linux-kernel - [PATCH 2/2] ARM: v7m: support undefined instruction hooks

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Message-Id: <20220801201347.1255392-3-Ben.Wolsieffer@hefring.com>
Date:   Mon,  1 Aug 2022 16:13:39 -0400
From:   Ben Wolsieffer <ben.wolsieffer@...ring.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Ben Wolsieffer <Ben.Wolsieffer@...ring.com>,
        Russell King <linux@...linux.org.uk>,
        Ard Biesheuvel <ardb@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Mark Rutland <mark.rutland@....com>,
        Marc Zyngier <maz@...nel.org>,
        Vladimir Murzin <vladimir.murzin@....com>,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "Steven Rostedt (Google)" <rostedt@...dmis.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Nicolas Pitre <nico@...xnic.net>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] ARM: v7m: support undefined instruction hooks

Call the common ARM undefined instruction handler, which handles running
hooks to enable ptrace breakpoints and other features.

Signed-off-by: Ben Wolsieffer <Ben.Wolsieffer@...ring.com>
---
 arch/arm/include/asm/traps.h | 2 ++
 arch/arm/kernel/traps-v7m.c  | 8 +++++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/traps.h b/arch/arm/include/asm/traps.h
index 987fefb0a4db..e4253f4a86e1 100644
--- a/arch/arm/include/asm/traps.h
+++ b/arch/arm/include/asm/traps.h
@@ -19,6 +19,8 @@ struct undef_hook {
 void register_undef_hook(struct undef_hook *hook);
 void unregister_undef_hook(struct undef_hook *hook);
 
+void do_undefinstr(struct pt_regs *regs);
+
 static inline int __in_irqentry_text(unsigned long ptr)
 {
 	extern char __irqentry_text_start[];
diff --git a/arch/arm/kernel/traps-v7m.c b/arch/arm/kernel/traps-v7m.c
index 5fd9943448e9..b324499e1010 100644
--- a/arch/arm/kernel/traps-v7m.c
+++ b/arch/arm/kernel/traps-v7m.c
@@ -20,6 +20,7 @@
 #include <asm/linkage.h>
 #include <asm/ptrace.h>
 #include <asm/system_misc.h>
+#include <asm/traps.h>
 #include <asm/v7m.h>
 
 enum fault {
@@ -49,7 +50,6 @@ static const struct exception exceptions[] = {
 	{"no coprocessor",			FAULT_USAGEFAULT,	V7M_SCB_CFSR_NOCP,		SIGILL,		ILL_COPROC,	UDBG_UNDEFINED},
 	{"return to invalid PC",		FAULT_USAGEFAULT,	V7M_SCB_CFSR_INVPC,		SIGSEGV,	SEGV_MAPERR,	UDBG_SEGV},
 	{"invalid ISA state",			FAULT_USAGEFAULT,	V7M_SCB_CFSR_INVSTATE,		SIGSEGV,	SEGV_MAPERR,	UDBG_SEGV},
-	{"undefined instruction",		FAULT_USAGEFAULT,	V7M_SCB_CFSR_UNDEFINSTR,	SIGILL,		ILL_ILLOPC,	UDBG_UNDEFINED},
 	{"floating point state error",		FAULT_BUSFAULT,		V7M_SCB_CFSR_LSPERR,		SIGBUS,		BUS_ADRERR,	UDBG_BUS},
 	{"exception stack push error",		FAULT_BUSFAULT,		V7M_SCB_CFSR_STKERR,		SIGBUS,		BUS_ADRERR,	UDBG_BUS},
 	{"exception stack pop error",		FAULT_BUSFAULT,		V7M_SCB_CFSR_UNSTKERR,		SIGBUS,		BUS_ADRERR,	UDBG_BUS},
@@ -95,6 +95,12 @@ static void traps_v7m_common(struct pt_regs *regs, int fault)
 	writel(hstatus, BASEADDR_V7M_SCB + V7M_SCB_HFSR);
 	writel(cstatus, BASEADDR_V7M_SCB + V7M_SCB_CFSR);
 
+	if (fault == FAULT_USAGEFAULT && cstatus & V7M_SCB_CFSR_UNDEFINSTR) {
+		/* Handle undefined instruction hooks */
+		do_undefinstr(regs);
+		return;
+	}
+
 	for (i = 0; exceptions[i].name != NULL; ++i) {
 		if (fault != exceptions[i].fault)
 			continue;
-- 
2.37.0