[Qemu-devel] qemu on Fedora Core 3 (Linux 2.6.9+), glibc-2.3.3

[Qemu-devel] qemu on Fedora Core 3 (Linux 2.6.9+), glibc-2.3.3

[John Reiser]

In order to run qemu-snapshot-2004-12-17_23.tar.bz2 on:
    Fedora Core 3  kernel-2.6.8-1.681_FC3  i686
    gcc (GCC) 3.4.2 20041017 (Red Hat 3.4.2-6.fc3)
    glibc-2.3.3
    binutils-2.15.92.0.2-5
I had to use the extra file and patch below.
Otherwise I got very early SIGSEGVs.

-----__restore.S  [append __restore.o to VL_OBJS in i386/Makefile]
#include <asm/unistd.h>

__restore: .globl __restore
	pop %eax
	movl $ __NR_sigreturn,%eax
	int $0x80

__restore_rt: .globl __restore_rt
	movl $ __NR_rt_sigreturn,%eax
	int $0x80
-----


--- vl.c.orig	2004-12-12 14:20:04.000000000 -0800
+++ vl.c	2004-12-18 20:53:09.496799856 -0800
@@ -882,6 +882,9 @@

#endif /* !defined(_WIN32) */

+extern void __restore(void);
+extern void __restore_rt(void);
+
static void init_timers(void)
{
     rt_clock = qemu_new_clock(QEMU_TIMER_REALTIME);
@@ -913,7 +916,9 @@
         sigfillset(&act.sa_mask);
         act.sa_flags = 0;
#if defined (TARGET_I386) && defined(USE_CODE_COPY)
-        act.sa_flags |= SA_ONSTACK;
+#define SA_RESTORER   0x04000000
+        act.sa_flags |= SA_ONSTACK | SA_RESTORER;
+	act.sa_restorer = __restore;
#endif
         act.sa_handler = host_alarm_handler;
         sigaction(SIGALRM, &act, NULL);
@@ -3402,7 +3407,8 @@
         sigfillset(&act.sa_mask);
         act.sa_flags = SA_SIGINFO;
#if defined (TARGET_I386) && defined(USE_CODE_COPY)
-        act.sa_flags |= SA_ONSTACK;
+        act.sa_flags |= SA_ONSTACK | SA_RESTORER;
+	act.sa_restorer = __restore_rt;
#endif
         act.sa_sigaction = host_segv_handler;
         sigaction(SIGSEGV, &act, NULL);

-- 

Re: [Qemu-devel] qemu on Fedora Core 3 (Linux 2.6.9+), glibc-2.3.3

[Hetz Ben Hamo]

Could you please re-send your patch, diffed, as an attachment please?

Thanks,
Hetz


On Sat, 18 Dec 2004 21:11:00 -0800, John Reiser <jreiser@bitwagon.com> wrote:
> In order to run qemu-snapshot-2004-12-17_23.tar.bz2 on:
>     Fedora Core 3  kernel-2.6.8-1.681_FC3  i686
>     gcc (GCC) 3.4.2 20041017 (Red Hat 3.4.2-6.fc3)
>     glibc-2.3.3
>     binutils-2.15.92.0.2-5
> I had to use the extra file and patch below.
> Otherwise I got very early SIGSEGVs.
> 
> -----__restore.S  [append __restore.o to VL_OBJS in i386/Makefile]
> #include <asm/unistd.h>
> 
> __restore: .globl __restore
>         pop %eax
>         movl $ __NR_sigreturn,%eax
>         int $0x80
> 
> __restore_rt: .globl __restore_rt
>         movl $ __NR_rt_sigreturn,%eax
>         int $0x80
> -----
> 
> --- vl.c.orig   2004-12-12 14:20:04.000000000 -0800
> +++ vl.c        2004-12-18 20:53:09.496799856 -0800
> @@ -882,6 +882,9 @@
> 
> #endif /* !defined(_WIN32) */
> 
> +extern void __restore(void);
> +extern void __restore_rt(void);
> +
> static void init_timers(void)
> {
>      rt_clock = qemu_new_clock(QEMU_TIMER_REALTIME);
> @@ -913,7 +916,9 @@
>          sigfillset(&act.sa_mask);
>          act.sa_flags = 0;
> #if defined (TARGET_I386) && defined(USE_CODE_COPY)
> -        act.sa_flags |= SA_ONSTACK;
> +#define SA_RESTORER   0x04000000
> +        act.sa_flags |= SA_ONSTACK | SA_RESTORER;
> +       act.sa_restorer = __restore;
> #endif
>          act.sa_handler = host_alarm_handler;
>          sigaction(SIGALRM, &act, NULL);
> @@ -3402,7 +3407,8 @@
>          sigfillset(&act.sa_mask);
>          act.sa_flags = SA_SIGINFO;
> #if defined (TARGET_I386) && defined(USE_CODE_COPY)
> -        act.sa_flags |= SA_ONSTACK;
> +        act.sa_flags |= SA_ONSTACK | SA_RESTORER;
> +       act.sa_restorer = __restore_rt;
> #endif
>          act.sa_sigaction = host_segv_handler;
>          sigaction(SIGSEGV, &act, NULL);
> 
> --
> 
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel
>

Re: [Qemu-devel] qemu on Fedora Core 3 (Linux 2.6.9+), glibc-2.3.3

[John Reiser]

[-- Attachment #1: Type: text/plain, Size: 340 bytes --]

> Could you please re-send your patch, diffed, as an attachment please?

The important part of the original post was output from "diff -Naur".
Does gmail mangle message bodies, or was the request due to the
other small manual adjustments (non-patch) noted in the original post?
Anyway, a 100% patch is attached for use by "patch -p1".

-- 

[-- Attachment #2: SA_RESTORER.patch --]
[-- Type: text/plain, Size: 2039 bytes --]

--- ./vl.c.orig	2004-12-12 14:20:04.000000000 -0800
+++ ./vl.c	2004-12-19 05:49:53.323570312 -0800
@@ -882,6 +882,9 @@
 
 #endif /* !defined(_WIN32) */
 
+extern void __restore(void);
+extern void __restore_rt(void);
+
 static void init_timers(void)
 {
     rt_clock = qemu_new_clock(QEMU_TIMER_REALTIME);
@@ -913,7 +916,9 @@
         sigfillset(&act.sa_mask);
         act.sa_flags = 0;
 #if defined (TARGET_I386) && defined(USE_CODE_COPY)
-        act.sa_flags |= SA_ONSTACK;
+#define SA_RESTORER   0x04000000
+        act.sa_flags |= SA_ONSTACK | SA_RESTORER;
+        act.sa_restorer = __restore;
 #endif
         act.sa_handler = host_alarm_handler;
         sigaction(SIGALRM, &act, NULL);
@@ -3402,7 +3407,8 @@
         sigfillset(&act.sa_mask);
         act.sa_flags = SA_SIGINFO;
 #if defined (TARGET_I386) && defined(USE_CODE_COPY)
-        act.sa_flags |= SA_ONSTACK;
+        act.sa_flags |= SA_ONSTACK | SA_RESTORER;
+        act.sa_restorer = __restore_rt;
 #endif
         act.sa_sigaction = host_segv_handler;
         sigaction(SIGSEGV, &act, NULL);
@@ -3449,6 +3455,7 @@
             exit(1);
         } else {
             printf("Waiting gdb connection on port %d\n", gdbstub_port);
+sleep(5);
         }
     } else 
 #endif
--- ./Makefile.target.orig	2004-12-12 08:56:30.000000000 -0800
+++ ./Makefile.target	2004-12-19 05:48:08.201551288 -0800
@@ -264,7 +264,7 @@
 endif
 
 # must use static linking to avoid leaving stuff in virtual address space
-VL_OBJS=vl.o osdep.o block.o readline.o monitor.o pci.o console.o 
+VL_OBJS=vl.o osdep.o block.o readline.o monitor.o pci.o console.o  __restore.o
 VL_OBJS+=block-cow.o block-qcow.o aes.o block-vmdk.o block-cloop.o block-dmg.o
 
 SOUND_HW = sb16.o
--- ./__restore.S.orig	2004-12-19 05:44:53.832099936 -0800
+++ ./__restore.S	2004-12-18 20:34:14.000000000 -0800
@@ -0,0 +1,10 @@
+#include <asm/unistd.h>
+
+__restore: .globl __restore
+	pop %eax
+	movl $ __NR_sigreturn,%eax
+	int $0x80
+
+__restore_rt: .globl __restore_rt
+	movl $ __NR_rt_sigreturn,%eax
+	int $0x80

Re: [Qemu-devel] qemu on Fedora Core 3 (Linux 2.6.9+), glibc-2.3.3

[John Reiser]

This optional part of the patch to vl.c:
-----
@@ -3449,6 +3455,7 @@
              exit(1);
          } else {
              printf("Waiting gdb connection on port %d\n", gdbstub_port);
+sleep(5);
          }
      } else
  #endif
-----
resulted from my misunderstanding of what qemu actually does.
I interpreted "Waiting" as a synchronizing rendezvous blocking wait,
while it seems that qemu is merely "Listening" without blocking.
The difference is important to me because I want to observe
the very first emulated instruction at hardware boot.  For the moment,
I have put an infinite loop there, then advance the instruction pointer
by hand once the gdb connection is established.

-- 

Re: [Qemu-devel] qemu on Fedora Core 3 (Linux 2.6.9+), glibc-2.3.3

[Fabrice Bellard]

Can you move the restorer patch in osdep.c:qemu_sigaction() ? I see no 
reason to do it in vl.c. Moreover, you should do it only for "qemu-fast".

Fabrice.

John Reiser wrote:
>> Could you please re-send your patch, diffed, as an attachment please?
> 
> 
> The important part of the original post was output from "diff -Naur".
> Does gmail mangle message bodies, or was the request due to the
> other small manual adjustments (non-patch) noted in the original post?
> Anyway, a 100% patch is attached for use by "patch -p1".
> 
> 
> ------------------------------------------------------------------------
> 
> --- ./vl.c.orig	2004-12-12 14:20:04.000000000 -0800
> +++ ./vl.c	2004-12-19 05:49:53.323570312 -0800
> @@ -882,6 +882,9 @@
>  
>  #endif /* !defined(_WIN32) */
>  
> +extern void __restore(void);
> +extern void __restore_rt(void);
> +
>  static void init_timers(void)
>  {
>      rt_clock = qemu_new_clock(QEMU_TIMER_REALTIME);
> @@ -913,7 +916,9 @@
>          sigfillset(&act.sa_mask);
>          act.sa_flags = 0;
>  #if defined (TARGET_I386) && defined(USE_CODE_COPY)
> -        act.sa_flags |= SA_ONSTACK;
> +#define SA_RESTORER   0x04000000
> +        act.sa_flags |= SA_ONSTACK | SA_RESTORER;
> +        act.sa_restorer = __restore;
>  #endif
>          act.sa_handler = host_alarm_handler;
>          sigaction(SIGALRM, &act, NULL);
> @@ -3402,7 +3407,8 @@
>          sigfillset(&act.sa_mask);
>          act.sa_flags = SA_SIGINFO;
>  #if defined (TARGET_I386) && defined(USE_CODE_COPY)
> -        act.sa_flags |= SA_ONSTACK;
> +        act.sa_flags |= SA_ONSTACK | SA_RESTORER;
> +        act.sa_restorer = __restore_rt;
>  #endif
>          act.sa_sigaction = host_segv_handler;
>          sigaction(SIGSEGV, &act, NULL);
> @@ -3449,6 +3455,7 @@
>              exit(1);
>          } else {
>              printf("Waiting gdb connection on port %d\n", gdbstub_port);
> +sleep(5);
>          }
>      } else 
>  #endif
> --- ./Makefile.target.orig	2004-12-12 08:56:30.000000000 -0800
> +++ ./Makefile.target	2004-12-19 05:48:08.201551288 -0800
> @@ -264,7 +264,7 @@
>  endif
>  
>  # must use static linking to avoid leaving stuff in virtual address space
> -VL_OBJS=vl.o osdep.o block.o readline.o monitor.o pci.o console.o 
> +VL_OBJS=vl.o osdep.o block.o readline.o monitor.o pci.o console.o  __restore.o
>  VL_OBJS+=block-cow.o block-qcow.o aes.o block-vmdk.o block-cloop.o block-dmg.o
>  
>  SOUND_HW = sb16.o
> --- ./__restore.S.orig	2004-12-19 05:44:53.832099936 -0800
> +++ ./__restore.S	2004-12-18 20:34:14.000000000 -0800
> @@ -0,0 +1,10 @@
> +#include <asm/unistd.h>
> +
> +__restore: .globl __restore
> +	pop %eax
> +	movl $ __NR_sigreturn,%eax
> +	int $0x80
> +
> +__restore_rt: .globl __restore_rt
> +	movl $ __NR_rt_sigreturn,%eax
> +	int $0x80
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel

Re: [Qemu-devel] qemu on Fedora Core 3 (Linux 2.6.9+), glibc-2.3.3

[John Reiser]

[-- Attachment #1: Type: text/plain, Size: 1028 bytes --]

Fabrice Bellard wrote:
> Can you move the restorer patch in osdep.c:qemu_sigaction() ? I see no 
> reason to do it in vl.c. Moreover, you should do it only for "qemu-fast".

The attached patch moves the changes out of vl.c and into osdep.c.
But the easiest and clearest code requires removing the 'const' attribute
for the new struct qemu_sigaction *.  This is OK because the only callers
are internal, and use temporary struct qemu_sigaction anyway.  To insist
on keeping the 'const' requires qemu_sigaction to perform a copy before
making the modifications for SA_RESTORER and .sa_restorer, and to pass
a pointer to the copy as the argument to the syscall.  If you want
that, then just copy the implementation out of glibc-2.3.

It seems to me that the restorer actions must apply to all qemu_sigaction
for Linux 2.6.x.  If restricted to qemu-fast only, then only qemu-fast
will work correctly; the other cases will get SIGSEGV upon return from
the corresponding signal handlers.  Why should qemu-fast be a special case?

-- 

[-- Attachment #2: SA_RESTORER-osdep.patch --]
[-- Type: text/plain, Size: 2411 bytes --]

--- qemu-snapshot-2004-12-17_23/Makefile.target.orig	2004-12-12 08:56:30.000000000 -0800
+++ qemu-snapshot-2004-12-17_23/Makefile.target	2004-12-19 05:48:08.000000000 -0800
@@ -264,7 +264,7 @@
 endif
 
 # must use static linking to avoid leaving stuff in virtual address space
-VL_OBJS=vl.o osdep.o block.o readline.o monitor.o pci.o console.o 
+VL_OBJS=vl.o osdep.o block.o readline.o monitor.o pci.o console.o  __restore.o
 VL_OBJS+=block-cow.o block-qcow.o aes.o block-vmdk.o block-cloop.o block-dmg.o
 
 SOUND_HW = sb16.o
--- qemu-snapshot-2004-12-17_23/__restore.S.orig	2004-12-19 05:44:53.000000000 -0800
+++ qemu-snapshot-2004-12-17_23/__restore.S	2004-12-18 20:34:14.000000000 -0800
@@ -0,0 +1,10 @@
+#include <asm/unistd.h>
+
+__restore: .globl __restore
+	pop %eax
+	movl $ __NR_sigreturn,%eax
+	int $0x80
+
+__restore_rt: .globl __restore_rt
+	movl $ __NR_rt_sigreturn,%eax
+	int $0x80
--- qemu-snapshot-2004-12-17_23/osdep.c.orig	2004-08-03 15:09:30.000000000 -0700
+++ qemu-snapshot-2004-12-17_23/osdep.c	2004-12-19 15:44:08.000000000 -0800
@@ -153,9 +153,25 @@
     QEMU_SYSCALL4(rt_sigaction, signum, act, oldact, sigsetsize);
 }
 
-int qemu_sigaction(int signum, const struct qemu_sigaction *act, 
+int qemu_sigaction(int signum, struct qemu_sigaction *act, 
                    struct qemu_sigaction *oldact)
 {
+#define SA_RESTORER   0x04000000
+    if (!(act->sa_flags & SA_RESTORER)) {
+        /* Required for Linux 2.6.x "no-exec stack": kernel does not
+         * push trampoline instructions for handler return,
+         * so user-mode code must supply the correct .sa_restorer.
+         */
+        extern void __restore(void);
+        extern void __restore_rt(void);
+        act->sa_flags |= SA_RESTORER;
+        if (act->sa_flags & SA_SIGINFO) {
+            act->sa_restorer = __restore_rt;
+        }
+        else {
+            act->sa_restorer = __restore;
+        }
+    }
     return kernel_sigaction(signum, act, oldact, 8);
 }
 
--- qemu-snapshot-2004-12-17_23/osdep.h.orig	2004-08-03 15:09:30.000000000 -0700
+++ qemu-snapshot-2004-12-17_23/osdep.h	2004-12-19 15:43:54.000000000 -0800
@@ -35,7 +35,7 @@
     sigset_t sa_mask;		/* mask last for extensibility */
 };
 
-int qemu_sigaction(int signum, const struct qemu_sigaction *act, 
+int qemu_sigaction(int signum, struct qemu_sigaction *act, 
                    struct qemu_sigaction *oldact);
 
 #undef sigaction

Re: [Qemu-devel] qemu on Fedora Core 3 (Linux 2.6.9+), glibc-2.3.3

[Johannes Schindelin]

Hi,

silly question: why don't you use inline assembly to make those two
functions?

Ciao,
Dscho

Re: [Qemu-devel] qemu on Fedora Core 3 (Linux 2.6.9+), glibc-2.3.3

[John Reiser]

> silly question: why don't you use inline assembly to make those two
> functions?
> 

The calls are not execution-time critical (fewer than 10 calls).
They are complexity, platform, and developer-time critical.
More time will be spent by developers and future maintainers
than the total machine cycles spent executing the code,
over all the machines in the world, ever.  So making the
developer+maintainer tasks simple and quick is more important
than cycle- or byte-efficiency.

-- 

Re: [Qemu-devel] qemu on Fedora Core 3 (Linux 2.6.9+), glibc-2.3.3

[Darrin Ritter]

where can I d/l the source code with this patch as I am having problems 
running qemu on FC3

DV

John Reiser wrote:

>> silly question: why don't you use inline assembly to make those two
>> functions?
>>
>
> The calls are not execution-time critical (fewer than 10 calls).
> They are complexity, platform, and developer-time critical.
> More time will be spent by developers and future maintainers
> than the total machine cycles spent executing the code,
> over all the machines in the world, ever.  So making the
> developer+maintainer tasks simple and quick is more important
> than cycle- or byte-efficiency.
>

Re: [Qemu-devel] qemu on Fedora Core 3 (Linux 2.6.9+), glibc-2.3.3

[John Reiser]

> where can I d/l the source code with this patch as I am having problems 
> running qemu on FC3

 From the qemu home page http://fabrice.bellard.free.fr/qemu/
follow the Link "Pending patches" to http://www.dad-answers.com/qemu/
and choose http://www.dad-answers.com/qemu/qemu-snapshot-2004-12-21_23.tar.bz2
The patch (your choice of 2) is in another message of this current thread
of this mailing list.  If necessary, see the archive at
http://lists.gnu.org/archive/html/qemu-devel/2004-12/threads.html

--