arm64: report EL1 UNDEFs better
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: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20220913101732.3925290-2-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>