Commit 0ef8047b authored by Juergen Gross's avatar Juergen Gross
Browse files

x86/static-call: provide a way to do very early static-call updates 



Add static_call_update_early() for updating static-call targets in
very early boot.

This will be needed for support of Xen guest type specific hypercall
functions.

This is part of XSA-466 / CVE-2024-53241.

Reported-by: default avatarAndrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Co-developed-by: default avatarPeter Zijlstra <peterz@infradead.org>
Co-developed-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
parent dda014ba

arch/x86/include/asm/static_call.h

+15 −0
Original line number Diff line number Diff line
@@ -65,4 +65,19 @@ 


extern bool __static_call_fixup(void *tramp, u8 op, void *dest);



extern void __static_call_update_early(void *tramp, void *func);



#define static_call_update_early(name, _func)				\

({									\

	typeof(&STATIC_CALL_TRAMP(name)) __F = (_func);			\

	if (static_call_initialized) {					\

		__static_call_update(&STATIC_CALL_KEY(name),		\

				     STATIC_CALL_TRAMP_ADDR(name), __F);\

	} else {							\

		WRITE_ONCE(STATIC_CALL_KEY(name).func, _func);		\

		__static_call_update_early(STATIC_CALL_TRAMP_ADDR(name),\

					   __F);			\

	}								\

})



#endif /* _ASM_STATIC_CALL_H */

arch/x86/include/asm/sync_core.h

+3 −3
Original line number Diff line number Diff line
@@ -8,7 +8,7 @@ 
#include <asm/special_insns.h>



#ifdef CONFIG_X86_32

static inline void iret_to_self(void)

static __always_inline void iret_to_self(void)

{

	asm volatile (

		"pushfl\n\t"
@@ -19,7 +19,7 @@ static inline void iret_to_self(void) 
		: ASM_CALL_CONSTRAINT : : "memory");

}

#else

static inline void iret_to_self(void)

static __always_inline void iret_to_self(void)

{

	unsigned int tmp;
@@ -55,7 +55,7 @@ static inline void iret_to_self(void) 
 * Like all of Linux's memory ordering operations, this is a

 * compiler barrier as well.

 */

static inline void sync_core(void)

static __always_inline void sync_core(void)

{

	/*

	 * The SERIALIZE instruction is the most straightforward way to

arch/x86/kernel/static_call.c

+9 −0
Original line number Diff line number Diff line
@@ -172,6 +172,15 @@ void arch_static_call_transform(void *site, void *tramp, void *func, bool tail) 
}

EXPORT_SYMBOL_GPL(arch_static_call_transform);



noinstr void __static_call_update_early(void *tramp, void *func)

{

	BUG_ON(system_state != SYSTEM_BOOTING);

	BUG_ON(!early_boot_irqs_disabled);

	BUG_ON(static_call_initialized);

	__text_gen_insn(tramp, JMP32_INSN_OPCODE, tramp, func, JMP32_INSN_SIZE);

	sync_core();

}



#ifdef CONFIG_MITIGATION_RETHUNK

/*

 * This is called by apply_returns() to fix up static call trampolines,

include/linux/compiler.h

+26 −11
Original line number Diff line number Diff line
@@ -216,6 +216,23 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, 


#endif /* __KERNEL__ */



/**

 * offset_to_ptr - convert a relative memory offset to an absolute pointer

 * @off:	the address of the 32-bit offset value

 */

static inline void *offset_to_ptr(const int *off)

{

	return (void *)((unsigned long)off + *off);

}



#endif /* __ASSEMBLY__ */



#ifdef CONFIG_64BIT

#define ARCH_SEL(a,b) a

#else

#define ARCH_SEL(a,b) b

#endif



/*

 * Force the compiler to emit 'sym' as a symbol, so that we can reference

 * it from inline assembler. Necessary in case 'sym' could be inlined
@@ -225,19 +242,17 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, 
#define ___ADDRESSABLE(sym, __attrs)						\

	static void * __used __attrs						\

	__UNIQUE_ID(__PASTE(__addressable_,sym)) = (void *)(uintptr_t)&sym;



#define __ADDRESSABLE(sym) \

	___ADDRESSABLE(sym, __section(".discard.addressable"))



/**

 * offset_to_ptr - convert a relative memory offset to an absolute pointer

 * @off:	the address of the 32-bit offset value

 */

static inline void *offset_to_ptr(const int *off)

{

	return (void *)((unsigned long)off + *off);

}

#define __ADDRESSABLE_ASM(sym)						\

	.pushsection .discard.addressable,"aw";				\

	.align ARCH_SEL(8,4);						\

	ARCH_SEL(.quad, .long) __stringify(sym);			\

	.popsection;



#endif /* __ASSEMBLY__ */

#define __ADDRESSABLE_ASM_STR(sym) __stringify(__ADDRESSABLE_ASM(sym))



#ifdef __CHECKER__

#define __BUILD_BUG_ON_ZERO_MSG(e, msg) (0)

include/linux/static_call.h

+1 −0
Original line number Diff line number Diff line
@@ -138,6 +138,7 @@ 
#ifdef CONFIG_HAVE_STATIC_CALL

#include <asm/static_call.h>



extern int static_call_initialized;

/*

 * Either @site or @tramp can be NULL.

 */