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Message-ID: <20070922153931.GA31436@router.lepton.home>
Date: Sat, 22 Sep 2007 23:39:32 +0800
From: lepton <ytht.net@...il.com>
To: jdike@...aya.com
Cc: lkm <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH] 2.6.22.6 user-mode linux: No need to new a stack for clone without CLONE_VM
Since we just call clone without CLONE_VM, it is no need to
use anoymous mmap to get a new stack frame.
Let's keep codes simple.
Signed-off-by: Lepton Wu <ytht.net@...il.com>
diff -X linux-2.6.22.6-uml/Documentation/dontdiff -pru linux-2.6.22.6/arch/um/os-Linux/start_up.c linux-2.6.22.6-uml/arch/um/os-Linux/start_up.c
--- linux-2.6.22.6/arch/um/os-Linux/start_up.c 2007-09-14 17:41:10.000000000 +0800
+++ linux-2.6.22.6-uml/arch/um/os-Linux/start_up.c 2007-09-22 23:28:49.000000000 +0800
@@ -101,19 +101,13 @@ static void non_fatal(char *fmt, ...)
fflush(stdout);
}
-static int start_ptraced_child(void **stack_out)
+static int start_ptraced_child(void)
{
- void *stack;
- unsigned long sp;
+ unsigned long sp = (((unsigned long) &sp) & ~(UM_KERN_PAGE_SIZE-1))
+ + UM_KERN_PAGE_SIZE - sizeof(void *);
int pid, n, status;
- stack = mmap(NULL, UM_KERN_PAGE_SIZE,
- PROT_READ | PROT_WRITE | PROT_EXEC,
- MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
- if(stack == MAP_FAILED)
- fatal_perror("check_ptrace : mmap failed");
- sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);
- pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);
+ pid = clone(ptrace_child, sp, SIGCHLD, NULL);
if(pid < 0)
fatal_perror("start_ptraced_child : clone failed");
CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
@@ -123,7 +117,6 @@ static int start_ptraced_child(void **st
fatal("check_ptrace : expected SIGSTOP, got status = %d",
status);
- *stack_out = stack;
return pid;
}
@@ -133,7 +126,7 @@ static int start_ptraced_child(void **st
* So only for SYSEMU features we test mustpanic, while normal host features
* must work anyway!
*/
-static int stop_ptraced_child(int pid, void *stack, int exitcode,
+static int stop_ptraced_child(int pid, int exitcode,
int mustexit)
{
int status, n, ret = 0;
@@ -154,8 +147,6 @@ static int stop_ptraced_child(int pid, v
ret = -1;
}
- if(munmap(stack, UM_KERN_PAGE_SIZE) < 0)
- fatal_perror("check_ptrace : munmap failed");
return ret;
}
@@ -207,13 +198,12 @@ __uml_setup("nosysemu", nosysemu_cmd_par
static void __init check_sysemu(void)
{
- void *stack;
unsigned long regs[MAX_REG_NR];
int pid, n, status, count=0;
non_fatal("Checking syscall emulation patch for ptrace...");
sysemu_supported = 0;
- pid = start_ptraced_child(&stack);
+ pid = start_ptraced_child();
if(ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
goto fail;
@@ -240,7 +230,7 @@ static void __init check_sysemu(void)
goto fail;
}
- if (stop_ptraced_child(pid, stack, 0, 0) < 0)
+ if (stop_ptraced_child(pid, 0, 0) < 0)
goto fail_stopped;
sysemu_supported = 1;
@@ -248,7 +238,7 @@ static void __init check_sysemu(void)
set_using_sysemu(!force_sysemu_disabled);
non_fatal("Checking advanced syscall emulation patch for ptrace...");
- pid = start_ptraced_child(&stack);
+ pid = start_ptraced_child();
if((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
(void *) PTRACE_O_TRACESYSGOOD) < 0))
@@ -279,7 +269,7 @@ static void __init check_sysemu(void)
fatal("check_ptrace : expected SIGTRAP or "
"(SIGTRAP | 0x80), got status = %d", status);
}
- if (stop_ptraced_child(pid, stack, 0, 0) < 0)
+ if (stop_ptraced_child(pid, 0, 0) < 0)
goto fail_stopped;
sysemu_supported = 2;
@@ -290,18 +280,17 @@ static void __init check_sysemu(void)
return;
fail:
- stop_ptraced_child(pid, stack, 1, 0);
+ stop_ptraced_child(pid, 1, 0);
fail_stopped:
non_fatal("missing\n");
}
static void __init check_ptrace(void)
{
- void *stack;
int pid, syscall, n, status;
non_fatal("Checking that ptrace can change system call numbers...");
- pid = start_ptraced_child(&stack);
+ pid = start_ptraced_child();
if((ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
(void *) PTRACE_O_TRACESYSGOOD) < 0))
@@ -331,7 +320,7 @@ static void __init check_ptrace(void)
break;
}
}
- stop_ptraced_child(pid, stack, 0, 1);
+ stop_ptraced_child(pid, 0, 1);
non_fatal("OK\n");
check_sysemu();
}
@@ -412,11 +401,10 @@ __uml_setup("noptraceldt", noptraceldt_c
static inline void check_skas3_ptrace_faultinfo(void)
{
struct ptrace_faultinfo fi;
- void *stack;
int pid, n;
non_fatal(" - PTRACE_FAULTINFO...");
- pid = start_ptraced_child(&stack);
+ pid = start_ptraced_child();
n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
if (n < 0) {
@@ -434,13 +422,12 @@ static inline void check_skas3_ptrace_fa
}
init_registers(pid);
- stop_ptraced_child(pid, stack, 1, 1);
+ stop_ptraced_child(pid, 1, 1);
}
static inline void check_skas3_ptrace_ldt(void)
{
#ifdef PTRACE_LDT
- void *stack;
int pid, n;
unsigned char ldtbuf[40];
struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
@@ -449,7 +436,7 @@ static inline void check_skas3_ptrace_ld
.bytecount = sizeof(ldtbuf)};
non_fatal(" - PTRACE_LDT...");
- pid = start_ptraced_child(&stack);
+ pid = start_ptraced_child();
n = ptrace(PTRACE_LDT, pid, 0, (unsigned long) &ldt_op);
if (n < 0) {
@@ -467,7 +454,7 @@ static inline void check_skas3_ptrace_ld
non_fatal("found, but use is disabled\n");
}
- stop_ptraced_child(pid, stack, 1, 1);
+ stop_ptraced_child(pid, 1, 1);
#else
/* PTRACE_LDT might be disabled via cmdline option.
* We want to override this, else we might use the stub
-
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