From 81c2949f7fdcf8ff681326669afde24962232670 Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Tue, 5 Jul 2016 00:31:27 +0200 Subject: x86/dumpstack: Add show_stack_regs() and use it Add a helper to dump supplied pt_regs and use it in the MSR exception handling code to have precise stack traces pointing to the actual function causing the MSR access exception and not the stack frame of the exception handler itself. The new output looks like this: unchecked MSR access error: RDMSR from 0xdeadbeef at rIP: 0xffffffff8102ddb6 (early_init_intel+0x16/0x3a0) 00000000756e6547 ffffffff81c03f68 ffffffff81dd0940 ffffffff81c03f10 ffffffff81d42e65 0000000001000000 ffffffff81c03f58 ffffffff81d3e5a3 0000800000000000 ffffffff81800080 ffffffffffffffff 0000000000000000 Call Trace: [] early_cpu_init+0xe7/0x136 [] setup_arch+0xa5/0x9df [] start_kernel+0x9f/0x43a [] x86_64_start_reservations+0x2f/0x31 [] x86_64_start_kernel+0x168/0x176 Signed-off-by: Borislav Petkov Reviewed-by: Andy Lutomirski Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1467671487-10344-4-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar --- arch/x86/mm/extable.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) (limited to 'arch/x86/mm/extable.c') diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c index 4bb53b8..fafc771 100644 --- a/arch/x86/mm/extable.c +++ b/arch/x86/mm/extable.c @@ -1,6 +1,7 @@ #include #include #include +#include typedef bool (*ex_handler_t)(const struct exception_table_entry *, struct pt_regs *, int); @@ -46,8 +47,9 @@ EXPORT_SYMBOL(ex_handler_ext); bool ex_handler_rdmsr_unsafe(const struct exception_table_entry *fixup, struct pt_regs *regs, int trapnr) { - WARN_ONCE(1, "unchecked MSR access error: RDMSR from 0x%x\n", - (unsigned int)regs->cx); + if (pr_warn_once("unchecked MSR access error: RDMSR from 0x%x at rIP: 0x%lx (%pF)\n", + (unsigned int)regs->cx, regs->ip, (void *)regs->ip)) + show_stack_regs(regs); /* Pretend that the read succeeded and returned 0. */ regs->ip = ex_fixup_addr(fixup); @@ -60,9 +62,10 @@ EXPORT_SYMBOL(ex_handler_rdmsr_unsafe); bool ex_handler_wrmsr_unsafe(const struct exception_table_entry *fixup, struct pt_regs *regs, int trapnr) { - WARN_ONCE(1, "unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x)\n", - (unsigned int)regs->cx, - (unsigned int)regs->dx, (unsigned int)regs->ax); + if (pr_warn_once("unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x) at rIP: 0x%lx (%pF)\n", + (unsigned int)regs->cx, (unsigned int)regs->dx, + (unsigned int)regs->ax, regs->ip, (void *)regs->ip)) + show_stack_regs(regs); /* Pretend that the write succeeded. */ regs->ip = ex_fixup_addr(fixup); -- cgit v1.1