[PATCH RESEND 1/2] ARM: v7m: handle faults
From: Ben Wolsieffer
Date: Fri Dec 09 2022 - 16:54:14 EST
Currently, any fault on an ARMv7M system will trigger the invalid entry
exception handler, bringing down the entire system.
This patch installs real handlers for the hard fault, memmanage, bus
fault and usage fault exceptions. For kernel space faults, an oops is
triggered, while user space faults kill the offending process with an
appropriate signal. The fault status registers are parsed to construct
an appropriate message and signal.
This is based on a patch from Emcraft Systems' kernel tree [1], but I
have significantly reworked it.
[1] https://github.com/EmcraftSystems/linux-upstream/commit/2882de1d86bd536c855feee582d44722434c2ac9
Signed-off-by: Ben Wolsieffer <benwolsieffer@xxxxxxxxx>
---
arch/arm/include/asm/v7m.h | 29 +++++++
arch/arm/kernel/Makefile | 2 +-
arch/arm/kernel/entry-v7m.S | 68 +++++++++++++++-
arch/arm/kernel/traps-v7m.c | 156 ++++++++++++++++++++++++++++++++++++
4 files changed, 250 insertions(+), 5 deletions(-)
create mode 100644 arch/arm/kernel/traps-v7m.c
diff --git a/arch/arm/include/asm/v7m.h b/arch/arm/include/asm/v7m.h
index 4512f7e1918f..b8c636a0578d 100644
--- a/arch/arm/include/asm/v7m.h
+++ b/arch/arm/include/asm/v7m.h
@@ -38,6 +38,35 @@
#define V7M_SCB_SHCSR_BUSFAULTENA (1 << 17)
#define V7M_SCB_SHCSR_MEMFAULTENA (1 << 16)
+#define V7M_SCB_CFSR 0x28
+
+#define V7M_SCB_CFSR_DIVBYZERO (1 << 25)
+#define V7M_SCB_CFSR_UNALIGNED (1 << 24)
+#define V7M_SCB_CFSR_NOCP (1 << 19)
+#define V7M_SCB_CFSR_INVPC (1 << 18)
+#define V7M_SCB_CFSR_INVSTATE (1 << 17)
+#define V7M_SCB_CFSR_UNDEFINSTR (1 << 16)
+#define V7M_SCB_CFSR_BFARVALID (1 << 15)
+#define V7M_SCB_CFSR_LSPERR (1 << 13)
+#define V7M_SCB_CFSR_STKERR (1 << 12)
+#define V7M_SCB_CFSR_UNSTKERR (1 << 11)
+#define V7M_SCB_CFSR_IMPRECISERR (1 << 10)
+#define V7M_SCB_CFSR_PRECISERR (1 << 9)
+#define V7M_SCB_CFSR_IBUSERR (1 << 8)
+#define V7M_SCB_CFSR_MMARVALID (1 << 7)
+#define V7M_SCB_CFSR_MLSPERR (1 << 5)
+#define V7M_SCB_CFSR_MSTKERR (1 << 4)
+#define V7M_SCB_CFSR_MUNSTKERR (1 << 3)
+#define V7M_SCB_CFSR_DACCVIOL (1 << 1)
+#define V7M_SCB_CFSR_IACCVIOL (1 << 0)
+
+#define V7M_SCB_HFSR 0x2c
+#define V7M_SCB_HFSR_FORCED (1 << 30)
+#define V7M_SCB_HFSR_VECTTBL (1 << 1)
+
+#define V7M_SCB_MMAR 0x34
+#define V7M_SCB_BFAR 0x38
+
#define V7M_xPSR_FRAMEPTRALIGN 0x00000200
#define V7M_xPSR_EXCEPTIONNO V7M_SCB_ICSR_VECTACTIVE
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 48737ec800eb..6d7b06b28113 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -34,7 +34,7 @@ obj-$(CONFIG_ATAGS_PROC) += atags_proc.o
obj-$(CONFIG_DEPRECATED_PARAM_STRUCT) += atags_compat.o
ifeq ($(CONFIG_CPU_V7M),y)
-obj-y += entry-v7m.o v7m.o
+obj-y += entry-v7m.o v7m.o traps-v7m.o
else
obj-y += entry-armv.o
endif
diff --git a/arch/arm/kernel/entry-v7m.S b/arch/arm/kernel/entry-v7m.S
index de8a60363c85..62909731cd1f 100644
--- a/arch/arm/kernel/entry-v7m.S
+++ b/arch/arm/kernel/entry-v7m.S
@@ -84,6 +84,66 @@ __irq_entry:
bx lr
ENDPROC(__irq_entry)
+__hardfault_entry:
+ v7m_exception_entry
+
+ @
+ @ Invoke the Hard Fault handler
+ @ routine called with r0 = struct pt_regs *
+ mov r0, sp
+ bl do_hardfault
+
+ @ execute the pending work, including reschedule
+ get_thread_info tsk
+ mov why, #0
+ b ret_to_user_from_irq
+ENDPROC(__hardfault_entry)
+
+__memmanage_entry:
+ v7m_exception_entry
+
+ @
+ @ Invoke the Mem Manage handler
+ @ routine called with r0 = struct pt_regs *
+ mov r0, sp
+ bl do_memmanage
+
+ @ execute the pending work, including reschedule
+ get_thread_info tsk
+ mov why, #0
+ b ret_to_user_from_irq
+ENDPROC(__memmanage_entry)
+
+__busfault_entry:
+ v7m_exception_entry
+
+ @
+ @ Invoke the Bus Fault handler
+ @ routine called with r0 = struct pt_regs *
+ mov r0, sp
+ bl do_busfault
+
+ @ execute the pending work, including reschedule
+ get_thread_info tsk
+ mov why, #0
+ b ret_to_user_from_irq
+ENDPROC(__busfault_entry)
+
+__usagefault_entry:
+ v7m_exception_entry
+
+ @
+ @ Invoke the Bus Fault handler
+ @ routine called with r0 = struct pt_regs *
+ mov r0, sp
+ bl do_usagefault
+
+ @ execute the pending work, including reschedule
+ get_thread_info tsk
+ mov why, #0
+ b ret_to_user_from_irq
+ENDPROC(__usagefault_entry)
+
__pendsv_entry:
v7m_exception_entry
@@ -138,10 +198,10 @@ ENTRY(vector_table)
.long 0 @ 0 - Reset stack pointer
.long __invalid_entry @ 1 - Reset
.long __invalid_entry @ 2 - NMI
- .long __invalid_entry @ 3 - HardFault
- .long __invalid_entry @ 4 - MemManage
- .long __invalid_entry @ 5 - BusFault
- .long __invalid_entry @ 6 - UsageFault
+ .long __hardfault_entry @ 3 - HardFault
+ .long __memmanage_entry @ 4 - MemManage
+ .long __busfault_entry @ 5 - BusFault
+ .long __usagefault_entry @ 6 - UsageFault
.long __invalid_entry @ 7 - Reserved
.long __invalid_entry @ 8 - Reserved
.long __invalid_entry @ 9 - Reserved
diff --git a/arch/arm/kernel/traps-v7m.c b/arch/arm/kernel/traps-v7m.c
new file mode 100644
index 000000000000..5fd9943448e9
--- /dev/null
+++ b/arch/arm/kernel/traps-v7m.c
@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2011 Dmitry Cherukhin, Emcraft Systems
+ * Copyright (C) 2022 Ben Wolsieffer, Hefring Engineering
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/io.h>
+#include <linux/sched.h>
+
+#include <asm/linkage.h>
+#include <asm/ptrace.h>
+#include <asm/system_misc.h>
+#include <asm/v7m.h>
+
+enum fault {
+ FAULT_HARDFALT = 3,
+ FAULT_MEMMANAGE = 4,
+ FAULT_BUSFAULT = 5,
+ FAULT_USAGEFAULT = 6
+};
+
+struct exception {
+ const char *name;
+ int fault;
+ int test_bit;
+ int signo;
+ int si_code;
+ unsigned int user_debug;
+};
+
+static const struct exception unknown_exception =
+ {"unknown exception", 0, 0, SIGSEGV, SEGV_MAPERR, UDBG_SEGV};
+
+static const struct exception exceptions[] = {
+ {"escalated to hard fault", FAULT_HARDFALT, V7M_SCB_HFSR_FORCED, SIGSEGV, SEGV_MAPERR, UDBG_SEGV},
+ {"vector read error", FAULT_HARDFALT, V7M_SCB_HFSR_VECTTBL, SIGSEGV, SEGV_MAPERR, UDBG_SEGV},
+ {"divide by 0", FAULT_USAGEFAULT, V7M_SCB_CFSR_DIVBYZERO, SIGSEGV, SEGV_MAPERR, UDBG_SEGV},
+ {"illegal unaligned access", FAULT_USAGEFAULT, V7M_SCB_CFSR_UNALIGNED, SIGBUS, BUS_ADRALN, UDBG_BUS},
+ {"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},
+ {"imprecise data bus error", FAULT_BUSFAULT, V7M_SCB_CFSR_IMPRECISERR, SIGBUS, BUS_ADRERR, UDBG_BUS},
+ {"precise data bus error", FAULT_BUSFAULT, V7M_SCB_CFSR_PRECISERR, SIGBUS, BUS_ADRERR, UDBG_BUS},
+ {"pre-fetch error", FAULT_BUSFAULT, V7M_SCB_CFSR_IBUSERR, SIGBUS, BUS_ADRERR, UDBG_BUS},
+ {"floating point state error", FAULT_MEMMANAGE, V7M_SCB_CFSR_MLSPERR, SIGSEGV, SEGV_MAPERR, UDBG_SEGV},
+ {"exception stack push error", FAULT_MEMMANAGE, V7M_SCB_CFSR_MSTKERR, SIGSEGV, SEGV_MAPERR, UDBG_SEGV},
+ {"exception stack pop error", FAULT_MEMMANAGE, V7M_SCB_CFSR_MUNSTKERR, SIGSEGV, SEGV_MAPERR, UDBG_SEGV},
+ {"data access violation", FAULT_MEMMANAGE, V7M_SCB_CFSR_DACCVIOL, SIGSEGV, SEGV_ACCERR, UDBG_SEGV},
+ {"instruction access violation", FAULT_MEMMANAGE, V7M_SCB_CFSR_IACCVIOL, SIGSEGV, SEGV_ACCERR, UDBG_SEGV},
+ {NULL}
+};
+
+/*
+ * Common routine for high-level exception handlers.
+ * @param regs state of registers when the exception occurs
+ * @param fault IPSR, the fault number
+ */
+static void traps_v7m_common(struct pt_regs *regs, int fault)
+{
+ unsigned long status;
+ unsigned long hstatus;
+ unsigned long cstatus;
+ unsigned long addr;
+ size_t i;
+ const struct exception *exc = &unknown_exception;
+
+
+ hstatus = readl(BASEADDR_V7M_SCB + V7M_SCB_HFSR);
+ cstatus = readl(BASEADDR_V7M_SCB + V7M_SCB_CFSR);
+
+ if (cstatus & V7M_SCB_CFSR_MMARVALID && (fault == FAULT_MEMMANAGE ||
+ (fault == FAULT_HARDFALT && hstatus & V7M_SCB_HFSR_FORCED))) {
+ addr = readl(BASEADDR_V7M_SCB + V7M_SCB_MMAR);
+ } else if (cstatus & V7M_SCB_CFSR_BFARVALID && (fault == FAULT_BUSFAULT ||
+ (fault == FAULT_HARDFALT && hstatus & V7M_SCB_HFSR_FORCED))) {
+ addr = readl(BASEADDR_V7M_SCB + V7M_SCB_BFAR);
+ } else {
+ addr = instruction_pointer(regs);
+ }
+
+ writel(hstatus, BASEADDR_V7M_SCB + V7M_SCB_HFSR);
+ writel(cstatus, BASEADDR_V7M_SCB + V7M_SCB_CFSR);
+
+ for (i = 0; exceptions[i].name != NULL; ++i) {
+ if (fault != exceptions[i].fault)
+ continue;
+
+ status = fault == FAULT_HARDFALT ? hstatus : cstatus;
+ if (!(status & exceptions[i].test_bit))
+ continue;
+
+ exc = &exceptions[i];
+ break;
+ }
+
+#ifdef CONFIG_DEBUG_USER
+ if (user_mode(regs) && (user_debug & exc->user_debug)) {
+ pr_info("%s (%d): %s: addr=0x%px\n",
+ current->comm, task_pid_nr(current), exc->name, (void *)addr);
+ __show_regs(regs);
+ }
+#endif
+
+ arm_notify_die(exc->name, regs, exc->signo, exc->si_code,
+ (void __user *)addr, 0, fault);
+}
+
+/*
+ * High-level exception handler for exception 3 (Hard Fault).
+ * @param regs state of registers when the exception occurred
+ */
+asmlinkage void do_hardfault(struct pt_regs *regs)
+{
+ traps_v7m_common(regs, FAULT_HARDFALT);
+}
+
+/*
+ * High-level exception handler for exception 4 (Mem Manage).
+ * @param regs state of registers when the exception occurred
+ */
+asmlinkage void do_memmanage(struct pt_regs *regs)
+{
+ traps_v7m_common(regs, FAULT_MEMMANAGE);
+}
+
+/*
+ * High-level exception handler for exception 5 (Bus Fault).
+ * @param regs state of registers when the exception occurred
+ */
+asmlinkage void do_busfault(struct pt_regs *regs)
+{
+ traps_v7m_common(regs, FAULT_BUSFAULT);
+}
+
+/*
+ * High-level exception handler for exception 6 (Usage Fault).
+ * @param regs state of registers when the exception occurred
+ */
+asmlinkage void do_usagefault(struct pt_regs *regs)
+{
+ traps_v7m_common(regs, FAULT_USAGEFAULT);
+}
--
2.38.1