RE: [WATCHDOG] v2.6.26 hpwdt.c fixes

[Mingarelli, Thomas]

I agree that that portion of the driver can be improved upon immensely. It was a pain getting something to work. Your 32 bit changes have been tested by two separate parties and proven to work without the -O flag.

I am in the process of testing the 64 bit changes and will post the results asap.


Thanks,

Tom

-----Original Message-----
From: Linus Torvalds [mailto:torvalds@xxxxxxxxxxxxxxxxxxxx]
Sent: Wednesday, June 18, 2008 3:30 PM
To: Wim Van Sebroeck
Cc: Andrew Morton; LKML; Mingarelli, Thomas
Subject: Re: [WATCHDOG] v2.6.26 hpwdt.c fixes



On Wed, 18 Jun 2008, Linus Torvalds wrote:
>
> Quite frankly, this is *not* the right thing to do either: the proper
> thing to do is to just move the low-level call into the "asm" statement,
> and leave all the function prologue/epilogue entirely to the compiler.

Something like the following.

AGAIN! This is totally untested. It's meant as an *example* of how to use
inline asm properly, not meant to necessarily work or do the right thing.
It may be buggy as hell, for all I know. And there are probably better
ways to do this.

(This one does just the 64-bit version, because it's a bit easier: the
32-bit version needs to probably do some of the loading and storing of
registers manually in the inline asm just to avoid running out of them,
since the register pressure is worse).

                Linus

---
 drivers/watchdog/hpwdt.c |   50 +++++++++++++++------------------------------
 1 files changed, 17 insertions(+), 33 deletions(-)

diff --git a/drivers/watchdog/hpwdt.c b/drivers/watchdog/hpwdt.c
index 2686f3e..028c957 100644
--- a/drivers/watchdog/hpwdt.c
+++ b/drivers/watchdog/hpwdt.c
@@ -336,39 +336,23 @@ static int __devinit detect_cru_service(void)
 asmlinkage void asminline_call(struct cmn_registers *pi86Regs,
                               unsigned long *pRomEntry)
 {
-       asm("pushq      %rbp            \n\t"
-           "movq       %rsp, %rbp      \n\t"
-           "pushq      %rax            \n\t"
-           "pushq      %rbx            \n\t"
-           "pushq      %rdx            \n\t"
-           "pushq      %r12            \n\t"
-           "pushq      %r9             \n\t"
-           "movq       %rsi, %r12      \n\t"
-           "movq       %rdi, %r9       \n\t"
-           "movl       4(%r9),%ebx     \n\t"
-           "movl       8(%r9),%ecx     \n\t"
-           "movl       12(%r9),%edx    \n\t"
-           "movl       16(%r9),%esi    \n\t"
-           "movl       20(%r9),%edi    \n\t"
-           "movl       (%r9),%eax      \n\t"
-           "call       *%r12           \n\t"
-           "pushfq                     \n\t"
-           "popq        %r12           \n\t"
-           "popfq                      \n\t"
-           "movl       %eax, (%r9)     \n\t"
-           "movl       %ebx, 4(%r9)    \n\t"
-           "movl       %ecx, 8(%r9)    \n\t"
-           "movl       %edx, 12(%r9)   \n\t"
-           "movl       %esi, 16(%r9)   \n\t"
-           "movl       %edi, 20(%r9)   \n\t"
-           "movq       %r12, %rax      \n\t"
-           "movl       %eax, 28(%r9)   \n\t"
-           "popq       %r9             \n\t"
-           "popq       %r12            \n\t"
-           "popq       %rdx            \n\t"
-           "popq       %rbx            \n\t"
-           "popq       %rax            \n\t"
-           "leave                      \n\t" "ret");
+       asm("pushq %0 ; popfq ; call *%6; pushfq; popfq %0"
+               :"=r" (pi86Regs->reflags),
+                "=a" (pi86Regs->u1.reax),
+                "=b" (pi86Regs->u2.rebx),
+                "=c" (pi86Regs->u3.recx),
+                "=d" (pi86Regs->u4.redx),
+                "=S" (pi86Regs->resi),
+                "=D" (pi86Regs->redi)
+               :"r" (pRomEntry),
+                "0" (pi86Regs->reflags),
+                "1" (pi86Regs->u1.reax),
+                "2" (pi86Regs->u2.rebx),
+                "3" (pi86Regs->u3.recx),
+                "4" (pi86Regs->u4.redx),
+                "5" (pi86Regs->resi),
+                "6" (pi86Regs->redi)
+               :"cc", "memory");
 }

 /*
--
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