From f911d731054ab3d82ee72a16b889e17ca3a2332a Mon Sep 17 00:00:00 2001 From: Richard Weinberger Date: Wed, 10 Dec 2014 13:53:51 +0100 Subject: [PATCH 1/2] um: Skip futex_atomic_cmpxchg_inatomic() test futex_atomic_cmpxchg_inatomic() does not work on UML because it triggers a copy_from_user() in kernel context. On UML copy_from_user() can only be used if the kernel was called by a real user space process such that UML can use ptrace() to fetch the value. Reported-by: Miklos Szeredi Suggested-by: Geert Uytterhoeven Signed-off-by: Richard Weinberger Tested-by: Daniel Walter --- arch/um/Kconfig.common | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/um/Kconfig.common b/arch/um/Kconfig.common index 87bc86821bc9..d195a87ca542 100644 --- a/arch/um/Kconfig.common +++ b/arch/um/Kconfig.common @@ -3,6 +3,7 @@ config UML default y select HAVE_ARCH_AUDITSYSCALL select HAVE_UID16 + select HAVE_FUTEX_CMPXCHG if FUTEX select GENERIC_IRQ_SHOW select GENERIC_CPU_DEVICES select GENERIC_IO From b485342bd79af363c77ef1a421c4a0aef2de9812 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Sat, 3 Jan 2015 13:11:10 +0100 Subject: [PATCH 2/2] x86, um: actually mark system call tables readonly Commit a074335a370e ("x86, um: Mark system call tables readonly") was supposed to mark the sys_call_table in UML as RO by adding the const, but it doesn't have the desired effect as it's nevertheless being placed into the data section since __cacheline_aligned enforces sys_call_table being placed into .data..cacheline_aligned instead. We need to use the ____cacheline_aligned version instead to fix this issue. Before: $ nm -v arch/x86/um/sys_call_table_64.o | grep -1 "sys_call_table" U sys_writev 0000000000000000 D sys_call_table 0000000000000000 D syscall_table_size After: $ nm -v arch/x86/um/sys_call_table_64.o | grep -1 "sys_call_table" U sys_writev 0000000000000000 R sys_call_table 0000000000000000 D syscall_table_size Fixes: a074335a370e ("x86, um: Mark system call tables readonly") Cc: H. Peter Anvin Cc: Andrew Morton Signed-off-by: Daniel Borkmann Signed-off-by: Richard Weinberger --- arch/x86/um/sys_call_table_32.c | 2 +- arch/x86/um/sys_call_table_64.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/um/sys_call_table_32.c b/arch/x86/um/sys_call_table_32.c index 531d4269e2e3..bd16d6c370ec 100644 --- a/arch/x86/um/sys_call_table_32.c +++ b/arch/x86/um/sys_call_table_32.c @@ -34,7 +34,7 @@ typedef asmlinkage void (*sys_call_ptr_t)(void); extern asmlinkage void sys_ni_syscall(void); -const sys_call_ptr_t sys_call_table[] __cacheline_aligned = { +const sys_call_ptr_t sys_call_table[] ____cacheline_aligned = { /* * Smells like a compiler bug -- it doesn't work * when the & below is removed. diff --git a/arch/x86/um/sys_call_table_64.c b/arch/x86/um/sys_call_table_64.c index 20c3649d0691..5cdfa9db2217 100644 --- a/arch/x86/um/sys_call_table_64.c +++ b/arch/x86/um/sys_call_table_64.c @@ -47,7 +47,7 @@ typedef void (*sys_call_ptr_t)(void); extern void sys_ni_syscall(void); -const sys_call_ptr_t sys_call_table[] __cacheline_aligned = { +const sys_call_ptr_t sys_call_table[] ____cacheline_aligned = { /* * Smells like a compiler bug -- it doesn't work * when the & below is removed.