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SubjectRe: [REVIEW][PATCH 08/22] signal/mips: Use force_sig_fault where appropriate
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Hi Eric,

On 20/04/18 15:37, Eric W. Biederman wrote:
> Filling in struct siginfo before calling force_sig_info a tedious and
> error prone process, where once in a great while the wrong fields
> are filled out, and siginfo has been inconsistently cleared.
>
> Simplify this process by using the helper force_sig_fault. Which
> takes as a parameters all of the information it needs, ensures
> all of the fiddly bits of filling in struct siginfo are done properly
> and then calls force_sig_info.
>
> In short about a 5 line reduction in code for every time force_sig_info
> is called, which makes the calling function clearer.
>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: James Hogan <jhogan@kernel.org>
> Cc: linux-mips@linux-mips.org
> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
> ---
> arch/mips/kernel/traps.c | 65 ++++++++++++++----------------------------------
> arch/mips/mm/fault.c | 19 ++++----------
> 2 files changed, 23 insertions(+), 61 deletions(-)
>
> diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
> index 967e9e4e795e..66ec4b0b484d 100644
> --- a/arch/mips/kernel/traps.c
> +++ b/arch/mips/kernel/traps.c
> @@ -699,17 +699,11 @@ static int simulate_sync(struct pt_regs *regs, unsigned int opcode)
> asmlinkage void do_ov(struct pt_regs *regs)
> {
> enum ctx_state prev_state;
> - siginfo_t info;
> -
> - clear_siginfo(&info);
> - info.si_signo = SIGFPE;
> - info.si_code = FPE_INTOVF;
> - info.si_addr = (void __user *)regs->cp0_epc;
>
> prev_state = exception_enter();
> die_if_kernel("Integer overflow", regs);
>
> - force_sig_info(SIGFPE, &info, current);
> + force_sig_fault(SIGFPE, FPE_INTOVF, (void __user *)regs->cp0_epc, current);
> exception_exit(prev_state);
> }
>
> @@ -722,32 +716,27 @@ asmlinkage void do_ov(struct pt_regs *regs)
> void force_fcr31_sig(unsigned long fcr31, void __user *fault_addr,
> struct task_struct *tsk)
> {
> - struct siginfo si;
> -
> - clear_siginfo(&si);
> - si.si_addr = fault_addr;
> - si.si_signo = SIGFPE;
> + int si_code;

This is giving build errors in Linux next
(https://storage.kernelci.org/next/master/next-20180509/mips/defconfig+kselftest/build.log)

si_code would have ended up as 0 before from the clear_siginfo(), but
perhaps

int si_code = FPE_FLTUNK;

Would make a more sensible default?

Thanks,
Matt


>
> if (fcr31 & FPU_CSR_INV_X)
> - si.si_code = FPE_FLTINV;
> + si_code = FPE_FLTINV;
> else if (fcr31 & FPU_CSR_DIV_X)
> - si.si_code = FPE_FLTDIV;
> + si_code = FPE_FLTDIV;
> else if (fcr31 & FPU_CSR_OVF_X)
> - si.si_code = FPE_FLTOVF;
> + si_code = FPE_FLTOVF;
> else if (fcr31 & FPU_CSR_UDF_X)
> - si.si_code = FPE_FLTUND;
> + si_code = FPE_FLTUND;
> else if (fcr31 & FPU_CSR_INE_X)
> - si.si_code = FPE_FLTRES;
> + si_code = FPE_FLTRES;
>
> - force_sig_info(SIGFPE, &si, tsk);
> + force_sig_fault(SIGFPE, si_code, fault_addr, tsk);
> }
>
> int process_fpemu_return(int sig, void __user *fault_addr, unsigned long fcr31)
> {
> - struct siginfo si;
> + int si_code;
> struct vm_area_struct *vma;
>
> - clear_siginfo(&si);
> switch (sig) {
> case 0:
> return 0;
> @@ -757,23 +746,18 @@ int process_fpemu_return(int sig, void __user *fault_addr, unsigned long fcr31)
> return 1;
>
> case SIGBUS:
> - si.si_addr = fault_addr;
> - si.si_signo = sig;
> - si.si_code = BUS_ADRERR;
> - force_sig_info(sig, &si, current);
> + force_sig_fault(SIGBUS, BUS_ADRERR, fault_addr, current);
> return 1;
>
> case SIGSEGV:
> - si.si_addr = fault_addr;
> - si.si_signo = sig;
> down_read(&current->mm->mmap_sem);
> vma = find_vma(current->mm, (unsigned long)fault_addr);
> if (vma && (vma->vm_start <= (unsigned long)fault_addr))
> - si.si_code = SEGV_ACCERR;
> + si_code = SEGV_ACCERR;
> else
> - si.si_code = SEGV_MAPERR;
> + si_code = SEGV_MAPERR;
> up_read(&current->mm->mmap_sem);
> - force_sig_info(sig, &si, current);
> + force_sig_fault(SIGSEGV, si_code, fault_addr, current);
> return 1;
>
> default:
> @@ -896,10 +880,8 @@ asmlinkage void do_fpe(struct pt_regs *regs, unsigned long fcr31)
> void do_trap_or_bp(struct pt_regs *regs, unsigned int code, int si_code,
> const char *str)
> {
> - siginfo_t info;
> char b[40];
>
> - clear_siginfo(&info);
> #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
> if (kgdb_ll_trap(DIE_TRAP, str, regs, code, current->thread.trap_nr,
> SIGTRAP) == NOTIFY_STOP)
> @@ -921,13 +903,9 @@ void do_trap_or_bp(struct pt_regs *regs, unsigned int code, int si_code,
> case BRK_DIVZERO:
> scnprintf(b, sizeof(b), "%s instruction in kernel code", str);
> die_if_kernel(b, regs);
> - if (code == BRK_DIVZERO)
> - info.si_code = FPE_INTDIV;
> - else
> - info.si_code = FPE_INTOVF;
> - info.si_signo = SIGFPE;
> - info.si_addr = (void __user *) regs->cp0_epc;
> - force_sig_info(SIGFPE, &info, current);
> + force_sig_fault(SIGFPE,
> + code == BRK_DIVZERO ? FPE_INTDIV : FPE_INTOVF,
> + (void __user *) regs->cp0_epc, current);
> break;
> case BRK_BUG:
> die_if_kernel("Kernel bug detected", regs);
> @@ -952,9 +930,7 @@ void do_trap_or_bp(struct pt_regs *regs, unsigned int code, int si_code,
> scnprintf(b, sizeof(b), "%s instruction in kernel code", str);
> die_if_kernel(b, regs);
> if (si_code) {
> - info.si_signo = SIGTRAP;
> - info.si_code = si_code;
> - force_sig_info(SIGTRAP, &info, current);
> + force_sig_fault(SIGTRAP, si_code, NULL, current);
> } else {
> force_sig(SIGTRAP, current);
> }
> @@ -1506,13 +1482,8 @@ asmlinkage void do_mdmx(struct pt_regs *regs)
> */
> asmlinkage void do_watch(struct pt_regs *regs)
> {
> - siginfo_t info;
> enum ctx_state prev_state;
>
> - clear_siginfo(&info);
> - info.si_signo = SIGTRAP;
> - info.si_code = TRAP_HWBKPT;
> -
> prev_state = exception_enter();
> /*
> * Clear WP (bit 22) bit of cause register so we don't loop
> @@ -1528,7 +1499,7 @@ asmlinkage void do_watch(struct pt_regs *regs)
> if (test_tsk_thread_flag(current, TIF_LOAD_WATCH)) {
> mips_read_watch_registers();
> local_irq_enable();
> - force_sig_info(SIGTRAP, &info, current);
> + force_sig_fault(SIGTRAP, TRAP_HWBKPT, NULL, current);
> } else {
> mips_clear_watch_registers();
> local_irq_enable();
> diff --git a/arch/mips/mm/fault.c b/arch/mips/mm/fault.c
> index 75392becd933..5f71f2b903b7 100644
> --- a/arch/mips/mm/fault.c
> +++ b/arch/mips/mm/fault.c
> @@ -42,7 +42,7 @@ static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
> struct task_struct *tsk = current;
> struct mm_struct *mm = tsk->mm;
> const int field = sizeof(unsigned long) * 2;
> - siginfo_t info;
> + int si_code;
> int fault;
> unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
>
> @@ -63,8 +63,7 @@ static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
> return;
> #endif
>
> - clear_siginfo(&info);
> - info.si_code = SEGV_MAPERR;
> + si_code = SEGV_MAPERR;
>
> /*
> * We fault-in kernel-space virtual memory on-demand. The
> @@ -113,7 +112,7 @@ static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
> * we can handle it..
> */
> good_area:
> - info.si_code = SEGV_ACCERR;
> + si_code = SEGV_ACCERR;
>
> if (write) {
> if (!(vma->vm_flags & VM_WRITE))
> @@ -224,11 +223,7 @@ static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
> pr_cont("\n");
> }
> current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f;
> - info.si_signo = SIGSEGV;
> - info.si_errno = 0;
> - /* info.si_code has been set above */
> - info.si_addr = (void __user *) address;
> - force_sig_info(SIGSEGV, &info, tsk);
> + force_sig_fault(SIGSEGV, si_code, (void __user *)address, tsk);
> return;
> }
>
> @@ -284,11 +279,7 @@ static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
> #endif
> current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f;
> tsk->thread.cp0_badvaddr = address;
> - info.si_signo = SIGBUS;
> - info.si_errno = 0;
> - info.si_code = BUS_ADRERR;
> - info.si_addr = (void __user *) address;
> - force_sig_info(SIGBUS, &info, tsk);
> + force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address, tsk);
>
> return;
> #ifndef CONFIG_64BIT
>

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