Hi. Le mercredi 8 juin 2022, 18:24:45 CEST Francis Laniel a écrit : > Hi. > > > First, I hope you are fine and the same for your relatives. > > With this contribution, I enabled using syscalls:sys_exit_execve and > syscalls:sys_exit_execveat as tracepoints on arm64. > Indeed, before this contribution, the above tracepoint would not print their > information as syscall number was set to -1 by calling forget_syscall(). > > I tested it by compiling a kernel for arm64 and running it within a VM: > # Perf was compiled with linux kernel source. > root@vm-arm64:~# perf record -ag -e 'syscalls:sys_exit_execve' -e > 'syscalls:sys_enter_execve' & [1] 263 > root@vm-arm64:~# ls > perf.data share > root@vm-arm64:~# fg > perf record -ag -e 'syscalls:sys_exit_execve' -e 'syscalls:sys_enter_execve' > ^C[ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0.061 MB perf.data (2 samples) ] > root@vm-arm64:~# perf script > bash 264 [000] 66.220187: syscalls:sys_enter_execve: filename: > 0xaaab05d9d ... > # Below line does not appear without this patch. > ls 264 [000] 66.226848: syscalls:sys_exit_execve: 0x0 > ... > > Forgetting the syscall number before starting a new thread was confirmed to > be a bug [1]. > Particularly, the following architectures do not forget the syscall number > before starting a new thread: > * arm (32 bits) EABI: start_thread() sets r7 to previous r7 for ELF FDPIC > and to 0 for other binfmts [2]. > * arm (32 bits) OABI: syscall number is set to -1 if > ptrace_report_syscall_entry() failed [3]. > * mips: start_thread() does not modify current_thread_info->syscall which is > taken directly from v0 [4, 5]. > * riscv: start_thread() does not modify a7 [6]. > * x86_64: start_thread_common() does not touch orig_ax which seems to > contain the syscall number [7]. > > If you see any way to improve this contribution, feel free to share! > > Change since: > v1: > * Remove call to forget_syscall() and store previous syscall number in > regs->syscallno unconditionnaly. > > Francis Laniel (1): > arm64: Do not forget syscall when starting a new thread. > > arch/arm64/include/asm/processor.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > > Best regards and thank you in advance. > --- > [1] https://lore.kernel.org/linux-arm-kernel/YoT1iLPEbteRTQGZ@xxxxxxx/ > [2] https://elixir.bootlin.com/linux/v5.18-rc6/source/arch/arm/include/asm/ > processor.h#L52 > [3] https://elixir.bootlin.com/linux/v5.18-rc6/source/arch/arm/kernel/ > ptrace.c#L847 > [4] https://elixir.bootlin.com/linux/v5.18-rc6/source/arch/mips/kernel/ > process.c#L52 > [5] https://elixir.bootlin.com/linux/v5.18-rc6/source/arch/mips/kernel/ > scall64-n64.S#L85 > [6] https://elixir.bootlin.com/linux/v5.18-rc6/source/arch/riscv/kernel/ > process.c#L87 > [7] https://elixir.bootlin.com/linux/v5.18-rc6/source/arch/x86/kernel/ > process_64.c#L505 Can someone please take a quick look at this patch? Best regards and thank you in advance.
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