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 <rusty@rustcorp.com.au>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/i386/kernel/alternative.c b/arch/i386/kernel/alternative.c
index c85598a..27a6b0c 100644
--- a/arch/i386/kernel/alternative.c
+++ b/arch/i386/kernel/alternative.c
@@ -11,6 +11,8 @@
#include <asm/mce.h>
#include <asm/nmi.h>
+#define MAX_PATCH_LEN (255-1)
+
#ifdef CONFIG_HOTPLUG_CPU
static int smp_alt_once;
@@ -148,7 +150,8 @@
#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 @@
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 @@
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 @@
__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_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 @@
struct paravirt_patch_site *end)
{
struct paravirt_patch_site *p;
+ char insnbuf[MAX_PATCH_LEN];
if (noreplace_paravirt)
return;
@@ -358,13 +365,15 @@
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 ea962c0..739cfb2 100644
--- a/arch/i386/kernel/paravirt.c
+++ b/arch/i386/kernel/paravirt.c
@@ -69,7 +69,8 @@
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 @@
#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 @@
break;
default:
- ret = paravirt_patch_default(type, clobbers, insns, len);
+ ret = paravirt_patch_default(type, clobbers, ibuf, addr, len);
break;
}
@@ -129,68 +130,67 @@
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 @@
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 72042bb..18673e0 100644
--- a/arch/i386/kernel/vmi.c
+++ b/arch/i386/kernel/vmi.c
@@ -87,12 +87,14 @@
#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 @@
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 @@
* 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;
}