From 0ef8047b737d7480a5d4c46d956e97c190f13050 Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Fri, 29 Nov 2024 16:15:54 +0100 Subject: [PATCH] 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: Andrew Cooper Signed-off-by: Juergen Gross Co-developed-by: Peter Zijlstra Co-developed-by: Josh Poimboeuf --- arch/x86/include/asm/static_call.h | 15 ++++++++++++ arch/x86/include/asm/sync_core.h | 6 ++--- arch/x86/kernel/static_call.c | 9 +++++++ include/linux/compiler.h | 39 +++++++++++++++++++++--------- include/linux/static_call.h | 1 + kernel/static_call_inline.c | 2 +- 6 files changed, 56 insertions(+), 16 deletions(-) diff --git a/arch/x86/include/asm/static_call.h b/arch/x86/include/asm/static_call.h index 125c407e2abe..41502bd2afd6 100644 --- a/arch/x86/include/asm/static_call.h +++ b/arch/x86/include/asm/static_call.h @@ -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 */ diff --git a/arch/x86/include/asm/sync_core.h b/arch/x86/include/asm/sync_core.h index ab7382f92aff..96bda43538ee 100644 --- a/arch/x86/include/asm/sync_core.h +++ b/arch/x86/include/asm/sync_core.h @@ -8,7 +8,7 @@ #include #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 diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c index 4eefaac64c6c..9eed0c144dad 100644 --- a/arch/x86/kernel/static_call.c +++ b/arch/x86/kernel/static_call.c @@ -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, diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 469a64dd6495..240c632c5b95 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -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__ */ diff --git a/include/linux/static_call.h b/include/linux/static_call.h index 141e6b176a1b..785980af8972 100644 --- a/include/linux/static_call.h +++ b/include/linux/static_call.h @@ -138,6 +138,7 @@ #ifdef CONFIG_HAVE_STATIC_CALL #include +extern int static_call_initialized; /* * Either @site or @tramp can be NULL. */ diff --git a/kernel/static_call_inline.c b/kernel/static_call_inline.c index 5259cda486d0..bb7d066a7c39 100644 --- a/kernel/static_call_inline.c +++ b/kernel/static_call_inline.c @@ -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.