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From: Will Deacon <will.deacon@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: catalin.marinas@arm.com, mark.rutland@arm.com,
	Will Deacon <will.deacon@arm.com>,
	stable@vger.kernel.org
Subject: [PATCH 01/10] arm64: debug: Don't propagate UNKNOWN FAR into si_code for debug signals
Date: Fri,  1 Mar 2019 13:28:00 +0000	[thread overview]
Message-ID: <20190301132809.24653-2-will.deacon@arm.com> (raw)
In-Reply-To: <20190301132809.24653-1-will.deacon@arm.com>

FAR_EL1 is UNKNOWN for all debug exceptions other than those caused by
taking a hardware watchpoint. Unfortunately, if a debug handler returns
a non-zero value, then we will propagate the UNKNOWN FAR value to
userspace via the si_addr field of the SIGTRAP siginfo_t.

Instead, let's set si_addr to take on the PC of the faulting instruction,
which we have available in the current pt_regs.

Cc: <stable@vger.kernel.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/mm/fault.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index efb7b2cbead5..ef46925096f0 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -824,11 +824,12 @@ void __init hook_debug_fault_code(int nr,
 	debug_fault_info[nr].name	= name;
 }
 
-asmlinkage int __exception do_debug_exception(unsigned long addr,
+asmlinkage int __exception do_debug_exception(unsigned long addr_if_watchpoint,
 					      unsigned int esr,
 					      struct pt_regs *regs)
 {
 	const struct fault_info *inf = esr_to_debug_fault_info(esr);
+	unsigned long pc = instruction_pointer(regs);
 	int rv;
 
 	/*
@@ -838,14 +839,14 @@ asmlinkage int __exception do_debug_exception(unsigned long addr,
 	if (interrupts_enabled(regs))
 		trace_hardirqs_off();
 
-	if (user_mode(regs) && !is_ttbr0_addr(instruction_pointer(regs)))
+	if (user_mode(regs) && !is_ttbr0_addr(pc))
 		arm64_apply_bp_hardening();
 
-	if (!inf->fn(addr, esr, regs)) {
+	if (!inf->fn(addr_if_watchpoint, esr, regs)) {
 		rv = 1;
 	} else {
 		arm64_notify_die(inf->name, regs,
-				 inf->sig, inf->code, (void __user *)addr, esr);
+				 inf->sig, inf->code, (void __user *)pc, esr);
 		rv = 0;
 	}
 
-- 
2.11.0


WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will.deacon@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: mark.rutland@arm.com, catalin.marinas@arm.com,
	Will Deacon <will.deacon@arm.com>,
	stable@vger.kernel.org
Subject: [PATCH 01/10] arm64: debug: Don't propagate UNKNOWN FAR into si_code for debug signals
Date: Fri,  1 Mar 2019 13:28:00 +0000	[thread overview]
Message-ID: <20190301132809.24653-2-will.deacon@arm.com> (raw)
In-Reply-To: <20190301132809.24653-1-will.deacon@arm.com>

FAR_EL1 is UNKNOWN for all debug exceptions other than those caused by
taking a hardware watchpoint. Unfortunately, if a debug handler returns
a non-zero value, then we will propagate the UNKNOWN FAR value to
userspace via the si_addr field of the SIGTRAP siginfo_t.

Instead, let's set si_addr to take on the PC of the faulting instruction,
which we have available in the current pt_regs.

Cc: <stable@vger.kernel.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/mm/fault.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index efb7b2cbead5..ef46925096f0 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -824,11 +824,12 @@ void __init hook_debug_fault_code(int nr,
 	debug_fault_info[nr].name	= name;
 }
 
-asmlinkage int __exception do_debug_exception(unsigned long addr,
+asmlinkage int __exception do_debug_exception(unsigned long addr_if_watchpoint,
 					      unsigned int esr,
 					      struct pt_regs *regs)
 {
 	const struct fault_info *inf = esr_to_debug_fault_info(esr);
+	unsigned long pc = instruction_pointer(regs);
 	int rv;
 
 	/*
@@ -838,14 +839,14 @@ asmlinkage int __exception do_debug_exception(unsigned long addr,
 	if (interrupts_enabled(regs))
 		trace_hardirqs_off();
 
-	if (user_mode(regs) && !is_ttbr0_addr(instruction_pointer(regs)))
+	if (user_mode(regs) && !is_ttbr0_addr(pc))
 		arm64_apply_bp_hardening();
 
-	if (!inf->fn(addr, esr, regs)) {
+	if (!inf->fn(addr_if_watchpoint, esr, regs)) {
 		rv = 1;
 	} else {
 		arm64_notify_die(inf->name, regs,
-				 inf->sig, inf->code, (void __user *)addr, esr);
+				 inf->sig, inf->code, (void __user *)pc, esr);
 		rv = 0;
 	}
 
-- 
2.11.0


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  reply	other threads:[~2019-03-01 13:28 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-01 13:27 [PATCH 00/10] Rework debug exception handling code Will Deacon
2019-03-01 13:28 ` Will Deacon [this message]
2019-03-01 13:28   ` [PATCH 01/10] arm64: debug: Don't propagate UNKNOWN FAR into si_code for debug signals Will Deacon
2019-03-01 13:45   ` Mark Rutland
2019-03-01 13:45     ` Mark Rutland
2019-03-05 13:35   ` Sasha Levin
2019-03-01 13:28 ` [PATCH 02/10] arm64: debug: Ensure debug handlers check triggering exception level Will Deacon
2019-03-01 13:28   ` Will Deacon
2019-03-01 13:46   ` Mark Rutland
2019-03-01 13:46     ` Mark Rutland
2019-03-05 13:35   ` Sasha Levin
2019-03-01 13:28 ` [PATCH 03/10] arm64: debug: Remove unused return value from do_debug_exception() Will Deacon
2019-03-01 13:48   ` Mark Rutland
2019-03-01 13:28 ` [PATCH 04/10] arm64: debug: Rename addr parameter for non-watchpoint exception hooks Will Deacon
2019-03-01 13:49   ` Mark Rutland
2019-03-01 13:28 ` [PATCH 05/10] arm64: debug: Remove meaningless comment Will Deacon
2019-03-01 14:08   ` Mark Rutland
2019-03-01 13:28 ` [PATCH 06/10] arm64: debug: Separate debug hooks based on target exception level Will Deacon
2019-03-01 14:07   ` Mark Rutland
2019-03-01 13:28 ` [PATCH 07/10] arm64: kprobes: Avoid calling kprobes debug handlers explicitly Will Deacon
2019-03-01 14:12   ` Mark Rutland
2019-03-01 13:28 ` [PATCH 08/10] arm64: debug: Remove redundant user_mode(regs) checks from debug handlers Will Deacon
2019-03-01 14:13   ` Mark Rutland
2019-03-01 13:28 ` [PATCH 09/10] arm64: probes: Move magic BRK values into brk-imm.h Will Deacon
2019-03-01 14:16   ` Mark Rutland
2019-03-01 13:28 ` [PATCH 10/10] arm64: debug: Clean up brk_handler() Will Deacon
2019-03-01 14:17   ` Mark Rutland
2019-03-01 16:24 ` [PATCH 00/10] Rework debug exception handling code Catalin Marinas

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