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Date: Fri, 26 Sep 2014 11:02:27 -0700
From: Andy Lutomirski <luto@...capital.net>
To: Stephen Rothwell <sfr@...b.auug.org.au>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
"H. Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>,
Eric Paris <eparis@...hat.com>,
"linux-next@...r.kernel.org" <linux-next@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: linux-next: manual merge of the tip tree with the audit tree
On Tue, Sep 23, 2014 at 10:47 PM, Stephen Rothwell <sfr@...b.auug.org.au> wrote:
> Hi all,
>
> Today's linux-next merge of the tip tree got a conflict in
> arch/x86/kernel/ptrace.c between commit 91397401bb50 ("ARCH: AUDIT:
> audit_syscall_entry() should not require the arch") from the audit tree
> and commit e0ffbaabc46d ("x86: Split syscall_trace_enter into two
> phases") from the tip tree.
>
> I fixed it up (see below - there is more cleanup possible since
> do_audit_syscall_entry() no longer needs its "arch" argument) and can
> carry the fix as necessary (no action is required).
I don't think that more cleanup is possible after all.
do_audit_syscall_entry may not need to pass the arch parameter to the
audit code, but it still needs it to choose the set of registers to
use.
--Andy
>
> --
> Cheers,
> Stephen Rothwell sfr@...b.auug.org.au
>
> diff --cc arch/x86/kernel/ptrace.c
> index eb1c87f0b03b,29576c244699..000000000000
> --- a/arch/x86/kernel/ptrace.c
> +++ b/arch/x86/kernel/ptrace.c
> @@@ -1441,24 -1441,126 +1441,126 @@@ void send_sigtrap(struct task_struct *t
> force_sig_info(SIGTRAP, &info, tsk);
> }
>
> -
> - #ifdef CONFIG_X86_32
> - # define IS_IA32 1
> - #elif defined CONFIG_IA32_EMULATION
> - # define IS_IA32 is_compat_task()
> - #else
> - # define IS_IA32 0
> + static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch)
> + {
> + #ifdef CONFIG_X86_64
> + if (arch == AUDIT_ARCH_X86_64) {
> - audit_syscall_entry(arch, regs->orig_ax, regs->di,
> ++ audit_syscall_entry(regs->orig_ax, regs->di,
> + regs->si, regs->dx, regs->r10);
> + } else
> #endif
> + {
> - audit_syscall_entry(arch, regs->orig_ax, regs->bx,
> ++ audit_syscall_entry(regs->orig_ax, regs->bx,
> + regs->cx, regs->dx, regs->si);
> + }
> + }
>
> /*
> - * We must return the syscall number to actually look up in the table.
> - * This can be -1L to skip running any syscall at all.
> + * We can return 0 to resume the syscall or anything else to go to phase
> + * 2. If we resume the syscall, we need to put something appropriate in
> + * regs->orig_ax.
> + *
> + * NB: We don't have full pt_regs here, but regs->orig_ax and regs->ax
> + * are fully functional.
> + *
> + * For phase 2's benefit, our return value is:
> + * 0: resume the syscall
> + * 1: go to phase 2; no seccomp phase 2 needed
> + * anything else: go to phase 2; pass return value to seccomp
> */
> - long syscall_trace_enter(struct pt_regs *regs)
> + unsigned long syscall_trace_enter_phase1(struct pt_regs *regs, u32 arch)
> + {
> + unsigned long ret = 0;
> + u32 work;
> +
> + BUG_ON(regs != task_pt_regs(current));
> +
> + work = ACCESS_ONCE(current_thread_info()->flags) &
> + _TIF_WORK_SYSCALL_ENTRY;
> +
> + /*
> + * If TIF_NOHZ is set, we are required to call user_exit() before
> + * doing anything that could touch RCU.
> + */
> + if (work & _TIF_NOHZ) {
> + user_exit();
> + work &= ~TIF_NOHZ;
> + }
> +
> + #ifdef CONFIG_SECCOMP
> + /*
> + * Do seccomp first -- it should minimize exposure of other
> + * code, and keeping seccomp fast is probably more valuable
> + * than the rest of this.
> + */
> + if (work & _TIF_SECCOMP) {
> + struct seccomp_data sd;
> +
> + sd.arch = arch;
> + sd.nr = regs->orig_ax;
> + sd.instruction_pointer = regs->ip;
> + #ifdef CONFIG_X86_64
> + if (arch == AUDIT_ARCH_X86_64) {
> + sd.args[0] = regs->di;
> + sd.args[1] = regs->si;
> + sd.args[2] = regs->dx;
> + sd.args[3] = regs->r10;
> + sd.args[4] = regs->r8;
> + sd.args[5] = regs->r9;
> + } else
> + #endif
> + {
> + sd.args[0] = regs->bx;
> + sd.args[1] = regs->cx;
> + sd.args[2] = regs->dx;
> + sd.args[3] = regs->si;
> + sd.args[4] = regs->di;
> + sd.args[5] = regs->bp;
> + }
> +
> + BUILD_BUG_ON(SECCOMP_PHASE1_OK != 0);
> + BUILD_BUG_ON(SECCOMP_PHASE1_SKIP != 1);
> +
> + ret = seccomp_phase1(&sd);
> + if (ret == SECCOMP_PHASE1_SKIP) {
> + regs->orig_ax = -1;
> + ret = 0;
> + } else if (ret != SECCOMP_PHASE1_OK) {
> + return ret; /* Go directly to phase 2 */
> + }
> +
> + work &= ~_TIF_SECCOMP;
> + }
> + #endif
> +
> + /* Do our best to finish without phase 2. */
> + if (work == 0)
> + return ret; /* seccomp and/or nohz only (ret == 0 here) */
> +
> + #ifdef CONFIG_AUDITSYSCALL
> + if (work == _TIF_SYSCALL_AUDIT) {
> + /*
> + * If there is no more work to be done except auditing,
> + * then audit in phase 1. Phase 2 always audits, so, if
> + * we audit here, then we can't go on to phase 2.
> + */
> + do_audit_syscall_entry(regs, arch);
> + return 0;
> + }
> + #endif
> +
> + return 1; /* Something is enabled that we can't handle in phase 1 */
> + }
> +
> + /* Returns the syscall nr to run (which should match regs->orig_ax). */
> + long syscall_trace_enter_phase2(struct pt_regs *regs, u32 arch,
> + unsigned long phase1_result)
> {
> long ret = 0;
> + u32 work = ACCESS_ONCE(current_thread_info()->flags) &
> + _TIF_WORK_SYSCALL_ENTRY;
>
> - user_exit();
> + BUG_ON(regs != task_pt_regs(current));
>
> /*
> * If we stepped into a sysenter/syscall insn, it trapped in
--
Andy Lutomirski
AMA Capital Management, LLC
--
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