From f386be577c6c62fdf0d70415a9601467644c0615 Mon Sep 17 00:00:00 2001 From: Chris Metcalf Date: Fri, 9 Aug 2013 15:42:56 -0400 Subject: [PATCH] tile: correct r1 value during syscall tracing The r1 value is set based on the r0 value as we return to user space. So tracing tools won't automatically see the right value. Fix this by generating the correct r1 value in do_syscall_trace_exit() rather than trying to tamper with the hot path in syscall return. Signed-off-by: Chris Metcalf --- arch/tile/kernel/ptrace.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/arch/tile/kernel/ptrace.c b/arch/tile/kernel/ptrace.c index bac187498d61a..de98c6ddf136d 100644 --- a/arch/tile/kernel/ptrace.c +++ b/arch/tile/kernel/ptrace.c @@ -265,6 +265,21 @@ int do_syscall_trace_enter(struct pt_regs *regs) void do_syscall_trace_exit(struct pt_regs *regs) { + long errno; + + /* + * The standard tile calling convention returns the value (or negative + * errno) in r0, and zero (or positive errno) in r1. + * It saves a couple of cycles on the hot path to do this work in + * registers only as we return, rather than updating the in-memory + * struct ptregs. + */ + errno = (long) regs->regs[0]; + if (errno < 0 && errno > -4096) + regs->regs[1] = -errno; + else + regs->regs[1] = 0; + if (test_thread_flag(TIF_SYSCALL_TRACE)) tracehook_report_syscall_exit(regs, 0); -- 2.39.5