linux-kernel - [PATCH 3/4] openrisc: Support floating point user api

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Date:   Tue, 18 Apr 2023 17:58:12 +0100
From:   Stafford Horne <shorne@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Linux OpenRISC <linux-openrisc@...r.kernel.org>,
        Stafford Horne <shorne@...il.com>,
        Jonas Bonn <jonas@...thpole.se>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Eric Biederman <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        linux-mm@...ck.org
Subject: [PATCH 3/4] openrisc: Support floating point user api

Add support for handling floating point exceptions and forwarding the
SIGFPE signal to processes.  Also, add fpu state to sigcontext.

Signed-off-by: Stafford Horne <shorne@...il.com>
---
 arch/openrisc/include/uapi/asm/elf.h        |  3 +--
 arch/openrisc/include/uapi/asm/ptrace.h     |  4 ++++
 arch/openrisc/include/uapi/asm/sigcontext.h |  1 +
 arch/openrisc/kernel/entry.S                | 11 +++++++++--
 arch/openrisc/kernel/head.S                 |  4 ++--
 arch/openrisc/kernel/signal.c               |  2 ++
 arch/openrisc/kernel/traps.c                | 22 +++++++++++++++++++++
 7 files changed, 41 insertions(+), 6 deletions(-)

diff --git a/arch/openrisc/include/uapi/asm/elf.h b/arch/openrisc/include/uapi/asm/elf.h
index e892d5061685..6868f81c281e 100644
--- a/arch/openrisc/include/uapi/asm/elf.h
+++ b/arch/openrisc/include/uapi/asm/elf.h
@@ -53,8 +53,7 @@ typedef unsigned long elf_greg_t;
 #define ELF_NGREG (sizeof(struct user_regs_struct) / sizeof(elf_greg_t))
 typedef elf_greg_t elf_gregset_t[ELF_NGREG];
 
-/* A placeholder; OR32 does not have fp support yes, so no fp regs for now.  */
-typedef unsigned long elf_fpregset_t;
+typedef struct __or1k_fpu_state elf_fpregset_t;
 
 /* EM_OPENRISC is defined in linux/elf-em.h */
 #define EM_OR32         0x8472
diff --git a/arch/openrisc/include/uapi/asm/ptrace.h b/arch/openrisc/include/uapi/asm/ptrace.h
index d4fab268f6aa..a77cc9915ca8 100644
--- a/arch/openrisc/include/uapi/asm/ptrace.h
+++ b/arch/openrisc/include/uapi/asm/ptrace.h
@@ -30,6 +30,10 @@ struct user_regs_struct {
 	unsigned long pc;
 	unsigned long sr;
 };
+
+struct __or1k_fpu_state {
+	unsigned long fpcsr;
+};
 #endif
 
 
diff --git a/arch/openrisc/include/uapi/asm/sigcontext.h b/arch/openrisc/include/uapi/asm/sigcontext.h
index 8ab775fc3450..ca585e4af6b8 100644
--- a/arch/openrisc/include/uapi/asm/sigcontext.h
+++ b/arch/openrisc/include/uapi/asm/sigcontext.h
@@ -28,6 +28,7 @@
 
 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/entry.S b/arch/openrisc/kernel/entry.S
index c7b47e571220..c9f48e750b72 100644
--- a/arch/openrisc/kernel/entry.S
+++ b/arch/openrisc/kernel/entry.S
@@ -848,9 +848,16 @@ _syscall_badsys:
 
 /******* END SYSCALL HANDLING *******/
 
-/* ---[ 0xd00: Trap exception ]------------------------------------------ */
+/* ---[ 0xd00: Floating Point exception ]-------------------------------- */
 
-UNHANDLED_EXCEPTION(_vector_0xd00,0xd00)
+EXCEPTION_ENTRY(_fpe_trap_handler)
+	CLEAR_LWA_FLAG(r3)
+	/* r4: EA of fault (set by EXCEPTION_HANDLE) */
+	l.jal   do_fpe_trap
+	 l.addi  r3,r1,0 /* pt_regs */
+
+	l.j     _ret_from_exception
+	 l.nop
 
 /* ---[ 0xe00: Trap exception ]------------------------------------------ */
 
diff --git a/arch/openrisc/kernel/head.S b/arch/openrisc/kernel/head.S
index e11699f3d6bd..439e00f81e5d 100644
--- a/arch/openrisc/kernel/head.S
+++ b/arch/openrisc/kernel/head.S
@@ -424,9 +424,9 @@ _dispatch_do_ipage_fault:
     .org 0xc00
 	EXCEPTION_HANDLE(_sys_call_handler)
 
-/* ---[ 0xd00: Trap exception ]------------------------------------------ */
+/* ---[ 0xd00: Floating point exception ]--------------------------------- */
     .org 0xd00
-	UNHANDLED_EXCEPTION(_vector_0xd00)
+	EXCEPTION_HANDLE(_fpe_trap_handler)
 
 /* ---[ 0xe00: Trap exception ]------------------------------------------ */
     .org 0xe00
diff --git a/arch/openrisc/kernel/signal.c b/arch/openrisc/kernel/signal.c
index 80f69740c731..4664a18f0787 100644
--- a/arch/openrisc/kernel/signal.c
+++ b/arch/openrisc/kernel/signal.c
@@ -50,6 +50,7 @@ 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;
@@ -112,6 +113,7 @@ 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;
 }
diff --git a/arch/openrisc/kernel/traps.c b/arch/openrisc/kernel/traps.c
index f5bbe6b55849..0aa6b07efda1 100644
--- a/arch/openrisc/kernel/traps.c
+++ b/arch/openrisc/kernel/traps.c
@@ -243,6 +243,28 @@ asmlinkage void unhandled_exception(struct pt_regs *regs, int ea, int vector)
 	die("Oops", regs, 9);
 }
 
+asmlinkage void do_fpe_trap(struct pt_regs *regs, unsigned long address)
+{
+	int code = FPE_FLTUNK;
+	unsigned long fpcsr = regs->fpcsr;
+
+	if (fpcsr & SPR_FPCSR_IVF)
+		code = FPE_FLTINV;
+	else if (fpcsr & SPR_FPCSR_OVF)
+		code = FPE_FLTOVF;
+	else if (fpcsr & SPR_FPCSR_UNF)
+		code = FPE_FLTUND;
+	else if (fpcsr & SPR_FPCSR_DZF)
+		code = FPE_FLTDIV;
+	else if (fpcsr & SPR_FPCSR_IXF)
+		code = FPE_FLTRES;
+
+	/* Clear all flags */
+	regs->fpcsr &= ~SPR_FPCSR_ALLF;
+
+	force_sig_fault(SIGFPE, code, (void __user *)regs->pc);
+}
+
 asmlinkage void do_trap(struct pt_regs *regs, unsigned long address)
 {
 	force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->pc);
-- 
2.39.1