kernel/arch/riscv/include/asm/asm.h, branch linux-rolling-stable

riscv: asm: use .insn for making custom instructions

2025-10-28T00:58:37Z

The assembler has .insn for building custom instructions now, so change the .4byte to .insn. This ensures the output is marked as an instruction and not as data which may confuse both debuggers and anything else that relies on this sort of marking. Add an ASM_INSN_I() wrapper in asm.h to allow the selecting of how this is output so older assemblers are still good. Reviewed-by: Andrew Jones Signed-off-by: Ben Dooks Link: https://lore.kernel.org/r/20251024171640.65232-1-ben.dooks@codethink.co.uk Signed-off-by: Paul Walmsley

riscv: Remove the PER_CPU_OFFSET_SHIFT macro

2025-10-18T04:00:29Z

__per_cpu_offset is an array of unsigned long, so we can reuse the existing RISCV_LGPTR macro. Signed-off-by: Samuel Holland Link: https://lore.kernel.org/r/20251015225604.3860409-1-samuel.holland@sifive.com Signed-off-by: Paul Walmsley

riscv: Replace ASSEMBLY with ASSEMBLER in non-uapi headers

2025-09-16T22:25:30Z

While the GCC and Clang compilers already define __ASSEMBLER__ automatically when compiling assembly code, __ASSEMBLY__ is a macro that only gets defined by the Makefiles in the kernel. This can be very confusing when switching between userspace and kernelspace coding, or when dealing with uapi headers that rather should use __ASSEMBLER__ instead. So let's standardize on the __ASSEMBLER__ macro that is provided by the compilers now. This originally was a completely mechanical patch (done with a simple "sed -i" statement), with some manual fixups during rebasing of the patch later. Cc: Paul Walmsley Cc: Palmer Dabbelt Cc: Albert Ou Cc: Alexandre Ghiti Cc: linux-riscv@lists.infradead.org Signed-off-by: Thomas Huth Link: https://lore.kernel.org/r/20250606070952.498274-3-thuth@redhat.com Signed-off-by: Paul Walmsley

riscv: use lw when reading int cpu in asm_per_cpu

2025-09-05T21:31:24Z

REG_L is wrong, because thread_info.cpu is 32-bit, not xlen-bit wide. The struct currently has a hole after cpu, so little endian accesses seemed fine. Fixes: be97d0db5f44 ("riscv: VMAP_STACK overflow detection thread-safe") Cc: stable@vger.kernel.org Reviewed-by: Alexandre Ghiti Signed-off-by: Radim Krčmář Link: https://lore.kernel.org/r/20250725165410.2896641-5-rkrcmar@ventanamicro.com Signed-off-by: Paul Walmsley

riscv: Add runtime constant support

2025-03-20T09:15:03Z

Implement the runtime constant infrastructure for riscv. Use this infrastructure to generate constants to be used by the d_hash() function. This is the riscv variant of commit 94a2bc0f611c ("arm64: add 'runtime constant' support") and commit e3c92e81711d ("runtime constants: add x86 architecture support"). [ alex: Remove trailing whitespace ] Signed-off-by: Charlie Jenkins Reviewed-by: Alexandre Ghiti Tested-by: Alexandre Ghiti Link: https://lore.kernel.org/r/20250319-runtime_const_riscv-v10-2-745b31a11d65@rivosinc.com Signed-off-by: Alexandre Ghiti

riscv: blacklist assembly symbols for kprobe

2024-01-24T23:59:42Z

Adding kprobes on some assembly functions (mainly exception handling) will result in crashes (either recursive trap or panic). To avoid such errors, add ASM_NOKPROBE() macro which allow adding specific symbols into the __kprobe_blacklist section and use to blacklist the following symbols that showed to be problematic: - handle_exception() - ret_from_exception() - handle_kernel_stack_overflow() Signed-off-by: Clément Léger Reviewed-by: Charlie Jenkins Link: https://lore.kernel.org/r/20231004131009.409193-1-cleger@rivosinc.com Signed-off-by: Palmer Dabbelt

riscv: Implement Shadow Call Stack

2023-10-27T21:43:08Z

Implement CONFIG_SHADOW_CALL_STACK for RISC-V. When enabled, the compiler injects instructions to all non-leaf C functions to store the return address to the shadow stack and unconditionally load it again before returning, which makes it harder to corrupt the return address through a stack overflow, for example. The active shadow call stack pointer is stored in the gp register, which makes SCS incompatible with gp relaxation. Use --no-relax-gp to ensure gp relaxation is disabled and disable global pointer loading. Add SCS pointers to struct thread_info, implement SCS initialization, and task switching Signed-off-by: Sami Tolvanen Tested-by: Nathan Chancellor Link: https://lore.kernel.org/r/20230927224757.1154247-12-samitolvanen@google.com Signed-off-by: Palmer Dabbelt

riscv: Move global pointer loading to a macro

2023-10-27T21:43:07Z

In Clang 17, -fsanitize=shadow-call-stack uses the newly declared platform register gp for storing shadow call stack pointers. As this is obviously incompatible with gp relaxation, in preparation for CONFIG_SHADOW_CALL_STACK support, move global pointer loading to a single macro, which we can cleanly disable when SCS is used instead. Link: https://reviews.llvm.org/rGaa1d2693c256 Link: https://github.com/riscv-non-isa/riscv-elf-psabi-doc/commit/a484e843e6eeb51f0cb7b8819e50da6d2444d769 Signed-off-by: Sami Tolvanen Tested-by: Nathan Chancellor Link: https://lore.kernel.org/r/20230927224757.1154247-11-samitolvanen@google.com Signed-off-by: Palmer Dabbelt

riscv: Deduplicate IRQ stack switching

2023-10-27T21:43:06Z

With CONFIG_IRQ_STACKS, we switch to a separate per-CPU IRQ stack before calling handle_riscv_irq or __do_softirq. We currently have duplicate inline assembly snippets for stack switching in both code paths. Now that we can access per-CPU variables in assembly, implement call_on_irq_stack in assembly, and use that instead of redundant inline assembly. Signed-off-by: Sami Tolvanen Tested-by: Nathan Chancellor Reviewed-by: Guo Ren Link: https://lore.kernel.org/r/20230927224757.1154247-10-samitolvanen@google.com Signed-off-by: Palmer Dabbelt

riscv: VMAP_STACK overflow detection thread-safe

2023-10-27T21:43:05Z

commit 31da94c25aea ("riscv: add VMAP_STACK overflow detection") added support for CONFIG_VMAP_STACK. If overflow is detected, CPU switches to `shadow_stack` temporarily before switching finally to per-cpu `overflow_stack`. If two CPUs/harts are racing and end up in over flowing kernel stack, one or both will end up corrupting each other state because `shadow_stack` is not per-cpu. This patch optimizes per-cpu overflow stack switch by directly picking per-cpu `overflow_stack` and gets rid of `shadow_stack`. Following are the changes in this patch - Defines an asm macro to obtain per-cpu symbols in destination register. - In entry.S, when overflow is detected, per-cpu overflow stack is located using per-cpu asm macro. Computing per-cpu symbol requires a temporary register. x31 is saved away into CSR_SCRATCH (CSR_SCRATCH is anyways zero since we're in kernel). Please see Links for additional relevant disccussion and alternative solution. Tested by `echo EXHAUST_STACK > /sys/kernel/debug/provoke-crash/DIRECT` Kernel crash log below Insufficient stack space to handle exception!/debug/provoke-crash/DIRECT Task stack: [0xff20000010a98000..0xff20000010a9c000] Overflow stack: [0xff600001f7d98370..0xff600001f7d99370] CPU: 1 PID: 205 Comm: bash Not tainted 6.1.0-rc2-00001-g328a1f96f7b9 #34 Hardware name: riscv-virtio,qemu (DT) epc : __memset+0x60/0xfc ra : recursive_loop+0x48/0xc6 [lkdtm] epc : ffffffff808de0e4 ra : ffffffff0163a752 sp : ff20000010a97e80 gp : ffffffff815c0330 tp : ff600000820ea280 t0 : ff20000010a97e88 t1 : 000000000000002e t2 : 3233206874706564 s0 : ff20000010a982b0 s1 : 0000000000000012 a0 : ff20000010a97e88 a1 : 0000000000000000 a2 : 0000000000000400 a3 : ff20000010a98288 a4 : 0000000000000000 a5 : 0000000000000000 a6 : fffffffffffe43f0 a7 : 00007fffffffffff s2 : ff20000010a97e88 s3 : ffffffff01644680 s4 : ff20000010a9be90 s5 : ff600000842ba6c0 s6 : 00aaaaaac29e42b0 s7 : 00fffffff0aa3684 s8 : 00aaaaaac2978040 s9 : 0000000000000065 s10: 00ffffff8a7cad10 s11: 00ffffff8a76a4e0 t3 : ffffffff815dbaf4 t4 : ffffffff815dbaf4 t5 : ffffffff815dbab8 t6 : ff20000010a9bb48 status: 0000000200000120 badaddr: ff20000010a97e88 cause: 000000000000000f Kernel panic - not syncing: Kernel stack overflow CPU: 1 PID: 205 Comm: bash Not tainted 6.1.0-rc2-00001-g328a1f96f7b9 #34 Hardware name: riscv-virtio,qemu (DT) Call Trace: [] dump_backtrace+0x30/0x38 [] show_stack+0x40/0x4c [] dump_stack_lvl+0x44/0x5c [] dump_stack+0x18/0x20 [] panic+0x126/0x2fe [] walk_stackframe+0x0/0xf0 [] recursive_loop+0x48/0xc6 [lkdtm] SMP: stopping secondary CPUs ---[ end Kernel panic - not syncing: Kernel stack overflow ]--- Cc: Guo Ren Cc: Jisheng Zhang Link: https://lore.kernel.org/linux-riscv/Y347B0x4VUNOd6V7@xhacker/T/#t Link: https://lore.kernel.org/lkml/20221124094845.1907443-1-debug@rivosinc.com/ Signed-off-by: Deepak Gupta Co-developed-by: Sami Tolvanen Signed-off-by: Sami Tolvanen Acked-by: Guo Ren Tested-by: Nathan Chancellor Link: https://lore.kernel.org/r/20230927224757.1154247-9-samitolvanen@google.com Signed-off-by: Palmer Dabbelt