Re: implementing linux mmap2 syscall
Kenneth Culver writes: OK, I THINK I found what calls the actual kernel syscall handler, and sets it's args first, but I'm not sure: from linux_locore.s NON_GPROF_ENTRY(linux_sigcode) ... Does anyone who actually knows assembly have any ideas? This is the linux sigtramp, or signal trampoline. It is used to wrap a signal handler. Eg, the kernel calls it (by returning to it) when it delivers a signal. It calls the apps signal handler. When the handler returns, it calls the linux sigreturn system call. This has essentially nothing to do with system calls. The system call entry point on x86 is int0x80_syscall, which is labled: /* * Call gate entry for FreeBSD ELF and Linux/NetBSD syscall (int 0x80) .. This then calls syscall2(), which calls the linux prepsyscall. Maybe the argument isn't where you expect it to be, but is there. Can you make a test program which calls mmap2 with its 6th arg as something unique like 0xdeadbeef? Then print out (in hex :) the trapframe from the linux prepsyscall routine see if you can find the deadbeef. Drew To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: implementing linux mmap2 syscall
On Wed, 2002-04-24 at 10:41, Andrew Gallatin wrote: Maybe the argument isn't where you expect it to be, but is there. Can you make a test program which calls mmap2 with its 6th arg as something unique like 0xdeadbeef? Then print out (in hex :) the trapframe from the linux prepsyscall routine see if you can find the deadbeef. My recollection is that beyond 5 arguments, a pointer to the remaining ones is passed. (But my recollection may be wrong and I don't wish to subject myself to the source cesspool at the moment) -- brandon s. allbery [os/2][linux][solaris][japh] [EMAIL PROTECTED] system administrator [WAY too many hats][EMAIL PROTECTED] electrical and computer engineeringKF8NH carnegie mellon university [better check the oblivious first -ke6sls] To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: implementing linux mmap2 syscall
Brandon S Allbery KF8NH writes: On Wed, 2002-04-24 at 10:41, Andrew Gallatin wrote: Maybe the argument isn't where you expect it to be, but is there. Can you make a test program which calls mmap2 with its 6th arg as something unique like 0xdeadbeef? Then print out (in hex :) the trapframe from the linux prepsyscall routine see if you can find the deadbeef. My recollection is that beyond 5 arguments, a pointer to the remaining ones is passed. (But my recollection may be wrong and I don't wish to subject myself to the source cesspool at the moment) I think that's how it used to work. Apparently, they've changed it recently and they now pass 6 args in registers. Eg, in the linux kernel sources, old_mmap() fetches its args via copy_from_user(), whereas the newer sys_mmap2() doesn't. Drew To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: implementing linux mmap2 syscall
I tried printing out everything in the trapframe in hex and nothing looke remotely right. Ken On 24 Apr 2002, Brandon S Allbery KF8NH wrote: On Wed, 2002-04-24 at 10:41, Andrew Gallatin wrote: Maybe the argument isn't where you expect it to be, but is there. Can you make a test program which calls mmap2 with its 6th arg as something unique like 0xdeadbeef? Then print out (in hex :) the trapframe from the linux prepsyscall routine see if you can find the deadbeef. My recollection is that beyond 5 arguments, a pointer to the remaining ones is passed. (But my recollection may be wrong and I don't wish to subject myself to the source cesspool at the moment) -- brandon s. allbery [os/2][linux][solaris][japh] [EMAIL PROTECTED] system administrator [WAY too many hats][EMAIL PROTECTED] electrical and computer engineeringKF8NH carnegie mellon university [better check the oblivious first -ke6sls] To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: implementing linux mmap2 syscall
Brandon S Allbery KF8NH writes: On Wed, 2002-04-24 at 10:41, Andrew Gallatin wrote: Maybe the argument isn't where you expect it to be, but is there. Can you make a test program which calls mmap2 with its 6th arg as something unique like 0xdeadbeef? Then print out (in hex :) the trapframe from the linux prepsyscall routine see if you can find the deadbeef. My recollection is that beyond 5 arguments, a pointer to the remaining ones is passed. (But my recollection may be wrong and I don't wish to subject myself to the source cesspool at the moment) I think that's how it used to work. Apparently, they've changed it recently and they now pass 6 args in registers. Eg, in the linux kernel sources, old_mmap() fetches its args via copy_from_user(), whereas the newer sys_mmap2() doesn't. Drew Yep, according to the docs and source code I looked at in the linux kernel, the sixth arg is in the ebp register. I've looked all over the FreeBSD kernel and the linux emulator for the place that actually sets these, and unfortunately, due to my lack of asm coding knowledge, I can't find anything. Ken To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: implementing linux mmap2 syscall
libc sets it before it enters the kernel. Then on kernel entry we save ebp in the trapframe. So in the case of linux emulation, the glibc that we're using in the linux-ulator isn't setting it properly? I'm using the linux_base-7 port for this, so as far as I can tell, it should work... assuming linux_base-7 is meant to run on a linux-2.4.x kernel (or kernel that's emulating that). I may have screwed up my linux libs somehow or another too... could this be causing the behavior I'm seeing? Ken To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: implementing linux mmap2 syscall
On 24-Apr-2002 Kenneth Culver wrote: libc sets it before it enters the kernel. Then on kernel entry we save ebp in the trapframe. So in the case of linux emulation, the glibc that we're using in the linux-ulator isn't setting it properly? I'm using the linux_base-7 port for this, so as far as I can tell, it should work... assuming linux_base-7 is meant to run on a linux-2.4.x kernel (or kernel that's emulating that). I may have screwed up my linux libs somehow or another too... could this be causing the behavior I'm seeing? Maybe. You could always try finding the mmap2() entry point and dissassembling it to see what it is doing. Ken -- John Baldwin [EMAIL PROTECTED]http://www.FreeBSD.org/~jhb/ Power Users Use the Power to Serve! - http://www.FreeBSD.org/ To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: implementing linux mmap2 syscall
On 24-Apr-2002 Kenneth Culver wrote: Brandon S Allbery KF8NH writes: On Wed, 2002-04-24 at 10:41, Andrew Gallatin wrote: Maybe the argument isn't where you expect it to be, but is there. Can you make a test program which calls mmap2 with its 6th arg as something unique like 0xdeadbeef? Then print out (in hex :) the trapframe from the linux prepsyscall routine see if you can find the deadbeef. My recollection is that beyond 5 arguments, a pointer to the remaining ones is passed. (But my recollection may be wrong and I don't wish to subject myself to the source cesspool at the moment) I think that's how it used to work. Apparently, they've changed it recently and they now pass 6 args in registers. Eg, in the linux kernel sources, old_mmap() fetches its args via copy_from_user(), whereas the newer sys_mmap2() doesn't. Drew Yep, according to the docs and source code I looked at in the linux kernel, the sixth arg is in the ebp register. I've looked all over the FreeBSD kernel and the linux emulator for the place that actually sets these, and unfortunately, due to my lack of asm coding knowledge, I can't find anything. libc sets it before it enters the kernel. Then on kernel entry we save ebp in the trapframe. -- John Baldwin [EMAIL PROTECTED]http://www.FreeBSD.org/~jhb/ Power Users Use the Power to Serve! - http://www.FreeBSD.org/ To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: implementing linux mmap2 syscall
libc sets it before it enters the kernel. Then on kernel entry we save ebp in the trapframe. So in the case of linux emulation, the glibc that we're using in the linux-ulator isn't setting it properly? I'm using the linux_base-7 port for this, so as far as I can tell, it should work... assuming linux_base-7 is meant to run on a linux-2.4.x kernel (or kernel that's emulating that). I may have screwed up my linux libs somehow or another too... could this be causing the behavior I'm seeing? Ken OK, I removed the linux_base packages that I had on here, and made some changes to the linux-ulator (added the arg[5] = tf-tf_ebp, and then re-installed the linux_base-7.1 package, and now things are working... winex is working fine now. :-) I'll clean up my changes to the linux-ulator, and submit them as a pr. Ken To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: implementing linux mmap2 syscall
libc sets it before it enters the kernel. Then on kernel entry we save ebp in the trapframe. So in the case of linux emulation, the glibc that we're using in the linux-ulator isn't setting it properly? I'm using the linux_base-7 port for this, so as far as I can tell, it should work... assuming linux_base-7 is meant to run on a linux-2.4.x kernel (or kernel that's emulating that). I may have screwed up my linux libs somehow or another too... could this be causing the behavior I'm seeing? Ken OK, I removed the linux_base packages that I had on here, and made some changes to the linux-ulator (added the arg[5] = tf-tf_ebp, and then re-installed the linux_base-7.1 package, and now things are working... winex is working fine now. :-) I'll clean up my changes to the linux-ulator, and submit them as a pr. I'm actually still not seeing a match between what's in truss, and what's in my printed-out args, but it seems to be working anyway... Ken To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: implementing linux mmap2 syscall
I'm actually still not seeing a match between what's in truss, and what's in my printed-out args, but it seems to be working anyway... Argh, it's not working again... It was working on an install of ms office, but it won't work on some old windows game.. (winex) and it's still not setting the last arg (or register properly): truss output: linux_mmap2(0x6543,0x10,0x3,0x11,0x9,0x6) = 1698889728 (0x6543) notice that the last arg is 0x6, that's the page offset... what the kernel prints for the same call: mmap2(0x6543, 1048576, 3, 0x0011, 9, 0) notice that they both have all the same values until you get to the last one... at which point the value is wrong... Apparently this only causes problems on some windows programs that one may try to execute, and not on others... So, where can I force this to get set? Ken To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: implementing linux mmap2 syscall
Here's where it happens:
sys/i386/linux/linux_sysvec.c
static void
linux_prepsyscall(struct trapframe *tf, int *args, u_int *code, caddr_t *params)
{
args[0] = tf-tf_ebx;
args[1] = tf-tf_ecx;
args[2] = tf-tf_edx;
args[3] = tf-tf_esi;
args[4] = tf-tf_edi;
*params = NULL; /* no copyin */
}
You probably want to add:
args[5] = tf-tf_ebp;
so that it ends up in the syscallargs struct.
Yeah, I did that... it still doesn't work, tf_ebp isn't getting set... So
I'm thinking that either I have a glibc that's too old, or something else
is wrong...
For FreeBSD syscalls, we copy this from the top of stack for the number of
32 bit words specified in the syscall table in i386/trap.c:
if (params (i = narg * sizeof(int))
(error = copyin(params, (caddr_t)args, (u_int)i))) {
(narg comes from the syscall table).
OK, that gives me an idea...
Ken
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Re: implementing linux mmap2 syscall
RCS file: /home/ncvs/src/sys/i386/linux/linux_sysvec.c,v retrieving revision 1.99 diff -u -2 -r1.99 linux_sysvec.c --- linux_sysvec.c 4 Apr 2002 17:49:46 - 1.99 +++ linux_sysvec.c 24 Apr 2002 23:57:23 - @@ -711,4 +711,5 @@ args[3] = tf-tf_esi; args[4] = tf-tf_edi; + args[5] = tf-tf_ebp; *params = NULL; /* no copyin */ } Cheers, -Peter -- Peter Wemm - [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED] All of this is for nothing if we don't go to the stars - JMS/B5 To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message yeah, I did that already, and have been running with that since yesterday :-P still not working right though... I think it has something to do with that nargs thing... I'm checking that out now... Ken To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: implementing linux mmap2 syscall
Kenneth Culver wrote:
Brandon S Allbery KF8NH writes:
On Wed, 2002-04-24 at 10:41, Andrew Gallatin wrote:
Maybe the argument isn't where you expect it to be, but is there.
Can you make a test program which calls mmap2 with its 6th arg as
something unique like 0xdeadbeef? Then print out (in hex :) the trapf
rame
from the linux prepsyscall routine see if you can find the deadbeef.
My recollection is that beyond 5 arguments, a pointer to the remaining
ones is passed. (But my recollection may be wrong and I don't wish to
subject myself to the source cesspool at the moment)
I think that's how it used to work. Apparently, they've changed it
recently and they now pass 6 args in registers. Eg, in the linux
kernel sources, old_mmap() fetches its args via copy_from_user(),
whereas the newer sys_mmap2() doesn't.
Drew
Yep, according to the docs and source code I looked at in the linux
kernel, the sixth arg is in the ebp register. I've looked all over the
FreeBSD kernel and the linux emulator for the place that actually sets
these, and unfortunately, due to my lack of asm coding knowledge, I can't
find anything.
Here's where it happens:
sys/i386/linux/linux_sysvec.c
static void
linux_prepsyscall(struct trapframe *tf, int *args, u_int *code, caddr_t *params)
{
args[0] = tf-tf_ebx;
args[1] = tf-tf_ecx;
args[2] = tf-tf_edx;
args[3] = tf-tf_esi;
args[4] = tf-tf_edi;
*params = NULL; /* no copyin */
}
You probably want to add:
args[5] = tf-tf_ebp;
so that it ends up in the syscallargs struct.
For FreeBSD syscalls, we copy this from the top of stack for the number of
32 bit words specified in the syscall table in i386/trap.c:
if (params (i = narg * sizeof(int))
(error = copyin(params, (caddr_t)args, (u_int)i))) {
(narg comes from the syscall table).
Cheers,
-Peter
--
Peter Wemm - [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]
All of this is for nothing if we don't go to the stars - JMS/B5
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Re: implementing linux mmap2 syscall
Alright, so I got tired of trying to figure out if glibc is doing something wierd or wrong so I downloaded the source for it, and I'm looking at it now... (for version 2.2.2 which is what we have on FreeBSD's linux_base-7) and here's what I'm seeing: pushl %ebp pushl %ebx pushl %esi pushl %edi movl OFFLO(%esp), %edx movl OFFHI(%esp), %ecx testl $0xfff, %edx jne L(einval) shrdl $12, %ecx, %edx /* mmap2 takes the offset in pages. */ shrl $12, %ecx jne L(einval) movl %edx, %ebp So above I'm seeing the offset arg get into register %ebp, which is what we expect... movl ADDR(%esp), %ebx movl LEN(%esp), %ecx movl PROT(%esp), %edx movl FLAGS(%esp), %esi movl FD(%esp), %edi Then I'm seeing all the other args getting put into the registers they belong in... (which matches up with our linux_prepsyscall() function) movl $SYS_ify(mmap2), %eax /* System call number in %eax. */ /* Do the system call trap. */ L(do_syscall): int $0x80 Now I'm seeing the int 0x80 trap /* Restore registers. */ popl %edi popl %esi popl %ebx popl %ebp So, as far as I can tell, this version of glibc is doing the Right Thing, and the ebp register is getting messed up somewhere along the line in either the assembly code that handles the 0x80 trap in FreeBSD, or in syscall2 (I think it's probably the asm that handles the 0x80 trap)... Can anyone confirm this? Ken To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: implementing linux mmap2 syscall
Basically, linux_mmap2 takes 6 args, and this looks here like only 5 args are making it in... I checked this because the sixth argument to linux_mmap2() in truss was showing 0x6, but when I printed out that arg from the kernel, it was showing 0x0. Am I correct here? Ken Yes. According to http://john.fremlin.de/linux/asm/, linux used to parse only 5 args but now it parses six. Try adding: args[5] = tf-tf_ebp; I don't think that arg is there: Apr 23 10:36:13 ken /kernel: tf-tf_ebp = -1077938040 Ken My guess is that we're not doing something we should be doing in int0x80_syscall in order to get that last arg. But I do not have enough x86 knowledge to understand how the trapframe is constructed, so I cannot tell what needs to be done. Perhaps somebody with more x86 fu can help. Sorry, Crap, I don't know what's going on either, I was just looking at the asm in src/sys/i386/i386/exception.s, but I'm not very good with asm either, Can anyone help? I'm cross-posting to -current since nobody on hackers or emulation is able to help. Ken To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-current in the body of the message
Re: implementing linux mmap2 syscall
Kenneth Culver writes:
OK, I found another problem, here it is:
static void
linux_prepsyscall(struct trapframe *tf, int *args, u_int *code, caddr_t
*params)
{
args[0] = tf-tf_ebx;
args[1] = tf-tf_ecx;
args[2] = tf-tf_edx;
args[3] = tf-tf_esi;
args[4] = tf-tf_edi;
*params = NULL; /* no copyin */
}
Basically, linux_mmap2 takes 6 args, and this looks here like only 5 args are
making it in... I checked this because the sixth argument to linux_mmap2() in
truss was showing 0x6, but when I printed out that arg from the kernel, it
was showing 0x0. Am I correct here?
Ken
Yes. According to http://john.fremlin.de/linux/asm/, linux used to
parse only 5 args but now it parses six. Try adding:
args[5] = tf-tf_ebp;
Drew
OK, I THINK I found what calls the actual kernel syscall handler, and
sets it's args first, but I'm not sure:
from linux_locore.s
NON_GPROF_ENTRY(linux_sigcode)
call*LINUX_SIGF_HANDLER(%esp)
lealLINUX_SIGF_SC(%esp),%ebx/* linux scp */
movlLINUX_SC_GS(%ebx),%gs
movl%esp, %ebx /* pass sigframe */
push%eax/* fake ret addr */
movl$LINUX_SYS_linux_sigreturn,%eax /* linux_sigreturn() */
int $0x80 /* enter kernel with args
*/
0: jmp 0b
ALIGN_TEXT
I think the stuff above copies the args, and whatnot, but I'm not really
sure where it does this exactly...
It calls LINUX_SIGF_HANDLER, which then calls %esp's sf_handler function.
That is where I draw a blank, I don't know which function this is calling,
and can't find where it's being set. I think this might be what I want to
change though. :-P
Does anyone who actually knows assembly have any ideas?
Ken
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