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-rw-r--r--arch/x86/include/asm/debugreg.h19
-rw-r--r--arch/x86/include/asm/kvm_host.h2
-rw-r--r--arch/x86/include/uapi/asm/debugreg.h21
-rw-r--r--arch/x86/kernel/cpu/common.c24
-rw-r--r--arch/x86/kernel/kgdb.c2
-rw-r--r--arch/x86/kernel/process_32.c2
-rw-r--r--arch/x86/kernel/process_64.c2
-rw-r--r--arch/x86/kernel/traps.c34
-rw-r--r--arch/x86/kvm/x86.c4
-rw-r--r--arch/x86/um/ptrace.c2
10 files changed, 73 insertions, 39 deletions
diff --git a/arch/x86/include/asm/debugreg.h b/arch/x86/include/asm/debugreg.h
index 363110e6b2e3..a2c1f2d24b64 100644
--- a/arch/x86/include/asm/debugreg.h
+++ b/arch/x86/include/asm/debugreg.h
@@ -9,6 +9,14 @@
#include <asm/cpufeature.h>
#include <asm/msr.h>
+/*
+ * Define bits that are always set to 1 in DR7, only bit 10 is
+ * architecturally reserved to '1'.
+ *
+ * This is also the init/reset value for DR7.
+ */
+#define DR7_FIXED_1 0x00000400
+
DECLARE_PER_CPU(unsigned long, cpu_dr7);
#ifndef CONFIG_PARAVIRT_XXL
@@ -100,8 +108,8 @@ static __always_inline void native_set_debugreg(int regno, unsigned long value)
static inline void hw_breakpoint_disable(void)
{
- /* Zero the control register for HW Breakpoint */
- set_debugreg(0UL, 7);
+ /* Reset the control register for HW Breakpoint */
+ set_debugreg(DR7_FIXED_1, 7);
/* Zero-out the individual HW breakpoint address registers */
set_debugreg(0UL, 0);
@@ -125,9 +133,12 @@ static __always_inline unsigned long local_db_save(void)
return 0;
get_debugreg(dr7, 7);
- dr7 &= ~0x400; /* architecturally set bit */
+
+ /* Architecturally set bit */
+ dr7 &= ~DR7_FIXED_1;
if (dr7)
- set_debugreg(0, 7);
+ set_debugreg(DR7_FIXED_1, 7);
+
/*
* Ensure the compiler doesn't lower the above statements into
* the critical section; disabling breakpoints late would not
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b4a391929cdb..639d9bcee842 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -31,6 +31,7 @@
#include <asm/apic.h>
#include <asm/pvclock-abi.h>
+#include <asm/debugreg.h>
#include <asm/desc.h>
#include <asm/mtrr.h>
#include <asm/msr-index.h>
@@ -249,7 +250,6 @@ enum x86_intercept_stage;
#define DR7_BP_EN_MASK 0x000000ff
#define DR7_GE (1 << 9)
#define DR7_GD (1 << 13)
-#define DR7_FIXED_1 0x00000400
#define DR7_VOLATILE 0xffff2bff
#define KVM_GUESTDBG_VALID_MASK \
diff --git a/arch/x86/include/uapi/asm/debugreg.h b/arch/x86/include/uapi/asm/debugreg.h
index 0007ba077c0c..41da492dfb01 100644
--- a/arch/x86/include/uapi/asm/debugreg.h
+++ b/arch/x86/include/uapi/asm/debugreg.h
@@ -15,7 +15,26 @@
which debugging register was responsible for the trap. The other bits
are either reserved or not of interest to us. */
-/* Define reserved bits in DR6 which are always set to 1 */
+/*
+ * Define bits in DR6 which are set to 1 by default.
+ *
+ * This is also the DR6 architectural value following Power-up, Reset or INIT.
+ *
+ * Note, with the introduction of Bus Lock Detection (BLD) and Restricted
+ * Transactional Memory (RTM), the DR6 register has been modified:
+ *
+ * 1) BLD flag (bit 11) is no longer reserved to 1 if the CPU supports
+ * Bus Lock Detection. The assertion of a bus lock could clear it.
+ *
+ * 2) RTM flag (bit 16) is no longer reserved to 1 if the CPU supports
+ * restricted transactional memory. #DB occurred inside an RTM region
+ * could clear it.
+ *
+ * Apparently, DR6.BLD and DR6.RTM are active low bits.
+ *
+ * As a result, DR6_RESERVED is an incorrect name now, but it is kept for
+ * compatibility.
+ */
#define DR6_RESERVED (0xFFFF0FF0)
#define DR_TRAP0 (0x1) /* db0 */
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 8feb8fd2957a..27125e009847 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2243,20 +2243,16 @@ EXPORT_PER_CPU_SYMBOL(__stack_chk_guard);
#endif
#endif
-/*
- * Clear all 6 debug registers:
- */
-static void clear_all_debug_regs(void)
+static void initialize_debug_regs(void)
{
- int i;
-
- for (i = 0; i < 8; i++) {
- /* Ignore db4, db5 */
- if ((i == 4) || (i == 5))
- continue;
-
- set_debugreg(0, i);
- }
+ /* Control register first -- to make sure everything is disabled. */
+ set_debugreg(DR7_FIXED_1, 7);
+ set_debugreg(DR6_RESERVED, 6);
+ /* dr5 and dr4 don't exist */
+ set_debugreg(0, 3);
+ set_debugreg(0, 2);
+ set_debugreg(0, 1);
+ set_debugreg(0, 0);
}
#ifdef CONFIG_KGDB
@@ -2417,7 +2413,7 @@ void cpu_init(void)
load_mm_ldt(&init_mm);
- clear_all_debug_regs();
+ initialize_debug_regs();
dbg_restore_debug_regs();
doublefault_init_cpu_tss();
diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index 102641fd2172..8b1a9733d13e 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -385,7 +385,7 @@ static void kgdb_disable_hw_debug(struct pt_regs *regs)
struct perf_event *bp;
/* Disable hardware debugging while we are in kgdb: */
- set_debugreg(0UL, 7);
+ set_debugreg(DR7_FIXED_1, 7);
for (i = 0; i < HBP_NUM; i++) {
if (!breakinfo[i].enabled)
continue;
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index a10e180cbf23..3ef15c2f152f 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -93,7 +93,7 @@ void __show_regs(struct pt_regs *regs, enum show_regs_mode mode,
/* Only print out debug registers if they are in their non-default state. */
if ((d0 == 0) && (d1 == 0) && (d2 == 0) && (d3 == 0) &&
- (d6 == DR6_RESERVED) && (d7 == 0x400))
+ (d6 == DR6_RESERVED) && (d7 == DR7_FIXED_1))
return;
printk("%sDR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 8d6cf25127aa..b972bf72fb8b 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -133,7 +133,7 @@ void __show_regs(struct pt_regs *regs, enum show_regs_mode mode,
/* Only print out debug registers if they are in their non-default state. */
if (!((d0 == 0) && (d1 == 0) && (d2 == 0) && (d3 == 0) &&
- (d6 == DR6_RESERVED) && (d7 == 0x400))) {
+ (d6 == DR6_RESERVED) && (d7 == DR7_FIXED_1))) {
printk("%sDR0: %016lx DR1: %016lx DR2: %016lx\n",
log_lvl, d0, d1, d2);
printk("%sDR3: %016lx DR6: %016lx DR7: %016lx\n",
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index c5c897a86418..36354b470590 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -1022,24 +1022,32 @@ static bool is_sysenter_singlestep(struct pt_regs *regs)
#endif
}
-static __always_inline unsigned long debug_read_clear_dr6(void)
+static __always_inline unsigned long debug_read_reset_dr6(void)
{
unsigned long dr6;
+ get_debugreg(dr6, 6);
+ dr6 ^= DR6_RESERVED; /* Flip to positive polarity */
+
/*
* The Intel SDM says:
*
- * Certain debug exceptions may clear bits 0-3. The remaining
- * contents of the DR6 register are never cleared by the
- * processor. To avoid confusion in identifying debug
- * exceptions, debug handlers should clear the register before
- * returning to the interrupted task.
+ * Certain debug exceptions may clear bits 0-3 of DR6.
+ *
+ * BLD induced #DB clears DR6.BLD and any other debug
+ * exception doesn't modify DR6.BLD.
*
- * Keep it simple: clear DR6 immediately.
+ * RTM induced #DB clears DR6.RTM and any other debug
+ * exception sets DR6.RTM.
+ *
+ * To avoid confusion in identifying debug exceptions,
+ * debug handlers should set DR6.BLD and DR6.RTM, and
+ * clear other DR6 bits before returning.
+ *
+ * Keep it simple: write DR6 with its architectural reset
+ * value 0xFFFF0FF0, defined as DR6_RESERVED, immediately.
*/
- get_debugreg(dr6, 6);
set_debugreg(DR6_RESERVED, 6);
- dr6 ^= DR6_RESERVED; /* Flip to positive polarity */
return dr6;
}
@@ -1239,13 +1247,13 @@ out:
/* IST stack entry */
DEFINE_IDTENTRY_DEBUG(exc_debug)
{
- exc_debug_kernel(regs, debug_read_clear_dr6());
+ exc_debug_kernel(regs, debug_read_reset_dr6());
}
/* User entry, runs on regular task stack */
DEFINE_IDTENTRY_DEBUG_USER(exc_debug)
{
- exc_debug_user(regs, debug_read_clear_dr6());
+ exc_debug_user(regs, debug_read_reset_dr6());
}
#ifdef CONFIG_X86_FRED
@@ -1264,7 +1272,7 @@ DEFINE_FREDENTRY_DEBUG(exc_debug)
{
/*
* FRED #DB stores DR6 on the stack in the format which
- * debug_read_clear_dr6() returns for the IDT entry points.
+ * debug_read_reset_dr6() returns for the IDT entry points.
*/
unsigned long dr6 = fred_event_data(regs);
@@ -1279,7 +1287,7 @@ DEFINE_FREDENTRY_DEBUG(exc_debug)
/* 32 bit does not have separate entry points. */
DEFINE_IDTENTRY_RAW(exc_debug)
{
- unsigned long dr6 = debug_read_clear_dr6();
+ unsigned long dr6 = debug_read_reset_dr6();
if (user_mode(regs))
exc_debug_user(regs, dr6);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b58a74c1722d..a9d992d5652f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11035,7 +11035,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
if (unlikely(vcpu->arch.switch_db_regs &&
!(vcpu->arch.switch_db_regs & KVM_DEBUGREG_AUTO_SWITCH))) {
- set_debugreg(0, 7);
+ set_debugreg(DR7_FIXED_1, 7);
set_debugreg(vcpu->arch.eff_db[0], 0);
set_debugreg(vcpu->arch.eff_db[1], 1);
set_debugreg(vcpu->arch.eff_db[2], 2);
@@ -11044,7 +11044,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
if (unlikely(vcpu->arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT))
kvm_x86_call(set_dr6)(vcpu, vcpu->arch.dr6);
} else if (unlikely(hw_breakpoint_active())) {
- set_debugreg(0, 7);
+ set_debugreg(DR7_FIXED_1, 7);
}
vcpu->arch.host_debugctl = get_debugctlmsr();
diff --git a/arch/x86/um/ptrace.c b/arch/x86/um/ptrace.c
index 3275870330fe..fae8aabad10f 100644
--- a/arch/x86/um/ptrace.c
+++ b/arch/x86/um/ptrace.c
@@ -161,7 +161,7 @@ static int fpregs_legacy_set(struct task_struct *target,
from = kbuf;
}
- return um_fxsr_from_i387(fxsave, &buf);
+ return um_fxsr_from_i387(fxsave, from);
}
#endif
generated by cgit (git 2.34.1) at 2025-06-29 19:30:25 +0000