
2.39.1