* [PATCH 1/3] riscv: Add the support for c.ebreak check in is_valid_bugaddr()
2019-02-28 10:31 [PATCH 0/3] riscv: Fix debug instruction check and support trap-based WARN() Vincent Chen
@ 2019-02-28 10:31 ` Vincent Chen
2019-02-28 10:31 ` [PATCH 2/3] riscv: Support BUG() in kernel module Vincent Chen
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Vincent Chen @ 2019-02-28 10:31 UTC (permalink / raw)
To: palmer, aou, ebiederm, jimw, arnd, linux-riscv, linux-kernel
Cc: deanbo422, vincentc
The is_valid_bugaddr() function compares the instruction pointed to by
$sepc with macro __BUG_INSN to check whether the current trap exception
is caused by an "ebreak" instruction. Hence the macro __BUG_INSN is
defined as "ebreak". However, this check flow is possibly erroneous
because the expected trap instruction possibly be translated to "c.ebreak"
by assembler if C extension is supported. Therefore, it requires
a mechanism to distinguish the length of the instruction in $spec and
compare it to the correct __BUG_INSN.
By the way, I make the kernel go to die() like BUG() when the trap
type is BUG_TRAP_TYPE_WARN because currently the WARN() does not trigger
any trap exception.
Signed-off-by: Vincent Chen <vincentc@andestech.com>
---
arch/riscv/include/asm/bug.h | 7 ++++++-
arch/riscv/kernel/traps.c | 8 +++++---
2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/arch/riscv/include/asm/bug.h b/arch/riscv/include/asm/bug.h
index bfc7f09..1cab7f4 100644
--- a/arch/riscv/include/asm/bug.h
+++ b/arch/riscv/include/asm/bug.h
@@ -21,7 +21,12 @@
#include <asm/asm.h>
#ifdef CONFIG_GENERIC_BUG
-#define __BUG_INSN _AC(0x00100073, UL) /* ebreak */
+#define __INSN_LENGTH_MASK _UL(0x3)
+#define __INSN_LENGTH_32 _UL(0x3)
+#define __COMPRESSED_INSN_MASK _UL(0xffff)
+
+#define __BUG_INSN_32 _UL(0x00100073) /* ebreak */
+#define __BUG_INSN_16 _UL(0x9002) /* c.ebreak */
#ifndef __ASSEMBLY__
typedef u32 bug_insn_t;
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 24a9333..deae0e5 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -129,8 +129,7 @@ asmlinkage void do_trap_break(struct pt_regs *regs)
case BUG_TRAP_TYPE_NONE:
break;
case BUG_TRAP_TYPE_WARN:
- regs->sepc += sizeof(bug_insn_t);
- return;
+ die(regs, "Kernel BUG. Kernel got an unexpected WARN trapped by ebreak");
case BUG_TRAP_TYPE_BUG:
die(regs, "Kernel BUG");
}
@@ -149,7 +148,10 @@ int is_valid_bugaddr(unsigned long pc)
return 0;
if (probe_kernel_address((bug_insn_t *)pc, insn))
return 0;
- return (insn == __BUG_INSN);
+ if ((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32)
+ return insn == __BUG_INSN_32;
+ else
+ return (insn & __COMPRESSED_INSN_MASK) == __BUG_INSN_16;
}
#endif /* CONFIG_GENERIC_BUG */
--
1.7.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH 2/3] riscv: Support BUG() in kernel module
2019-02-28 10:31 [PATCH 0/3] riscv: Fix debug instruction check and support trap-based WARN() Vincent Chen
2019-02-28 10:31 ` [PATCH 1/3] riscv: Add the support for c.ebreak check in is_valid_bugaddr() Vincent Chen
@ 2019-02-28 10:31 ` Vincent Chen
2019-02-28 10:31 ` [PATCH 3/3] riscv: Make WARN() related functions able to trigger a trap exception Vincent Chen
2019-03-04 20:35 ` [PATCH 0/3] riscv: Fix debug instruction check and support trap-based WARN() Palmer Dabbelt
3 siblings, 0 replies; 6+ messages in thread
From: Vincent Chen @ 2019-02-28 10:31 UTC (permalink / raw)
To: palmer, aou, ebiederm, jimw, arnd, linux-riscv, linux-kernel
Cc: deanbo422, vincentc
The kernel module is loaded into vmalloc region which is located below
to the PAGE_OFFSET. Hence the condition, pc < PAGE_OFFSET, in the
is_valid_bugaddr() will filter out all trap exceptions triggered
by kernel module. To support BUG() in kernel module, the condition is
changed to pc < VMALLOC_START.
Signed-off-by: Vincent Chen <vincentc@andestech.com>
---
arch/riscv/kernel/traps.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index deae0e5..dee0e5e 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -144,7 +144,7 @@ int is_valid_bugaddr(unsigned long pc)
{
bug_insn_t insn;
- if (pc < PAGE_OFFSET)
+ if (pc < VMALLOC_START)
return 0;
if (probe_kernel_address((bug_insn_t *)pc, insn))
return 0;
--
1.7.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH 3/3] riscv: Make WARN() related functions able to trigger a trap exception
2019-02-28 10:31 [PATCH 0/3] riscv: Fix debug instruction check and support trap-based WARN() Vincent Chen
2019-02-28 10:31 ` [PATCH 1/3] riscv: Add the support for c.ebreak check in is_valid_bugaddr() Vincent Chen
2019-02-28 10:31 ` [PATCH 2/3] riscv: Support BUG() in kernel module Vincent Chen
@ 2019-02-28 10:31 ` Vincent Chen
2019-03-04 20:35 ` [PATCH 0/3] riscv: Fix debug instruction check and support trap-based WARN() Palmer Dabbelt
3 siblings, 0 replies; 6+ messages in thread
From: Vincent Chen @ 2019-02-28 10:31 UTC (permalink / raw)
To: palmer, aou, ebiederm, jimw, arnd, linux-riscv, linux-kernel
Cc: deanbo422, vincentc
This can help developers to analyze the cause of WARN() because the
control will be transferred to debugging environment if the debugger is
connected.
Signed-off-by: Vincent Chen <vincentc@andestech.com>
---
arch/riscv/include/asm/bug.h | 27 ++++++++++++++++++---------
arch/riscv/kernel/traps.c | 19 ++++++++++++++++---
2 files changed, 34 insertions(+), 12 deletions(-)
diff --git a/arch/riscv/include/asm/bug.h b/arch/riscv/include/asm/bug.h
index 1cab7f4..b2aa88f 100644
--- a/arch/riscv/include/asm/bug.h
+++ b/arch/riscv/include/asm/bug.h
@@ -43,38 +43,47 @@
#define __BUG_ENTRY \
__BUG_ENTRY_ADDR "\n\t" \
__BUG_ENTRY_FILE "\n\t" \
- RISCV_SHORT " %1"
+ RISCV_SHORT " %1 \n\t" \
+ RISCV_SHORT " %2"
#else
#define __BUG_ENTRY \
- __BUG_ENTRY_ADDR
+ __BUG_ENTRY_ADDR "\n\t" \
+ RISCV_SHORT " %2"
#endif
-#define BUG() \
+#define __BUG_FLAGS(flags) \
do { \
__asm__ __volatile__ ( \
"1:\n\t" \
"ebreak\n" \
- ".pushsection __bug_table,\"a\"\n\t" \
+ ".pushsection __bug_table,\"aw\"\n\t" \
"2:\n\t" \
__BUG_ENTRY "\n\t" \
- ".org 2b + %2\n\t" \
+ ".org 2b + %3\n\t" \
".popsection" \
: \
: "i" (__FILE__), "i" (__LINE__), \
- "i" (sizeof(struct bug_entry))); \
- unreachable(); \
+ "i" (flags), \
+ "i" (sizeof(struct bug_entry))); \
} while (0)
+
#endif /* !__ASSEMBLY__ */
#else /* CONFIG_GENERIC_BUG */
#ifndef __ASSEMBLY__
-#define BUG() \
+#define __BUG_FLAGS(flags) \
do { \
__asm__ __volatile__ ("ebreak\n"); \
- unreachable(); \
} while (0)
#endif /* !__ASSEMBLY__ */
#endif /* CONFIG_GENERIC_BUG */
+#define BUG() do { \
+ __BUG_FLAGS(0); \
+ unreachable(); \
+} while (0)
+
+#define __WARN_FLAGS(flags) __BUG_FLAGS(BUGFLAG_WARNING|(flags))
+
#define HAVE_ARCH_BUG
#include <asm-generic/bug.h>
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index dee0e5e..023208b 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -118,6 +118,17 @@ asmlinkage void name(struct pt_regs *regs) \
DO_ERROR_INFO(do_trap_ecall_m,
SIGILL, ILL_ILLTRP, "environment call from M-mode");
+#ifdef CONFIG_GENERIC_BUG
+static inline unsigned long get_break_insn_length(unsigned long pc)
+{
+ bug_insn_t insn;
+
+ if (probe_kernel_address((bug_insn_t *)pc, insn))
+ return 0;
+ return ((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32) ? 4UL : 2UL;
+}
+#endif /* CONFIG_GENERIC_BUG */
+
asmlinkage void do_trap_break(struct pt_regs *regs)
{
#ifdef CONFIG_GENERIC_BUG
@@ -129,7 +140,8 @@ asmlinkage void do_trap_break(struct pt_regs *regs)
case BUG_TRAP_TYPE_NONE:
break;
case BUG_TRAP_TYPE_WARN:
- die(regs, "Kernel BUG. Kernel got an unexpected WARN trapped by ebreak");
+ regs->sepc += get_break_insn_length(regs->sepc);
+ break;
case BUG_TRAP_TYPE_BUG:
die(regs, "Kernel BUG");
}
@@ -149,12 +161,13 @@ int is_valid_bugaddr(unsigned long pc)
if (probe_kernel_address((bug_insn_t *)pc, insn))
return 0;
if ((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32)
- return insn == __BUG_INSN_32;
+ return (insn == __BUG_INSN_32);
else
- return (insn & __COMPRESSED_INSN_MASK) == __BUG_INSN_16;
+ return ((insn & __COMPRESSED_INSN_MASK) == __BUG_INSN_16);
}
#endif /* CONFIG_GENERIC_BUG */
+
void __init trap_init(void)
{
/*
--
1.7.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH 0/3] riscv: Fix debug instruction check and support trap-based WARN()
2019-02-28 10:31 [PATCH 0/3] riscv: Fix debug instruction check and support trap-based WARN() Vincent Chen
` (2 preceding siblings ...)
2019-02-28 10:31 ` [PATCH 3/3] riscv: Make WARN() related functions able to trigger a trap exception Vincent Chen
@ 2019-03-04 20:35 ` Palmer Dabbelt
2019-03-05 0:21 ` Vincent Chen
3 siblings, 1 reply; 6+ messages in thread
From: Palmer Dabbelt @ 2019-03-04 20:35 UTC (permalink / raw)
To: vincentc
Cc: aou, ebiederm, Jim Wilson, Arnd Bergmann, linux-riscv,
linux-kernel, deanbo422, vincentc
On Thu, 28 Feb 2019 02:31:28 PST (-0800), vincentc@andestech.com wrote:
> The handler for the debug exception will call is_valid_bugaddr(bugaddr) to
> check if the instruction in bugaddr is a real debug instruction. However,
> the expected instruction, ebreak, is possibly translated to c.ebreak by
> assmebler when C extension is supported. This patchset will add c.ebreak
> into the check mechanism. In addition, BUG() is currently unable to work in
> the kernel module due to an inappropriated condition in is_valid_bugaddr().
> This issue will be fixed in this patchset. Finally, this patchset enables
> WARN() related functions to trap the code to help developers debug it.
>
>
>
>
>
> Vincent Chen (3):
> riscv: Add the support for c.ebreak check in is_valid_bugaddr()
> riscv: Support BUG() in kernel module
> riscv: Make WARN() related functions able to trigger a trap exception
I'm finding this patch set a bit hard to follow, and I think it has more diff
than is necessary. For example, the first patch introduces a new die() only to
have it removed by the third patch. There's also some unnecessary
non-functional diff, like
@@ -149,12 +161,13 @@ int is_valid_bugaddr(unsigned long pc)
if (probe_kernel_address((bug_insn_t *)pc, insn))
return 0;
if ((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32)
- return insn == __BUG_INSN_32;
+ return (insn == __BUG_INSN_32);
else
- return (insn & __COMPRESSED_INSN_MASK) == __BUG_INSN_16;
+ return ((insn & __COMPRESSED_INSN_MASK) == __BUG_INSN_16);
}
#endif /* CONFIG_GENERIC_BUG */
+
void __init trap_init(void)
{
/*
I like the idea of the patch set, though. Do you have time to clean it up and
submit a v2?
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH 0/3] riscv: Fix debug instruction check and support trap-based WARN()
2019-03-04 20:35 ` [PATCH 0/3] riscv: Fix debug instruction check and support trap-based WARN() Palmer Dabbelt
@ 2019-03-05 0:21 ` Vincent Chen
0 siblings, 0 replies; 6+ messages in thread
From: Vincent Chen @ 2019-03-05 0:21 UTC (permalink / raw)
To: Palmer Dabbelt
Cc: aou, ebiederm, Jim Wilson, Arnd Bergmann, linux-riscv,
linux-kernel, deanbo422
On Tue, Mar 05, 2019 at 04:35:08AM +0800, Palmer Dabbelt wrote:
> On Thu, 28 Feb 2019 02:31:28 PST (-0800), vincentc@andestech.com wrote:
> > The handler for the debug exception will call is_valid_bugaddr(bugaddr) to
> > check if the instruction in bugaddr is a real debug instruction. However,
> > the expected instruction, ebreak, is possibly translated to c.ebreak by
> > assmebler when C extension is supported. This patchset will add c.ebreak
> > into the check mechanism. In addition, BUG() is currently unable to work in
> > the kernel module due to an inappropriated condition in is_valid_bugaddr().
> > This issue will be fixed in this patchset. Finally, this patchset enables
> > WARN() related functions to trap the code to help developers debug it.
> >
> >
> >
> >
> >
> > Vincent Chen (3):
> > riscv: Add the support for c.ebreak check in is_valid_bugaddr()
> > riscv: Support BUG() in kernel module
> > riscv: Make WARN() related functions able to trigger a trap exception
>
> I'm finding this patch set a bit hard to follow, and I think it has more diff
> than is necessary. For example, the first patch introduces a new die() only to
> have it removed by the third patch. There's also some unnecessary
> non-functional diff, like
>
> @@ -149,12 +161,13 @@ int is_valid_bugaddr(unsigned long pc)
> if (probe_kernel_address((bug_insn_t *)pc, insn))
> return 0;
> if ((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32)
> - return insn == __BUG_INSN_32;
> + return (insn == __BUG_INSN_32);
> else
> - return (insn & __COMPRESSED_INSN_MASK) == __BUG_INSN_16;
> + return ((insn & __COMPRESSED_INSN_MASK) == __BUG_INSN_16);
> }
> #endif /* CONFIG_GENERIC_BUG */
>
> +
> void __init trap_init(void)
> {
> /*
>
> I like the idea of the patch set, though. Do you have time to clean it up and
> submit a v2?
OK, I will improve it and submit a v2 patch.
^ permalink raw reply [flat|nested] 6+ messages in thread