Message ID | 20220913101732.3925290-2-mark.rutland@arm.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | arm64: report EL1 exceptions better | expand |
On 9/13/22 15:47, Mark Rutland wrote: > 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> Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com> > 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);
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);