From 9c2598d43510eff09c658f9c0e0f921ba1871c4b Mon Sep 17 00:00:00 2001 From: Björn Töpel Date: Mon, 3 Apr 2023 08:52:07 +0200 Subject: riscv: entry: Save a0 prior syscall_enter_from_user_mode() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Tested-by: Heiko Stuebner Signed-off-by: Björn Töpel Reported-by: Conor Dooley Reviewed-by: Conor Dooley Tested-by: Conor Dooley Tested-by: Geert Uytterhoeven Tested-by: Andy Chiu Link: https://lore.kernel.org/r/20230403065207.1070974-1-bjorn@kernel.org Signed-off-by: Palmer Dabbelt --- arch/riscv/kernel/traps.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'arch') 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 -- cgit