| Message ID | CADUS3o=F4diU-xG8DsE6c+Zm6juQetJ0kmMtKNdz8pOXBRxq=A@mail.gmail.com (mailing list archive) |
|---|---|
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On Mon, Oct 19, 2015 at 05:55:29PM +0800, yoma sophian wrote: > hi all: > I use linaro toolchain which libc is compile in thumb mode and if any > user mode program call sleep, the lr of its task_pt_regs will be 0, no > matter how many function level I called. It depends on the userspace code at the time that the system call is made. If it's setting LR to zero, then you'll read zero. I don't think it has anything to do with the toolchain either. Check the libc code around the site for the system call.
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index 3ee4d06..3fff0fe 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -1646,7 +1646,10 @@ SYSCALL_DEFINE2(nanosleep, struct timespec __user *, rqtp, struct timespec __user *, rmtp) { struct timespec tu; - + struct pt_regs *regs; + regs = task_pt_regs(current); + printk(KERN_ERR"calling %s, current->pid = %d, current->common =%s regs->ARM_lr= 0x%lx\n", __func__, current->pid, current->comm,regs->ARM_lr) if (copy_from_user(&tu, rqtp, sizeof(tu)))
hi all: I use linaro toolchain which libc is compile in thumb mode and if any user mode program call sleep, the lr of its task_pt_regs will be 0, no matter how many function level I called. Would anyone let me know where the source code that updates LR of task_pt_regs in arm? appreciate your kind help in advancd, Below are environments and experiments I did: a. I use below linaro toolchain to compile a user mode program. https://releases.linaro.org/14.08/components/toolchain/binaries/gcc-linaro-arm-linux-gnueabihf-4.9-2014.08_linux.tar.xz b. my kerenl is 3.10 c. my cpu is cortexA9 mp core. I did below things in a simple user mode program: 1. create a child thread 2. both parent and child do the while loop to sleep like below function call depth (I purposely use 2 level call function before sleep) void go_to_sleep_lv2(void) { printf( "%s \n",__func__); while(1) { sleep(30); } } void go_to_sleep_lv1(void) { printf( "%s \n",__func__); go_to_sleep_lv2(); } void * simple_thread_1(void * dummy) { go_to_sleep_lv1(); return NULL; } int main() { int error; pthread_t tid0 = 0; error = pthread_create(&tid0, 0, &simple_thread_1, 0); assert(error == 0); while(1){ go_to_sleep_lv1(); } error = pthread_join(tid0, NULL); assert(error == 0); return 0; } I found the lr of parent and child task_pt_regs are all 0 with below print patch I add in kernel. return -EFAULT; the kernel output like below: [ 1961.298882] calling SYSC_nanosleep, current->pid = 1248, current->common =simple.thread regs->ARM_lr= 0x0 I found something instresting: 1. the toolchain's libc is build in thumb mode. 2. if I change while loop like belwo without calling sleep.like below, the LR of task_pt_regs will be not 0. void go_to_sleep_lv2(void) { printf( "%s \n",__func__); while(1); }