The following commit has been merged into the x86/entry branch of tip:
Commit-ID: 61382281e9054df523d3f9cfdba2faff88955f97
Gitweb: https://git.kernel.org/tip/61382281e9054df523d3f9cfdba2faff88955f97
Author: Nikolay Borisov <nik.borisov@xxxxxxxx>
AuthorDate: Fri, 23 Jun 2023 14:14:08 +03:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Thu, 14 Sep 2023 13:19:53 +02:00
x86/entry: Make IA32 syscalls' availability depend on ia32_enabled()
Another major aspect of supporting running of 32bit processes is the
ability to access 32bit syscalls. Such syscalls can be invoked by
using the legacy int 0x80 handler and sysenter/syscall instructions.
If IA32 emulation is disabled ensure that each of those 3 distinct
mechanisms are also disabled. For int 0x80 a #GP exception would be
generated since the respective descriptor is not going to be loaded at
all. Invoking sysenter will also result in a #GP since IA32_SYSENTER_CS
contains an invalid segment. Finally, syscall instruction cannot really
be disabled so it's configured to execute a minimal handler.
Signed-off-by: Nikolay Borisov <nik.borisov@xxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230623111409.3047467-6-nik.borisov@xxxxxxxx
---
arch/x86/include/asm/proto.h | 3 +++-
arch/x86/kernel/cpu/common.c | 37 +++++++++++++++++------------------
arch/x86/kernel/idt.c | 7 +++++++-
3 files changed, 29 insertions(+), 18 deletions(-)
diff --git a/arch/x86/include/asm/proto.h b/arch/x86/include/asm/proto.h
index 12ef86b..4d84122 100644
--- a/arch/x86/include/asm/proto.h
+++ b/arch/x86/include/asm/proto.h
@@ -36,6 +36,9 @@ void entry_INT80_compat(void);
#ifdef CONFIG_XEN_PV
void xen_entry_INT80_compat(void);
#endif
+#else /* !CONFIG_IA32_EMULATION */
+#define entry_SYSCALL_compat NULL
+#define entry_SYSENTER_compat NULL
#endif
void x86_configure_nx(void);
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index b3f8cba..afa755e 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -62,6 +62,7 @@
#include <asm/intel-family.h>
#include <asm/cpu_device_id.h>
#include <asm/uv/uv.h>
+#include <asm/ia32.h>
#include <asm/set_memory.h>
#include <asm/traps.h>
#include <asm/sev.h>
@@ -2074,24 +2075,24 @@ void syscall_init(void)
wrmsr(MSR_STAR, 0, (__USER32_CS << 16) | __KERNEL_CS);
wrmsrl(MSR_LSTAR, (unsigned long)entry_SYSCALL_64);
-#ifdef CONFIG_IA32_EMULATION
- wrmsrl_cstar((unsigned long)entry_SYSCALL_compat);
- /*
- * This only works on Intel CPUs.
- * On AMD CPUs these MSRs are 32-bit, CPU truncates MSR_IA32_SYSENTER_EIP.
- * This does not cause SYSENTER to jump to the wrong location, because
- * AMD doesn't allow SYSENTER in long mode (either 32- or 64-bit).
- */
- wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
- wrmsrl_safe(MSR_IA32_SYSENTER_ESP,
- (unsigned long)(cpu_entry_stack(smp_processor_id()) + 1));
- wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)entry_SYSENTER_compat);
-#else
- wrmsrl_cstar((unsigned long)entry_SYSCALL32_ignore);
- wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)GDT_ENTRY_INVALID_SEG);
- wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL);
- wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL);
-#endif
+ if (ia32_enabled()) {
+ wrmsrl_cstar((unsigned long)entry_SYSCALL_compat);
+ /*
+ * This only works on Intel CPUs.
+ * On AMD CPUs these MSRs are 32-bit, CPU truncates MSR_IA32_SYSENTER_EIP.
+ * This does not cause SYSENTER to jump to the wrong location, because
+ * AMD doesn't allow SYSENTER in long mode (either 32- or 64-bit).
+ */
+ wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
+ wrmsrl_safe(MSR_IA32_SYSENTER_ESP,
+ (unsigned long)(cpu_entry_stack(smp_processor_id()) + 1));
+ wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)entry_SYSENTER_compat);
+ } else {
+ wrmsrl_cstar((unsigned long)entry_SYSCALL32_ignore);
+ wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)GDT_ENTRY_INVALID_SEG);
+ wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL);
+ wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL);
+ }
/*
* Flags to clear on syscall; clear as much as possible
diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index b786d48..8857abc 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -10,6 +10,7 @@
#include <asm/proto.h>
#include <asm/desc.h>
#include <asm/hw_irq.h>
+#include <asm/ia32.h>
#include <asm/idtentry.h>
#define DPL0 0x0
@@ -116,6 +117,9 @@ static const __initconst struct idt_data def_idts[] = {
#endif
SYSG(X86_TRAP_OF, asm_exc_overflow),
+};
+
+static const struct idt_data ia32_idt[] __initconst = {
#if defined(CONFIG_IA32_EMULATION)
SYSG(IA32_SYSCALL_VECTOR, entry_INT80_compat),
#elif defined(CONFIG_X86_32)
@@ -225,6 +229,9 @@ void __init idt_setup_early_traps(void)
void __init idt_setup_traps(void)
{
idt_setup_from_table(idt_table, def_idts, ARRAY_SIZE(def_idts), true);
+
+ if (ia32_enabled())
+ idt_setup_from_table(idt_table, ia32_idt, ARRAY_SIZE(ia32_idt), true);
}
#ifdef CONFIG_X86_64
|