Do not read syscall no in get_scno_on_sysexit
* syscall.c (get_scno_on_sysexit): Remove scno retrieval code, since we don't save it anyway. This is the first real logic change which should make strace faster: for example, on x64 ORIG_EAX is no longer read in each syscall exit. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
This commit is contained in:
Denys Vlasenko
parent
8cd1acd46f
commit
77a7459536
219
syscall.c
219
syscall.c
@ -1296,124 +1296,18 @@ get_scno_on_sysenter(struct tcb *tcp)
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static int
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get_scno_on_sysexit(struct tcb *tcp)
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{
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long scno = 0;
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#ifdef LINUX
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# if defined(S390) || defined(S390X)
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if (tcp->flags & TCB_WAITEXECVE) {
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/*
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* When the execve system call completes successfully, the
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* new process still has -ENOSYS (old style) or __NR_execve
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* (new style) in gpr2. We cannot recover the scno again
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* by disassembly, because the image that executed the
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* syscall is gone now. Fortunately, we don't want it. We
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* leave the flag set so that syscall_fixup can fake the
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* result.
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*/
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return 1;
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}
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if (upeek(tcp, PT_GPR2, &syscall_mode) < 0)
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return -1;
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if (syscall_mode != -ENOSYS) {
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/*
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* Since kernel version 2.5.44 the scno gets passed in gpr2.
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*/
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scno = syscall_mode;
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} else {
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/*
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* Old style of "passing" the scno via the SVC instruction.
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*/
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long opcode, offset_reg, tmp;
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void * svc_addr;
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static const int gpr_offset[16] = {
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PT_GPR0, PT_GPR1, PT_ORIGGPR2, PT_GPR3,
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PT_GPR4, PT_GPR5, PT_GPR6, PT_GPR7,
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PT_GPR8, PT_GPR9, PT_GPR10, PT_GPR11,
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PT_GPR12, PT_GPR13, PT_GPR14, PT_GPR15
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};
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if (upeek(tcp, PT_PSWADDR, &pc) < 0)
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return -1;
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errno = 0;
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opcode = ptrace(PTRACE_PEEKTEXT, tcp->pid, (char *)(pc-sizeof(long)), 0);
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if (errno) {
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perror("peektext(pc-oneword)");
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return -1;
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}
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/*
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* We have to check if the SVC got executed directly or via an
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* EXECUTE instruction. In case of EXECUTE it is necessary to do
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* instruction decoding to derive the system call number.
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* Unfortunately the opcode sizes of EXECUTE and SVC are differently,
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* so that this doesn't work if a SVC opcode is part of an EXECUTE
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* opcode. Since there is no way to find out the opcode size this
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* is the best we can do...
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*/
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if ((opcode & 0xff00) == 0x0a00) {
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/* SVC opcode */
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scno = opcode & 0xff;
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}
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else {
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/* SVC got executed by EXECUTE instruction */
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/*
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* Do instruction decoding of EXECUTE. If you really want to
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* understand this, read the Principles of Operations.
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*/
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svc_addr = (void *) (opcode & 0xfff);
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tmp = 0;
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offset_reg = (opcode & 0x000f0000) >> 16;
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if (offset_reg && (upeek(tcp, gpr_offset[offset_reg], &tmp) < 0))
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return -1;
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svc_addr += tmp;
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tmp = 0;
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offset_reg = (opcode & 0x0000f000) >> 12;
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if (offset_reg && (upeek(tcp, gpr_offset[offset_reg], &tmp) < 0))
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return -1;
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svc_addr += tmp;
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scno = ptrace(PTRACE_PEEKTEXT, tcp->pid, svc_addr, 0);
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if (errno)
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return -1;
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# if defined(S390X)
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scno >>= 48;
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# else
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scno >>= 16;
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# endif
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tmp = 0;
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offset_reg = (opcode & 0x00f00000) >> 20;
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if (offset_reg && (upeek(tcp, gpr_offset[offset_reg], &tmp) < 0))
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return -1;
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scno = (scno | tmp) & 0xff;
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}
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}
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# elif defined (POWERPC)
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if (upeek(tcp, sizeof(unsigned long)*PT_R0, &scno) < 0)
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return -1;
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# elif defined(AVR32)
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/*
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* Read complete register set in one go.
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*/
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if (ptrace(PTRACE_GETREGS, tcp->pid, NULL, ®s) < 0)
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return -1;
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# elif defined(BFIN)
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if (upeek(tcp, PT_ORIG_P0, &scno))
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return -1;
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# elif defined (I386)
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if (upeek(tcp, 4*ORIG_EAX, &scno) < 0)
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return -1;
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# elif defined (X86_64)
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if (upeek(tcp, 8*ORIG_RAX, &scno) < 0)
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return -1;
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# elif defined(IA64)
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# define IA64_PSR_IS ((long)1 << 34)
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if (upeek(tcp, PT_CR_IPSR, &psr) >= 0)
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@ -1428,71 +1322,7 @@ get_scno_on_sysexit(struct tcb *tcp)
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*/
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if (ptrace(PTRACE_GETREGS, tcp->pid, NULL, (void *)®s) == -1)
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return -1;
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/*
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* We only need to grab the syscall number on syscall entry.
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*/
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if (regs.ARM_ip == 0) {
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/*
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* Note: we only deal with only 32-bit CPUs here.
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*/
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if (regs.ARM_cpsr & 0x20) {
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/*
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* Get the Thumb-mode system call number
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*/
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scno = regs.ARM_r7;
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} else {
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/*
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* Get the ARM-mode system call number
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*/
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errno = 0;
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scno = ptrace(PTRACE_PEEKTEXT, tcp->pid, (void *)(regs.ARM_pc - 4), NULL);
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if (errno)
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return -1;
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/* FIXME: bogus check? it is already done on entering before,
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* so we never can see it here?
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*/
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if (scno == 0 && (tcp->flags & TCB_WAITEXECVE)) {
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tcp->flags &= ~TCB_WAITEXECVE;
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return 0;
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}
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/* Handle the EABI syscall convention. We do not
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bother converting structures between the two
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ABIs, but basic functionality should work even
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if strace and the traced program have different
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ABIs. */
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if (scno == 0xef000000) {
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scno = regs.ARM_r7;
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} else {
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if ((scno & 0x0ff00000) != 0x0f900000) {
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fprintf(stderr, "syscall: unknown syscall trap 0x%08lx\n",
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scno);
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return -1;
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}
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/*
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* Fixup the syscall number
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*/
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scno &= 0x000fffff;
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}
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}
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if (scno & 0x0f0000) {
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/*
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* Handle ARM specific syscall
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*/
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set_personality(1);
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scno &= 0x0000ffff;
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} else
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set_personality(0);
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fprintf(stderr, "pid %d stray syscall exit\n", tcp->pid);
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tcp->flags &= ~TCB_INSYSCALL;
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}
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# elif defined (M68K)
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if (upeek(tcp, 4*PT_ORIG_D0, &scno) < 0)
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return -1;
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# elif defined (LINUX_MIPSN32)
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unsigned long long regs[38];
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@ -1515,47 +1345,15 @@ get_scno_on_sysexit(struct tcb *tcp)
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if (ptrace(PTRACE_GETREGS, tcp->pid, (char *)®s, 0) < 0)
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return -1;
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# elif defined(HPPA)
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if (upeek(tcp, PT_GR20, &scno) < 0)
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return -1;
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# elif defined(SH)
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/*
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* In the new syscall ABI, the system call number is in R3.
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*/
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if (upeek(tcp, 4*(REG_REG0+3), &scno) < 0)
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return -1;
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if (scno < 0) {
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/* Odd as it may seem, a glibc bug has been known to cause
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glibc to issue bogus negative syscall numbers. So for
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our purposes, make strace print what it *should* have been */
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long correct_scno = (scno & 0xff);
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if (debug)
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fprintf(stderr,
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"Detected glibc bug: bogus system call"
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" number = %ld, correcting to %ld\n",
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scno,
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correct_scno);
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scno = correct_scno;
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}
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# elif defined(SH64)
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if (upeek(tcp, REG_SYSCALL, &scno) < 0)
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return -1;
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scno &= 0xFFFF;
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# elif defined(CRISV10) || defined(CRISV32)
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if (upeek(tcp, 4*PT_R9, &scno) < 0)
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return -1;
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# elif defined(TILE)
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if (upeek(tcp, PTREGS_OFFSET_REG(10), &scno) < 0)
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return -1;
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# elif defined(MICROBLAZE)
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if (upeek(tcp, 0, &scno) < 0)
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return -1;
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# endif
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#endif /* LINUX */
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#ifdef SUNOS4
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if (upeek(tcp, uoff(u_arg[7]), &scno) < 0)
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return -1;
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#elif defined(SH)
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/* new syscall ABI returns result in R0 */
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if (upeek(tcp, 4*REG_REG0, (long *)&r0) < 0)
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@ -1567,25 +1365,12 @@ get_scno_on_sysexit(struct tcb *tcp)
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#endif
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#ifdef USE_PROCFS
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# ifdef HAVE_PR_SYSCALL
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scno = tcp->status.PR_SYSCALL;
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# else
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# ifndef FREEBSD
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scno = tcp->status.PR_WHAT;
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# else
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# ifndef HAVE_PR_SYSCALL
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# ifdef FREEBSD
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if (pread(tcp->pfd_reg, ®s, sizeof(regs), 0) < 0) {
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perror("pread");
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return -1;
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}
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switch (regs.r_eax) {
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case SYS_syscall:
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case SYS___syscall:
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pread(tcp->pfd, &scno, sizeof(scno), regs.r_esp + sizeof(int));
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break;
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default:
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scno = regs.r_eax;
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break;
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}
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# endif /* FREEBSD */
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# endif /* !HAVE_PR_SYSCALL */
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#endif /* USE_PROCFS */
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