Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Tue, 4 Apr 2023 17:06:35 +0200 | Subject | Re: [PATCH] riscv: entry: Save a0 prior syscall_enter_from_user_mode() |
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On Mon, Apr 3, 2023 at 8:54 AM Björn Töpel <bjorn@kernel.org> wrote: > From: Björn Töpel <bjorn@rivosinc.com> > > 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>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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