ARC: Signal handling
Includes following fixes courtesy review by Al-Viro * Tracer poke to Callee-regs were lost Before going off into do_signal( ) we save the user-mode callee regs (as they are not saved by default as part of pt_regs). This is to make sure that that a Tracer (if tracing related signal) is able to do likes of PEEKUSR(callee-reg). However in return path we were simply discarding the user-mode callee regs, which would break a POKEUSR(callee-reg) from a tracer. * Issue related to multiple syscall restarts are addressed in next patch Signed-off-by: Vineet Gupta <vgupta@synopsys.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Acked-by: Jonas Bonn <jonas@southpole.se>
This commit is contained in:
Vineet Gupta
Родитель
d8005e6b95
Коммит
c3581039b6
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@ -20,6 +20,7 @@ config ARC
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select GENERIC_KERNEL_EXECVE
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select GENERIC_KERNEL_THREAD
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select GENERIC_PENDING_IRQ if SMP
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select GENERIC_SIGALTSTACK
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select GENERIC_SMP_IDLE_THREAD
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select HAVE_GENERIC_HARDIRQS
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select MODULES_USE_ELF_RELA
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@ -165,6 +165,41 @@
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.endm
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/*--------------------------------------------------------------
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* RESTORE_CALLEE_SAVED_USER:
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* This is called after do_signal where tracer might have changed callee regs
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* thus we need to restore the reg file.
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* Special case handling is required for r25 in case it is used by kernel
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* for caching task ptr. Ptrace would have modified on-kernel-stack value of
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* r25, which needs to be shoved back into task->thread.user_r25 where from
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* Low level exception/ISR return code will retrieve to populate with rest of
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* callee reg-file.
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*-------------------------------------------------------------*/
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.macro RESTORE_CALLEE_SAVED_USER
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add sp, sp, 4 /* skip "callee_regs->stack_place_holder" */
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#ifdef CONFIG_ARC_CURR_IN_REG
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ld.ab r12, [sp, 4]
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st r12, [r25, TASK_THREAD + THREAD_USER_R25]
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#else
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ld.ab r25, [sp, 4]
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#endif
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ld.ab r24, [sp, 4]
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ld.ab r23, [sp, 4]
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ld.ab r22, [sp, 4]
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ld.ab r21, [sp, 4]
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ld.ab r20, [sp, 4]
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ld.ab r19, [sp, 4]
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ld.ab r18, [sp, 4]
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ld.ab r17, [sp, 4]
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ld.ab r16, [sp, 4]
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ld.ab r15, [sp, 4]
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ld.ab r14, [sp, 4]
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ld.ab r13, [sp, 4]
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.endm
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/*--------------------------------------------------------------
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* Super FAST Restore callee saved regs by simply re-adjusting SP
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*-------------------------------------------------------------*/
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@ -0,0 +1,22 @@
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/*
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef _ASM_ARC_SIGCONTEXT_H
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#define _ASM_ARC_SIGCONTEXT_H
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#include <asm/ptrace.h>
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/*
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* Signal context structure - contains all info to do with the state
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* before the signal handler was invoked.
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*/
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struct sigcontext {
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struct user_regs_struct regs;
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};
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#endif /* _ASM_ARC_SIGCONTEXT_H */
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@ -0,0 +1,27 @@
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/*
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* Amit Bhor, Sameer Dhavale: Codito Technologies 2004
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*/
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#ifndef _ASM_ARC_SIGNAL_H
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#define _ASM_ARC_SIGNAL_H
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/*
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* This is much needed for ARC sigreturn optimization.
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* This allows uClibc to piggback the addr of a sigreturn stub in sigaction,
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* which allows sigreturn based re-entry into kernel after handling signal.
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* W/o this kernel needs to "synthesize" the sigreturn trampoline on user
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* mode stack which in turn forces the following:
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* -TLB Flush (after making the stack page executable)
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* -Cache line Flush (to make I/D Cache lines coherent)
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*/
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#define SA_RESTORER 0x04000000
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#include <asm-generic/signal.h>
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#endif /* _ASM_ARC_SIGNAL_H */
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@ -470,7 +470,11 @@ resume_user_mode_begin:
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bbit0 r9, TIF_SIGPENDING, .Lchk_notify_resume
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; save CALLEE Regs.
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; Normal Trap/IRQ entry only saves Scratch (caller-saved) regs
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; in pt_reg since the "C" ABI (kernel code) will automatically
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; save/restore callee-saved regs.
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;
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; However, here we need to explicitly save callee regs because
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; (i) If this signal causes coredump - full regfile needed
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; (ii) If signal is SIGTRAP/SIGSTOP, task is being traced thus
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; tracer might call PEEKUSR(CALLEE reg)
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@ -484,8 +488,9 @@ resume_user_mode_begin:
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bl @do_signal
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; unwind SP for cheap discard of Callee saved Regs
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DISCARD_CALLEE_SAVED_USER
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; Ideally we want to discard the Callee reg above, however if this was
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; a tracing signal, tracer could have done a POKEUSR(CALLEE reg)
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RESTORE_CALLEE_SAVED_USER
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b resume_user_mode_begin ; loop back to start of U mode ret
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@ -0,0 +1,356 @@
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/*
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* Signal Handling for ARC
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*
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* vineetg: Jan 2010 (Restarting of timer related syscalls)
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*
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* vineetg: Nov 2009 (Everything needed for TIF_RESTORE_SIGMASK)
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* -do_signal() supports TIF_RESTORE_SIGMASK
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* -do_signal() no loner needs oldset, required by OLD sys_sigsuspend
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* -sys_rt_sigsuspend() now comes from generic code, so discard arch implemen
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* -sys_sigsuspend() no longer needs to fudge ptregs, hence that arg removed
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* -sys_sigsuspend() no longer loops for do_signal(), sets TIF_xxx and leaves
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* the job to do_signal()
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*
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* vineetg: July 2009
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* -Modified Code to support the uClibc provided userland sigreturn stub
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* to avoid kernel synthesing it on user stack at runtime, costing TLB
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* probes and Cache line flushes.
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*
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* vineetg: July 2009
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* -In stash_usr_regs( ) and restore_usr_regs( ), save/restore of user regs
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* in done in block copy rather than one word at a time.
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* This saves around 2K of code and improves LMBench lat_sig <catch>
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*
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* rajeshwarr: Feb 2009
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* - Support for Realtime Signals
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*
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* vineetg: Aug 11th 2008: Bug #94183
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* -ViXS were still seeing crashes when using insmod to load drivers.
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* It turned out that the code to change Execute permssions for TLB entries
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* of user was not guarded for interrupts (mod_tlb_permission)
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* This was cauing TLB entries to be overwritten on unrelated indexes
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*
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* Vineetg: July 15th 2008: Bug #94183
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* -Exception happens in Delay slot of a JMP, and before user space resumes,
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* Signal is delivered (Ctrl + C) = >SIGINT.
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* setup_frame( ) sets up PC,SP,BLINK to enable user space signal handler
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* to run, but doesn't clear the Delay slot bit from status32. As a result,
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* on resuming user mode, signal handler branches off to BTA of orig JMP
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* -FIX: clear the DE bit from status32 in setup_frame( )
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*
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* Rahul Trivedi, Kanika Nema: Codito Technologies 2004
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*/
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#include <linux/signal.h>
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#include <linux/ptrace.h>
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#include <linux/personality.h>
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#include <linux/uaccess.h>
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#include <linux/syscalls.h>
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#include <linux/tracehook.h>
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#include <asm/ucontext.h>
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struct rt_sigframe {
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struct siginfo info;
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struct ucontext uc;
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#define MAGIC_SIGALTSTK 0x07302004
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unsigned int sigret_magic;
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};
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static int
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stash_usr_regs(struct rt_sigframe __user *sf, struct pt_regs *regs,
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sigset_t *set)
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{
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int err;
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err = __copy_to_user(&(sf->uc.uc_mcontext.regs), regs,
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sizeof(sf->uc.uc_mcontext.regs.scratch));
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err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(sigset_t));
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return err;
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}
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static int restore_usr_regs(struct pt_regs *regs, struct rt_sigframe __user *sf)
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{
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sigset_t set;
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int err;
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err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
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if (!err)
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set_current_blocked(&set);
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err |= __copy_from_user(regs, &(sf->uc.uc_mcontext.regs),
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sizeof(sf->uc.uc_mcontext.regs.scratch));
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return err;
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}
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static inline int is_do_ss_needed(unsigned int magic)
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{
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if (MAGIC_SIGALTSTK == magic)
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return 1;
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else
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return 0;
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}
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SYSCALL_DEFINE0(rt_sigreturn)
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{
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struct rt_sigframe __user *sf;
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unsigned int magic;
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int err;
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struct pt_regs *regs = current_pt_regs();
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/* Always make any pending restarted system calls return -EINTR */
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current_thread_info()->restart_block.fn = do_no_restart_syscall;
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/* Since we stacked the signal on a word boundary,
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* then 'sp' should be word aligned here. If it's
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* not, then the user is trying to mess with us.
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*/
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if (regs->sp & 3)
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goto badframe;
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sf = (struct rt_sigframe __force __user *)(regs->sp);
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if (!access_ok(VERIFY_READ, sf, sizeof(*sf)))
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goto badframe;
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err = restore_usr_regs(regs, sf);
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err |= __get_user(magic, &sf->sigret_magic);
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if (err)
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goto badframe;
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if (unlikely(is_do_ss_needed(magic)))
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if (restore_altstack(&sf->uc.uc_stack))
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goto badframe;
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return regs->r0;
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badframe:
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force_sig(SIGSEGV, current);
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return 0;
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}
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/*
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* Determine which stack to use..
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*/
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static inline void __user *get_sigframe(struct k_sigaction *ka,
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struct pt_regs *regs,
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unsigned long framesize)
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{
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unsigned long sp = regs->sp;
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void __user *frame;
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/* This is the X/Open sanctioned signal stack switching */
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if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(sp))
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sp = current->sas_ss_sp + current->sas_ss_size;
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/* No matter what happens, 'sp' must be word
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* aligned otherwise nasty things could happen
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*/
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/* ATPCS B01 mandates 8-byte alignment */
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frame = (void __user *)((sp - framesize) & ~7);
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/* Check that we can actually write to the signal frame */
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if (!access_ok(VERIFY_WRITE, frame, framesize))
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frame = NULL;
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return frame;
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}
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/*
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* translate the signal
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*/
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static inline int map_sig(int sig)
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{
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struct thread_info *thread = current_thread_info();
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if (thread->exec_domain && thread->exec_domain->signal_invmap
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&& sig < 32)
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sig = thread->exec_domain->signal_invmap[sig];
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return sig;
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}
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static int
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setup_rt_frame(int signo, struct k_sigaction *ka, siginfo_t *info,
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sigset_t *set, struct pt_regs *regs)
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{
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struct rt_sigframe __user *sf;
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unsigned int magic = 0;
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int err = 0;
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sf = get_sigframe(ka, regs, sizeof(struct rt_sigframe));
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if (!sf)
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return 1;
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/*
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* SA_SIGINFO requires 3 args to signal handler:
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* #1: sig-no (common to any handler)
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* #2: struct siginfo
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* #3: struct ucontext (completely populated)
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*/
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if (unlikely(ka->sa.sa_flags & SA_SIGINFO)) {
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err |= copy_siginfo_to_user(&sf->info, info);
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err |= __put_user(0, &sf->uc.uc_flags);
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err |= __put_user(NULL, &sf->uc.uc_link);
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err |= __save_altstack(&sf->uc.uc_stack, regs->sp);
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|
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/* setup args 2 and 3 for user mode handler */
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regs->r1 = (unsigned long)&sf->info;
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regs->r2 = (unsigned long)&sf->uc;
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|
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/*
|
||||
* small optim to avoid unconditonally calling do_sigaltstack
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* in sigreturn path, now that we only have rt_sigreturn
|
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*/
|
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magic = MAGIC_SIGALTSTK;
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}
|
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|
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/*
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||||
* w/o SA_SIGINFO, struct ucontext is partially populated (only
|
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* uc_mcontext/uc_sigmask) for kernel's normal user state preservation
|
||||
* during signal handler execution. This works for SA_SIGINFO as well
|
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* although the semantics are now overloaded (the same reg state can be
|
||||
* inspected by userland: but are they allowed to fiddle with it ?
|
||||
*/
|
||||
err |= stash_usr_regs(sf, regs, set);
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err |= __put_user(magic, &sf->sigret_magic);
|
||||
if (err)
|
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return err;
|
||||
|
||||
/* #1 arg to the user Signal handler */
|
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regs->r0 = map_sig(signo);
|
||||
|
||||
/* setup PC of user space signal handler */
|
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regs->ret = (unsigned long)ka->sa.sa_handler;
|
||||
|
||||
/*
|
||||
* handler returns using sigreturn stub provided already by userpsace
|
||||
*/
|
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BUG_ON(!(ka->sa.sa_flags & SA_RESTORER));
|
||||
regs->blink = (unsigned long)ka->sa.sa_restorer;
|
||||
|
||||
/* User Stack for signal handler will be above the frame just carved */
|
||||
regs->sp = (unsigned long)sf;
|
||||
|
||||
/*
|
||||
* Bug 94183, Clear the DE bit, so that when signal handler
|
||||
* starts to run, it doesn't use BTA
|
||||
*/
|
||||
regs->status32 &= ~STATUS_DE_MASK;
|
||||
regs->status32 |= STATUS_L_MASK;
|
||||
|
||||
return err;
|
||||
}
|
||||
|
||||
static void arc_restart_syscall(struct k_sigaction *ka, struct pt_regs *regs)
|
||||
{
|
||||
switch (regs->r0) {
|
||||
case -ERESTART_RESTARTBLOCK:
|
||||
case -ERESTARTNOHAND:
|
||||
/*
|
||||
* ERESTARTNOHAND means that the syscall should
|
||||
* only be restarted if there was no handler for
|
||||
* the signal, and since we only get here if there
|
||||
* is a handler, we don't restart
|
||||
*/
|
||||
regs->r0 = -EINTR; /* ERESTART_xxx is internal */
|
||||
break;
|
||||
|
||||
case -ERESTARTSYS:
|
||||
/*
|
||||
* ERESTARTSYS means to restart the syscall if
|
||||
* there is no handler or the handler was
|
||||
* registered with SA_RESTART
|
||||
*/
|
||||
if (!(ka->sa.sa_flags & SA_RESTART)) {
|
||||
regs->r0 = -EINTR;
|
||||
break;
|
||||
}
|
||||
/* fallthrough */
|
||||
|
||||
case -ERESTARTNOINTR:
|
||||
/*
|
||||
* ERESTARTNOINTR means that the syscall should
|
||||
* be called again after the signal handler returns.
|
||||
* Setup reg state just as it was before doing the trap
|
||||
* r0 has been clobbered with sys call ret code thus it
|
||||
* needs to be reloaded with orig first arg to syscall
|
||||
* in orig_r0. Rest of relevant reg-file:
|
||||
* r8 (syscall num) and (r1 - r7) will be reset to
|
||||
* their orig user space value when we ret from kernel
|
||||
*/
|
||||
regs->r0 = regs->orig_r0;
|
||||
regs->ret -= 4;
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* OK, we're invoking a handler
|
||||
*/
|
||||
static void
|
||||
handle_signal(unsigned long sig, struct k_sigaction *ka, siginfo_t *info,
|
||||
struct pt_regs *regs)
|
||||
{
|
||||
sigset_t *oldset = sigmask_to_save();
|
||||
int ret;
|
||||
|
||||
/* Set up the stack frame */
|
||||
ret = setup_rt_frame(sig, ka, info, oldset, regs);
|
||||
|
||||
if (ret)
|
||||
force_sigsegv(sig, current);
|
||||
else
|
||||
signal_delivered(sig, info, ka, regs, 0);
|
||||
}
|
||||
|
||||
void do_signal(struct pt_regs *regs)
|
||||
{
|
||||
struct k_sigaction ka;
|
||||
siginfo_t info;
|
||||
int signr;
|
||||
int restart_scall;
|
||||
|
||||
signr = get_signal_to_deliver(&info, &ka, regs, NULL);
|
||||
|
||||
/* Are we from a system call? */
|
||||
restart_scall = in_syscall(regs);
|
||||
|
||||
if (signr > 0) {
|
||||
if (restart_scall)
|
||||
arc_restart_syscall(&ka, regs);
|
||||
|
||||
handle_signal(signr, &ka, &info, regs);
|
||||
return;
|
||||
}
|
||||
|
||||
if (restart_scall) {
|
||||
/* No handler for syscall: restart it */
|
||||
if (regs->r0 == -ERESTARTNOHAND ||
|
||||
regs->r0 == -ERESTARTSYS || regs->r0 == -ERESTARTNOINTR) {
|
||||
regs->r0 = regs->orig_r0;
|
||||
regs->ret -= 4;
|
||||
} else if (regs->r0 == -ERESTART_RESTARTBLOCK) {
|
||||
regs->r8 = __NR_restart_syscall;
|
||||
regs->ret -= 4;
|
||||
}
|
||||
}
|
||||
|
||||
/* If there's no signal to deliver, restore the saved sigmask back */
|
||||
restore_saved_sigmask();
|
||||
}
|
||||
|
||||
void do_notify_resume(struct pt_regs *regs)
|
||||
{
|
||||
/*
|
||||
* ASM glue gaurantees that this is only called when returning to
|
||||
* user mode
|
||||
*/
|
||||
if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
|
||||
tracehook_notify_resume(regs);
|
||||
}
|
||||
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