linux-user/arm: Fix identification of syscall numbers
Our code to identify syscall numbers has some issues: * for Thumb mode, we never need the immediate value from the insn, but we always read it anyway * bad immediate values in the svc insn should cause a SIGILL, but we were abort()ing instead (via "goto error") We can fix both these things by refactoring the code that identifies the syscall number to more closely follow the kernel COMPAT_OABI code: * for Thumb it is always r7 * for Arm, if the immediate value is 0, then this is an EABI call with the syscall number in r7 * otherwise, we XOR the immediate value with 0x900000 (ARM_SYSCALL_BASE for QEMU; __NR_OABI_SYSCALL_BASE in the kernel), which converts valid syscall immediates into the desired value, and puts all invalid immediates in the range 0x100000 or above * then we can just let the existing "value too large, deliver SIGILL" case handle invalid numbers, and drop the 'goto error' Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com> Message-id: 20200420212206.12776-5-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell
parent
ab546bd238
commit
3986a1721e
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@ -299,85 +299,96 @@ void cpu_loop(CPUARMState *env)
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env->eabi = 1;
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/* system call */
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if (env->thumb) {
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/* FIXME - what to do if get_user() fails? */
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get_user_code_u16(insn, env->regs[15] - 2, env);
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n = insn & 0xff;
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/* Thumb is always EABI style with syscall number in r7 */
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n = env->regs[7];
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} else {
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/*
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* Equivalent of kernel CONFIG_OABI_COMPAT: read the
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* Arm SVC insn to extract the immediate, which is the
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* syscall number in OABI.
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*/
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/* FIXME - what to do if get_user() fails? */
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get_user_code_u32(insn, env->regs[15] - 4, env);
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n = insn & 0xffffff;
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}
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if (n == 0 || n >= ARM_SYSCALL_BASE || env->thumb) {
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/* linux syscall */
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if (env->thumb || n == 0) {
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if (n == 0) {
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/* zero immediate: EABI, syscall number in r7 */
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n = env->regs[7];
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} else {
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n -= ARM_SYSCALL_BASE;
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/*
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* This XOR matches the kernel code: an immediate
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* in the valid range (0x900000 .. 0x9fffff) is
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* converted into the correct EABI-style syscall
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* number; invalid immediates end up as values
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* > 0xfffff and are handled below as out-of-range.
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*/
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n ^= ARM_SYSCALL_BASE;
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env->eabi = 0;
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}
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if ( n > ARM_NR_BASE) {
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switch (n) {
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case ARM_NR_cacheflush:
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/* nop */
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break;
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case ARM_NR_set_tls:
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cpu_set_tls(env, env->regs[0]);
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env->regs[0] = 0;
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break;
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case ARM_NR_breakpoint:
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env->regs[15] -= env->thumb ? 2 : 4;
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goto excp_debug;
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case ARM_NR_get_tls:
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env->regs[0] = cpu_get_tls(env);
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break;
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default:
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if (n < 0xf0800) {
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/*
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* Syscalls 0xf0000..0xf07ff (or 0x9f0000..
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* 0x9f07ff in OABI numbering) are defined
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* to return -ENOSYS rather than raising
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* SIGILL. Note that we have already
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* removed the 0x900000 prefix.
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*/
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qemu_log_mask(LOG_UNIMP,
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"qemu: Unsupported ARM syscall: 0x%x\n",
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n);
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env->regs[0] = -TARGET_ENOSYS;
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}
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if (n > ARM_NR_BASE) {
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switch (n) {
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case ARM_NR_cacheflush:
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/* nop */
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break;
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case ARM_NR_set_tls:
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cpu_set_tls(env, env->regs[0]);
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env->regs[0] = 0;
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break;
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case ARM_NR_breakpoint:
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env->regs[15] -= env->thumb ? 2 : 4;
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goto excp_debug;
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case ARM_NR_get_tls:
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env->regs[0] = cpu_get_tls(env);
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break;
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default:
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if (n < 0xf0800) {
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/*
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* Syscalls 0xf0000..0xf07ff (or 0x9f0000..
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* 0x9f07ff in OABI numbering) are defined
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* to return -ENOSYS rather than raising
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* SIGILL. Note that we have already
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* removed the 0x900000 prefix.
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*/
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qemu_log_mask(LOG_UNIMP,
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"qemu: Unsupported ARM syscall: 0x%x\n",
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n);
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env->regs[0] = -TARGET_ENOSYS;
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} else {
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/*
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* Otherwise SIGILL. This includes any SWI with
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* immediate not originally 0x9fxxxx, because
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* of the earlier XOR.
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*/
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info.si_signo = TARGET_SIGILL;
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info.si_errno = 0;
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info.si_code = TARGET_ILL_ILLTRP;
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info._sifields._sigfault._addr = env->regs[15];
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if (env->thumb) {
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info._sifields._sigfault._addr -= 2;
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} else {
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/* Otherwise SIGILL */
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info.si_signo = TARGET_SIGILL;
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info.si_errno = 0;
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info.si_code = TARGET_ILL_ILLTRP;
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info._sifields._sigfault._addr = env->regs[15];
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if (env->thumb) {
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info._sifields._sigfault._addr -= 2;
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} else {
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info._sifields._sigfault._addr -= 4;
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}
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queue_signal(env, info.si_signo,
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QEMU_SI_FAULT, &info);
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info._sifields._sigfault._addr -= 4;
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}
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break;
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}
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} else {
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ret = do_syscall(env,
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n,
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env->regs[0],
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env->regs[1],
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env->regs[2],
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env->regs[3],
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env->regs[4],
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env->regs[5],
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0, 0);
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if (ret == -TARGET_ERESTARTSYS) {
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env->regs[15] -= env->thumb ? 2 : 4;
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} else if (ret != -TARGET_QEMU_ESIGRETURN) {
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env->regs[0] = ret;
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queue_signal(env, info.si_signo,
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QEMU_SI_FAULT, &info);
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}
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break;
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}
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} else {
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goto error;
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ret = do_syscall(env,
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n,
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env->regs[0],
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env->regs[1],
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env->regs[2],
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env->regs[3],
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env->regs[4],
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env->regs[5],
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0, 0);
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if (ret == -TARGET_ERESTARTSYS) {
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env->regs[15] -= env->thumb ? 2 : 4;
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} else if (ret != -TARGET_QEMU_ESIGRETURN) {
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env->regs[0] = ret;
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}
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}
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}
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break;
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