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Adds the "nosysemu" command line parameter to disable SYSEMU
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>
---
uml-linux-2.6.7-paolo/arch/um/kernel/process.c | 26 +++++++++++++++++++++----
1 files changed, 22 insertions(+), 4 deletions(-)
diff -puN arch/um/kernel/process.c~sysemu_cmdParam arch/um/kernel/process.c
--- uml-linux-2.6.7/arch/um/kernel/process.c~sysemu_cmdParam 2004-06-29 21:03:04.131009360 +0200
+++ uml-linux-2.6.7-paolo/arch/um/kernel/process.c 2004-06-29 21:03:04.134008904 +0200
@@ -196,6 +196,22 @@ static void stop_ptraced_child(int pid,
panic("check_ptrace : munmap failed, errno = %d", errno);
}
+static int force_sysemu_disabled = 0;
+
+static int __init nosysemu_cmd_param(char *str, int* add)
+{
+ force_sysemu_disabled = 1;
+ return 0;
+}
+
+__uml_setup("nosysemu", nosysemu_cmd_param,
+ "nosysemu\n"
+ " Turns off syscall emulation patch for ptrace (SYSEMU) on.\n"
+ " SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n"
+ " behaviour of ptrace() and helps reducing host context switch rate.\n"
+ " To make it working, you need a kernel patch for your host, too.\n"
+ " See http://perso.wanadoo.fr/laurent.vivier/UML/ for further information.\n");
+
void __init check_ptrace(void)
{
void *stack;
@@ -229,7 +245,6 @@ void __init check_ptrace(void)
stop_ptraced_child(pid, stack, 0);
printk("OK\n");
-#ifdef PTRACE_SYSEMU
printk("Checking syscall emulation patch for ptrace...");
use_sysemu = 0;
pid = start_ptraced_child(&stack);
@@ -252,8 +267,12 @@ void __init check_ptrace(void)
stop_ptraced_child(pid, stack, 0);
- printk("OK\n");
- use_sysemu = 1;
+ if (!force_sysemu_disabled) {
+ printk("found\n");
+ use_sysemu = 1;
+ } else {
+ printk("found but disabled\n");
+ }
}
else
{
@@ -261,7 +280,6 @@ void __init check_ptrace(void)
stop_ptraced_child(pid, stack, 1);
}
-# endif /* PTRACE_SYSEMU */
}
int run_kernel_thread(int (*fn)(void *), void *arg, void **jmp_ptr)
_
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