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    Subject[RFC PATCH] sysrq: Show architectural registers
    Date
    From: Borislav Petkov <borislav.petkov@amd.com>

    One day I was playing with disabling the caches over CR0.CD and I wanted
    to check the current setting of the CD bit but there wasn't a way to do
    so from userspace because we #GP when accessing CR0.

    And then I thought, well, sysrq must have this. And it does:

    $ echo p > /proc/sysrq-trigger

    dumps the current registers. However, we don't dump the registers when
    we can't get the last exception frame through get_irq_regs().

    But, there are registers (CR0 included) which aren't in the exception
    frame and which can be dumped regardless. This patch does exactly that;
    with it, the output looks like this:

    [ 1759.206042] SysRq : Show Regs
    [ 1759.209194] FS: 00007fb1eada3700(0000) GS:ffff880c27c00000(0000) knlGS:0000000000000000
    [ 1759.217593] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    [ 1759.223554] CR2: 0000000000910390 CR3: 0000001020b48000 CR4: 00000000000007e0
    [ 1759.230956] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    [ 1759.244974] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
    [ 1759.259052] CPU#18: active: 0000000000000000
    [ 1759.270539] CPU#18: gen-PMC0 ctrl: 0000030e011afcf6
    [ 1759.270543] CPU#18: gen-PMC0 count: 00009007d003b500
    [ 1759.270545] CPU#18: gen-PMC0 left: 0000000000000000
    [ 1759.270548] CPU#18: gen-PMC1 ctrl: 0000030f059b7efc
    [ 1759.270550] CPU#18: gen-PMC1 count: 00008003c823b4a0
    [ 1759.270552] CPU#18: gen-PMC1 left: 0000000000000000
    [ 1759.270555] CPU#18: gen-PMC2 ctrl: 00000104fe97c87c
    [ 1759.270557] CPU#18: gen-PMC2 count: 00007c6277e7f5fe
    [ 1759.270560] CPU#18: gen-PMC2 left: 0000000000000000
    [ 1759.270562] CPU#18: gen-PMC3 ctrl: 000000040000f0e2
    [ 1759.270564] CPU#18: gen-PMC3 count: 0000000000000000
    [ 1759.270566] CPU#18: gen-PMC3 left: 0000000000000000

    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: Arnd Bergmann <arnd@arndb.de>
    Cc: Jan Beulich <jbeulich@suse.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
    Cc: Josh Triplett <josh@joshtriplett.org>
    Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
    ---
    arch/x86/include/asm/bug.h | 3 +++
    arch/x86/kernel/process_32.c | 43 ++++++++++++++++++++++------------------
    arch/x86/kernel/process_64.c | 47 ++++++++++++++++++++++++--------------------
    drivers/tty/sysrq.c | 1 +
    include/asm-generic/bug.h | 9 +++++++++
    5 files changed, 63 insertions(+), 40 deletions(-)

    diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h
    index 11e1152222d0..e60cf51fdfbd 100644
    --- a/arch/x86/include/asm/bug.h
    +++ b/arch/x86/include/asm/bug.h
    @@ -35,6 +35,9 @@ do { \

    #endif /* !CONFIG_BUG */

    +extern void _arch_show_regs(void);
    +#define _arch_show_regs _arch_show_regs
    +
    #include <asm-generic/bug.h>


    diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
    index 516fa186121b..6b01b6260f5d 100644
    --- a/arch/x86/kernel/process_32.c
    +++ b/arch/x86/kernel/process_32.c
    @@ -66,10 +66,32 @@ unsigned long thread_saved_pc(struct task_struct *tsk)
    return ((unsigned long *)tsk->thread.sp)[3];
    }

    -void __show_regs(struct pt_regs *regs, int all)
    +void _arch_show_regs(void)
    {
    unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
    unsigned long d0, d1, d2, d3, d6, d7;
    +
    + cr0 = read_cr0();
    + cr2 = read_cr2();
    + cr3 = read_cr3();
    + cr4 = read_cr4_safe();
    + printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
    + cr0, cr2, cr3, cr4);
    +
    + get_debugreg(d0, 0);
    + get_debugreg(d1, 1);
    + get_debugreg(d2, 2);
    + get_debugreg(d3, 3);
    + printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
    + d0, d1, d2, d3);
    +
    + get_debugreg(d6, 6);
    + get_debugreg(d7, 7);
    + printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n", d6, d7);
    +}
    +
    +void __show_regs(struct pt_regs *regs, int all)
    +{
    unsigned long sp;
    unsigned short ss, gs;

    @@ -100,24 +122,7 @@ void __show_regs(struct pt_regs *regs, int all)
    if (!all)
    return;

    - cr0 = read_cr0();
    - cr2 = read_cr2();
    - cr3 = read_cr3();
    - cr4 = read_cr4_safe();
    - printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
    - cr0, cr2, cr3, cr4);
    -
    - get_debugreg(d0, 0);
    - get_debugreg(d1, 1);
    - get_debugreg(d2, 2);
    - get_debugreg(d3, 3);
    - printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
    - d0, d1, d2, d3);
    -
    - get_debugreg(d6, 6);
    - get_debugreg(d7, 7);
    - printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n",
    - d6, d7);
    + _arch_show_regs();
    }

    void release_thread(struct task_struct *dead_task)
    diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
    index 0a980c9d7cb8..dbe93bae6524 100644
    --- a/arch/x86/kernel/process_64.c
    +++ b/arch/x86/kernel/process_64.c
    @@ -54,30 +54,14 @@ asmlinkage extern void ret_from_fork(void);

    DEFINE_PER_CPU(unsigned long, old_rsp);

    -/* Prints also some state that isn't saved in the pt_regs */
    -void __show_regs(struct pt_regs *regs, int all)
    +/* Print also some state that isn't saved in the pt_regs */
    +void _arch_show_regs(void)
    {
    unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L, fs, gs, shadowgs;
    unsigned long d0, d1, d2, d3, d6, d7;
    unsigned int fsindex, gsindex;
    unsigned int ds, cs, es;

    - show_regs_common();
    - printk(KERN_DEFAULT "RIP: %04lx:[<%016lx>] ", regs->cs & 0xffff, regs->ip);
    - printk_address(regs->ip, 1);
    - printk(KERN_DEFAULT "RSP: %04lx:%016lx EFLAGS: %08lx\n", regs->ss,
    - regs->sp, regs->flags);
    - printk(KERN_DEFAULT "RAX: %016lx RBX: %016lx RCX: %016lx\n",
    - regs->ax, regs->bx, regs->cx);
    - printk(KERN_DEFAULT "RDX: %016lx RSI: %016lx RDI: %016lx\n",
    - regs->dx, regs->si, regs->di);
    - printk(KERN_DEFAULT "RBP: %016lx R08: %016lx R09: %016lx\n",
    - regs->bp, regs->r8, regs->r9);
    - printk(KERN_DEFAULT "R10: %016lx R11: %016lx R12: %016lx\n",
    - regs->r10, regs->r11, regs->r12);
    - printk(KERN_DEFAULT "R13: %016lx R14: %016lx R15: %016lx\n",
    - regs->r13, regs->r14, regs->r15);
    -
    asm("movl %%ds,%0" : "=r" (ds));
    asm("movl %%cs,%0" : "=r" (cs));
    asm("movl %%es,%0" : "=r" (es));
    @@ -88,9 +72,6 @@ void __show_regs(struct pt_regs *regs, int all)
    rdmsrl(MSR_GS_BASE, gs);
    rdmsrl(MSR_KERNEL_GS_BASE, shadowgs);

    - if (!all)
    - return;
    -
    cr0 = read_cr0();
    cr2 = read_cr2();
    cr3 = read_cr3();
    @@ -113,6 +94,30 @@ void __show_regs(struct pt_regs *regs, int all)
    printk(KERN_DEFAULT "DR3: %016lx DR6: %016lx DR7: %016lx\n", d3, d6, d7);
    }

    +void __show_regs(struct pt_regs *regs, int all)
    +{
    + show_regs_common();
    + printk(KERN_DEFAULT "RIP: %04lx:[<%016lx>] ", regs->cs & 0xffff, regs->ip);
    + printk_address(regs->ip, 1);
    + printk(KERN_DEFAULT "RSP: %04lx:%016lx EFLAGS: %08lx\n", regs->ss,
    + regs->sp, regs->flags);
    + printk(KERN_DEFAULT "RAX: %016lx RBX: %016lx RCX: %016lx\n",
    + regs->ax, regs->bx, regs->cx);
    + printk(KERN_DEFAULT "RDX: %016lx RSI: %016lx RDI: %016lx\n",
    + regs->dx, regs->si, regs->di);
    + printk(KERN_DEFAULT "RBP: %016lx R08: %016lx R09: %016lx\n",
    + regs->bp, regs->r8, regs->r9);
    + printk(KERN_DEFAULT "R10: %016lx R11: %016lx R12: %016lx\n",
    + regs->r10, regs->r11, regs->r12);
    + printk(KERN_DEFAULT "R13: %016lx R14: %016lx R15: %016lx\n",
    + regs->r13, regs->r14, regs->r15);
    +
    + if (!all)
    + return;
    +
    + _arch_show_regs();
    +}
    +
    void release_thread(struct task_struct *dead_task)
    {
    if (dead_task->mm) {
    diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
    index 05728894a88c..4ad0f884e08e 100644
    --- a/drivers/tty/sysrq.c
    +++ b/drivers/tty/sysrq.c
    @@ -254,6 +254,7 @@ static void sysrq_handle_showregs(int key)
    struct pt_regs *regs = get_irq_regs();
    if (regs)
    show_regs(regs);
    + arch_show_regs();
    perf_event_print_debug();
    }
    static struct sysrq_key_op sysrq_showregs_op = {
    diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
    index 7d10f962aa13..e96d6c31c222 100644
    --- a/include/asm-generic/bug.h
    +++ b/include/asm-generic/bug.h
    @@ -202,6 +202,15 @@ extern void warn_slowpath_null(const char *file, const int line);
    # define WARN_ON_SMP(x) ({0;})
    #endif

    +#ifdef _arch_show_regs
    +static inline void arch_show_regs(void)
    +{
    + _arch_show_regs();
    +}
    +#else
    +static inline void arch_show_regs(void) { }
    +#endif
    +
    #endif /* __ASSEMBLY__ */

    #endif
    --
    1.7.11.rc1


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