From 516949480d3700cbde4272228a102c84721d6007 Mon Sep 17 00:00:00 2001 From: Paolo 'Blaisorblade' Giarrusso Date: Thu, 29 Dec 2005 17:39:51 +0100 Subject: [PATCH] [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, ¤t is evaluated with CONFIG_DEBUG_SPINLOCK to check the spinlock owner task). And this leads to random segmentation faults. Exactly, what happens is that ¤t = *(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 Signed-off-by: Linus Torvalds --- arch/um/os-Linux/start_up.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) diff --git a/arch/um/os-Linux/start_up.c b/arch/um/os-Linux/start_up.c index 37517d49c4a..29a9e3f4376 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; -- 2.41.1