[tip:,x86/paravirt] x86/paravirt: Convert simple paravirt functions to asm
Commit Message
The following commit has been merged into the x86/paravirt branch of tip:
Commit-ID: 11af36cb898123fd4e0034f1bc6550aedcc87800
Gitweb: https://git.kernel.org/tip/11af36cb898123fd4e0034f1bc6550aedcc87800
Author: Juergen Gross <jgross@suse.com>
AuthorDate: Fri, 17 Mar 2023 07:33:25 +01:00
Committer: Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 17 Mar 2023 13:29:47 +01:00
x86/paravirt: Convert simple paravirt functions to asm
All functions referenced via __PV_IS_CALLEE_SAVE() need to be assembler
functions, as those functions calls are hidden from the compiler.
In case the kernel is compiled with "-fzero-call-used-regs" the compiler
will clobber caller-saved registers at the end of C functions, which
will result in unexpectedly zeroed registers at the call site of the
related paravirt functions.
Replace the C functions with DEFINE_PARAVIRT_ASM() constructs using
the same instructions as the related paravirt calls in the
PVOP_ALT_[V]CALLEE*() macros. And since they're not C functions visible
to the compiler anymore, latter won't do the callee-clobbered zeroing
invoked by -fzero-call-used-regs and thus won't corrupt registers.
[ bp: Extend commit message. ]
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230317063325.361-1-jgross@suse.com
---
arch/x86/include/asm/paravirt_types.h | 8 +++++++-
arch/x86/kernel/paravirt.c | 27 +++++---------------------
2 files changed, 13 insertions(+), 22 deletions(-)
@@ -559,8 +559,14 @@ void paravirt_flush_lazy_mmu(void);
void _paravirt_nop(void);
void paravirt_BUG(void);
-u64 _paravirt_ident_64(u64);
unsigned long paravirt_ret0(void);
+#ifdef CONFIG_PARAVIRT_XXL
+u64 _paravirt_ident_64(u64);
+unsigned long pv_native_save_fl(void);
+void pv_native_irq_disable(void);
+void pv_native_irq_enable(void);
+unsigned long pv_native_read_cr2(void);
+#endif
#define paravirt_nop ((void *)_paravirt_nop)
@@ -64,11 +64,11 @@ static unsigned paravirt_patch_call(void *insn_buff, const void *target,
}
#ifdef CONFIG_PARAVIRT_XXL
-/* identity function, which can be inlined */
-u64 notrace _paravirt_ident_64(u64 x)
-{
- return x;
-}
+DEFINE_PARAVIRT_ASM(_paravirt_ident_64, "mov %rdi, %rax", .text);
+DEFINE_PARAVIRT_ASM(pv_native_save_fl, "pushf; pop %rax", .noinstr.text);
+DEFINE_PARAVIRT_ASM(pv_native_irq_disable, "cli", .noinstr.text);
+DEFINE_PARAVIRT_ASM(pv_native_irq_enable, "sti", .noinstr.text);
+DEFINE_PARAVIRT_ASM(pv_native_read_cr2, "mov %cr2, %rax", .noinstr.text);
#endif
DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key);
@@ -197,11 +197,6 @@ void paravirt_end_context_switch(struct task_struct *next)
arch_enter_lazy_mmu_mode();
}
-static noinstr unsigned long pv_native_read_cr2(void)
-{
- return native_read_cr2();
-}
-
static noinstr void pv_native_write_cr2(unsigned long val)
{
native_write_cr2(val);
@@ -222,16 +217,6 @@ noinstr void pv_native_wbinvd(void)
native_wbinvd();
}
-static noinstr void pv_native_irq_enable(void)
-{
- native_irq_enable();
-}
-
-static noinstr void pv_native_irq_disable(void)
-{
- native_irq_disable();
-}
-
static noinstr void pv_native_safe_halt(void)
{
native_safe_halt();
@@ -298,7 +283,7 @@ struct paravirt_patch_template pv_ops = {
.cpu.end_context_switch = paravirt_nop,
/* Irq ops. */
- .irq.save_fl = __PV_IS_CALLEE_SAVE(native_save_fl),
+ .irq.save_fl = __PV_IS_CALLEE_SAVE(pv_native_save_fl),
.irq.irq_disable = __PV_IS_CALLEE_SAVE(pv_native_irq_disable),
.irq.irq_enable = __PV_IS_CALLEE_SAVE(pv_native_irq_enable),
.irq.safe_halt = pv_native_safe_halt,