On MIPS, __current_thread_info is defined as global register variable
locating in $gp, and is simply assigned with new address during kernel
relocation.
This however is broken with LLVM, which always restores $gp if it finds
$gp is clobbered in any form, including when intentionally through a
global register variable. This is against GCC's documentation[1], which
requires a callee-saved register used as global register variable not to
be restored if it's clobbered.
As a result, $gp will continue to point to the unrelocated kernel after
the epilog of relocate_kernel(), leading to an early crash in init_idle,
[ 0.000000] CPU 0 Unable to handle kernel paging request at virtual address 0000000000000000, epc == ffffffff81afada8, ra == ffffffff81afad90
[ 0.000000] Oops[#1]:
[ 0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper Tainted: G W 6.19.0-rc5-00262-gd3eeb99bbc99-dirty #188 VOLUNTARY
[ 0.000000] Tainted: [W]=WARN
[ 0.000000] Hardware name: loongson,loongson64v-4core-virtio
[ 0.000000] $ 0 : 0000000000000000 0000000000000000 0000000000000001 0000000000000000
[ 0.000000] $ 4 : ffffffff80b80ec0 ffffffff80b53d48 0000000000000000 00000000000f4240
[ 0.000000] $ 8 : 0000000000000100 ffffffff81d82f80 ffffffff81d82f80 0000000000000001
[ 0.000000] $12 : 0000000000000000 ffffffff81776f58 00000000000005da 0000000000000002
[ 0.000000] $16 : ffffffff80b80e40 0000000000000000 ffffffff80b81614 9800000005dfbe80
[ 0.000000] $20 : 00000000540000e0 ffffffff81980000 0000000000000000 ffffffff80f81c80
[ 0.000000] $24 : 0000000000000a26 ffffffff8114fb90
[ 0.000000] $28 : ffffffff80b50000 ffffffff80b53d40 0000000000000000 ffffffff81afad90
[ 0.000000] Hi : 0000000000000000
[ 0.000000] Lo : 0000000000000000
[ 0.000000] epc : ffffffff81afada8 init_idle+0x130/0x270
[ 0.000000] ra : ffffffff81afad90 init_idle+0x118/0x270
[ 0.000000] Status: 540000e2 KX SX UX KERNEL EXL
[ 0.000000] Cause : 00000008 (ExcCode 02)
[ 0.000000] BadVA : 0000000000000000
[ 0.000000] PrId : 00006305 (ICT Loongson-3)
[ 0.000000] Process swapper (pid: 0, threadinfo=(____ptrval____), task=(____ptrval____), tls=0000000000000000)
[ 0.000000] Stack : 9800000005dfbf00 ffffffff8178e950 0000000000000000 0000000000000000
[ 0.000000] 0000000000000000 ffffffff81970000 000000000000003f ffffffff810a6528
[ 0.000000] 0000000000000001 9800000005dfbe80 9800000005dfbf00 ffffffff81980000
[ 0.000000] ffffffff810a6450 ffffffff81afb6c0 0000000000000000 ffffffff810a2258
[ 0.000000] ffffffff81d82ec8 ffffffff8198d010 ffffffff81b67e80 ffffffff8197dd98
[ 0.000000] ffffffff81d81c80 ffffffff81930000 0000000000000040 0000000000000000
[ 0.000000] 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[ 0.000000] 0000000000000000 000000000000009e ffffffff9fc01000 0000000000000000
[ 0.000000] 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[ 0.000000] 0000000000000000 ffffffff81ae86dc ffffffff81b3c741 0000000000000002
[ 0.000000] ...
[ 0.000000] Call Trace:
[ 0.000000] [<ffffffff81afada8>] init_idle+0x130/0x270
[ 0.000000] [<ffffffff81afb6c0>] sched_init+0x5c8/0x6c0
[ 0.000000] [<ffffffff81ae86dc>] start_kernel+0x27c/0x7a8
This bug has been reported to LLVM[2] and affects version from (at
least) 18 to 21. Let's work around this by using inline assembly to
assign $gp before a fix is widely available.
Cc: stable@vger.kernel.org
Link: https://gcc.gnu.org/onlinedocs/gcc-15.2.0/gcc/Global-Register-Variables.html # [1]
Link: https://github.com/llvm/llvm-project/issues/176546 # [2]
Signed-off-by: Yao Zi <me@ziyao.cc>
Acked-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
Commit 69896119dc9d ("MIPS: vdso: Switch to generic storage
implementation") switches to a generic vdso storage, which increases
the number of data pages from 1 to 4. But there is only one page
reserved, which causes segementation faults depending where the VDSO
area is randomized to. To fix this use the same size of reservation
and allocation of the VDSO data pages.
Fixes: 69896119dc9d ("MIPS: vdso: Switch to generic storage implementation")
Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
Not all tasks have an ABI associated or vDSO mapped,
for example kthreads never do.
If such a task ever ends up calling stack_top(), it will derefence the
NULL ABI pointer and crash.
This can for example happen when using kunit:
mips_stack_top+0x28/0xc0
arch_pick_mmap_layout+0x190/0x220
kunit_vm_mmap_init+0xf8/0x138
__kunit_add_resource+0x40/0xa8
kunit_vm_mmap+0x88/0xd8
usercopy_test_init+0xb8/0x240
kunit_try_run_case+0x5c/0x1a8
kunit_generic_run_threadfn_adapter+0x28/0x50
kthread+0x118/0x240
ret_from_kernel_thread+0x14/0x1c
Only dereference the ABI point if it is set.
The GIC page is also included as it is specific to the vDSO.
Also move the randomization adjustment into the same conditional.
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: David Gow <davidgow@google.com>
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
Yao Zi