On Wed, Jun 22, 2016 at 8:28 PM, Avantika Rawat <avani.rawat@xxxxxxxxx> wrote:
> Hi ,
>
> Thanks for the link but i am getting "Function not implemented" error.
> I have added a custom syscall in kernel for testing, getting similar
> error for that also. I am working on 3.10.20 Kernel and MIPS
> architecture. Pasting the kernel changes done to spport getrandom
> syscall in 3.10.20 kernel. Can someone please help me here that what
> needs to be done.
>
> --- linux-3.10.20/arch/x86/syscalls/syscall_32.tbl 2016-06-15
> 11:51:27.950025308 +0530
> +++ linux-3.10.20_mod/arch/x86/syscalls/syscall_32.tbl 2016-06-15
> 11:48:02.222020102 +0530
> @@ -358,3 +358,4 @@
> 349 i386 kcmp sys_kcmp
> 350 i386 finit_module sys_finit_module
> 351 i386 msa sys_msa
> +352 i386 getrandom sys_getrandom
> --- linux-3.10.20/arch/x86/syscalls/syscall_64.tbl 2016-06-15
> 11:51:27.950025308 +0530
> +++ linux-3.10.20_mod/arch/x86/syscalls/syscall_64.tbl 2016-06-15
> 11:48:16.118020453 +0530
> @@ -321,6 +321,7 @@
> 312 common kcmp sys_kcmp
> 313 common finit_module sys_finit_module
> 314 common msa sys_msa
> +315 common getrandom sys_getrandom
>
> #
> # x32-specific system call numbers start at 512 to avoid cache impact
> --- linux-3.10.20/drivers/char/random.c 2016-06-15 11:51:27.998025309 +0530
> +++ linux-3.10.20_mod/drivers/char/random.c 2016-06-15 11:48:34.774020925 +0530
> @@ -265,6 +265,8 @@
> #include <asm/irq.h>
> #include <asm/irq_regs.h>
> #include <asm/io.h>
> +#include <linux/syscalls.h>
> +#include <linux/completion.h>
>
> #define CREATE_TRACE_POINTS
> #include <trace/events/random.h>
> @@ -397,6 +399,7 @@ static struct poolinfo {
> */
> static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
> static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
> +static DECLARE_WAIT_QUEUE_HEAD(urandom_init_wait);
> static struct fasync_struct *fasync;
>
> static bool debug;
> @@ -1018,13 +1021,14 @@ static ssize_t extract_entropy_user(stru
> {
> ssize_t ret = 0, i;
> __u8 tmp[EXTRACT_SIZE];
> + int large_request = (nbytes > 256);
>
> trace_extract_entropy_user(r->name, nbytes, r->entropy_count, _RET_IP_);
> xfer_secondary_pool(r, nbytes);
> nbytes = account(r, nbytes, 0, 0);
>
> while (nbytes) {
> - if (need_resched()) {
> + if (large_request && need_resched()) {
> if (signal_pending(current)) {
> if (ret == 0)
> ret = -ERESTARTSYS;
> @@ -1158,7 +1162,7 @@ void rand_initialize_disk(struct gendisk
> #endif
>
> static ssize_t
> -random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
> +_random_read(int nonblock, char __user *buf, size_t nbytes)
> {
> ssize_t n, retval = 0, count = 0;
>
> @@ -1183,7 +1187,7 @@ random_read(struct file *file, char __us
> n*8, (nbytes-n)*8);
>
> if (n == 0) {
> - if (file->f_flags & O_NONBLOCK) {
> + if (nonblock) {
> retval = -EAGAIN;
> break;
> }
> @@ -1215,6 +1219,13 @@ random_read(struct file *file, char __us
> }
>
> static ssize_t
> +random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
> + {
> + return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
> + }
> +
> +
> +static ssize_t
> urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
> {
> return extract_entropy_user(&nonblocking_pool, buf, nbytes);
> @@ -1340,6 +1351,29 @@ const struct file_operations urandom_fop
> .llseek = noop_llseek,
> };
>
> +SYSCALL_DEFINE3 (getrandom, char __user *, buf, size_t, count,
> + unsigned int, flags)
> + {
> + if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
> + return -EINVAL;
> +
> + if (count > INT_MAX)
> + count = INT_MAX;
> +
> + if (flags & GRND_RANDOM)
> + return _random_read(flags & GRND_NONBLOCK, buf, count);
> +
> + if (unlikely(nonblocking_pool.initialized == 0)) {
> + if (flags & GRND_NONBLOCK)
> + return -EAGAIN;
> + wait_event_interruptible(urandom_init_wait,
> + nonblocking_pool.initialized);
> + if (signal_pending(current))
> + return -ERESTARTSYS;
> + }
> + return urandom_read(NULL, buf, count, NULL);
> + }
> +
> /***************************************************************
> * Random UUID interface
> *
> --- linux-3.10.20/include/linux/syscalls.h 2016-06-15 11:51:28.246025315 +0530
> +++ linux-3.10.20_mod/include/linux/syscalls.h 2016-06-15
> 11:49:11.918021865 +0530
> @@ -852,4 +852,6 @@ asmlinkage long sys_process_vm_writev(pi
> asmlinkage long sys_kcmp(pid_t pid1, pid_t pid2, int type,
> unsigned long idx1, unsigned long idx2);
> asmlinkage long sys_finit_module(int fd, const char __user *uargs, int flags);
> +asmlinkage long sys_getrandom(char __user *buf, size_t count,
> + unsigned int flags);
> #endif
> --- linux-3.10.20/include/uapi/asm-generic/unistd.h 2016-06-15
> 11:51:28.258025315 +0530
> +++ linux-3.10.20_mod/include/uapi/asm-generic/unistd.h 2016-06-15
> 11:49:32.558022388 +0530
> @@ -694,9 +694,11 @@ __SYSCALL(__NR_kcmp, sys_kcmp)
> __SYSCALL(__NR_finit_module, sys_finit_module)
> #define __NR_msa 274
> __SYSCALL(__NR_msa, sys_msa)
> +#define __NR_getrandom 275
> +__SYSCALL(__NR_getrandom, sys_getrandom)
>
> #undef __NR_syscalls
> -#define __NR_syscalls 275
> +#define __NR_syscalls 276
>
> /*
> * All syscalls below here should go away really,
> --- linux-3.10.20/include/uapi/linux/random.h 2013-11-21
> 01:58:01.000000000 +0530
> +++ linux-3.10.20_mod/include/uapi/linux/random.h 2016-06-15
> 11:50:06.350023243 +0530
> @@ -40,6 +40,15 @@ struct rand_pool_info {
> __u32 buf[0];
> };
>
> +/*
> + * Flags for getrandom(2)
> + *
> + * GRND_NONBLOCK Don't block and return EAGAIN instead
> + * GRND_RANDOM Use the /dev/random pool instead of /dev/urandom
> + */
> +#define GRND_NONBLOCK 0x0001
> +#define GRND_RANDOM 0x0002
> +
> struct rnd_state {
> __u32 s1, s2, s3;
> };
>
>
> On Wed, Jun 22, 2016 at 12:40 AM, Manuel Pégourié-Gonnard
> <mpg@xxxxxxxxxx> wrote:
>> Hi,
>>
>> Maybe your unistd.h comes from an older kernel? That would explain why
>> it doesn't define that symbol.
>>
>> Here [1] is some code using that syscall successfully, you can see it
>> looks a lot like Sayutin's code, except it does a few more compile-time
>> and runtime checks to fallback on using /dev/urandom if necessary.
>>
>> [1]:
>> https://github.com/ARMmbed/mbedtls/blob/dd9895d8101f17ce804830472cbb140eba1c46a0/library/entropy_poll.c#L85
>>
>> Manuel.
>>
>>
>> On 21/06/2016 15:41, Avantika Rawat wrote:
>>> Hi,
>>>
>>> Thanks for the suggestion but i am getting following error
>>>
>>> error: 'SYS_getrandom' undeclared (first use in this function)
>>>
>>> then i have replaced the SYS_getrandom by 275 in syscall(275, -- args--);
>>> as 275 is the __NR_getrandom defines in unistd.h file, but it is
>>> returning -1.
>>> Can somebody tell me what i am missing here??
>>>
>>> . Also in /proc/kallsyms it is showing two syscalls added for getrandom
>>>
>>> ffffffff80417a38 T SyS_getrandom
>>> ffffffff80417a38 T sys_getrandom
>>>
>>> On Sat, Jun 18, 2016 at 7:12 PM, Sayutin Dmitry <cdkrot@xxxxxxxxx> wrote:
>>>> Well, in fact it is not hard.
>>>>
>>>> Just use syscall(2) provided by libc.
>>>>
>>>> You need to provide to this function syscall id and syscall args.
>>>> Syscall id can be retrieved from macro constant
>>>> Should look something like:
>>>>
>>>> #define _GNU_SOURCE
>>>> #include <unistd.h>
>>>> #include <sys/syscall.h>
>>>>
>>>> syscall(SYS_getrandom, -- your - args - here --);
>>>>
>>>> It returns long value - the result of syscall.
>>>> If it is between [-4095; -1] then it is negated errno, otherways it is return value.
>>>>
>>>>
>>>> 18.06.2016, 16:32, "Anoop" <anoop.chargotra@xxxxxxxxx>:
>>>>> Hi Avantika,
>>>>>
>>>>> On Sat, Jun 18, 2016 at 5:32 PM, Avantika Rawat <avani.rawat@xxxxxxxxx> wrote:
>>>>>> Hi ALL,
>>>>>>
>>>>>> I am trying to use getrandom syscall in kernel 3.10.20 by following this
>>>>>> link
>>>>>>
>>>>>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c6e9d6f38894798696f23c8084ca7edbf16ee895
>>>>>>
>>>>>> i have compiled the kernel and now want to call the getrandom syscall from
>>>>>> userspace to generate random numbers. But i am getting following error while
>>>>>> calling the getrandom () from userspace.
>>>>>>
>>>>>> (.text.startup+0x18): undefined reference to `getrandom'
>>>>>> (.text.startup+0x1c): undefined reference to `getrandom'
>>>>>
>>>>> Your user space program will not know where 'getrandom' is defined
>>>>> unless it's in the C library. You need to research more on how to call
>>>>> custom system calls.
>>>>>
>>>>> -Anoop
>>>>>
>>>>>> --
>>>>>> Regards,
>>>>>> Avantika Rawat
>>>>>>
>>>>>> _______________________________________________
>>>>>> Kernelnewbies mailing list
>>>>>> Kernelnewbies@xxxxxxxxxxxxxxxxx
>>>>>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>>>>
>>>>> _______________________________________________
>>>>> Kernelnewbies mailing list
>>>>> Kernelnewbies@xxxxxxxxxxxxxxxxx
>>>>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>>>
>>>> -----
>>>> Sayutin Dmitry <cdkrot@xxxxxxxxxx>
>>>
>>>
>>>
>
>
>
> --
> Regards,
> Avantika Rawat
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies@xxxxxxxxxxxxxxxxx
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
I think you need to 352 or 315 ie the values from .tbl (so 315 if you
are calling on a x64 kernel or 352 if you are calling x86 kernel). The
275 is for the uapi but syscall accepts the 315 value on a x64.
Please try with 315 and 352 after running your modified kernel and
report back. Atleast that is the way it worked for me on a 4.x kernel.
Ideally uapi is for userspace like glibc and they come man 3 where as
the syscall is (man 2) ie system call.
--
-- Navin
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