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

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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: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Co-developed-by: Peter Zijlstra <peterz@infradead.org>
Co-developed-by: Josh Poimboeuf <jpoimboe@redhat.com>
This commit is contained in:
Juergen Gross 2024-11-29 16:15:54 +01:00
parent dda014ba59
commit 0ef8047b73
6 changed files with 56 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
arch/x86/include/asm/static_call.h
View File

@ -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 */

6
arch/x86/include/asm/sync_core.h
View File

@ -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

9
arch/x86/kernel/static_call.c
View File

@ -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,

39
include/linux/compiler.h
View File

@ -216,18 +216,6 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
#endif /* __KERNEL__ */
/*
* 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
* otherwise, or eliminated entirely due to lack of references that are
* visible to the compiler.
*/
#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
@ -239,6 +227,33 @@ static inline void *offset_to_ptr(const int *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
* otherwise, or eliminated entirely due to lack of references that are
* visible to the compiler.
*/
#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"))
#define __ADDRESSABLE_ASM(sym) \
.pushsection .discard.addressable,"aw"; \
.align ARCH_SEL(8,4); \
ARCH_SEL(.quad, .long) __stringify(sym); \
.popsection;
#define __ADDRESSABLE_ASM_STR(sym) __stringify(__ADDRESSABLE_ASM(sym))
#ifdef __CHECKER__
#define __BUILD_BUG_ON_ZERO_MSG(e, msg) (0)
#else /* __CHECKER__ */

1
include/linux/static_call.h
View File

@ -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.
*/

2
kernel/static_call_inline.c
View File

@ -15,7 +15,7 @@ extern struct static_call_site __start_static_call_sites[],
extern struct static_call_tramp_key __start_static_call_tramp_key[],
__stop_static_call_tramp_key[];
static int static_call_initialized;
int static_call_initialized;
/*
* Must be called before early_initcall() to be effective.