kernel.git/arch/riscv/kernel/traps.c, branch linux-6.0.y

RISC-V: Align the shadow stack

2022-12-31T12:26:23Z

[ Upstream commit b003b3b77d65133a0011ae3b7b255347438c12f6 ] The standard RISC-V ABIs all require 16-byte stack alignment. We're only calling that one function on the shadow stack so I doubt it'd result in a real issue, but might as well keep this lined up. Fixes: 31da94c25aea ("riscv: add VMAP_STACK overflow detection") Reviewed-by: Jisheng Zhang Link: https://lore.kernel.org/r/20221130023515.20217-1-palmer@rivosinc.com Signed-off-by: Palmer Dabbelt Signed-off-by: Sasha Levin

riscv: fix race when vmap stack overflow

2022-12-08T10:30:20Z

[ Upstream commit 7e1864332fbc1b993659eab7974da9fe8bf8c128 ] Currently, when detecting vmap stack overflow, riscv firstly switches to the so called shadow stack, then use this shadow stack to call the get_overflow_stack() to get the overflow stack. However, there's a race here if two or more harts use the same shadow stack at the same time. To solve this race, we introduce spin_shadow_stack atomic var, which will be swap between its own address and 0 in atomic way, when the var is set, it means the shadow_stack is being used; when the var is cleared, it means the shadow_stack isn't being used. Fixes: 31da94c25aea ("riscv: add VMAP_STACK overflow detection") Signed-off-by: Jisheng Zhang Suggested-by: Guo Ren Reviewed-by: Guo Ren Link: https://lore.kernel.org/r/20221030124517.2370-1-jszhang@kernel.org [Palmer: Add AQ to the swap, and also some comments.] Signed-off-by: Palmer Dabbelt Signed-off-by: Sasha Levin

riscv: traps: add missing prototype

2022-08-18T21:42:58Z

Sparse complains: arch/riscv/kernel/traps.c:213:6: warning: symbol 'shadow_stack' was not declared. Should it be static? The variable is used in entry.S, so declare shadow_stack there alongside SHADOW_OVERFLOW_STACK_SIZE. Fixes: 31da94c25aea ("riscv: add VMAP_STACK overflow detection") Signed-off-by: Conor Dooley Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220814141237.493457-5-mail@conchuod.ie Signed-off-by: Palmer Dabbelt

RISC-V: Add fast call path of crash_kexec()

2022-07-21T23:40:03Z

Currently, almost all archs (x86, arm64, mips...) support fast call of crash_kexec() when "regs && kexec_should_crash()" is true. But RISC-V not, it can only enter crash system via panic(). However panic() doesn't pass the regs of the real accident scene to crash_kexec(), it caused we can't get accurate backtrace via gdb, $ riscv64-linux-gnu-gdb vmlinux vmcore Reading symbols from vmlinux... [New LWP 95] #0 console_unlock () at kernel/printk/printk.c:2557 2557 if (do_cond_resched) (gdb) bt #0 console_unlock () at kernel/printk/printk.c:2557 #1 0x0000000000000000 in ?? () With the patch we can get the accurate backtrace, $ riscv64-linux-gnu-gdb vmlinux vmcore Reading symbols from vmlinux... [New LWP 95] #0 0xffffffe00063a4e0 in test_thread (data=) at drivers/test_crash.c:81 81 *(int *)p = 0xdead; (gdb) (gdb) bt #0 0xffffffe00064d5c0 in test_thread (data=) at drivers/test_crash.c:81 #1 0x0000000000000000 in ?? () Test code to produce NULL address dereference in test_crash.c, void *p = NULL; *(int *)p = 0xdead; Reviewed-by: Guo Ren Tested-by: Xianting Tian Signed-off-by: Xianting Tian Link: https://lore.kernel.org/r/20220606082308.2883458-1-xianting.tian@linux.alibaba.com Signed-off-by: Palmer Dabbelt

riscv: integrate alternatives better into the main architecture

2022-05-12T04:36:31Z

Right now the alternatives need to be explicitly enabled and erratas are limited to SiFive ones. We want to use alternatives not only for patching soc erratas, but in the future also for handling different behaviour depending on the existence of future extensions. So move the core alternatives over to the kernel subdirectory and move the CONFIG_RISCV_ALTERNATIVE to be a hidden symbol which we expect relevant erratas and extensions to just select if needed. Signed-off-by: Heiko Stuebner Reviewed-by: Philipp Tomsich Link: https://lore.kernel.org/r/20220511192921.2223629-2-heiko@sntech.de Signed-off-by: Palmer Dabbelt

exit: Add and use make_task_dead.

2021-12-13T18:04:45Z

There are two big uses of do_exit. The first is it's design use to be the guts of the exit(2) system call. The second use is to terminate a task after something catastrophic has happened like a NULL pointer in kernel code. Add a function make_task_dead that is initialy exactly the same as do_exit to cover the cases where do_exit is called to handle catastrophic failure. In time this can probably be reduced to just a light wrapper around do_task_dead. For now keep it exactly the same so that there will be no behavioral differences introducing this new concept. Replace all of the uses of do_exit that use it for catastraphic task cleanup with make_task_dead to make it clear what the code is doing. As part of this rename rewind_stack_do_exit rewind_stack_and_make_dead. Signed-off-by: "Eric W. Biederman"

trap: cleanup trap_init()

2021-09-08T18:50:27Z

There are some empty trap_init() definitions in different ARCHs, Introduce a new weak trap_init() function to clean them up. Link: https://lkml.kernel.org/r/20210812123602.76356-1-wangkefeng.wang@huawei.com Signed-off-by: Kefeng Wang Acked-by: Russell King (Oracle) [arm32] Acked-by: Vineet Gupta [arc] Acked-by: Michael Ellerman [powerpc] Cc: Yoshinori Sato Cc: Ley Foon Tan Cc: Jonas Bonn Cc: Stefan Kristiansson Cc: Stafford Horne Cc: James E.J. Bottomley Cc: Helge Deller Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Paul Walmsley Cc: Jeff Dike Cc: Richard Weinberger Cc: Anton Ivanov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge tag 'riscv-for-linus-5.14-mw0' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

2021-07-09T17:36:29Z

Pull RISC-V updates from Palmer Dabbelt: "We have a handful of new features for 5.14: - Support for transparent huge pages. - Support for generic PCI resources mapping. - Support for the mem= kernel parameter. - Support for KFENCE. - A handful of fixes to avoid W+X mappings in the kernel. - Support for VMAP_STACK based overflow detection. - An optimized copy_{to,from}_user" * tag 'riscv-for-linus-5.14-mw0' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux: (37 commits) riscv: xip: Fix duplicate included asm/pgtable.h riscv: Fix PTDUMP output now BPF region moved back to module region riscv: __asm_copy_to-from_user: Optimize unaligned memory access and pipeline stall riscv: add VMAP_STACK overflow detection riscv: ptrace: add argn syntax riscv: mm: fix build errors caused by mk_pmd() riscv: Introduce structure that group all variables regarding kernel mapping riscv: Map the kernel with correct permissions the first time riscv: Introduce set_kernel_memory helper riscv: Enable KFENCE for riscv64 RISC-V: Use asm-generic for {in,out}{bwlq} riscv: add ASID-based tlbflushing methods riscv: pass the mm_struct to __sbi_tlb_flush_range riscv: Add mem kernel parameter support riscv: Simplify xip and !xip kernel address conversion macros riscv: Remove CONFIG_PHYS_RAM_BASE_FIXED riscv: Only initialize swiotlb when necessary riscv: fix typo in init.c riscv: Cleanup unused functions riscv: mm: Use better bitmap_zalloc() ...

riscv: add VMAP_STACK overflow detection

2021-07-06T19:11:38Z

This patch adds stack overflow detection to riscv, usable when CONFIG_VMAP_STACK=y. Overflow is detected in kernel exception entry(kernel/entry.S), if the kernel stack is overflow and been detected, the overflow handler is invoked on a per-cpu overflow stack. This approach preserves GPRs and the original exception information. The overflow detect is performed before any attempt is made to access the stack and the principle of stack overflow detection: kernel stacks are aligned to double their size, enabling overflow to be detected with a single bit test. For example, a 16K stack is aligned to 32K, ensuring that bit 14 of the SP must be zero. On an overflow (or underflow), this bit is flipped. Thus, overflow (of less than the size of the stack) can be detected by testing whether this bit is set. This gives us a useful error message on stack overflow, as can be trigger with the LKDTM overflow test: [ 388.053267] lkdtm: Performing direct entry EXHAUST_STACK [ 388.053663] lkdtm: Calling function with 1024 frame size to depth 32 ... [ 388.054016] lkdtm: loop 32/32 ... [ 388.054186] lkdtm: loop 31/32 ... [ 388.054491] lkdtm: loop 30/32 ... [ 388.054672] lkdtm: loop 29/32 ... [ 388.054859] lkdtm: loop 28/32 ... [ 388.055010] lkdtm: loop 27/32 ... [ 388.055163] lkdtm: loop 26/32 ... [ 388.055309] lkdtm: loop 25/32 ... [ 388.055481] lkdtm: loop 24/32 ... [ 388.055653] lkdtm: loop 23/32 ... [ 388.055837] lkdtm: loop 22/32 ... [ 388.056015] lkdtm: loop 21/32 ... [ 388.056188] lkdtm: loop 20/32 ... [ 388.058145] Insufficient stack space to handle exception! [ 388.058153] Task stack: [0xffffffd014260000..0xffffffd014264000] [ 388.058160] Overflow stack: [0xffffffe1f8d2c220..0xffffffe1f8d2d220] [ 388.058168] CPU: 0 PID: 89 Comm: bash Not tainted 5.12.0-rc8-dirty #90 [ 388.058175] Hardware name: riscv-virtio,qemu (DT) [ 388.058187] epc : number+0x32/0x2c0 [ 388.058247] ra : vsnprintf+0x2ae/0x3f0 [ 388.058255] epc : ffffffe0002d38f6 ra : ffffffe0002d814e sp : ffffffd01425ffc0 [ 388.058263] gp : ffffffe0012e4010 tp : ffffffe08014da00 t0 : ffffffd0142606e8 [ 388.058271] t1 : 0000000000000000 t2 : 0000000000000000 s0 : ffffffd014260070 [ 388.058303] s1 : ffffffd014260158 a0 : ffffffd01426015e a1 : ffffffd014260158 [ 388.058311] a2 : 0000000000000013 a3 : ffff0a01ffffff10 a4 : ffffffe000c398e0 [ 388.058319] a5 : 511b02ec65f3e300 a6 : 0000000000a1749a a7 : 0000000000000000 [ 388.058327] s2 : ffffffff000000ff s3 : 00000000ffff0a01 s4 : ffffffe0012e50a8 [ 388.058335] s5 : 0000000000ffff0a s6 : ffffffe0012e50a8 s7 : ffffffe000da1cc0 [ 388.058343] s8 : ffffffffffffffff s9 : ffffffd0142602b0 s10: ffffffd0142602a8 [ 388.058351] s11: ffffffd01426015e t3 : 00000000000f0000 t4 : ffffffffffffffff [ 388.058359] t5 : 000000000000002f t6 : ffffffd014260158 [ 388.058366] status: 0000000000000100 badaddr: ffffffd01425fff8 cause: 000000000000000f [ 388.058374] Kernel panic - not syncing: Kernel stack overflow [ 388.058381] CPU: 0 PID: 89 Comm: bash Not tainted 5.12.0-rc8-dirty #90 [ 388.058387] Hardware name: riscv-virtio,qemu (DT) [ 388.058393] Call Trace: [ 388.058400] [] walk_stackframe+0x0/0xce [ 388.058406] [] dump_backtrace+0x38/0x46 [ 388.058412] [] show_stack+0x10/0x18 [ 388.058418] [] dump_stack+0x74/0x8e [ 388.058424] [] panic+0xfc/0x2b2 [ 388.058430] [] print_trace_address+0x0/0x24 [ 388.058436] [] vsnprintf+0x2ae/0x3f0 [ 388.058956] SMP: stopping secondary CPUs Signed-off-by: Tong Tiangen Reviewed-by: Kefeng Wang Signed-off-by: Palmer Dabbelt

riscv: xip: support runtime trap patching

2021-06-10T23:16:06Z

RISCV_ERRATA_ALTERNATIVE patches text at runtime which is currently not possible when the kernel is executed from the flash in XIP mode. Since runtime patching concerns only traps at the moment, let's just have all the traps reside in RAM anyway if RISCV_ERRATA_ALTERNATIVE is set. Thus, these functions will be patch-able even when the .text section is in flash. Signed-off-by: Vitaly Wool Signed-off-by: Palmer Dabbelt