From ab144f5ec64c42218a555ec1dbde6b60cf2982d6 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Fri, 10 Aug 2007 22:31:03 +0200 Subject: [PATCH] i386: Make patching more robust, fix paravirt issue Commit 19d36ccdc34f5ed444f8a6af0cbfdb6790eb1177 "x86: Fix alternatives and kprobes to remap write-protected kernel text" uses code which is being patched for patching. In particular, paravirt_ops does patching in two stages: first it calls paravirt_ops.patch, then it fills any remaining instructions with nop_out(). nop_out calls text_poke() which calls lookup_address() which calls pgd_val() (aka paravirt_ops.pgd_val): that call site is one of the places we patch. If we always do patching as one single call to text_poke(), we only need make sure we're not patching the memcpy in text_poke itself. This means the prototype to paravirt_ops.patch needs to change, to marshal the new code into a buffer rather than patching in place as it does now. It also means all patching goes through text_poke(), which is known to be safe (apply_alternatives is also changed to make a single patch). AK: fix compilation on x86-64 (bad rusty!) AK: fix boot on x86-64 (sigh) AK: merged with other patches Signed-off-by: Rusty Russell Signed-off-by: Andi Kleen Signed-off-by: Linus Torvalds --- arch/i386/kernel/alternative.c | 33 +++++++++++++-------- arch/i386/kernel/paravirt.c | 52 +++++++++++++++++----------------- arch/i386/kernel/vmi.c | 35 ++++++++++++++--------- arch/i386/xen/enlighten.c | 12 ++++---- drivers/lguest/lguest.c | 9 +++--- include/asm-i386/paravirt.h | 16 +++++++---- 6 files changed, 90 insertions(+), 67 deletions(-) diff --git a/arch/i386/kernel/alternative.c b/arch/i386/kernel/alternative.c index c85598acb8f..27a6b0c9a7c 100644 --- a/arch/i386/kernel/alternative.c +++ b/arch/i386/kernel/alternative.c @@ -11,6 +11,8 @@ #include #include +#define MAX_PATCH_LEN (255-1) + #ifdef CONFIG_HOTPLUG_CPU static int smp_alt_once; @@ -148,7 +150,8 @@ static unsigned char** find_nop_table(void) #endif /* CONFIG_X86_64 */ -static void nop_out(void *insns, unsigned int len) +/* Use this to add nops to a buffer, then text_poke the whole buffer. */ +static void add_nops(void *insns, unsigned int len) { unsigned char **noptable = find_nop_table(); @@ -156,7 +159,7 @@ static void nop_out(void *insns, unsigned int len) unsigned int noplen = len; if (noplen > ASM_NOP_MAX) noplen = ASM_NOP_MAX; - text_poke(insns, noptable[noplen], noplen); + memcpy(insns, noptable[noplen], noplen); insns += noplen; len -= noplen; } @@ -174,15 +177,15 @@ extern u8 *__smp_locks[], *__smp_locks_end[]; void apply_alternatives(struct alt_instr *start, struct alt_instr *end) { struct alt_instr *a; - u8 *instr; - int diff; + char insnbuf[MAX_PATCH_LEN]; DPRINTK("%s: alt table %p -> %p\n", __FUNCTION__, start, end); for (a = start; a < end; a++) { + u8 *instr = a->instr; BUG_ON(a->replacementlen > a->instrlen); + BUG_ON(a->instrlen > sizeof(insnbuf)); if (!boot_cpu_has(a->cpuid)) continue; - instr = a->instr; #ifdef CONFIG_X86_64 /* vsyscall code is not mapped yet. resolve it manually. */ if (instr >= (u8 *)VSYSCALL_START && instr < (u8*)VSYSCALL_END) { @@ -191,9 +194,10 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end) __FUNCTION__, a->instr, instr); } #endif - memcpy(instr, a->replacement, a->replacementlen); - diff = a->instrlen - a->replacementlen; - nop_out(instr + a->replacementlen, diff); + memcpy(insnbuf, a->replacement, a->replacementlen); + add_nops(insnbuf + a->replacementlen, + a->instrlen - a->replacementlen); + text_poke(instr, insnbuf, a->instrlen); } } @@ -215,16 +219,18 @@ static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end) static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end) { u8 **ptr; + char insn[1]; if (noreplace_smp) return; + add_nops(insn, 1); for (ptr = start; ptr < end; ptr++) { if (*ptr < text) continue; if (*ptr > text_end) continue; - nop_out(*ptr, 1); + text_poke(*ptr, insn, 1); }; } @@ -351,6 +357,7 @@ void apply_paravirt(struct paravirt_patch_site *start, struct paravirt_patch_site *end) { struct paravirt_patch_site *p; + char insnbuf[MAX_PATCH_LEN]; if (noreplace_paravirt) return; @@ -358,13 +365,15 @@ void apply_paravirt(struct paravirt_patch_site *start, for (p = start; p < end; p++) { unsigned int used; - used = paravirt_ops.patch(p->instrtype, p->clobbers, p->instr, - p->len); + BUG_ON(p->len > MAX_PATCH_LEN); + used = paravirt_ops.patch(p->instrtype, p->clobbers, insnbuf, + (unsigned long)p->instr, p->len); BUG_ON(used > p->len); /* Pad the rest with nops */ - nop_out(p->instr + used, p->len - used); + add_nops(insnbuf + used, p->len - used); + text_poke(p->instr, insnbuf, p->len); } } extern struct paravirt_patch_site __start_parainstructions[], diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c index ea962c0667d..739cfb207dd 100644 --- a/arch/i386/kernel/paravirt.c +++ b/arch/i386/kernel/paravirt.c @@ -69,7 +69,8 @@ DEF_NATIVE(read_tsc, "rdtsc"); DEF_NATIVE(ud2a, "ud2a"); -static unsigned native_patch(u8 type, u16 clobbers, void *insns, unsigned len) +static unsigned native_patch(u8 type, u16 clobbers, void *ibuf, + unsigned long addr, unsigned len) { const unsigned char *start, *end; unsigned ret; @@ -90,7 +91,7 @@ static unsigned native_patch(u8 type, u16 clobbers, void *insns, unsigned len) #undef SITE patch_site: - ret = paravirt_patch_insns(insns, len, start, end); + ret = paravirt_patch_insns(ibuf, len, start, end); break; case PARAVIRT_PATCH(make_pgd): @@ -107,7 +108,7 @@ static unsigned native_patch(u8 type, u16 clobbers, void *insns, unsigned len) break; default: - ret = paravirt_patch_default(type, clobbers, insns, len); + ret = paravirt_patch_default(type, clobbers, ibuf, addr, len); break; } @@ -129,68 +130,67 @@ struct branch { u32 delta; } __attribute__((packed)); -unsigned paravirt_patch_call(void *target, u16 tgt_clobbers, - void *site, u16 site_clobbers, +unsigned paravirt_patch_call(void *insnbuf, + const void *target, u16 tgt_clobbers, + unsigned long addr, u16 site_clobbers, unsigned len) { - unsigned char *call = site; - unsigned long delta = (unsigned long)target - (unsigned long)(call+5); - struct branch b; + struct branch *b = insnbuf; + unsigned long delta = (unsigned long)target - (addr+5); if (tgt_clobbers & ~site_clobbers) return len; /* target would clobber too much for this site */ if (len < 5) return len; /* call too long for patch site */ - b.opcode = 0xe8; /* call */ - b.delta = delta; - BUILD_BUG_ON(sizeof(b) != 5); - text_poke(call, (unsigned char *)&b, 5); + b->opcode = 0xe8; /* call */ + b->delta = delta; + BUILD_BUG_ON(sizeof(*b) != 5); return 5; } -unsigned paravirt_patch_jmp(void *target, void *site, unsigned len) +unsigned paravirt_patch_jmp(const void *target, void *insnbuf, + unsigned long addr, unsigned len) { - unsigned char *jmp = site; - unsigned long delta = (unsigned long)target - (unsigned long)(jmp+5); - struct branch b; + struct branch *b = insnbuf; + unsigned long delta = (unsigned long)target - (addr+5); if (len < 5) return len; /* call too long for patch site */ - b.opcode = 0xe9; /* jmp */ - b.delta = delta; - text_poke(jmp, (unsigned char *)&b, 5); + b->opcode = 0xe9; /* jmp */ + b->delta = delta; return 5; } -unsigned paravirt_patch_default(u8 type, u16 clobbers, void *site, unsigned len) +unsigned paravirt_patch_default(u8 type, u16 clobbers, void *insnbuf, + unsigned long addr, unsigned len) { void *opfunc = *((void **)¶virt_ops + type); unsigned ret; if (opfunc == NULL) /* If there's no function, patch it with a ud2a (BUG) */ - ret = paravirt_patch_insns(site, len, start_ud2a, end_ud2a); + ret = paravirt_patch_insns(insnbuf, len, start_ud2a, end_ud2a); else if (opfunc == paravirt_nop) /* If the operation is a nop, then nop the callsite */ ret = paravirt_patch_nop(); else if (type == PARAVIRT_PATCH(iret) || type == PARAVIRT_PATCH(irq_enable_sysexit)) /* If operation requires a jmp, then jmp */ - ret = paravirt_patch_jmp(opfunc, site, len); + ret = paravirt_patch_jmp(opfunc, insnbuf, addr, len); else /* Otherwise call the function; assume target could clobber any caller-save reg */ - ret = paravirt_patch_call(opfunc, CLBR_ANY, - site, clobbers, len); + ret = paravirt_patch_call(insnbuf, opfunc, CLBR_ANY, + addr, clobbers, len); return ret; } -unsigned paravirt_patch_insns(void *site, unsigned len, +unsigned paravirt_patch_insns(void *insnbuf, unsigned len, const char *start, const char *end) { unsigned insn_len = end - start; @@ -198,7 +198,7 @@ unsigned paravirt_patch_insns(void *site, unsigned len, if (insn_len > len || start == NULL) insn_len = len; else - memcpy(site, start, insn_len); + memcpy(insnbuf, start, insn_len); return insn_len; } diff --git a/arch/i386/kernel/vmi.c b/arch/i386/kernel/vmi.c index 72042bb7ec9..18673e0f193 100644 --- a/arch/i386/kernel/vmi.c +++ b/arch/i386/kernel/vmi.c @@ -87,12 +87,14 @@ struct vmi_timer_ops vmi_timer_ops; #define IRQ_PATCH_INT_MASK 0 #define IRQ_PATCH_DISABLE 5 -static inline void patch_offset(unsigned char *eip, unsigned char *dest) +static inline void patch_offset(void *insnbuf, + unsigned long eip, unsigned long dest) { - *(unsigned long *)(eip+1) = dest-eip-5; + *(unsigned long *)(insnbuf+1) = dest-eip-5; } -static unsigned patch_internal(int call, unsigned len, void *insns) +static unsigned patch_internal(int call, unsigned len, void *insnbuf, + unsigned long eip) { u64 reloc; struct vmi_relocation_info *const rel = (struct vmi_relocation_info *)&reloc; @@ -100,14 +102,14 @@ static unsigned patch_internal(int call, unsigned len, void *insns) switch(rel->type) { case VMI_RELOCATION_CALL_REL: BUG_ON(len < 5); - *(char *)insns = MNEM_CALL; - patch_offset(insns, rel->eip); + *(char *)insnbuf = MNEM_CALL; + patch_offset(insnbuf, eip, (unsigned long)rel->eip); return 5; case VMI_RELOCATION_JUMP_REL: BUG_ON(len < 5); - *(char *)insns = MNEM_JMP; - patch_offset(insns, rel->eip); + *(char *)insnbuf = MNEM_JMP; + patch_offset(insnbuf, eip, (unsigned long)rel->eip); return 5; case VMI_RELOCATION_NOP: @@ -128,21 +130,26 @@ static unsigned patch_internal(int call, unsigned len, void *insns) * Apply patch if appropriate, return length of new instruction * sequence. The callee does nop padding for us. */ -static unsigned vmi_patch(u8 type, u16 clobbers, void *insns, unsigned len) +static unsigned vmi_patch(u8 type, u16 clobbers, void *insns, + unsigned long eip, unsigned len) { switch (type) { case PARAVIRT_PATCH(irq_disable): - return patch_internal(VMI_CALL_DisableInterrupts, len, insns); + return patch_internal(VMI_CALL_DisableInterrupts, len, + insns, eip); case PARAVIRT_PATCH(irq_enable): - return patch_internal(VMI_CALL_EnableInterrupts, len, insns); + return patch_internal(VMI_CALL_EnableInterrupts, len, + insns, eip); case PARAVIRT_PATCH(restore_fl): - return patch_internal(VMI_CALL_SetInterruptMask, len, insns); + return patch_internal(VMI_CALL_SetInterruptMask, len, + insns, eip); case PARAVIRT_PATCH(save_fl): - return patch_internal(VMI_CALL_GetInterruptMask, len, insns); + return patch_internal(VMI_CALL_GetInterruptMask, len, + insns, eip); case PARAVIRT_PATCH(iret): - return patch_internal(VMI_CALL_IRET, len, insns); + return patch_internal(VMI_CALL_IRET, len, insns, eip); case PARAVIRT_PATCH(irq_enable_sysexit): - return patch_internal(VMI_CALL_SYSEXIT, len, insns); + return patch_internal(VMI_CALL_SYSEXIT, len, insns, eip); default: break; } diff --git a/arch/i386/xen/enlighten.c b/arch/i386/xen/enlighten.c index 9a8c1181c00..f0c37511d8d 100644 --- a/arch/i386/xen/enlighten.c +++ b/arch/i386/xen/enlighten.c @@ -842,7 +842,8 @@ void __init xen_setup_vcpu_info_placement(void) } } -static unsigned xen_patch(u8 type, u16 clobbers, void *insns, unsigned len) +static unsigned xen_patch(u8 type, u16 clobbers, void *insnbuf, + unsigned long addr, unsigned len) { char *start, *end, *reloc; unsigned ret; @@ -869,7 +870,7 @@ static unsigned xen_patch(u8 type, u16 clobbers, void *insns, unsigned len) if (start == NULL || (end-start) > len) goto default_patch; - ret = paravirt_patch_insns(insns, len, start, end); + ret = paravirt_patch_insns(insnbuf, len, start, end); /* Note: because reloc is assigned from something that appears to be an array, gcc assumes it's non-null, @@ -877,8 +878,8 @@ static unsigned xen_patch(u8 type, u16 clobbers, void *insns, unsigned len) end. */ if (reloc > start && reloc < end) { int reloc_off = reloc - start; - long *relocp = (long *)(insns + reloc_off); - long delta = start - (char *)insns; + long *relocp = (long *)(insnbuf + reloc_off); + long delta = start - (char *)addr; *relocp += delta; } @@ -886,7 +887,8 @@ static unsigned xen_patch(u8 type, u16 clobbers, void *insns, unsigned len) default_patch: default: - ret = paravirt_patch_default(type, clobbers, insns, len); + ret = paravirt_patch_default(type, clobbers, insnbuf, + addr, len); break; } diff --git a/drivers/lguest/lguest.c b/drivers/lguest/lguest.c index 524beea7fb1..6e135ac0834 100644 --- a/drivers/lguest/lguest.c +++ b/drivers/lguest/lguest.c @@ -936,23 +936,24 @@ static const struct lguest_insns /* Now our patch routine is fairly simple (based on the native one in * paravirt.c). If we have a replacement, we copy it in and return how much of * the available space we used. */ -static unsigned lguest_patch(u8 type, u16 clobber, void *insns, unsigned len) +static unsigned lguest_patch(u8 type, u16 clobber, void *ibuf, + unsigned long addr, unsigned len) { unsigned int insn_len; /* Don't do anything special if we don't have a replacement */ if (type >= ARRAY_SIZE(lguest_insns) || !lguest_insns[type].start) - return paravirt_patch_default(type, clobber, insns, len); + return paravirt_patch_default(type, clobber, ibuf, addr, len); insn_len = lguest_insns[type].end - lguest_insns[type].start; /* Similarly if we can't fit replacement (shouldn't happen, but let's * be thorough). */ if (len < insn_len) - return paravirt_patch_default(type, clobber, insns, len); + return paravirt_patch_default(type, clobber, ibuf, addr, len); /* Copy in our instructions. */ - memcpy(insns, lguest_insns[type].start, insn_len); + memcpy(ibuf, lguest_insns[type].start, insn_len); return insn_len; } diff --git a/include/asm-i386/paravirt.h b/include/asm-i386/paravirt.h index 7df88be2dd9..9fa3fa9e62d 100644 --- a/include/asm-i386/paravirt.h +++ b/include/asm-i386/paravirt.h @@ -47,7 +47,8 @@ struct paravirt_ops * The patch function should return the number of bytes of code * generated, as we nop pad the rest in generic code. */ - unsigned (*patch)(u8 type, u16 clobber, void *firstinsn, unsigned len); + unsigned (*patch)(u8 type, u16 clobber, void *insnbuf, + unsigned long addr, unsigned len); /* Basic arch-specific setup */ void (*arch_setup)(void); @@ -253,13 +254,16 @@ extern struct paravirt_ops paravirt_ops; unsigned paravirt_patch_nop(void); unsigned paravirt_patch_ignore(unsigned len); -unsigned paravirt_patch_call(void *target, u16 tgt_clobbers, - void *site, u16 site_clobbers, +unsigned paravirt_patch_call(void *insnbuf, + const void *target, u16 tgt_clobbers, + unsigned long addr, u16 site_clobbers, unsigned len); -unsigned paravirt_patch_jmp(void *target, void *site, unsigned len); -unsigned paravirt_patch_default(u8 type, u16 clobbers, void *site, unsigned len); +unsigned paravirt_patch_jmp(const void *target, void *insnbuf, + unsigned long addr, unsigned len); +unsigned paravirt_patch_default(u8 type, u16 clobbers, void *insnbuf, + unsigned long addr, unsigned len); -unsigned paravirt_patch_insns(void *site, unsigned len, +unsigned paravirt_patch_insns(void *insnbuf, unsigned len, const char *start, const char *end); int paravirt_disable_iospace(void); -- 2.41.1