diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index dbe3b00d1eb7..c0ebe6fade63 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -60,6 +60,14 @@ #define COMPAT_PT_TEXT_ADDR 0x10000 #define COMPAT_PT_DATA_ADDR 0x10004 #define COMPAT_PT_TEXT_END_ADDR 0x10008 + +/* + * used to skip a system call when tracer changes its number to -1 + * with ptrace(PTRACE_SET_SYSCALL) + */ +#define RET_SKIP_SYSCALL -1 +#define IS_SKIP_SYSCALL(no) ((int)(no & 0xffffffff) == -1) + #ifndef __ASSEMBLY__ /* sizeof(struct user) for AArch32 */ diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 3c93e1a9ea8d..a30fab9ea2a3 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -25,6 +25,7 @@ #include #include #include +#include #include #include @@ -662,6 +663,8 @@ __sys_trace: mov x0, sp bl syscall_trace_enter adr lr, __sys_trace_return // return address + cmp w0, #RET_SKIP_SYSCALL // skip syscall? + b.eq __sys_trace_return_skipped uxtw scno, w0 // syscall number (possibly new) mov x1, sp // pointer to regs cmp scno, sc_nr // check upper syscall limit @@ -675,6 +678,7 @@ __sys_trace: __sys_trace_return: str x0, [sp] // save returned x0 +__sys_trace_return_skipped: // x0 already in regs[0] mov x0, sp bl syscall_trace_exit b ret_to_user diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index 56a62ebf2baf..2a6edfb0079b 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -1108,9 +1108,29 @@ static void tracehook_report_syscall(struct pt_regs *regs, asmlinkage int syscall_trace_enter(struct pt_regs *regs) { + unsigned int saved_syscallno = regs->syscallno; + if (test_thread_flag(TIF_SYSCALL_TRACE)) tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER); + if (IS_SKIP_SYSCALL(regs->syscallno)) { + /* + * RESTRICTION: we can't modify a return value of user + * issued syscall(-1) here. In order to ease this flavor, + * we need to treat whatever value in x0 as a return value, + * but this might result in a bogus value being returned. + */ + /* + * NOTE: syscallno may also be set to -1 if fatal signal is + * detected in tracehook_report_syscall_entry(), but since + * a value set to x0 here is not used in this case, we may + * neglect the case. + */ + if (!test_thread_flag(TIF_SYSCALL_TRACE) || + (IS_SKIP_SYSCALL(saved_syscallno))) + regs->regs[0] = -ENOSYS; + } + audit_syscall_entry(syscall_get_arch(), regs->syscallno, regs->orig_x0, regs->regs[1], regs->regs[2], regs->regs[3]);