From 3986a1721e10aebe0dc2c17f262ebf067e7414df Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Mon, 20 Apr 2020 22:22:06 +0100 Subject: 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 Reviewed-by: Edgar E. Iglesias Message-id: 20200420212206.12776-5-peter.maydell@linaro.org --- linux-user/arm/cpu_loop.c | 143 +++++++++++++++++++++++++--------------------- 1 file changed, 77 insertions(+), 66 deletions(-) diff --git a/linux-user/arm/cpu_loop.c b/linux-user/arm/cpu_loop.c index df8b7b3..13629ee 100644 --- a/linux-user/arm/cpu_loop.c +++ b/linux-user/arm/cpu_loop.c @@ -299,85 +299,96 @@ void cpu_loop(CPUARMState *env) env->eabi = 1; /* system call */ if (env->thumb) { - /* FIXME - what to do if get_user() fails? */ - get_user_code_u16(insn, env->regs[15] - 2, env); - n = insn & 0xff; + /* Thumb is always EABI style with syscall number in r7 */ + n = env->regs[7]; } else { + /* + * Equivalent of kernel CONFIG_OABI_COMPAT: read the + * Arm SVC insn to extract the immediate, which is the + * syscall number in OABI. + */ /* FIXME - what to do if get_user() fails? */ get_user_code_u32(insn, env->regs[15] - 4, env); n = insn & 0xffffff; - } - - if (n == 0 || n >= ARM_SYSCALL_BASE || env->thumb) { - /* linux syscall */ - if (env->thumb || n == 0) { + if (n == 0) { + /* zero immediate: EABI, syscall number in r7 */ n = env->regs[7]; } else { - n -= ARM_SYSCALL_BASE; + /* + * This XOR matches the kernel code: an immediate + * in the valid range (0x900000 .. 0x9fffff) is + * converted into the correct EABI-style syscall + * number; invalid immediates end up as values + * > 0xfffff and are handled below as out-of-range. + */ + n ^= ARM_SYSCALL_BASE; env->eabi = 0; } - if ( n > ARM_NR_BASE) { - switch (n) { - case ARM_NR_cacheflush: - /* nop */ - break; - case ARM_NR_set_tls: - cpu_set_tls(env, env->regs[0]); - env->regs[0] = 0; - break; - case ARM_NR_breakpoint: - env->regs[15] -= env->thumb ? 2 : 4; - goto excp_debug; - case ARM_NR_get_tls: - env->regs[0] = cpu_get_tls(env); - break; - default: - if (n < 0xf0800) { - /* - * Syscalls 0xf0000..0xf07ff (or 0x9f0000.. - * 0x9f07ff in OABI numbering) are defined - * to return -ENOSYS rather than raising - * SIGILL. Note that we have already - * removed the 0x900000 prefix. - */ - qemu_log_mask(LOG_UNIMP, - "qemu: Unsupported ARM syscall: 0x%x\n", - n); - env->regs[0] = -TARGET_ENOSYS; + } + + if (n > ARM_NR_BASE) { + switch (n) { + case ARM_NR_cacheflush: + /* nop */ + break; + case ARM_NR_set_tls: + cpu_set_tls(env, env->regs[0]); + env->regs[0] = 0; + break; + case ARM_NR_breakpoint: + env->regs[15] -= env->thumb ? 2 : 4; + goto excp_debug; + case ARM_NR_get_tls: + env->regs[0] = cpu_get_tls(env); + break; + default: + if (n < 0xf0800) { + /* + * Syscalls 0xf0000..0xf07ff (or 0x9f0000.. + * 0x9f07ff in OABI numbering) are defined + * to return -ENOSYS rather than raising + * SIGILL. Note that we have already + * removed the 0x900000 prefix. + */ + qemu_log_mask(LOG_UNIMP, + "qemu: Unsupported ARM syscall: 0x%x\n", + n); + env->regs[0] = -TARGET_ENOSYS; + } else { + /* + * Otherwise SIGILL. This includes any SWI with + * immediate not originally 0x9fxxxx, because + * of the earlier XOR. + */ + info.si_signo = TARGET_SIGILL; + info.si_errno = 0; + info.si_code = TARGET_ILL_ILLTRP; + info._sifields._sigfault._addr = env->regs[15]; + if (env->thumb) { + info._sifields._sigfault._addr -= 2; } else { - /* Otherwise SIGILL */ - info.si_signo = TARGET_SIGILL; - info.si_errno = 0; - info.si_code = TARGET_ILL_ILLTRP; - info._sifields._sigfault._addr = env->regs[15]; - if (env->thumb) { - info._sifields._sigfault._addr -= 2; - } else { - info._sifields._sigfault._addr -= 4; - } - queue_signal(env, info.si_signo, - QEMU_SI_FAULT, &info); + info._sifields._sigfault._addr -= 4; } - break; - } - } else { - ret = do_syscall(env, - n, - env->regs[0], - env->regs[1], - env->regs[2], - env->regs[3], - env->regs[4], - env->regs[5], - 0, 0); - if (ret == -TARGET_ERESTARTSYS) { - env->regs[15] -= env->thumb ? 2 : 4; - } else if (ret != -TARGET_QEMU_ESIGRETURN) { - env->regs[0] = ret; + queue_signal(env, info.si_signo, + QEMU_SI_FAULT, &info); } + break; } } else { - goto error; + ret = do_syscall(env, + n, + env->regs[0], + env->regs[1], + env->regs[2], + env->regs[3], + env->regs[4], + env->regs[5], + 0, 0); + if (ret == -TARGET_ERESTARTSYS) { + env->regs[15] -= env->thumb ? 2 : 4; + } else if (ret != -TARGET_QEMU_ESIGRETURN) { + env->regs[0] = ret; + } } } break; -- cgit v1.1