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@@ -8,7 +8,8 @@
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#include <asm/kdebug.h>
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#include <asm/kdebug.h>
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typedef bool (*ex_handler_t)(const struct exception_table_entry *,
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typedef bool (*ex_handler_t)(const struct exception_table_entry *,
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- struct pt_regs *, int);
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+ struct pt_regs *, int, unsigned long,
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+ unsigned long);
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static inline unsigned long
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static inline unsigned long
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ex_fixup_addr(const struct exception_table_entry *x)
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ex_fixup_addr(const struct exception_table_entry *x)
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@@ -22,7 +23,9 @@ ex_fixup_handler(const struct exception_table_entry *x)
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}
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}
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__visible bool ex_handler_default(const struct exception_table_entry *fixup,
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__visible bool ex_handler_default(const struct exception_table_entry *fixup,
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- struct pt_regs *regs, int trapnr)
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+ struct pt_regs *regs, int trapnr,
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+ unsigned long error_code,
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+ unsigned long fault_addr)
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{
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{
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regs->ip = ex_fixup_addr(fixup);
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regs->ip = ex_fixup_addr(fixup);
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return true;
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return true;
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@@ -30,7 +33,9 @@ __visible bool ex_handler_default(const struct exception_table_entry *fixup,
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EXPORT_SYMBOL(ex_handler_default);
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EXPORT_SYMBOL(ex_handler_default);
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__visible bool ex_handler_fault(const struct exception_table_entry *fixup,
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__visible bool ex_handler_fault(const struct exception_table_entry *fixup,
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- struct pt_regs *regs, int trapnr)
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+ struct pt_regs *regs, int trapnr,
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+ unsigned long error_code,
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+ unsigned long fault_addr)
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{
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{
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regs->ip = ex_fixup_addr(fixup);
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regs->ip = ex_fixup_addr(fixup);
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regs->ax = trapnr;
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regs->ax = trapnr;
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@@ -43,7 +48,9 @@ EXPORT_SYMBOL_GPL(ex_handler_fault);
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* result of a refcount inc/dec/add/sub.
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* result of a refcount inc/dec/add/sub.
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*/
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*/
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__visible bool ex_handler_refcount(const struct exception_table_entry *fixup,
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__visible bool ex_handler_refcount(const struct exception_table_entry *fixup,
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- struct pt_regs *regs, int trapnr)
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+ struct pt_regs *regs, int trapnr,
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+ unsigned long error_code,
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+ unsigned long fault_addr)
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{
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{
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/* First unconditionally saturate the refcount. */
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/* First unconditionally saturate the refcount. */
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*(int *)regs->cx = INT_MIN / 2;
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*(int *)regs->cx = INT_MIN / 2;
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@@ -96,7 +103,9 @@ EXPORT_SYMBOL(ex_handler_refcount);
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* out all the FPU registers) if we can't restore from the task's FPU state.
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* out all the FPU registers) if we can't restore from the task's FPU state.
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*/
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*/
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__visible bool ex_handler_fprestore(const struct exception_table_entry *fixup,
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__visible bool ex_handler_fprestore(const struct exception_table_entry *fixup,
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- struct pt_regs *regs, int trapnr)
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+ struct pt_regs *regs, int trapnr,
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+ unsigned long error_code,
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+ unsigned long fault_addr)
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{
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{
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regs->ip = ex_fixup_addr(fixup);
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regs->ip = ex_fixup_addr(fixup);
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@@ -108,9 +117,79 @@ __visible bool ex_handler_fprestore(const struct exception_table_entry *fixup,
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}
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}
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EXPORT_SYMBOL_GPL(ex_handler_fprestore);
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EXPORT_SYMBOL_GPL(ex_handler_fprestore);
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+/* Helper to check whether a uaccess fault indicates a kernel bug. */
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+static bool bogus_uaccess(struct pt_regs *regs, int trapnr,
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+ unsigned long fault_addr)
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+{
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+ /* This is the normal case: #PF with a fault address in userspace. */
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+ if (trapnr == X86_TRAP_PF && fault_addr < TASK_SIZE_MAX)
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+ return false;
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+
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+ /*
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+ * This code can be reached for machine checks, but only if the #MC
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+ * handler has already decided that it looks like a candidate for fixup.
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+ * This e.g. happens when attempting to access userspace memory which
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+ * the CPU can't access because of uncorrectable bad memory.
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+ */
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+ if (trapnr == X86_TRAP_MC)
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+ return false;
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+
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+ /*
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+ * There are two remaining exception types we might encounter here:
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+ * - #PF for faulting accesses to kernel addresses
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+ * - #GP for faulting accesses to noncanonical addresses
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+ * Complain about anything else.
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+ */
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+ if (trapnr != X86_TRAP_PF && trapnr != X86_TRAP_GP) {
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+ WARN(1, "unexpected trap %d in uaccess\n", trapnr);
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+ return false;
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+ }
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+
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+ /*
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+ * This is a faulting memory access in kernel space, on a kernel
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+ * address, in a usercopy function. This can e.g. be caused by improper
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+ * use of helpers like __put_user and by improper attempts to access
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+ * userspace addresses in KERNEL_DS regions.
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+ * The one (semi-)legitimate exception are probe_kernel_{read,write}(),
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+ * which can be invoked from places like kgdb, /dev/mem (for reading)
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+ * and privileged BPF code (for reading).
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+ * The probe_kernel_*() functions set the kernel_uaccess_faults_ok flag
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+ * to tell us that faulting on kernel addresses, and even noncanonical
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+ * addresses, in a userspace accessor does not necessarily imply a
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+ * kernel bug, root might just be doing weird stuff.
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+ */
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+ if (current->kernel_uaccess_faults_ok)
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+ return false;
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+
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+ /* This is bad. Refuse the fixup so that we go into die(). */
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+ if (trapnr == X86_TRAP_PF) {
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+ pr_emerg("BUG: pagefault on kernel address 0x%lx in non-whitelisted uaccess\n",
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+ fault_addr);
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+ } else {
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+ pr_emerg("BUG: GPF in non-whitelisted uaccess (non-canonical address?)\n");
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+ }
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+ return true;
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+}
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+
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+__visible bool ex_handler_uaccess(const struct exception_table_entry *fixup,
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+ struct pt_regs *regs, int trapnr,
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+ unsigned long error_code,
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+ unsigned long fault_addr)
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+{
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+ if (bogus_uaccess(regs, trapnr, fault_addr))
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+ return false;
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+ regs->ip = ex_fixup_addr(fixup);
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+ return true;
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+}
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+EXPORT_SYMBOL(ex_handler_uaccess);
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+
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__visible bool ex_handler_ext(const struct exception_table_entry *fixup,
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__visible bool ex_handler_ext(const struct exception_table_entry *fixup,
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- struct pt_regs *regs, int trapnr)
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+ struct pt_regs *regs, int trapnr,
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+ unsigned long error_code,
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+ unsigned long fault_addr)
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{
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{
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+ if (bogus_uaccess(regs, trapnr, fault_addr))
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+ return false;
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/* Special hack for uaccess_err */
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/* Special hack for uaccess_err */
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current->thread.uaccess_err = 1;
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current->thread.uaccess_err = 1;
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regs->ip = ex_fixup_addr(fixup);
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regs->ip = ex_fixup_addr(fixup);
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@@ -119,7 +198,9 @@ __visible bool ex_handler_ext(const struct exception_table_entry *fixup,
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EXPORT_SYMBOL(ex_handler_ext);
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EXPORT_SYMBOL(ex_handler_ext);
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__visible bool ex_handler_rdmsr_unsafe(const struct exception_table_entry *fixup,
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__visible bool ex_handler_rdmsr_unsafe(const struct exception_table_entry *fixup,
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- struct pt_regs *regs, int trapnr)
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+ struct pt_regs *regs, int trapnr,
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+ unsigned long error_code,
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+ unsigned long fault_addr)
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{
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{
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if (pr_warn_once("unchecked MSR access error: RDMSR from 0x%x at rIP: 0x%lx (%pF)\n",
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if (pr_warn_once("unchecked MSR access error: RDMSR from 0x%x at rIP: 0x%lx (%pF)\n",
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(unsigned int)regs->cx, regs->ip, (void *)regs->ip))
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(unsigned int)regs->cx, regs->ip, (void *)regs->ip))
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@@ -134,7 +215,9 @@ __visible bool ex_handler_rdmsr_unsafe(const struct exception_table_entry *fixup
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EXPORT_SYMBOL(ex_handler_rdmsr_unsafe);
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EXPORT_SYMBOL(ex_handler_rdmsr_unsafe);
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__visible bool ex_handler_wrmsr_unsafe(const struct exception_table_entry *fixup,
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__visible bool ex_handler_wrmsr_unsafe(const struct exception_table_entry *fixup,
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- struct pt_regs *regs, int trapnr)
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+ struct pt_regs *regs, int trapnr,
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+ unsigned long error_code,
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+ unsigned long fault_addr)
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{
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{
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if (pr_warn_once("unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x) at rIP: 0x%lx (%pF)\n",
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if (pr_warn_once("unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x) at rIP: 0x%lx (%pF)\n",
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(unsigned int)regs->cx, (unsigned int)regs->dx,
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(unsigned int)regs->cx, (unsigned int)regs->dx,
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@@ -148,12 +231,14 @@ __visible bool ex_handler_wrmsr_unsafe(const struct exception_table_entry *fixup
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EXPORT_SYMBOL(ex_handler_wrmsr_unsafe);
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EXPORT_SYMBOL(ex_handler_wrmsr_unsafe);
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__visible bool ex_handler_clear_fs(const struct exception_table_entry *fixup,
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__visible bool ex_handler_clear_fs(const struct exception_table_entry *fixup,
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- struct pt_regs *regs, int trapnr)
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+ struct pt_regs *regs, int trapnr,
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+ unsigned long error_code,
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+ unsigned long fault_addr)
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{
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{
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if (static_cpu_has(X86_BUG_NULL_SEG))
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if (static_cpu_has(X86_BUG_NULL_SEG))
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asm volatile ("mov %0, %%fs" : : "rm" (__USER_DS));
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asm volatile ("mov %0, %%fs" : : "rm" (__USER_DS));
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asm volatile ("mov %0, %%fs" : : "rm" (0));
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asm volatile ("mov %0, %%fs" : : "rm" (0));
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- return ex_handler_default(fixup, regs, trapnr);
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+ return ex_handler_default(fixup, regs, trapnr, error_code, fault_addr);
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}
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}
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EXPORT_SYMBOL(ex_handler_clear_fs);
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EXPORT_SYMBOL(ex_handler_clear_fs);
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@@ -170,7 +255,8 @@ __visible bool ex_has_fault_handler(unsigned long ip)
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return handler == ex_handler_fault;
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return handler == ex_handler_fault;
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}
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}
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-int fixup_exception(struct pt_regs *regs, int trapnr)
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+int fixup_exception(struct pt_regs *regs, int trapnr, unsigned long error_code,
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+ unsigned long fault_addr)
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{
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{
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const struct exception_table_entry *e;
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const struct exception_table_entry *e;
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ex_handler_t handler;
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ex_handler_t handler;
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@@ -194,7 +280,7 @@ int fixup_exception(struct pt_regs *regs, int trapnr)
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return 0;
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return 0;
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handler = ex_fixup_handler(e);
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handler = ex_fixup_handler(e);
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- return handler(e, regs, trapnr);
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+ return handler(e, regs, trapnr, error_code, fault_addr);
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}
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}
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extern unsigned int early_recursion_flag;
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extern unsigned int early_recursion_flag;
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@@ -230,9 +316,9 @@ void __init early_fixup_exception(struct pt_regs *regs, int trapnr)
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* result in a hard-to-debug panic.
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* result in a hard-to-debug panic.
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*
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*
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* Keep in mind that not all vectors actually get here. Early
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* Keep in mind that not all vectors actually get here. Early
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- * fage faults, for example, are special.
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+ * page faults, for example, are special.
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*/
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*/
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- if (fixup_exception(regs, trapnr))
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+ if (fixup_exception(regs, trapnr, regs->orig_ax, 0))
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return;
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return;
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if (fixup_bug(regs, trapnr))
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if (fixup_bug(regs, trapnr))
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