Messages in this thread Patch in this message | | | Date | Fri, 10 Mar 2006 14:42:12 -0800 | From | Markus Gutschke <> | Subject | Re: [PATCH 1/1] x86: Make _syscallX() macros compile in PIC mode on i386 (updated patch) |
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From: Markus Gutschke <markus@google.com>
Gcc reserves %ebx when compiling position-independent-code on i386. This means, the _syscallX() macros in include/asm-i386/unistd.h will not compile. This patch is against 2.6.15.6 and changes the existing macros to take special care to preserve %ebx.
The bug can be tracked at http://bugzilla.kernel.org/show_bug.cgi?id=6204
Signed-off-by: Markus Gutschke <markus@google.com>
---
Andrew Morton wrote: > Markus Gutschke <markus@google.com> wrote: >>That is certainly possible. The new macros work in both modes, but they >>are slightly less efficient than the old macros, if you have access to >>%ebx (i.e. in non-PIC code). If you prefer, we could just remove the old >>macros and unconditionally replace them with the new ones. > > I'd be OK with that - the kernel doesn't (shouldn't) care about the > performance of __KERNEL_SYSCALLS__ stuff. I doubt if glibc is borrowing > the kernel's macros.
Would you like this patch better? It now unconditionally replaces the old macros with a fixed version. This will entail a minor performance penalty in non-PIC mode. But for the vast majority of applications the difference should be entire negligible.
Once this change has made it into the kernel, I will try to get it propagated into libc.
Markus --- linux-2.6.15.6/include/asm-i386/unistd.h.orig 2006-03-05 11:07:54.000000000 -0800 +++ linux-2.6.15.6/include/asm-i386/unistd.h 2006-03-10 14:33:10.000000000 -0800 @@ -330,9 +330,9 @@ type name(type1 arg1) \ { \ long __res; \ -__asm__ volatile ("int $0x80" \ +__asm__ volatile ("push %%ebx ; movl %2,%%ebx ; int $0x80 ; pop %%ebx" \ : "=a" (__res) \ - : "0" (__NR_##name),"b" ((long)(arg1)) : "memory"); \ + : "0" (__NR_##name),"ri" ((long)(arg1)) : "memory"); \ __syscall_return(type,__res); \ } @@ -340,9 +340,10 @@ type name(type1 arg1,type2 arg2) \ { \ long __res; \ -__asm__ volatile ("int $0x80" \ +__asm__ volatile ("push %%ebx ; movl %2,%%ebx ; int $0x80 ; pop %%ebx" \ : "=a" (__res) \ - : "0" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)) : "memory"); \ + : "0" (__NR_##name),"ri" ((long)(arg1)),"c" ((long)(arg2)) \ + : "memory"); \ __syscall_return(type,__res); \ } @@ -350,9 +351,9 @@ type name(type1 arg1,type2 arg2,type3 arg3) \ { \ long __res; \ -__asm__ volatile ("int $0x80" \ +__asm__ volatile ("push %%ebx ; movl %2,%%ebx ; int $0x80 ; pop %%ebx" \ : "=a" (__res) \ - : "0" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \ + : "0" (__NR_##name),"ri" ((long)(arg1)),"c" ((long)(arg2)), \ "d" ((long)(arg3)) : "memory"); \ __syscall_return(type,__res); \ } @@ -361,9 +362,9 @@ type name (type1 arg1, type2 arg2, type3 arg3, type4 arg4) \ { \ long __res; \ -__asm__ volatile ("int $0x80" \ +__asm__ volatile ("push %%ebx ; movl %2,%%ebx ; int $0x80 ; pop %%ebx" \ : "=a" (__res) \ - : "0" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \ + : "0" (__NR_##name),"ri" ((long)(arg1)),"c" ((long)(arg2)), \ "d" ((long)(arg3)),"S" ((long)(arg4)) : "memory"); \ __syscall_return(type,__res); \ } @@ -373,10 +374,12 @@ type name (type1 arg1,type2 arg2,type3 arg3,type4 arg4,type5 arg5) \ { \ long __res; \ -__asm__ volatile ("int $0x80" \ +__asm__ volatile ("push %%ebx ; movl %2,%%ebx ; movl %1,%%eax ; " \ + "int $0x80 ; pop %%ebx" \ : "=a" (__res) \ - : "0" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \ - "d" ((long)(arg3)),"S" ((long)(arg4)),"D" ((long)(arg5)) : "memory"); \ + : "i" (__NR_##name),"ri" ((long)(arg1)),"c" ((long)(arg2)), \ + "d" ((long)(arg3)),"S" ((long)(arg4)),"D" ((long)(arg5)) \ + : "memory"); \ __syscall_return(type,__res); \ } @@ -385,11 +388,14 @@ type name (type1 arg1,type2 arg2,type3 arg3,type4 arg4,type5 arg5,type6 arg6) \ { \ long __res; \ -__asm__ volatile ("push %%ebp ; movl %%eax,%%ebp ; movl %1,%%eax ; int $0x80 ; pop %%ebp" \ - : "=a" (__res) \ - : "i" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \ - "d" ((long)(arg3)),"S" ((long)(arg4)),"D" ((long)(arg5)), \ - "0" ((long)(arg6)) : "memory"); \ + struct { long __a1; long __a6; } __s = { (long)arg1, (long)arg6 }; \ +__asm__ volatile ("push %%ebp ; push %%ebx ; movl 4(%2),%%ebp ; " \ + "movl 0(%2),%%ebx ; movl %1,%%eax ; int $0x80 ; " \ + "pop %%ebx ; pop %%ebp" \ + : "=a" (__res) \ + : "i" (__NR_##name),"0" ((long)(&__s)),"c" ((long)(arg2)), \ + "d" ((long)(arg3)),"S" ((long)(arg4)),"D" ((long)(arg5)) \ + : "memory"); \ __syscall_return(type,__res); \ } | |