diff options
Diffstat (limited to 'arch/x86/entry/common.c')
| -rw-r--r-- | arch/x86/entry/common.c | 49 |
1 files changed, 46 insertions, 3 deletions
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index bd3f14175193..e83b3f14897c 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -45,6 +45,32 @@ #define CREATE_TRACE_POINTS #include <trace/events/syscalls.h> +/* Check that the stack and regs on entry from user mode are sane. */ +static void check_user_regs(struct pt_regs *regs) +{ + if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) { + /* + * Make sure that the entry code gave us a sensible EFLAGS + * register. Native because we want to check the actual CPU + * state, not the interrupt state as imagined by Xen. + */ + unsigned long flags = native_save_fl(); + WARN_ON_ONCE(flags & (X86_EFLAGS_AC | X86_EFLAGS_DF | + X86_EFLAGS_NT)); + + /* We think we came from user mode. Make sure pt_regs agrees. */ + WARN_ON_ONCE(!user_mode(regs)); + + /* + * All entries from user mode (except #DF) should be on the + * normal thread stack and should have user pt_regs in the + * correct location. + */ + WARN_ON_ONCE(!on_thread_stack()); + WARN_ON_ONCE(regs != task_pt_regs(current)); + } +} + #ifdef CONFIG_CONTEXT_TRACKING /** * enter_from_user_mode - Establish state when coming from user mode @@ -127,9 +153,6 @@ static long syscall_trace_enter(struct pt_regs *regs) unsigned long ret = 0; u32 work; - if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) - BUG_ON(regs != task_pt_regs(current)); - work = READ_ONCE(ti->flags); if (work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) { @@ -346,6 +369,8 @@ __visible noinstr void do_syscall_64(unsigned long nr, struct pt_regs *regs) { struct thread_info *ti; + check_user_regs(regs); + enter_from_user_mode(); instrumentation_begin(); @@ -409,6 +434,8 @@ static void do_syscall_32_irqs_on(struct pt_regs *regs) /* Handles int $0x80 */ __visible noinstr void do_int80_syscall_32(struct pt_regs *regs) { + check_user_regs(regs); + enter_from_user_mode(); instrumentation_begin(); @@ -460,6 +487,8 @@ __visible noinstr long do_fast_syscall_32(struct pt_regs *regs) vdso_image_32.sym_int80_landing_pad; bool success; + check_user_regs(regs); + /* * SYSENTER loses EIP, and even SYSCALL32 needs us to skip forward * so that 'regs->ip -= 2' lands back on an int $0x80 instruction. @@ -510,6 +539,18 @@ __visible noinstr long do_fast_syscall_32(struct pt_regs *regs) (regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF | X86_EFLAGS_VM)) == 0; #endif } + +/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */ +__visible noinstr long do_SYSENTER_32(struct pt_regs *regs) +{ + /* SYSENTER loses RSP, but the vDSO saved it in RBP. */ + regs->sp = regs->bp; + + /* SYSENTER clobbers EFLAGS.IF. Assume it was set in usermode. */ + regs->flags |= X86_EFLAGS_IF; + + return do_fast_syscall_32(regs); +} #endif SYSCALL_DEFINE0(ni_syscall) @@ -553,6 +594,7 @@ SYSCALL_DEFINE0(ni_syscall) bool noinstr idtentry_enter_cond_rcu(struct pt_regs *regs) { if (user_mode(regs)) { + check_user_regs(regs); enter_from_user_mode(); return false; } @@ -686,6 +728,7 @@ void noinstr idtentry_exit_cond_rcu(struct pt_regs *regs, bool rcu_exit) */ void noinstr idtentry_enter_user(struct pt_regs *regs) { + check_user_regs(regs); enter_from_user_mode(); } |