x86/msr: Remove .fixup usage
Rework the MSR accessors to remove .fixup usage. Add two new extable
types (to the 4 already existing msr ones) using the new register
infrastructure to record which register should get the error value.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20211110101325.364084212@infradead.org
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index cef8901..717cd35 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -83,28 +83,29 @@ static bool ex_handler_copy(const struct exception_table_entry *fixup,
return ex_handler_fault(fixup, regs, trapnr);
}
-static bool ex_handler_rdmsr_unsafe(const struct exception_table_entry *fixup,
- struct pt_regs *regs)
+static bool ex_handler_msr(const struct exception_table_entry *fixup,
+ struct pt_regs *regs, bool wrmsr, bool safe, int reg)
{
- if (pr_warn_once("unchecked MSR access error: RDMSR from 0x%x at rIP: 0x%lx (%pS)\n",
- (unsigned int)regs->cx, regs->ip, (void *)regs->ip))
- show_stack_regs(regs);
-
- /* Pretend that the read succeeded and returned 0. */
- regs->ax = 0;
- regs->dx = 0;
- return ex_handler_default(fixup, regs);
-}
-
-static bool ex_handler_wrmsr_unsafe(const struct exception_table_entry *fixup,
- struct pt_regs *regs)
-{
- if (pr_warn_once("unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x) at rIP: 0x%lx (%pS)\n",
+ if (!safe && wrmsr &&
+ pr_warn_once("unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x) at rIP: 0x%lx (%pS)\n",
(unsigned int)regs->cx, (unsigned int)regs->dx,
(unsigned int)regs->ax, regs->ip, (void *)regs->ip))
show_stack_regs(regs);
- /* Pretend that the write succeeded. */
+ if (!safe && !wrmsr &&
+ pr_warn_once("unchecked MSR access error: RDMSR from 0x%x at rIP: 0x%lx (%pS)\n",
+ (unsigned int)regs->cx, regs->ip, (void *)regs->ip))
+ show_stack_regs(regs);
+
+ if (!wrmsr) {
+ /* Pretend that the read succeeded and returned 0. */
+ regs->ax = 0;
+ regs->dx = 0;
+ }
+
+ if (safe)
+ *pt_regs_nr(regs, reg) = -EIO;
+
return ex_handler_default(fixup, regs);
}
@@ -186,18 +187,22 @@ int fixup_exception(struct pt_regs *regs, int trapnr, unsigned long error_code,
return ex_handler_clear_fs(e, regs);
case EX_TYPE_FPU_RESTORE:
return ex_handler_fprestore(e, regs);
- case EX_TYPE_RDMSR:
- return ex_handler_rdmsr_unsafe(e, regs);
- case EX_TYPE_WRMSR:
- return ex_handler_wrmsr_unsafe(e, regs);
case EX_TYPE_BPF:
return ex_handler_bpf(e, regs);
- case EX_TYPE_RDMSR_IN_MCE:
- ex_handler_msr_mce(regs, false);
- break;
+ case EX_TYPE_WRMSR:
+ return ex_handler_msr(e, regs, true, false, reg);
+ case EX_TYPE_RDMSR:
+ return ex_handler_msr(e, regs, false, false, reg);
+ case EX_TYPE_WRMSR_SAFE:
+ return ex_handler_msr(e, regs, true, true, reg);
+ case EX_TYPE_RDMSR_SAFE:
+ return ex_handler_msr(e, regs, false, true, reg);
case EX_TYPE_WRMSR_IN_MCE:
ex_handler_msr_mce(regs, true);
break;
+ case EX_TYPE_RDMSR_IN_MCE:
+ ex_handler_msr_mce(regs, false);
+ break;
case EX_TYPE_POP_ZERO:
return ex_handler_pop_zero(e, regs);
case EX_TYPE_IMM_REG: