From 5b7b15afee89d6940482259b54d0864b7b2302b0 Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Sun, 18 Dec 2005 17:50:39 +0100 Subject: [PATCH] [PATCH] uml skas0: stop gcc's insanity With Paolo 'Blaisorblade' Giarrusso UML skas0 stub has been miscompiling for many people (incidentally not the authors), depending on the used GCC versions. I think (and testing on some GCC versions shows) this patch avoids the fundamental issue which is behind this, namely gcc using the stack when we have just replaced it, behind gcc's back. The remapping and storage of the return value is hidden in a blob of asm, hopefully giving gcc no room for creativity. Signed-off-by: Paolo 'Blaisorblade' Giarrusso Signed-off-by: Linus Torvalds --- arch/um/include/sysdep-i386/stub.h | 29 +++++++++++++++------------ arch/um/include/sysdep-x86_64/stub.h | 30 ++++++++++++++++------------ arch/um/kernel/skas/clone.c | 23 +++++++++++---------- 3 files changed, 46 insertions(+), 36 deletions(-) diff --git a/arch/um/include/sysdep-i386/stub.h b/arch/um/include/sysdep-i386/stub.h index 6ba8cbbe0d..b492b12b4a 100644 --- a/arch/um/include/sysdep-i386/stub.h +++ b/arch/um/include/sysdep-i386/stub.h @@ -6,8 +6,12 @@ #ifndef __SYSDEP_STUB_H #define __SYSDEP_STUB_H +#include #include #include +#include "stub-data.h" +#include "kern_constants.h" +#include "uml-config.h" extern void stub_segv_handler(int sig); extern void stub_clone_handler(void); @@ -76,23 +80,22 @@ static inline long stub_syscall5(long syscall, long arg1, long arg2, long arg3, return ret; } -static inline long stub_syscall6(long syscall, long arg1, long arg2, long arg3, - long arg4, long arg5, long arg6) +static inline void trap_myself(void) { - long ret; - - __asm__ volatile ("push %%ebp ; movl %%eax,%%ebp ; movl %1,%%eax ; " - "int $0x80 ; pop %%ebp" - : "=a" (ret) - : "g" (syscall), "b" (arg1), "c" (arg2), "d" (arg3), - "S" (arg4), "D" (arg5), "0" (arg6)); - - return ret; + __asm("int3"); } -static inline void trap_myself(void) +static inline void remap_stack(int fd, unsigned long offset) { - __asm("int3"); + __asm__ volatile ("movl %%eax,%%ebp ; movl %0,%%eax ; int $0x80 ;" + "movl %7, %%ebx ; movl %%eax, (%%ebx)" + : : "g" (STUB_MMAP_NR), "b" (UML_CONFIG_STUB_DATA), + "c" (UM_KERN_PAGE_SIZE), + "d" (PROT_READ | PROT_WRITE), + "S" (MAP_FIXED | MAP_SHARED), "D" (fd), + "a" (offset), + "i" (&((struct stub_data *) UML_CONFIG_STUB_DATA)->err) + : "memory"); } #endif diff --git a/arch/um/include/sysdep-x86_64/stub.h b/arch/um/include/sysdep-x86_64/stub.h index c41689c13d..92e989f817 100644 --- a/arch/um/include/sysdep-x86_64/stub.h +++ b/arch/um/include/sysdep-x86_64/stub.h @@ -6,8 +6,12 @@ #ifndef __SYSDEP_STUB_H #define __SYSDEP_STUB_H +#include #include #include +#include "stub-data.h" +#include "kern_constants.h" +#include "uml-config.h" extern void stub_segv_handler(int sig); extern void stub_clone_handler(void); @@ -81,23 +85,23 @@ static inline long stub_syscall5(long syscall, long arg1, long arg2, long arg3, return ret; } -static inline long stub_syscall6(long syscall, long arg1, long arg2, long arg3, - long arg4, long arg5, long arg6) +static inline void trap_myself(void) { - long ret; - - __asm__ volatile ("movq %5,%%r10 ; movq %6,%%r8 ; " - "movq %7, %%r9; " __syscall : "=a" (ret) - : "0" (syscall), "D" (arg1), "S" (arg2), "d" (arg3), - "g" (arg4), "g" (arg5), "g" (arg6) - : __syscall_clobber, "r10", "r8", "r9" ); - - return ret; + __asm("int3"); } -static inline void trap_myself(void) +static inline void remap_stack(long fd, unsigned long offset) { - __asm("int3"); + __asm__ volatile ("movq %4,%%r10 ; movq %5,%%r8 ; " + "movq %6, %%r9; " __syscall "; movq %7, %%rbx ; " + "movq %%rax, (%%rbx)": + : "a" (STUB_MMAP_NR), "D" (UML_CONFIG_STUB_DATA), + "S" (UM_KERN_PAGE_SIZE), + "d" (PROT_READ | PROT_WRITE), + "g" (MAP_FIXED | MAP_SHARED), "g" (fd), + "g" (offset), + "i" (&((struct stub_data *) UML_CONFIG_STUB_DATA)->err) + : __syscall_clobber, "r10", "r8", "r9" ); } #endif diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c index cb37ce9124..47b812b3bc 100644 --- a/arch/um/kernel/skas/clone.c +++ b/arch/um/kernel/skas/clone.c @@ -18,11 +18,10 @@ * on some systems. */ -#define STUB_DATA(field) (((struct stub_data *) UML_CONFIG_STUB_DATA)->field) - void __attribute__ ((__section__ (".__syscall_stub"))) stub_clone_handler(void) { + struct stub_data *data = (struct stub_data *) UML_CONFIG_STUB_DATA; long err; err = stub_syscall2(__NR_clone, CLONE_PARENT | CLONE_FILES | SIGCHLD, @@ -35,17 +34,21 @@ stub_clone_handler(void) if(err) goto out; - err = stub_syscall3(__NR_setitimer, ITIMER_VIRTUAL, - (long) &STUB_DATA(timer), 0); + err = stub_syscall3(__NR_setitimer, ITIMER_VIRTUAL, + (long) &data->timer, 0); if(err) goto out; - err = stub_syscall6(STUB_MMAP_NR, UML_CONFIG_STUB_DATA, - UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE, - MAP_FIXED | MAP_SHARED, STUB_DATA(fd), - STUB_DATA(offset)); + remap_stack(data->fd, data->offset); + goto done; + out: - /* save current result. Parent: pid; child: retcode of mmap */ - STUB_DATA(err) = err; + /* save current result. + * Parent: pid; + * child: retcode of mmap already saved and it jumps around this + * assignment + */ + data->err = err; + done: trap_myself(); } -- 2.39.5