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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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