From 9a93848fe787a53aec404e4e00d8f7f9bbdaebb4 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 2 Feb 2017 14:43:51 +0100 Subject: x86/debug: Implement __WARN() using UD0 By using "UD0" for WARN()s we remove the function call and its possible __FILE__ and __LINE__ immediate arguments from the instruction stream. Total image size will not change much, what we win in the instruction stream we'll lose because of the __bug_table entries. Still, saves on I$ footprint and the total image size does go down a bit. text data filename 10702123 4530992 defconfig-build/vmlinux.orig 10682460 4530992 defconfig-build/vmlinux.patched (UML didn't seem to use GENERIC_BUG at all, so remove it) Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Josh Poimboeuf Cc: Arjan van de Ven Cc: Borislav Petkov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Richard Weinberger Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- arch/x86/kernel/dumpstack.c | 3 --- 1 file changed, 3 deletions(-) (limited to 'arch/x86/kernel/dumpstack.c') diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index 09d4ac0d2661..924f45ea4382 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -289,9 +289,6 @@ void die(const char *str, struct pt_regs *regs, long err) unsigned long flags = oops_begin(); int sig = SIGSEGV; - if (!user_mode(regs)) - report_bug(regs->ip, regs); - if (__die(str, regs, err)) sig = 0; oops_end(flags, regs, sig); -- cgit v1.2.3 From e335bb51cc15e80ac180701a0d335ef1c050828e Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 17 Apr 2017 08:44:00 -0500 Subject: x86/unwind: Ensure stack pointer is aligned With frame pointers disabled, on some older versions of GCC (like 4.8.3), it's possible for the stack pointer to get aligned at a half-word boundary: 00000000000004d0 : 4d0: 41 57 push %r15 4d2: 41 56 push %r14 4d4: 41 55 push %r13 4d6: 41 54 push %r12 4d8: 55 push %rbp 4d9: 53 push %rbx 4da: 48 83 ec 24 sub $0x24,%rsp In such a case, the unwinder ends up reading the entire stack at the wrong alignment. Then the last read goes past the end of the stack, hitting the stack guard page: BUG: stack guard page was hit at ffffc900217c4000 (stack is ffffc900217c0000..ffffc900217c3fff) kernel stack overflow (page fault): 0000 [#1] SMP ... Fix it by ensuring the stack pointer is properly aligned before unwinding. Reported-by: Jirka Hladky Signed-off-by: Josh Poimboeuf Acked-by: Thomas Gleixner Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Fixes: 7c7900f89770 ("x86/unwind: Add new unwind interface and implementations") Link: http://lkml.kernel.org/r/cff33847cc9b02fa548625aa23268ac574460d8d.1492436590.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/dumpstack.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86/kernel/dumpstack.c') diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index 924f45ea4382..dbce3cca94cb 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -77,7 +77,7 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs, * - softirq stack * - hardirq stack */ - for (regs = NULL; stack; stack = stack_info.next_sp) { + for (regs = NULL; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) { const char *stack_name; /* -- cgit v1.2.3