Re: [PATCH] Define sigcontext ABI of ColdFire

[Maxim Kuvyrkov <maxim@codesourcery.com>]

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Maxim Kuvyrkov wrote:
> The following patch define sigcontext ABI of ColdFire.
...
> --- a/arch/m68k/kernel/signal.c
> +++ b/arch/m68k/kernel/signal.c
> @@ -897,9 +897,15 @@ static void setup_rt_frame (int sig, struct k_sigaction *ka, siginfo_t *info,
>  
>  	/* Set up to return from userspace.  */
>  	err |= __put_user(frame->retcode, &frame->pretcode);
> +#ifdef __mcoldfire__
> +	/* move.w #,d0; trap #0 */
> +	err |= __put_user(0x303c0000 + __NR_rt_sigreturn,
> +			  (long __user *)(frame->retcode + 0));
> +#else
>  	/* moveq #,d0; notb d0; trap #0 */
>  	err |= __put_user(0x70004600 + ((__NR_rt_sigreturn ^ 0xff) << 16),
>  			  (long __user *)(frame->retcode + 0));
> +#endif
>  	err |= __put_user(0x4e40, (short __user *)(frame->retcode + 4));
>  
>  	if (err)

This turned out to be buggy: move.w will only set the lower 16 bits of 
%d0 so if the signal handler leaves something in the high-order bits, 
then the trampoline will trap into a non-existent syscall.  The attached 
patch fixes this; nothing else in it has changed since the initial revision.

I was lured into thinking that the above sequence is OK by m68knommu's 
version of the trampoline.  Arch/m68knommu/kernel/entry.S uses "move 
#__NR_rt_sigreturn,%d0" which assembles into "move.w".  This is too is 
buggy and I'm also attaching the fix for the nommu version.

Regards,

--
Maxim K.
CodeSourcery

[-- Attachment #2: 0001-Define-sigcontext-ABI-of-ColdFire.patch --]
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>From bafb4e11ac13ea3095d9e8510f9a58c4cdc0481d Mon Sep 17 00:00:00 2001
From: Maxim Kuvyrkov <maxim@codesourcery.com>
Date: Wed, 23 Sep 2009 01:22:43 +0400
Subject: [PATCH 1/2] Define sigcontext ABI of ColdFire

The following patch defines sigcontext ABI of ColdFire.  Due to ISA
restrictions ColdFire needs different rt_sigreturn trampoline.

And due to ColdFire FP registers being 8-bytes instead of 12-bytes on
m68k, sigcontext and fpregset structures should be updated.

Regarding the sc_fpstate[16+6*8] field, it would've been enough 16
bytes to store ColdFire's FP state.  To accomodate GLIBC's libSegFault
it would'be been enough 6*8 bytes (room for the 6 non-call-clobbered
FP registers).  I set it to 16+6*8 to provide some extra space for any
future changes in the ColdFire FPU.

Signed-off-by: Maxim Kuvyrkov <maxim@codesourcery.com>
---
 arch/m68k/include/asm/sigcontext.h |    6 ++++++
 arch/m68k/include/asm/ucontext.h   |    4 ++++
 arch/m68k/kernel/signal.c          |    7 +++++++
 3 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/arch/m68k/include/asm/sigcontext.h b/arch/m68k/include/asm/sigcontext.h
index 523db2a..1320eaa 100644
--- a/arch/m68k/include/asm/sigcontext.h
+++ b/arch/m68k/include/asm/sigcontext.h
@@ -15,9 +15,15 @@ struct sigcontext {
 	unsigned long  sc_pc;
 	unsigned short sc_formatvec;
 #ifndef __uClinux__
+# ifdef __mcoldfire__
+	unsigned long  sc_fpregs[2][2];	/* room for two fp registers */
+	unsigned long  sc_fpcntl[3];
+	unsigned char  sc_fpstate[16+6*8];
+# else
 	unsigned long  sc_fpregs[2*3];  /* room for two fp registers */
 	unsigned long  sc_fpcntl[3];
 	unsigned char  sc_fpstate[216];
+# endif
 #endif
 };
 
diff --git a/arch/m68k/include/asm/ucontext.h b/arch/m68k/include/asm/ucontext.h
index e4e2266..00dcc51 100644
--- a/arch/m68k/include/asm/ucontext.h
+++ b/arch/m68k/include/asm/ucontext.h
@@ -7,7 +7,11 @@ typedef greg_t gregset_t[NGREG];
 
 typedef struct fpregset {
 	int f_fpcntl[3];
+#ifdef __mcoldfire__
+	int f_fpregs[8][2];
+#else
 	int f_fpregs[8*3];
+#endif
 } fpregset_t;
 
 struct mcontext {
diff --git a/arch/m68k/kernel/signal.c b/arch/m68k/kernel/signal.c
index de2d05d..4b38753 100644
--- a/arch/m68k/kernel/signal.c
+++ b/arch/m68k/kernel/signal.c
@@ -897,10 +897,17 @@ static void setup_rt_frame (int sig, struct k_sigaction *ka, siginfo_t *info,
 
 	/* Set up to return from userspace.  */
 	err |= __put_user(frame->retcode, &frame->pretcode);
+#ifdef __mcoldfire__
+	/* movel #__NR_rt_sigreturn,d0; trap #0 */
+	err |= __put_user(0x203c0000, (long __user *)(frame->retcode + 0));
+	err |= __put_user(0x00004e40 + (__NR_rt_sigreturn << 16),
+			  (long __user *)(frame->retcode + 4));
+#else
 	/* moveq #,d0; notb d0; trap #0 */
 	err |= __put_user(0x70004600 + ((__NR_rt_sigreturn ^ 0xff) << 16),
 			  (long __user *)(frame->retcode + 0));
 	err |= __put_user(0x4e40, (short __user *)(frame->retcode + 4));
+#endif
 
 	if (err)
 		goto give_sigsegv;
-- 
1.6.4


[-- Attachment #3: 0002-Fix-m68k-uclinux-s-rt_sigreturn-trampoline.patch --]
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>From ac003b05af17bb48e6acffd454cae6fdf6e80737 Mon Sep 17 00:00:00 2001
From: Maxim Kuvyrkov <maxim@codesourcery.com>
Date: Wed, 23 Sep 2009 01:25:44 +0400
Subject: [PATCH 2/2] Fix m68k-uclinux's rt_sigreturn trampoline


Signed-off-by: Maxim Kuvyrkov <maxim@codesourcery.com>
---
 arch/m68knommu/kernel/entry.S |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/m68knommu/kernel/entry.S b/arch/m68knommu/kernel/entry.S
index f56faa5..2717605 100644
--- a/arch/m68knommu/kernel/entry.S
+++ b/arch/m68knommu/kernel/entry.S
@@ -145,6 +145,6 @@ ENTRY(ret_from_user_signal)
 	trap #0
 
 ENTRY(ret_from_user_rt_signal)
-	move #__NR_rt_sigreturn,%d0
+	movel #__NR_rt_sigreturn,%d0
 	trap #0
 
-- 
1.6.4