From 3c88c692c28746473791276f8b42d2c989d6cbe6 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 7 May 2019 23:25:54 +0200 Subject: x86/stackframe/32: Provide consistent pt_regs Currently pt_regs on x86_32 has an oddity in that kernel regs (!user_mode(regs)) are short two entries (esp/ss). This means that any code trying to use them (typically: regs->sp) needs to jump through some unfortunate hoops. Change the entry code to fix this up and create a full pt_regs frame. This then simplifies various trampolines in ftrace and kprobes, the stack unwinder, ptrace, kdump and kgdb. Much thanks to Josh for help with the cleanups! Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Josh Poimboeuf Acked-by: Masami Hiramatsu Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar --- arch/x86/kernel/unwind_frame.c | 32 ++++---------------------------- 1 file changed, 4 insertions(+), 28 deletions(-) (limited to 'arch/x86/kernel/unwind_frame.c') diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c index 6106760de716..a224b5ab103f 100644 --- a/arch/x86/kernel/unwind_frame.c +++ b/arch/x86/kernel/unwind_frame.c @@ -70,15 +70,6 @@ static void unwind_dump(struct unwind_state *state) } } -static size_t regs_size(struct pt_regs *regs) -{ - /* x86_32 regs from kernel mode are two words shorter: */ - if (IS_ENABLED(CONFIG_X86_32) && !user_mode(regs)) - return sizeof(*regs) - 2*sizeof(long); - - return sizeof(*regs); -} - static bool in_entry_code(unsigned long ip) { char *addr = (char *)ip; @@ -198,12 +189,6 @@ static struct pt_regs *decode_frame_pointer(unsigned long *bp) } #endif -#ifdef CONFIG_X86_32 -#define KERNEL_REGS_SIZE (sizeof(struct pt_regs) - 2*sizeof(long)) -#else -#define KERNEL_REGS_SIZE (sizeof(struct pt_regs)) -#endif - static bool update_stack_state(struct unwind_state *state, unsigned long *next_bp) { @@ -214,7 +199,7 @@ static bool update_stack_state(struct unwind_state *state, size_t len; if (state->regs) - prev_frame_end = (void *)state->regs + regs_size(state->regs); + prev_frame_end = (void *)state->regs + sizeof(*state->regs); else prev_frame_end = (void *)state->bp + FRAME_HEADER_SIZE; @@ -222,7 +207,7 @@ static bool update_stack_state(struct unwind_state *state, regs = decode_frame_pointer(next_bp); if (regs) { frame = (unsigned long *)regs; - len = KERNEL_REGS_SIZE; + len = sizeof(*regs); state->got_irq = true; } else { frame = next_bp; @@ -246,14 +231,6 @@ static bool update_stack_state(struct unwind_state *state, frame < prev_frame_end) return false; - /* - * On 32-bit with user mode regs, make sure the last two regs are safe - * to access: - */ - if (IS_ENABLED(CONFIG_X86_32) && regs && user_mode(regs) && - !on_stack(info, frame, len + 2*sizeof(long))) - return false; - /* Move state to the next frame: */ if (regs) { state->regs = regs; @@ -412,10 +389,9 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, * Pretend that the frame is complete and that BP points to it, but save * the real BP so that we can use it when looking for the next frame. */ - if (regs && regs->ip == 0 && - (unsigned long *)kernel_stack_pointer(regs) >= first_frame) { + if (regs && regs->ip == 0 && (unsigned long *)regs->sp >= first_frame) { state->next_bp = bp; - bp = ((unsigned long *)kernel_stack_pointer(regs)) - 1; + bp = ((unsigned long *)regs->sp) - 1; } /* Initialize stack info and make sure the frame data is accessible: */ -- cgit v1.2.3