From: Mark Rutland <mark.rutland@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: alexandru.elisei@arm.com, amit.kachhap@arm.com,
anshuman.khandual@arm.com, broonie@kernel.org,
catalin.marinas@arm.com, james.morse@arm.com,
mark.rutland@arm.com, will@kernel.org
Subject: [PATCH v2 1/5] arm64: report EL1 UNDEFs better
Date: Tue, 13 Sep 2022 11:17:28 +0100 [thread overview]
Message-ID: <20220913101732.3925290-2-mark.rutland@arm.com> (raw)
In-Reply-To: <20220913101732.3925290-1-mark.rutland@arm.com>
If an UNDEFINED exception is taken from EL1, and do_undefinstr() doesn't
find any suitable undef_hook, it will call:
BUG_ON(!user_mode(regs))
... and the kernel will report a failure witin do_undefinstr() rather
than reporting the original context that the UNDEFINED exception was
taken from. The pt_regs and ESR value reported within the BUG() handler
will be from within do_undefinstr() and the code dump will be for the
BRK in BUG_ON(), which isn't sufficient to debug the cause of the
original exception.
This patch makes the reporting better by having do_undefinstr() call
die() directly in this case to report the original context from which
the UNDEFINED exception was taken.
Prior to this patch, an undefined instruction is reported as:
| kernel BUG at arch/arm64/kernel/traps.c:497!
| Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
| Modules linked in:
| CPU: 0 PID: 0 Comm: swapper Not tainted 5.19.0-rc3-00127-geff044f1b04e-dirty #3
| Hardware name: linux,dummy-virt (DT)
| pstate: 000000c5 (nzcv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
| pc : do_undefinstr+0x28c/0x2ac
| lr : do_undefinstr+0x298/0x2ac
| sp : ffff800009f63bc0
| x29: ffff800009f63bc0 x28: ffff800009f73c00 x27: ffff800009644a70
| x26: ffff8000096778a8 x25: 0000000000000040 x24: 0000000000000000
| x23: 00000000800000c5 x22: ffff800009894060 x21: ffff800009f63d90
| x20: 0000000000000000 x19: ffff800009f63c40 x18: 0000000000000006
| x17: 0000000000403000 x16: 00000000bfbfd000 x15: ffff800009f63830
| x14: ffffffffffffffff x13: 0000000000000000 x12: 0000000000000019
| x11: 0101010101010101 x10: 0000000000161b98 x9 : 0000000000000000
| x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
| x5 : ffff800009f761d0 x4 : 0000000000000000 x3 : ffff80000a2b80f8
| x2 : 0000000000000000 x1 : ffff800009f73c00 x0 : 00000000800000c5
| Call trace:
| do_undefinstr+0x28c/0x2ac
| el1_undef+0x2c/0x4c
| el1h_64_sync_handler+0x84/0xd0
| el1h_64_sync+0x64/0x68
| setup_arch+0x550/0x598
| start_kernel+0x88/0x6ac
| __primary_switched+0xb8/0xc0
| Code: 17ffff95 a9425bf5 17ffffb8 a9025bf5 (d4210000)
With this patch applied, an undefined instruction is reported as:
| Internal error: Oops - Undefined instruction: 0 [#1] PREEMPT SMP
| Modules linked in:
| CPU: 0 PID: 0 Comm: swapper Not tainted 5.19.0-rc3-00128-gf27cfcc80e52-dirty #5
| Hardware name: linux,dummy-virt (DT)
| pstate: 800000c5 (Nzcv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
| pc : setup_arch+0x550/0x598
| lr : setup_arch+0x50c/0x598
| sp : ffff800009f63d90
| x29: ffff800009f63d90 x28: 0000000081000200 x27: ffff800009644a70
| x26: ffff8000096778c8 x25: 0000000000000040 x24: 0000000000000000
| x23: 0000000000000100 x22: ffff800009f69a58 x21: ffff80000a2b80b8
| x20: 0000000000000000 x19: 0000000000000000 x18: 0000000000000006
| x17: 0000000000403000 x16: 00000000bfbfd000 x15: ffff800009f63830
| x14: ffffffffffffffff x13: 0000000000000000 x12: 0000000000000019
| x11: 0101010101010101 x10: 0000000000161b98 x9 : 0000000000000000
| x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
| x5 : 0000000000000008 x4 : 0000000000000010 x3 : 0000000000000000
| x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000
| Call trace:
| setup_arch+0x550/0x598
| start_kernel+0x88/0x6ac
| __primary_switched+0xb8/0xc0
| Code: b4000080 90ffed80 912ac000 97db745f (00000000)
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Cc: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
---
arch/arm64/kernel/traps.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index b7fed33981f7b..eac4f7a831750 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -494,7 +494,9 @@ void do_undefinstr(struct pt_regs *regs)
if (call_undef_hook(regs) == 0)
return;
- BUG_ON(!user_mode(regs));
+ if (!user_mode(regs))
+ die("Oops - Undefined instruction", regs, 0);
+
force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc, 0);
}
NOKPROBE_SYMBOL(do_undefinstr);
--
2.30.2
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next prev parent reply other threads:[~2022-09-13 10:20 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-13 10:17 [PATCH v2 0/5] arm64: report EL1 exceptions better Mark Rutland
2022-09-13 10:17 ` Mark Rutland [this message]
2022-09-14 5:32 ` [PATCH v2 1/5] arm64: report EL1 UNDEFs better Anshuman Khandual
2022-09-13 10:17 ` [PATCH v2 2/5] arm64: die(): pass 'err' as long Mark Rutland
2022-09-13 10:17 ` [PATCH v2 3/5] arm64: consistently pass ESR_ELx to die() Mark Rutland
2022-09-13 11:48 ` Mark Brown
2022-09-14 5:52 ` Anshuman Khandual
2022-09-13 10:17 ` [PATCH v2 4/5] arm64: rework FPAC exception handling Mark Rutland
2022-09-13 10:17 ` [PATCH v2 5/5] arm64: rework BTI " Mark Rutland
2022-09-16 17:46 ` [PATCH v2 0/5] arm64: report EL1 exceptions better Catalin Marinas
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