From b85e9680a33ae2df04bd493f220a76dcf183ce80 Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Thu, 28 Jul 2005 21:16:01 -0700 Subject: [PATCH] [PATCH] uml: fix TT mode by reverting "use fork instead of clone" With Paolo 'Blaisorblade' Giarrusso Revert the following patch, because of miscompilation problems in different environments leading to UML not working *at all* in TT mode; it was merged lately in 2.6 development cycle, a little after being written, and has caused problems to lots of people; I know it's a bit too long, but it shouldn't have been merged in first place, so I still apply for inclusion in the -stable tree. Anyone using this feature currently is either using some older kernel (some reports even used 2.6.12-rc4-mm2) or using this patch, as included in my -bs patchset. For now there's not yet a fix for this patch, so for now the best thing is to drop it (which was widely reported to give a working kernel, and as such was even merged in -stable tree). "Convert the boot-time host ptrace testing from clone to fork. They were essentially doing fork anyway. This cleans up the code a bit, and makes valgrind a bit happier about grinding it." URL: http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=98fdffccea6cc3fe9dba32c0fcc310bcb5d71529 Signed-off-by: Jeff Dike Signed-off-by: Paolo 'Blaisorblade' Giarrusso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/kernel/process.c | 48 ++++++++++++++++++++++++---------------- 1 file changed, 29 insertions(+), 19 deletions(-) diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c index 8b01a5584e..67acd92c53 100644 --- a/arch/um/kernel/process.c +++ b/arch/um/kernel/process.c @@ -131,7 +131,7 @@ int start_fork_tramp(void *thread_arg, unsigned long temp_stack, return(arg.pid); } -static int ptrace_child(void) +static int ptrace_child(void *arg) { int ret; int pid = os_getpid(), ppid = getppid(); @@ -160,16 +160,20 @@ static int ptrace_child(void) _exit(ret); } -static int start_ptraced_child(void) +static int start_ptraced_child(void **stack_out) { + void *stack; + unsigned long sp; int pid, n, status; - pid = fork(); - if(pid == 0) - ptrace_child(); - + stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if(stack == MAP_FAILED) + panic("check_ptrace : mmap failed, errno = %d", errno); + sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *); + pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL); if(pid < 0) - panic("check_ptrace : fork failed, errno = %d", errno); + panic("check_ptrace : clone failed, errno = %d", errno); CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED)); if(n < 0) panic("check_ptrace : wait failed, errno = %d", errno); @@ -177,6 +181,7 @@ static int start_ptraced_child(void) panic("check_ptrace : expected SIGSTOP, got status = %d", status); + *stack_out = stack; return(pid); } @@ -184,12 +189,12 @@ static int start_ptraced_child(void) * just avoid using sysemu, not panic, but only if SYSEMU features are broken. * So only for SYSEMU features we test mustpanic, while normal host features * must work anyway!*/ -static int stop_ptraced_child(int pid, int exitcode, int mustexit) +static int stop_ptraced_child(int pid, void *stack, int exitcode, int mustpanic) { int status, n, ret = 0; if(ptrace(PTRACE_CONT, pid, 0, 0) < 0) - panic("stop_ptraced_child : ptrace failed, errno = %d", errno); + panic("check_ptrace : ptrace failed, errno = %d", errno); CATCH_EINTR(n = waitpid(pid, &status, 0)); if(!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) { int exit_with = WEXITSTATUS(status); @@ -200,13 +205,15 @@ static int stop_ptraced_child(int pid, int exitcode, int mustexit) printk("check_ptrace : child exited with exitcode %d, while " "expecting %d; status 0x%x", exit_with, exitcode, status); - if (mustexit) + if (mustpanic) panic("\n"); else printk("\n"); ret = -1; } + if(munmap(stack, PAGE_SIZE) < 0) + panic("check_ptrace : munmap failed, errno = %d", errno); return ret; } @@ -242,11 +249,12 @@ __uml_setup("nosysemu", nosysemu_cmd_param, static void __init check_sysemu(void) { + void *stack; int pid, syscall, n, status, count=0; printk("Checking syscall emulation patch for ptrace..."); sysemu_supported = 0; - pid = start_ptraced_child(); + pid = start_ptraced_child(&stack); if(ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0) goto fail; @@ -264,7 +272,7 @@ static void __init check_sysemu(void) panic("check_sysemu : failed to modify system " "call return, errno = %d", errno); - if (stop_ptraced_child(pid, 0, 0) < 0) + if (stop_ptraced_child(pid, stack, 0, 0) < 0) goto fail_stopped; sysemu_supported = 1; @@ -272,7 +280,7 @@ static void __init check_sysemu(void) set_using_sysemu(!force_sysemu_disabled); printk("Checking advanced syscall emulation patch for ptrace..."); - pid = start_ptraced_child(); + pid = start_ptraced_child(&stack); while(1){ count++; if(ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0) @@ -297,7 +305,7 @@ static void __init check_sysemu(void) break; } } - if (stop_ptraced_child(pid, 0, 0) < 0) + if (stop_ptraced_child(pid, stack, 0, 0) < 0) goto fail_stopped; sysemu_supported = 2; @@ -308,17 +316,18 @@ static void __init check_sysemu(void) return; fail: - stop_ptraced_child(pid, 1, 0); + stop_ptraced_child(pid, stack, 1, 0); fail_stopped: printk("missing\n"); } void __init check_ptrace(void) { + void *stack; int pid, syscall, n, status; printk("Checking that ptrace can change system call numbers..."); - pid = start_ptraced_child(); + pid = start_ptraced_child(&stack); if (ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0) panic("check_ptrace: PTRACE_SETOPTIONS failed, errno = %d", errno); @@ -345,7 +354,7 @@ void __init check_ptrace(void) break; } } - stop_ptraced_child(pid, 0, 1); + stop_ptraced_child(pid, stack, 0, 1); printk("OK\n"); check_sysemu(); } @@ -380,10 +389,11 @@ extern void *__syscall_stub_start, __syscall_stub_end; static inline void check_skas3_ptrace_support(void) { struct ptrace_faultinfo fi; + void *stack; int pid, n; printf("Checking for the skas3 patch in the host..."); - pid = start_ptraced_child(); + pid = start_ptraced_child(&stack); n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi); if (n < 0) { @@ -402,7 +412,7 @@ static inline void check_skas3_ptrace_support(void) } init_registers(pid); - stop_ptraced_child(pid, 1, 1); + stop_ptraced_child(pid, stack, 1, 1); } int can_do_skas(void) -- 2.39.5