kernel.git/arch/riscv/kernel/traps.c, branch linux-6.19.y

riscv: Sanitize syscall table indexing under speculation

2025-12-31T02:57:55Z

The syscall number is a user-controlled value used to index into the syscall table. Use array_index_nospec() to clamp this value after the bounds check to prevent speculative out-of-bounds access and subsequent data leakage via cache side channels. Signed-off-by: Lukas Gerlach Link: https://patch.msgid.link/20251218191332.35849-3-lukas.gerlach@cispa.de Signed-off-by: Paul Walmsley

riscv: Enable interrupt during exception handling

2025-07-16T16:05:26Z

force_sig_fault() takes a spinlock, which is a sleeping lock with CONFIG_PREEMPT_RT=y. However, exception handling calls force_sig_fault() with interrupt disabled, causing a sleeping in atomic context warning. This can be reproduced using userspace programs such as: int main() { asm ("ebreak"); } or int main() { asm ("unimp"); } There is no reason that interrupt must be disabled while handling exceptions from userspace. Enable interrupt while handling user exceptions. This also has the added benefit of avoiding unnecessary delays in interrupt handling. Fixes: f0bddf50586d ("riscv: entry: Convert to generic entry") Suggested-by: Sebastian Andrzej Siewior Signed-off-by: Nam Cao Reviewed-by: Alexandre Ghiti Link: https://lore.kernel.org/r/20250625085630.3649485-1-namcao@linutronix.de Signed-off-by: Palmer Dabbelt

riscv: misaligned: enable IRQs while handling misaligned accesses

2025-05-08T12:00:36Z

We can safely reenable IRQs if coming from userspace. This allows to access user memory that could potentially trigger a page fault. Fixes: b686ecdeacf6 ("riscv: misaligned: Restrict user access to kernel memory") Signed-off-by: Clément Léger Reviewed-by: Alexandre Ghiti Link: https://lore.kernel.org/r/20250422162324.956065-3-cleger@rivosinc.com Signed-off-by: Alexandre Ghiti

riscv: misaligned: factorize trap handling

2025-05-08T12:00:13Z

Since both load/store and user/kernel should use almost the same path and that we are going to add some code around that, factorize it. Signed-off-by: Clément Léger Reviewed-by: Alexandre Ghiti Link: https://lore.kernel.org/r/20250422162324.956065-2-cleger@rivosinc.com Signed-off-by: Alexandre Ghiti

riscv: Fix sleeping in invalid context in die()

2025-01-08T18:23:17Z

die() can be called in exception handler, and therefore cannot sleep. However, die() takes spinlock_t which can sleep with PREEMPT_RT enabled. That causes the following warning: BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 285, name: mutex preempt_count: 110001, expected: 0 RCU nest depth: 0, expected: 0 CPU: 0 UID: 0 PID: 285 Comm: mutex Not tainted 6.12.0-rc7-00022-ge19049cf7d56-dirty #234 Hardware name: riscv-virtio,qemu (DT) Call Trace: dump_backtrace+0x1c/0x24 show_stack+0x2c/0x38 dump_stack_lvl+0x5a/0x72 dump_stack+0x14/0x1c __might_resched+0x130/0x13a rt_spin_lock+0x2a/0x5c die+0x24/0x112 do_trap_insn_illegal+0xa0/0xea _new_vmalloc_restore_context_a0+0xcc/0xd8 Oops - illegal instruction [#1] Switch to use raw_spinlock_t, which does not sleep even with PREEMPT_RT enabled. Fixes: 76d2a0493a17 ("RISC-V: Init and Halt Code") Signed-off-by: Nam Cao Cc: stable@vger.kernel.org Reviewed-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20241118091333.1185288-1-namcao@linutronix.de Signed-off-by: Palmer Dabbelt

riscv: entry: always initialize regs->a0 to -ENOSYS

2024-08-14T20:12:22Z

Otherwise when the tracer changes syscall number to -1, the kernel fails to initialize a0 with -ENOSYS and subsequently fails to return the error code of the failed syscall to userspace. For example, it will break strace syscall tampering. Fixes: 52449c17bdd1 ("riscv: entry: set a0 = -ENOSYS only when syscall != -1") Reported-by: "Dmitry V. Levin" Reviewed-by: Björn Töpel Cc: stable@vger.kernel.org Signed-off-by: Celeste Liu Link: https://lore.kernel.org/r/20240627142338.5114-2-CoelacanthusHex@gmail.com Signed-off-by: Palmer Dabbelt

riscv: use KERN_INFO in do_trap

2024-04-04T19:12:14Z

Print the instruction dump with info instead of emergency level. The unhandled signal message is only for informational purpose. Fixes: b8a03a634129 ("riscv: add userland instruction dump to RISC-V splats") Signed-off-by: Andreas Schwab Reviewed-by: Conor Dooley Reviewed-by: Atish Patra Reviewed-by: Yunhui Cui Link: https://lore.kernel.org/r/mvmy1aegrhm.fsf@suse.de Signed-off-by: Palmer Dabbelt

riscv: Support RANDOMIZE_KSTACK_OFFSET

2024-01-25T01:24:24Z

Inspired from arm64's implement -- commit 70918779aec9 ("arm64: entry: Enable random_kstack_offset support") Add support of kernel stack offset randomization while handling syscall, the offset is defaultly limited by KSTACK_OFFSET_MAX() (i.e. 10 bits). In order to avoid trigger stack canaries (due to __builtin_alloca) and slowing down the entry path, use __no_stack_protector attribute to disable stack protector for do_trap_ecall_u() at the function level. Acked-by: Palmer Dabbelt Reviewed-by: Kees Cook Signed-off-by: Song Shuai Link: https://lore.kernel.org/r/20231109133751.212079-1-songshuaishuai@tinylab.org Signed-off-by: Palmer Dabbelt

Merge patch "drivers: perf: Do not broadcast to other cpus when starting a counter"

2023-11-09T14:44:13Z

This is really just a single patch, but since the offending fix hasn't yet made it to my for-next I'm merging it here. Signed-off-by: Palmer Dabbelt

riscv: add userland instruction dump to RISC-V splats

2023-11-05T22:14:13Z

Add userland instruction dump and rename dump_kernel_instr() to dump_instr(). An example: [ 0.822439] Freeing unused kernel image (initmem) memory: 6916K [ 0.823817] Run /init as init process [ 0.839411] init[1]: unhandled signal 4 code 0x1 at 0x000000000005be18 in bb[10000+5fb000] [ 0.840751] CPU: 0 PID: 1 Comm: init Not tainted 5.14.0-rc4-00049-gbd644290aa72-dirty #187 [ 0.841373] Hardware name: , BIOS [ 0.841743] epc : 000000000005be18 ra : 0000000000079e74 sp : 0000003fffcafda0 [ 0.842271] gp : ffffffff816e9dc8 tp : 0000000000000000 t0 : 0000000000000000 [ 0.842947] t1 : 0000003fffc9fdf0 t2 : 0000000000000000 s0 : 0000000000000000 [ 0.843434] s1 : 0000000000000000 a0 : 0000003fffca0190 a1 : 0000003fffcafe18 [ 0.843891] a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000 [ 0.844357] a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000000000000 [ 0.844803] s2 : 0000000000000000 s3 : 0000000000000000 s4 : 0000000000000000 [ 0.845253] s5 : 0000000000000000 s6 : 0000000000000000 s7 : 0000000000000000 [ 0.845722] s8 : 0000000000000000 s9 : 0000000000000000 s10: 0000000000000000 [ 0.846180] s11: 0000000000d144e0 t3 : 0000000000000000 t4 : 0000000000000000 [ 0.846616] t5 : 0000000000000000 t6 : 0000000000000000 [ 0.847204] status: 0000000200000020 badaddr: 00000000f0028053 cause: 0000000000000002 [ 0.848219] Code: f06f ff5f 3823 fa11 0113 fb01 2e23 0201 0293 0000 (8053) f002 [ 0.851016] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004 Signed-off-by: Yunhui Cui Reviewed-by: Björn Töpel Link: https://lore.kernel.org/r/20230912021349.28302-1-cuiyunhui@bytedance.com Signed-off-by: Palmer Dabbelt