aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>2005-12-29 17:39:51 +0100
committerLinus Torvalds <torvalds@g5.osdl.org>2005-12-29 09:48:15 -0800
commit516949480d3700cbde4272228a102c84721d6007 (patch)
treeb7fef00010e2ad97a9fdab4f683c1516948749cb
parent3603bc8dc5ab33941e6378fe52ea03b7f5561109 (diff)
downloadlinux-linaro-stable-516949480d3700cbde4272228a102c84721d6007.tar.gz
[PATCH] uml: fix random segfaults at bootup
Don't use printk() where "current_thread_info()" is crap. Until when we switch to running on init_stack, current_thread_info() evaluates to crap. Printk uses "current" at times (in detail, &current is evaluated with CONFIG_DEBUG_SPINLOCK to check the spinlock owner task). And this leads to random segmentation faults. Exactly, what happens is that &current = *(current_thread_info()), i.e. round down $esp and dereference the value. I.e. access the stack below $esp, which causes SIGSEGV on a VM_GROWSDOWN vma (see arch/i386/mm/fault.c). Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--arch/um/os-Linux/start_up.c22
1 files changed, 12 insertions, 10 deletions
diff --git a/arch/um/os-Linux/start_up.c b/arch/um/os-Linux/start_up.c
index 37517d49c4ae..29a9e3f43763 100644
--- a/arch/um/os-Linux/start_up.c
+++ b/arch/um/os-Linux/start_up.c
@@ -116,16 +116,16 @@ static int stop_ptraced_child(int pid, void *stack, int exitcode,
if(!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) {
int exit_with = WEXITSTATUS(status);
if (exit_with == 2)
- printk("check_ptrace : child exited with status 2. "
+ printf("check_ptrace : child exited with status 2. "
"Serious trouble happening! Try updating your "
"host skas patch!\nDisabling SYSEMU support.");
- printk("check_ptrace : child exited with exitcode %d, while "
+ printf("check_ptrace : child exited with exitcode %d, while "
"expecting %d; status 0x%x", exit_with,
exitcode, status);
if (mustpanic)
panic("\n");
else
- printk("\n");
+ printf("\n");
ret = -1;
}
@@ -183,7 +183,7 @@ static void __init check_sysemu(void)
void *stack;
int pid, n, status, count=0;
- printk("Checking syscall emulation patch for ptrace...");
+ printf("Checking syscall emulation patch for ptrace...");
sysemu_supported = 0;
pid = start_ptraced_child(&stack);
@@ -207,10 +207,10 @@ static void __init check_sysemu(void)
goto fail_stopped;
sysemu_supported = 1;
- printk("OK\n");
+ printf("OK\n");
set_using_sysemu(!force_sysemu_disabled);
- printk("Checking advanced syscall emulation patch for ptrace...");
+ printf("Checking advanced syscall emulation patch for ptrace...");
pid = start_ptraced_child(&stack);
if(ptrace(PTRACE_OLDSETOPTIONS, pid, 0,
@@ -246,7 +246,7 @@ static void __init check_sysemu(void)
goto fail_stopped;
sysemu_supported = 2;
- printk("OK\n");
+ printf("OK\n");
if ( !force_sysemu_disabled )
set_using_sysemu(sysemu_supported);
@@ -255,7 +255,7 @@ static void __init check_sysemu(void)
fail:
stop_ptraced_child(pid, stack, 1, 0);
fail_stopped:
- printk("missing\n");
+ printf("missing\n");
}
static void __init check_ptrace(void)
@@ -263,7 +263,7 @@ static void __init check_ptrace(void)
void *stack;
int pid, syscall, n, status;
- printk("Checking that ptrace can change system call numbers...");
+ printf("Checking that ptrace can change system call numbers...");
pid = start_ptraced_child(&stack);
if(ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
@@ -292,7 +292,7 @@ static void __init check_ptrace(void)
}
}
stop_ptraced_child(pid, stack, 0, 1);
- printk("OK\n");
+ printf("OK\n");
check_sysemu();
}
@@ -472,6 +472,8 @@ int can_do_skas(void)
int have_devanon = 0;
+/* Runs on boot kernel stack - already safe to use printk. */
+
void check_devanon(void)
{
int fd;