linux.git/arch/riscv/kernel/entry.S, branch v6.5

riscv: replace deprecated scall with ecall

2023-06-20T16:02:09+00:00

scall is a deprecated alias for ecall. ecall is used in several places,
so there is no assembler compatibility concern.

Signed-off-by: Fangrui Song 
Link: https://lore.kernel.org/r/20230423223210.126948-1-maskray@google.com
Signed-off-by: Palmer Dabbelt

riscv: Disable Vector Instructions for kernel itself

2023-06-08T14:16:39+00:00

Disable vector instructions execution for kernel mode at its entrances.
This helps find illegal uses of vector in the kernel space, which is
similar to the fpu.

Signed-off-by: Guo Ren 
Co-developed-by: Vincent Chen 
Signed-off-by: Vincent Chen 
Co-developed-by: Han-Kuan Chen 
Signed-off-by: Han-Kuan Chen 
Co-developed-by: Greentime Hu 
Signed-off-by: Greentime Hu 
Signed-off-by: Vineet Gupta 
Signed-off-by: Andy Chiu 
Reviewed-by: Conor Dooley 
Reviewed-by: Heiko Stuebner 
Tested-by: Heiko Stuebner 
Reviewed-by: Palmer Dabbelt 
Link: https://lore.kernel.org/r/20230605110724.21391-7-andy.chiu@sifive.com
Signed-off-by: Palmer Dabbelt

riscv: entry: Consolidate general regs saving/restoring

2023-03-23T15:47:03+00:00

Consolidate the saving/restoring GPs (except zero, ra, sp, gp,
tp and t0) into save_from_x6_to_x31/restore_from_x6_to_x31 macros.

No functional change intended.

Signed-off-by: Jisheng Zhang 
Reviewed-by: Guo Ren 
Reviewed-by: Björn Töpel 
Tested-by: Guo Ren 
Signed-off-by: Guo Ren 
Link: https://lore.kernel.org/r/20230222033021.983168-8-guoren@kernel.org
Signed-off-by: Palmer Dabbelt

riscv: entry: Consolidate ret_from_kernel_thread into ret_from_fork

2023-03-23T15:47:02+00:00

The ret_from_kernel_thread() behaves similarly with ret_from_fork(),
the only difference is whether call the fn(arg) or not, this can be
achieved by testing fn is NULL or not, I.E s0 is 0 or not. Many
architectures have done the same thing, it makes entry.S more clean.

Signed-off-by: Jisheng Zhang 
Reviewed-by: Björn Töpel 
Reviewed-by: Guo Ren 
Tested-by: Guo Ren 
Signed-off-by: Guo Ren 
Link: https://lore.kernel.org/r/20230222033021.983168-7-guoren@kernel.org
Signed-off-by: Palmer Dabbelt

riscv: entry: Convert to generic entry

2023-03-23T15:47:00+00:00

This patch converts riscv to use the generic entry infrastructure from
kernel/entry/*. The generic entry makes maintainers' work easier and
codes more elegant. Here are the changes:

 - More clear entry.S with handle_exception and ret_from_exception
 - Get rid of complex custom signal implementation
 - Move syscall procedure from assembly to C, which is much more
   readable.
 - Connect ret_from_fork & ret_from_kernel_thread to generic entry.
 - Wrap with irqentry_enter/exit and syscall_enter/exit_from_user_mode
 - Use the standard preemption code instead of custom

Suggested-by: Huacai Chen 
Reviewed-by: Björn Töpel 
Tested-by: Yipeng Zou 
Tested-by: Jisheng Zhang 
Signed-off-by: Guo Ren 
Signed-off-by: Guo Ren 
Cc: Ben Hutchings 
Link: https://lore.kernel.org/r/20230222033021.983168-5-guoren@kernel.org
Signed-off-by: Palmer Dabbelt

Merge patch series "RISC-V: Align the shadow stack"

2022-12-12T17:30:37+00:00

Palmer Dabbelt  says:

This contains a pair of cleanups that depend on a fix that has already
landed upstream.

* b4-shazam-merge:
  RISC-V: Add some comments about the shadow and overflow stacks
  RISC-V: Align the shadow stack
  riscv: fix race when vmap stack overflow

Link: https://lore.kernel.org/r/20221130023515.20217-1-palmer@rivosinc.com
Signed-off-by: Palmer Dabbelt

Merge patch "RISC-V: Fix unannoted hardirqs-on in return to userspace slow-path"

2022-12-08T23:31:44+00:00

I'm merging this in as a single patch to make it easier to handle the
backports.

* b4-shazam-merge:
  RISC-V: Fix unannoted hardirqs-on in return to userspace slow-path

Link: https://lore.kernel.org/r/20221111223108.1976562-1-abrestic@rivosinc.com
Signed-off-by: Palmer Dabbelt

RISC-V: Fix unannoted hardirqs-on in return to userspace slow-path

2022-12-08T23:31:41+00:00

The return to userspace path in entry.S may enable interrupts without the
corresponding lockdep annotation, producing a splat[0] when DEBUG_LOCKDEP
is enabled. Simply calling __trace_hardirqs_on() here gets a bit messy
due to the use of RA to point back to ret_from_exception, so just move
the whole slow-path loop into C. It's more readable and it lets us use
local_irq_{enable,disable}(), avoiding the need for manual annotations
altogether.

[0]:
  ------------[ cut here ]------------
  DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled())
  WARNING: CPU: 2 PID: 1 at kernel/locking/lockdep.c:5512 check_flags+0x10a/0x1e0
  Modules linked in:
  CPU: 2 PID: 1 Comm: init Not tainted 6.1.0-rc4-00160-gb56b6e2b4f31 #53
  Hardware name: riscv-virtio,qemu (DT)
  epc : check_flags+0x10a/0x1e0
  ra : check_flags+0x10a/0x1e0
  
   status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000003
  [] lock_is_held_type+0x78/0x14e
  [] __might_resched+0x26/0x22c
  [] __might_sleep+0x3c/0x66
  [] get_signal+0x9e/0xa70
  [] do_notify_resume+0x6e/0x422
  [] ret_from_exception+0x0/0x10
  irq event stamp: 44512
  hardirqs last  enabled at (44511): [] _raw_spin_unlock_irqrestore+0x54/0x62
  hardirqs last disabled at (44512): [] __trace_hardirqs_off+0xc/0x14
  softirqs last  enabled at (44472): [] __do_softirq+0x3de/0x51e
  softirqs last disabled at (44467): [] irq_exit+0xd6/0x104
  ---[ end trace 0000000000000000 ]---
  possible reason: unannotated irqs-on.

Signed-off-by: Andrew Bresticker 
Fixes: 3c4697982982 ("riscv: Enable LOCKDEP_SUPPORT & fixup TRACE_IRQFLAGS_SUPPORT")
Link: https://lore.kernel.org/r/20221111223108.1976562-1-abrestic@rivosinc.com
Signed-off-by: Palmer Dabbelt

riscv: stacktrace: Make walk_stackframe cross pt_regs frame

2022-12-06T02:13:34+00:00

The current walk_stackframe with FRAME_POINTER would stop unwinding at
ret_from_exception:
  BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1518
  in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 1, name: init
  CPU: 0 PID: 1 Comm: init Not tainted 5.10.113-00021-g15c15974895c-dirty #192
  Call Trace:
  [] walk_stackframe+0x0/0xee
  [] show_stack+0x32/0x4a
  [] dump_stack_lvl+0x72/0x8e
  [] dump_stack+0x14/0x1c
  [] ___might_sleep+0x12e/0x138
  [] __might_sleep+0x10/0x18
  [] down_read+0x22/0xa4
  [] do_page_fault+0xb0/0x2fe
  [] ret_from_exception+0x0/0xc

The optimization would help walk_stackframe cross the pt_regs frame and
get more backtrace of debug info:
  BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1518
  in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 1, name: init
  CPU: 0 PID: 1 Comm: init Not tainted 5.10.113-00021-g15c15974895c-dirty #192
  Call Trace:
  [] walk_stackframe+0x0/0xee
  [] show_stack+0x32/0x4a
  [] dump_stack_lvl+0x72/0x8e
  [] dump_stack+0x14/0x1c
  [] ___might_sleep+0x12e/0x138
  [] __might_sleep+0x10/0x18
  [] down_read+0x22/0xa4
  [] do_page_fault+0xb0/0x2fe
  [] ret_from_exception+0x0/0xc
  [] riscv_intc_irq+0x1a/0x72
  [] ret_from_exception+0x0/0xc
  [] vma_link+0x54/0x160
  [] mmap_region+0x2cc/0x4d0
  [] do_mmap+0x2d8/0x3ac
  [] vm_mmap_pgoff+0x70/0xb8
  [] vm_mmap+0x2a/0x36
  [] elf_map+0x72/0x84
  [] load_elf_binary+0x69a/0xec8
  [] bprm_execve+0x246/0x53a
  [] kernel_execve+0xe8/0x124
  [] run_init_process+0xfa/0x10c
  [] try_to_run_init_process+0x12/0x3c
  [] kernel_init+0xb4/0xf8
  [] ret_from_exception+0x0/0xc

Here is the error injection test code for the above output:
 drivers/irqchip/irq-riscv-intc.c:
 static asmlinkage void riscv_intc_irq(struct pt_regs *regs)
 {
        unsigned long cause = regs->cause & ~CAUSE_IRQ_FLAG;
+       u32 tmp; __get_user(tmp, (u32 *)0);

Signed-off-by: Guo Ren 
Signed-off-by: Guo Ren 
Link: https://lore.kernel.org/r/20221109064937.3643993-3-guoren@kernel.org
[Palmer: use SYM_CODE_*]
Signed-off-by: Palmer Dabbelt

riscv: fix race when vmap stack overflow

2022-11-30T02:16:55+00:00

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