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c317d306d5
The function try_to_clear_window_buffer is only called from rtrap_32.c. After it is called the signal pending state is retested, and signals are handled if TIF_SIGPENDING is set. This allows try_to_clear_window_buffer to call force_fatal_signal and then rely on the signal being delivered to kill the process, without any danger of returning to userspace, or otherwise using possible corrupt state on failure. The functional difference between force_fatal_sig and do_exit is that do_exit will only terminate a single thread, and will never trigger a core-dump. A multi-threaded program for which a single thread terminates unexpectedly is hard to reason about. Calling force_fatal_sig does not give userspace a chance to catch the signal, but otherwise is an ordinary fatal signal exit, and it will trigger a coredump of the offending process if core dumps are enabled. Cc: David Miller <davem@davemloft.net> Cc: sparclinux@vger.kernel.org Link: https://lkml.kernel.org/r/20211020174406.17889-15-ebiederm@xmission.com Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
131 lines
3.3 KiB
C
131 lines
3.3 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* windows.c: Routines to deal with register window management
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* at the C-code level.
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*
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* Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
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*/
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/string.h>
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#include <linux/mm.h>
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#include <linux/smp.h>
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#include <asm/cacheflush.h>
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#include <linux/uaccess.h>
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#include "kernel.h"
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/* Do save's until all user register windows are out of the cpu. */
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void flush_user_windows(void)
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{
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register int ctr asm("g5");
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ctr = 0;
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__asm__ __volatile__(
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"\n1:\n\t"
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"ld [%%g6 + %2], %%g4\n\t"
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"orcc %%g0, %%g4, %%g0\n\t"
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"add %0, 1, %0\n\t"
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"bne 1b\n\t"
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" save %%sp, -64, %%sp\n"
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"2:\n\t"
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"subcc %0, 1, %0\n\t"
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"bne 2b\n\t"
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" restore %%g0, %%g0, %%g0\n"
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: "=&r" (ctr)
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: "0" (ctr),
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"i" ((const unsigned long)TI_UWINMASK)
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: "g4", "cc");
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}
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static inline void shift_window_buffer(int first_win, int last_win, struct thread_info *tp)
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{
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int i;
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for(i = first_win; i < last_win; i++) {
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tp->rwbuf_stkptrs[i] = tp->rwbuf_stkptrs[i+1];
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memcpy(&tp->reg_window[i], &tp->reg_window[i+1], sizeof(struct reg_window32));
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}
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}
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/* Place as many of the user's current register windows
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* on the stack that we can. Even if the %sp is unaligned
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* we still copy the window there, the only case that we don't
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* succeed is if the %sp points to a bum mapping altogether.
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* setup_frame() and do_sigreturn() use this before shifting
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* the user stack around. Future instruction and hardware
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* bug workaround routines will need this functionality as
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* well.
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*/
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void synchronize_user_stack(void)
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{
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struct thread_info *tp = current_thread_info();
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int window;
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flush_user_windows();
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if(!tp->w_saved)
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return;
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/* Ok, there is some dirty work to do. */
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for(window = tp->w_saved - 1; window >= 0; window--) {
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unsigned long sp = tp->rwbuf_stkptrs[window];
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/* Ok, let it rip. */
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if (copy_to_user((char __user *) sp, &tp->reg_window[window],
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sizeof(struct reg_window32)))
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continue;
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shift_window_buffer(window, tp->w_saved - 1, tp);
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tp->w_saved--;
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}
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}
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#if 0
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/* An optimization. */
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static inline void copy_aligned_window(void *dest, const void *src)
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{
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__asm__ __volatile__("ldd [%1], %%g2\n\t"
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"ldd [%1 + 0x8], %%g4\n\t"
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"std %%g2, [%0]\n\t"
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"std %%g4, [%0 + 0x8]\n\t"
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"ldd [%1 + 0x10], %%g2\n\t"
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"ldd [%1 + 0x18], %%g4\n\t"
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"std %%g2, [%0 + 0x10]\n\t"
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"std %%g4, [%0 + 0x18]\n\t"
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"ldd [%1 + 0x20], %%g2\n\t"
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"ldd [%1 + 0x28], %%g4\n\t"
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"std %%g2, [%0 + 0x20]\n\t"
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"std %%g4, [%0 + 0x28]\n\t"
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"ldd [%1 + 0x30], %%g2\n\t"
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"ldd [%1 + 0x38], %%g4\n\t"
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"std %%g2, [%0 + 0x30]\n\t"
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"std %%g4, [%0 + 0x38]\n\t" : :
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"r" (dest), "r" (src) :
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"g2", "g3", "g4", "g5");
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}
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#endif
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/* Try to push the windows in a threads window buffer to the
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* user stack. Unaligned %sp's are not allowed here.
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*/
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void try_to_clear_window_buffer(struct pt_regs *regs, int who)
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{
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struct thread_info *tp = current_thread_info();
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int window;
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flush_user_windows();
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for(window = 0; window < tp->w_saved; window++) {
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unsigned long sp = tp->rwbuf_stkptrs[window];
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if ((sp & 7) ||
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copy_to_user((char __user *) sp, &tp->reg_window[window],
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sizeof(struct reg_window32))) {
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force_fatal_sig(SIGILL);
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return;
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}
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}
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tp->w_saved = 0;
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}
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