diff options
| author | Björn Töpel <bjorn@rivosinc.com> | 2023-04-03 08:52:07 +0200 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2023-04-11 08:25:29 -0700 |
| commit | 9c2598d43510eff09c658f9c0e0f921ba1871c4b (patch) | |
| tree | e1f96c7d2da401538346861fb5bb904495275891 /arch/riscv/kernel/traps.c | |
| parent | d34a6b715a23ccd9c9d0bc7a475bea59dc3e28b2 (diff) | |
riscv: entry: Save a0 prior syscall_enter_from_user_mode()
The RISC-V calling convention passes the first argument, and the
return value in the a0 register. For this reason, the a0 register
needs some extra care; When handling syscalls, the a0 register is
saved into regs->orig_a0, so a0 can be properly restored for,
e.g. interrupted syscalls.
This functionality was broken with the introduction of the generic
entry patches. Here, a0 was saved into orig_a0 after calling
syscall_enter_from_user_mode(), which can change regs->a0 for some
paths, incorrectly restoring a0.
This is resolved, by saving a0 prior doing the
syscall_enter_from_user_mode() call.
Fixes: f0bddf50586d ("riscv: entry: Convert to generic entry")
Reviewed-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Tested-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Reported-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Andy Chiu <andy.chiu@sifive.com>
Link: https://lore.kernel.org/r/20230403065207.1070974-1-bjorn@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch/riscv/kernel/traps.c')
| -rw-r--r-- | arch/riscv/kernel/traps.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index 1f4e37be7eb3..8c258b78c925 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -270,11 +270,11 @@ asmlinkage __visible __trap_section void do_trap_ecall_u(struct pt_regs *regs) if (user_mode(regs)) { ulong syscall = regs->a7; - syscall = syscall_enter_from_user_mode(regs, syscall); - regs->epc += 4; regs->orig_a0 = regs->a0; + syscall = syscall_enter_from_user_mode(regs, syscall); + if (syscall < NR_syscalls) syscall_handler(regs, syscall); else |