Messages in this thread Patch in this message | | | Date | Mon, 26 Nov 2018 15:26:28 -0600 | From | Josh Poimboeuf <> | Subject | Re: [PATCH v2 4/4] x86/static_call: Add inline static call implementation for x86-64 |
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On Mon, Nov 26, 2018 at 09:08:01PM +0100, Peter Zijlstra wrote: > On Mon, Nov 26, 2018 at 11:56:24AM -0600, Josh Poimboeuf wrote: > > diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c > > index d3869295b88d..8fd6c8556750 100644 > > --- a/arch/x86/kernel/static_call.c > > +++ b/arch/x86/kernel/static_call.c > > @@ -7,24 +7,19 @@ > > > > #define CALL_INSN_SIZE 5 > > > > +unsigned long bp_handler_call_return_addr; > > > > +static void static_call_bp_handler(struct pt_regs *regs) > > +{ > > #ifdef CONFIG_HAVE_STATIC_CALL_INLINE > > + /* > > + * Push the return address on the stack so the "called" function will > > + * return to immediately after the call site. > > + */ > > + regs->sp -= sizeof(long); > > + *(unsigned long *)regs->sp = bp_handler_call_return_addr; > > #endif > > +} > > > > void arch_static_call_transform(void *site, void *tramp, void *func) > > { > > @@ -52,14 +47,12 @@ void arch_static_call_transform(void *site, void *tramp, void *func) > > opcodes[0] = insn_opcode; > > memcpy(&opcodes[1], &dest_relative, CALL_INSN_SIZE - 1); > > > > if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE)) > > + bp_handler_call_return_addr = insn + CALL_INSN_SIZE; > > > > /* Patch the call site: */ > > text_poke_bp((void *)insn, opcodes, CALL_INSN_SIZE, > > - static_call_bp_handler); > > + static_call_bp_handler, func); > > > > done: > > mutex_unlock(&text_mutex); > > > like maybe something along the lines of: > > struct sc_data { > unsigned long ret; > unsigned long ip; > }; > > void sc_handler(struct pt_regs *regs, void *data) > { > struct sc_data *scd = data; > > regs->sp -= sizeof(long); > *(unsigned long *)regs->sp = scd->ret; > regs->ip = scd->ip; > } > > arch_static_call_transform() > { > ... > > scd = (struct sc_data){ > .ret = insn + CALL_INSN_SIZE, > .ip = (unsigned long)func, > }; > > text_poke_bp((void *)insn, opcodes, CALL_INSN_SIZE, > sc_handler, (void *)&scd); > > ... > }
Yeah, that's probably better. I assume you also mean that we would have all text_poke_bp() users create a handler callback? That way the interface is clear and consistent for everybody. Like:
diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h index e85ff65c43c3..04d6cf838fb7 100644 --- a/arch/x86/include/asm/text-patching.h +++ b/arch/x86/include/asm/text-patching.h @@ -20,6 +20,8 @@ static inline void apply_paravirt(struct paravirt_patch_site *start, extern void *text_poke_early(void *addr, const void *opcode, size_t len); +typedef void (*bp_handler_t)(struct pt_regs *regs, void *data); + /* * Clear and restore the kernel write-protection flag on the local CPU. * Allows the kernel to edit read-only pages. @@ -36,7 +38,8 @@ extern void *text_poke_early(void *addr, const void *opcode, size_t len); */ extern void *text_poke(void *addr, const void *opcode, size_t len); extern int poke_int3_handler(struct pt_regs *regs); -extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler); +extern void *text_poke_bp(void *addr, const void *opcode, size_t len, + bp_handler_t handler, void *data); extern int after_bootmem; #endif /* _ASM_X86_TEXT_PATCHING_H */ diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index ebeac487a20c..547af714bd60 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -738,7 +738,8 @@ static void do_sync_core(void *info) } static bool bp_patching_in_progress; -static void *bp_int3_handler, *bp_int3_addr; +static void *bp_int3_data, *bp_int3_addr; +static bp_handler_t bp_int3_handler; int poke_int3_handler(struct pt_regs *regs) { @@ -746,11 +747,11 @@ int poke_int3_handler(struct pt_regs *regs) * Having observed our INT3 instruction, we now must observe * bp_patching_in_progress. * - * in_progress = TRUE INT3 - * WMB RMB - * write INT3 if (in_progress) + * in_progress = TRUE INT3 + * WMB RMB + * write INT3 if (in_progress) * - * Idem for bp_int3_handler. + * Idem for bp_int3_data. */ smp_rmb(); @@ -760,8 +761,7 @@ int poke_int3_handler(struct pt_regs *regs) if (user_mode(regs) || regs->ip != (unsigned long)bp_int3_addr) return 0; - /* set up the specified breakpoint handler */ - regs->ip = (unsigned long) bp_int3_handler; + bp_int3_handler(regs, bp_int3_data); return 1; @@ -772,7 +772,8 @@ int poke_int3_handler(struct pt_regs *regs) * @addr: address to patch * @opcode: opcode of new instruction * @len: length to copy - * @handler: address to jump to when the temporary breakpoint is hit + * @handler: handler to call from int3 context + * @data: opaque data passed to handler * * Modify multi-byte instruction by using int3 breakpoint on SMP. * We completely avoid stop_machine() here, and achieve the @@ -787,11 +788,13 @@ int poke_int3_handler(struct pt_regs *regs) * replacing opcode * - sync cores */ -void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler) +void *text_poke_bp(void *addr, const void *opcode, size_t len, + bp_handler_t handler, void *data) { unsigned char int3 = 0xcc; bp_int3_handler = handler; + bp_int3_data = data; bp_int3_addr = (u8 *)addr + sizeof(int3); bp_patching_in_progress = true; diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c index aac0c1f7e354..d4b0abe4912d 100644 --- a/arch/x86/kernel/jump_label.c +++ b/arch/x86/kernel/jump_label.c @@ -37,6 +37,11 @@ static void bug_at(unsigned char *ip, int line) BUG(); } +static inline void jump_label_bp_handler(struct pt_regs *regs, void *data) +{ + regs->ip += JUMP_LABEL_NOP_SIZE - 1; +} + static void __ref __jump_label_transform(struct jump_entry *entry, enum jump_label_type type, void *(*poker)(void *, const void *, size_t), @@ -91,7 +96,7 @@ static void __ref __jump_label_transform(struct jump_entry *entry, } text_poke_bp((void *)jump_entry_code(entry), code, JUMP_LABEL_NOP_SIZE, - (void *)jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE); + jump_label_bp_handler, NULL); } void arch_jump_label_transform(struct jump_entry *entry, diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c index 40b16b270656..b2dffdd6068d 100644 --- a/arch/x86/kernel/kprobes/opt.c +++ b/arch/x86/kernel/kprobes/opt.c @@ -424,6 +424,11 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, goto out; } +static void kprobes_poke_bp_handler(struct pt_regs *regs, void *data) +{ + regs->ip = data; +} + /* * Replace breakpoints (int3) with relative jumps. * Caller must call with locking kprobe_mutex and text_mutex. @@ -447,7 +452,7 @@ void arch_optimize_kprobes(struct list_head *oplist) *(s32 *)(&insn_buf[1]) = rel; text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE, - op->optinsn.insn); + kprobes_poke_bp_handler, op->optinsn.insn); list_del_init(&op->list); } @@ -462,7 +467,7 @@ void arch_unoptimize_kprobe(struct optimized_kprobe *op) insn_buf[0] = BREAKPOINT_INSTRUCTION; memcpy(insn_buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE); text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE, - op->optinsn.insn); + kprobes_poke_bp_handler, op->optinsn.insn); } /* diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c index d3869295b88d..e05ebc6d4db5 100644 --- a/arch/x86/kernel/static_call.c +++ b/arch/x86/kernel/static_call.c @@ -7,24 +7,30 @@ #define CALL_INSN_SIZE 5 -void static_call_bp_handler(void); -void *bp_handler_dest; -void *bp_handler_continue; - -asm(".pushsection .text, \"ax\" \n" - ".globl static_call_bp_handler \n" - ".type static_call_bp_handler, @function \n" - "static_call_bp_handler: \n" -#ifdef CONFIG_HAVE_STATIC_CALL_INLINE - ANNOTATE_RETPOLINE_SAFE - "call *bp_handler_dest \n" - ANNOTATE_RETPOLINE_SAFE - "jmp *bp_handler_continue \n" -#else /* !CONFIG_HAVE_STATIC_CALL_INLINE */ - ANNOTATE_RETPOLINE_SAFE - "jmp *bp_handler_dest \n" -#endif - ".popsection \n"); +struct static_call_bp_data { + unsigned long func, ret; +}; + +static void static_call_bp_handler(struct pt_regs *regs, void *_data) +{ + struct static_call_bp_data *data = _data; + + /* + * For inline static calls, push the return address on the stack so the + * "called" function will return to the location immediately after the + * call site. + * + * NOTE: This code will need to be revisited when kernel CET gets + * implemented. + */ + if (data->ret) { + regs->sp -= sizeof(long); + *(unsigned long *)regs->sp = data->ret; + } + + /* The exception handler will 'return' to the destination function. */ + regs->ip = data->func; +} void arch_static_call_transform(void *site, void *tramp, void *func) { @@ -32,11 +38,17 @@ void arch_static_call_transform(void *site, void *tramp, void *func) unsigned long insn; unsigned char insn_opcode; unsigned char opcodes[CALL_INSN_SIZE]; + struct static_call_bp_data handler_data; + + handler_data.func = (unsigned long)func; - if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE)) + if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE)) { insn = (unsigned long)site; - else + handler_data.ret = insn + CALL_INSN_SIZE; + } else { insn = (unsigned long)tramp; + handler_data.ret = 0; + } mutex_lock(&text_mutex); @@ -52,14 +64,9 @@ void arch_static_call_transform(void *site, void *tramp, void *func) opcodes[0] = insn_opcode; memcpy(&opcodes[1], &dest_relative, CALL_INSN_SIZE - 1); - /* Set up the variables for the breakpoint handler: */ - bp_handler_dest = func; - if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE)) - bp_handler_continue = (void *)(insn + CALL_INSN_SIZE); - /* Patch the call site: */ text_poke_bp((void *)insn, opcodes, CALL_INSN_SIZE, - static_call_bp_handler); + static_call_bp_handler, &handler_data); done: mutex_unlock(&text_mutex);
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