From 1da185fc8288fadb952e06881d0b75e924780103 Mon Sep 17 00:00:00 2001 From: Guo Hui Date: Fri, 26 May 2023 10:47:15 +0800 Subject: arm64: syscall: unmask DAIF for tracing status The following code: static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr, const syscall_fn_t syscall_table[]) { ... if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) { local_daif_mask(); flags = read_thread_flags(); -------------------------------- A if (!has_syscall_work(flags) && !(flags & _TIF_SINGLESTEP)) return; local_daif_restore(DAIF_PROCCTX); } trace_exit: syscall_trace_exit(regs); ------- B } 1. The flags in the if conditional statement should be used in the same way as the flags in the function syscall_trace_exit, because DAIF is not shielded in the function syscall_trace_exit, so when the flags are obtained in line A of the code, there is no need to shield DAIF. Don't care about the modification of flags after line A. 2. Masking DAIF caused syscall performance to deteriorate by about 10%. The Unixbench single core syscall performance data is as follows: Machine: Kunpeng 920 Mask DAIF: System Call Overhead 1172314.1 lps (10.0 s, 7 samples) System Benchmarks Partial Index BASELINE RESULT INDEX System Call Overhead 15000.0 1172314.1 781.5 ======== System Benchmarks Index Score (Partial Only) 781.5 Unmask DAIF: System Call Overhead 1287944.6 lps (10.0 s, 7 samples) System Benchmarks Partial Index BASELINE RESULT INDEX System Call Overhead 15000.0 1287944.6 858.6 ======== System Benchmarks Index Score (Partial Only) 858.6 Rationale from Mark Rutland as for why this is safe: This masking is an artifact of the old "ret_fast_syscall" assembly that was converted to C in commit: f37099b6992a0b81 ("arm64: convert syscall trace logic to C") The assembly would mask DAIF, check the thread flags, and fall through to kernel_exit without unmasking if no tracing was needed. The conversion copied this masking into the C version, though this wasn't strictly necessary. As (in general) thread flags can be manipulated by other threads, it's not safe to manipulate the thread flags with plain reads and writes, and since commit: 342b3808786518ce ("arm64: Snapshot thread flags") ... we use read_thread_flags() to read the flags atomically. With this, there is no need to mask DAIF transiently around reading the flags, as we only decide whether to trace while DAIF is masked, and the actual tracing occurs with DAIF unmasked. When el0_svc_common() returns its caller will unconditionally mask DAIF via exit_to_user_mode(), so the masking is redundant. Signed-off-by: Guo Hui Reviewed-by: Mark Rutland Link: https://lore.kernel.org/r/20230526024715.8773-1-guohui@uniontech.com [catalin.marinas@arm.com: updated comment with Mark's rationale] Signed-off-by: Catalin Marinas --- arch/arm64/kernel/syscall.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'arch/arm64/kernel/syscall.c') diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c index da84cf855c44..5a668d7f3c1f 100644 --- a/arch/arm64/kernel/syscall.c +++ b/arch/arm64/kernel/syscall.c @@ -147,11 +147,9 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr, * exit regardless, as the old entry assembly did. */ if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) { - local_daif_mask(); flags = read_thread_flags(); if (!has_syscall_work(flags) && !(flags & _TIF_SINGLESTEP)) return; - local_daif_restore(DAIF_PROCCTX); } trace_exit: -- cgit v1.2.3 From 7d8b31b73c79835572611ed1eed649e4d2e14245 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Wed, 17 May 2023 14:51:48 +0200 Subject: tracing: arm64: Avoid missing-prototype warnings These are all tracing W=1 warnings in arm64 allmodconfig about missing prototypes: kernel/trace/trace_kprobe_selftest.c:7:5: error: no previous prototype for 'kprobe_trace_selftest_target' [-Werror=missing-pro totypes] kernel/trace/ftrace.c:329:5: error: no previous prototype for '__register_ftrace_function' [-Werror=missing-prototypes] kernel/trace/ftrace.c:372:5: error: no previous prototype for '__unregister_ftrace_function' [-Werror=missing-prototypes] kernel/trace/ftrace.c:4130:15: error: no previous prototype for 'arch_ftrace_match_adjust' [-Werror=missing-prototypes] kernel/trace/fgraph.c:243:15: error: no previous prototype for 'ftrace_return_to_handler' [-Werror=missing-prototypes] kernel/trace/fgraph.c:358:6: error: no previous prototype for 'ftrace_graph_sleep_time_control' [-Werror=missing-prototypes] arch/arm64/kernel/ftrace.c:460:6: error: no previous prototype for 'prepare_ftrace_return' [-Werror=missing-prototypes] arch/arm64/kernel/ptrace.c:2172:5: error: no previous prototype for 'syscall_trace_enter' [-Werror=missing-prototypes] arch/arm64/kernel/ptrace.c:2195:6: error: no previous prototype for 'syscall_trace_exit' [-Werror=missing-prototypes] Move the declarations to an appropriate header where they can be seen by the caller and callee, and make sure the headers are included where needed. Link: https://lore.kernel.org/linux-trace-kernel/20230517125215.930689-1-arnd@kernel.org Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Will Deacon Cc: Kees Cook Cc: Florent Revest Signed-off-by: Arnd Bergmann Acked-by: Catalin Marinas [ Fixed ftrace_return_to_handler() to handle CONFIG_HAVE_FUNCTION_GRAPH_RETVAL case ] Signed-off-by: Steven Rostedt (Google) --- arch/arm64/include/asm/ftrace.h | 4 ++++ arch/arm64/include/asm/syscall.h | 3 +++ arch/arm64/kernel/syscall.c | 3 --- include/linux/ftrace.h | 9 +++++++++ kernel/trace/fgraph.c | 1 + kernel/trace/ftrace_internal.h | 5 +++-- kernel/trace/trace_kprobe_selftest.c | 3 +++ 7 files changed, 23 insertions(+), 5 deletions(-) (limited to 'arch/arm64/kernel/syscall.c') diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h index 21ac1c5c71d3..ab158196480c 100644 --- a/arch/arm64/include/asm/ftrace.h +++ b/arch/arm64/include/asm/ftrace.h @@ -211,6 +211,10 @@ static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs { return ret_regs->fp; } + +void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent, + unsigned long frame_pointer); + #endif /* ifdef CONFIG_FUNCTION_GRAPH_TRACER */ #endif diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h index 4cfe9b49709b..ab8e14b96f68 100644 --- a/arch/arm64/include/asm/syscall.h +++ b/arch/arm64/include/asm/syscall.h @@ -85,4 +85,7 @@ static inline int syscall_get_arch(struct task_struct *task) return AUDIT_ARCH_AARCH64; } +int syscall_trace_enter(struct pt_regs *regs); +void syscall_trace_exit(struct pt_regs *regs); + #endif /* __ASM_SYSCALL_H */ diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c index 5a668d7f3c1f..b1ae2f2eaf77 100644 --- a/arch/arm64/kernel/syscall.c +++ b/arch/arm64/kernel/syscall.c @@ -75,9 +75,6 @@ static inline bool has_syscall_work(unsigned long flags) return unlikely(flags & _TIF_SYSCALL_WORK); } -int syscall_trace_enter(struct pt_regs *regs); -void syscall_trace_exit(struct pt_regs *regs); - static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr, const syscall_fn_t syscall_table[]) { diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 8e59bd954153..ce156c7704ee 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -41,6 +41,15 @@ struct ftrace_ops; struct ftrace_regs; struct dyn_ftrace; +char *arch_ftrace_match_adjust(char *str, const char *search); + +#ifdef CONFIG_HAVE_FUNCTION_GRAPH_RETVAL +struct fgraph_ret_regs; +unsigned long ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs); +#else +unsigned long ftrace_return_to_handler(unsigned long frame_pointer); +#endif + #ifdef CONFIG_FUNCTION_TRACER /* * If the arch's mcount caller does not support all of ftrace's diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c index cd2c35b1dd8f..c83c005e654e 100644 --- a/kernel/trace/fgraph.c +++ b/kernel/trace/fgraph.c @@ -15,6 +15,7 @@ #include #include "ftrace_internal.h" +#include "trace.h" #ifdef CONFIG_DYNAMIC_FTRACE #define ASSIGN_OPS_HASH(opsname, val) \ diff --git a/kernel/trace/ftrace_internal.h b/kernel/trace/ftrace_internal.h index 382775edf690..5012c04f92c0 100644 --- a/kernel/trace/ftrace_internal.h +++ b/kernel/trace/ftrace_internal.h @@ -2,6 +2,9 @@ #ifndef _LINUX_KERNEL_FTRACE_INTERNAL_H #define _LINUX_KERNEL_FTRACE_INTERNAL_H +int __register_ftrace_function(struct ftrace_ops *ops); +int __unregister_ftrace_function(struct ftrace_ops *ops); + #ifdef CONFIG_FUNCTION_TRACER extern struct mutex ftrace_lock; @@ -15,8 +18,6 @@ int ftrace_ops_test(struct ftrace_ops *ops, unsigned long ip, void *regs); #else /* !CONFIG_DYNAMIC_FTRACE */ -int __register_ftrace_function(struct ftrace_ops *ops); -int __unregister_ftrace_function(struct ftrace_ops *ops); /* Keep as macros so we do not need to define the commands */ # define ftrace_startup(ops, command) \ ({ \ diff --git a/kernel/trace/trace_kprobe_selftest.c b/kernel/trace/trace_kprobe_selftest.c index 16548ee4c8c6..3851cd1e6a62 100644 --- a/kernel/trace/trace_kprobe_selftest.c +++ b/kernel/trace/trace_kprobe_selftest.c @@ -1,4 +1,7 @@ // SPDX-License-Identifier: GPL-2.0 + +#include "trace_kprobe_selftest.h" + /* * Function used during the kprobe self test. This function is in a separate * compile unit so it can be compile with CC_FLAGS_FTRACE to ensure that it -- cgit v1.2.3