mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-02-13 10:42:02 -05:00
f49ecf5e11
In most cases, the use of "fast 32-bit system call" depends either on X86_FEATURE_SEP or X86_FEATURE_SYSENTER32 || X86_FEATURE_SYSCALL32. However, nearly all the logic for both is identical. Define X86_FEATURE_SYSFAST32 which indicates that *either* SYSENTER32 or SYSCALL32 should be used, for either 32- or 64-bit kernels. This defaults to SYSENTER; use SYSCALL if the SYSCALL32 bit is also set. As this removes ALL existing uses of X86_FEATURE_SYSENTER32, which is a kernel-only synthetic feature bit, simply remove it and replace it with X86_FEATURE_SYSFAST32. This leaves an unused alternative for a true 32-bit kernel, but that should really not matter in any way. The clearing of X86_FEATURE_SYSCALL32 can be removed once the patches for automatically clearing disabled features has been merged. Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Link: https://patch.msgid.link/20251216212606.1325678-10-hpa@zytor.com
94 lines
3.1 KiB
C
94 lines
3.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#include <linux/kernel.h>
|
|
|
|
#include <asm/desc.h>
|
|
#include <asm/fred.h>
|
|
#include <asm/msr.h>
|
|
#include <asm/tlbflush.h>
|
|
#include <asm/traps.h>
|
|
|
|
/* #DB in the kernel would imply the use of a kernel debugger. */
|
|
#define FRED_DB_STACK_LEVEL 1UL
|
|
#define FRED_NMI_STACK_LEVEL 2UL
|
|
#define FRED_MC_STACK_LEVEL 2UL
|
|
/*
|
|
* #DF is the highest level because a #DF means "something went wrong
|
|
* *while delivering an exception*." The number of cases for which that
|
|
* can happen with FRED is drastically reduced and basically amounts to
|
|
* "the stack you pointed me to is broken." Thus, always change stacks
|
|
* on #DF, which means it should be at the highest level.
|
|
*/
|
|
#define FRED_DF_STACK_LEVEL 3UL
|
|
|
|
#define FRED_STKLVL(vector, lvl) ((lvl) << (2 * (vector)))
|
|
|
|
DEFINE_PER_CPU(unsigned long, fred_rsp0);
|
|
EXPORT_PER_CPU_SYMBOL(fred_rsp0);
|
|
|
|
void cpu_init_fred_exceptions(void)
|
|
{
|
|
/* When FRED is enabled by default, remove this log message */
|
|
pr_info("Initialize FRED on CPU%d\n", smp_processor_id());
|
|
|
|
/*
|
|
* If a kernel event is delivered before a CPU goes to user level for
|
|
* the first time, its SS is NULL thus NULL is pushed into the SS field
|
|
* of the FRED stack frame. But before ERETS is executed, the CPU may
|
|
* context switch to another task and go to user level. Then when the
|
|
* CPU comes back to kernel mode, SS is changed to __KERNEL_DS. Later
|
|
* when ERETS is executed to return from the kernel event handler, a #GP
|
|
* fault is generated because SS doesn't match the SS saved in the FRED
|
|
* stack frame.
|
|
*
|
|
* Initialize SS to __KERNEL_DS when enabling FRED to avoid such #GPs.
|
|
*/
|
|
loadsegment(ss, __KERNEL_DS);
|
|
|
|
wrmsrq(MSR_IA32_FRED_CONFIG,
|
|
/* Reserve for CALL emulation */
|
|
FRED_CONFIG_REDZONE |
|
|
FRED_CONFIG_INT_STKLVL(0) |
|
|
FRED_CONFIG_ENTRYPOINT(asm_fred_entrypoint_user));
|
|
|
|
wrmsrq(MSR_IA32_FRED_STKLVLS, 0);
|
|
|
|
/*
|
|
* Ater a CPU offline/online cycle, the FRED RSP0 MSR should be
|
|
* resynchronized with its per-CPU cache.
|
|
*/
|
|
wrmsrq(MSR_IA32_FRED_RSP0, __this_cpu_read(fred_rsp0));
|
|
|
|
wrmsrq(MSR_IA32_FRED_RSP1, 0);
|
|
wrmsrq(MSR_IA32_FRED_RSP2, 0);
|
|
wrmsrq(MSR_IA32_FRED_RSP3, 0);
|
|
|
|
/* Enable FRED */
|
|
cr4_set_bits(X86_CR4_FRED);
|
|
/* Any further IDT use is a bug */
|
|
idt_invalidate();
|
|
|
|
/* Use int $0x80 for 32-bit system calls in FRED mode */
|
|
setup_clear_cpu_cap(X86_FEATURE_SYSFAST32);
|
|
setup_clear_cpu_cap(X86_FEATURE_SYSCALL32);
|
|
}
|
|
|
|
/* Must be called after setup_cpu_entry_areas() */
|
|
void cpu_init_fred_rsps(void)
|
|
{
|
|
/*
|
|
* The purpose of separate stacks for NMI, #DB and #MC *in the kernel*
|
|
* (remember that user space faults are always taken on stack level 0)
|
|
* is to avoid overflowing the kernel stack.
|
|
*/
|
|
wrmsrq(MSR_IA32_FRED_STKLVLS,
|
|
FRED_STKLVL(X86_TRAP_DB, FRED_DB_STACK_LEVEL) |
|
|
FRED_STKLVL(X86_TRAP_NMI, FRED_NMI_STACK_LEVEL) |
|
|
FRED_STKLVL(X86_TRAP_MC, FRED_MC_STACK_LEVEL) |
|
|
FRED_STKLVL(X86_TRAP_DF, FRED_DF_STACK_LEVEL));
|
|
|
|
/* The FRED equivalents to IST stacks... */
|
|
wrmsrq(MSR_IA32_FRED_RSP1, __this_cpu_ist_top_va(DB));
|
|
wrmsrq(MSR_IA32_FRED_RSP2, __this_cpu_ist_top_va(NMI));
|
|
wrmsrq(MSR_IA32_FRED_RSP3, __this_cpu_ist_top_va(DF));
|
|
}
|