> Can you turn these two arrays into a bitmap please?
Ok.
> This shouldn't be opencoded here. Instead make a utility function
> like vmalloc_range() that takes a start and end address and
> make the module allocation use it too.
>
> Also you should fix up asm-x86_64/page.h and Documentation/x86_64/mm.txt
> with the new fixed allocation.
[...]
> I think Andrea has just changed that and the patch went into
> mainline. Be careful with merging.
Since __get_vm_area has been changed to make it harder to avoid the guard
page, I decided just to punt and use module_alloc instead. This works
either with or without the -mm patches that clean it up to use __vmalloc_area.
There is enough address space in the module area that I'm not going to
worry about each page kprobes uses wasting a second page of address space.
Here is a new version of the patch that addresses your comments.
Thanks,
Roland
Signed-off-by: Roland McGrath <[EMAIL PROTECTED]>
--- linux-2.6/arch/x86_64/kernel/kprobes.c
+++ linux-2.6/arch/x86_64/kernel/kprobes.c
@@ -25,6 +25,8 @@
* interface to access function arguments.
* 2004-Oct Jim Keniston <[EMAIL PROTECTED]> and Prasanna S Panchamukhi
* <[EMAIL PROTECTED]> adapted for x86_64
+ * 2005-Mar Roland McGrath <[EMAIL PROTECTED]>
+ * Fixed to handle %rip-relative addressing mode correctly.
*/
#include <linux/config.h>
@@ -34,7 +36,7 @@
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/preempt.h>
-#include <linux/vmalloc.h>
+#include <linux/moduleloader.h>
#include <asm/pgtable.h>
#include <asm/kdebug.h>
@@ -86,9 +88,132 @@ int arch_prepare_kprobe(struct kprobe *p
return 0;
}
+/*
+ * Determine if the instruction uses the %rip-relative addressing mode.
+ * If it does, return the address of the 32-bit displacement word.
+ * If not, return null.
+ */
+static inline s32 *is_riprel(u8 *insn)
+{
+#define W(row,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf) \
+ (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
+ (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \
+ (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \
+ (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \
+ << (row % 64))
+ static const u64 onebyte_has_modrm[256 / 64] = {
+ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
+ /* ------------------------------- */
+ W(0x00, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 00 */
+ W(0x10, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 10 */
+ W(0x20, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 20 */
+ W(0x30, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0), /* 30 */
+ W(0x40, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 40 */
+ W(0x50, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 50 */
+ W(0x60, 0,0,1,1,0,0,0,0,0,1,0,1,0,0,0,0)| /* 60 */
+ W(0x70, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 70 */
+ W(0x80, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 80 */
+ W(0x90, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 90 */
+ W(0xa0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* a0 */
+ W(0xb0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* b0 */
+ W(0xc0, 1,1,0,0,1,1,1,1,0,0,0,0,0,0,0,0)| /* c0 */
+ W(0xd0, 1,1,1,1,0,0,0,0,1,1,1,1,1,1,1,1)| /* d0 */
+ W(0xe0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* e0 */
+ W(0xf0, 0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1) /* f0 */
+ /* ------------------------------- */
+ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
+ };
+ static const u64 twobyte_has_modrm[256 / 64] = {
+ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
+ /* ------------------------------- */
+ W(0x00, 1,1,1,1,0,0,0,0,0,0,0,0,0,1,0,1)| /* 0f */
+ W(0x10, 1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0)| /* 1f */
+ W(0x20, 1,1,1,1,1,0,1,0,1,1,1,1,1,1,1,1)| /* 2f */
+ W(0x30, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 3f */
+ W(0x40, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 4f */
+ W(0x50, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 5f */
+ W(0x60, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 6f */
+ W(0x70, 1,1,1,1,1,1,1,0,0,0,0,0,1,1,1,1), /* 7f */
+ W(0x80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 8f */
+ W(0x90, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 9f */
+ W(0xa0, 0,0,0,1,1,1,1,1,0,0,0,1,1,1,1,1)| /* af */
+ W(0xb0, 1,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1), /* bf */
+ W(0xc0, 1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0)| /* cf */
+ W(0xd0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* df */
+ W(0xe0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* ef */
+ W(0xf0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0) /* ff */
+ /* ------------------------------- */
+ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
+ };
+#undef W
+ int need_modrm;
+
+ /* Skip legacy instruction prefixes. */
+ while (1) {
+ switch (*insn) {
+ case 0x66:
+ case 0x67:
+ case 0x2e:
+ case 0x3e:
+ case 0x26:
+ case 0x64:
+ case 0x65:
+ case 0x36:
+ case 0xf0:
+ case 0xf3:
+ case 0xf2:
+ ++insn;
+ continue;
+ }
+ break;
+ }
+
+ /* Skip REX instruction prefix. */
+ if ((*insn & 0xf0) == 0x40)
+ ++insn;
+
+ if (*insn == 0x0f) { /* Two-byte opcode. */
+ ++insn;
+ need_modrm = test_bit(*insn, twobyte_has_modrm);
+ } else { /* One-byte opcode. */
+ need_modrm = test_bit(*insn, onebyte_has_modrm);
+ }
+
+ if (need_modrm) {
+ u8 modrm = *++insn;
+ if ((modrm & 0xc7) == 0x05) { /* %rip+disp32 addressing mode */
+ /* Displacement follows ModRM byte. */
+ return (s32 *) ++insn;
+ }
+ }
+
+ /* No %rip-relative addressing mode here. */
+ return NULL;
+}
+
void arch_copy_kprobe(struct kprobe *p)
{
+ s32 *ripdisp;
memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE);
+ ripdisp = is_riprel(p->ainsn.insn);
+ if (ripdisp) {
+ /*
+ * The copied instruction uses the %rip-relative
+ * addressing mode. Adjust the displacement for the
+ * difference between the original location of this
+ * instruction and the location of the copy that will
+ * actually be run. The tricky bit here is making sure
+ * that the sign extension happens correctly in this
+ * calculation, since we need a signed 32-bit result to
+ * be sign-extended to 64 bits when it's added to the
+ * %rip value and yield the same 64-bit result that the
+ * sign-extension of the original signed 32-bit
+ * displacement would have given.
+ */
+ s64 disp = (u8 *) p->addr + *ripdisp - (u8 *) p->ainsn.insn;
+ BUG_ON((s64) (s32) disp != disp); /* Sanity check. */
+ *ripdisp = disp;
+ }
}
void arch_remove_kprobe(struct kprobe *p)
@@ -439,8 +564,15 @@ static kprobe_opcode_t *get_insn_slot(vo
if (!kip) {
return NULL;
}
- kip->insns = (kprobe_opcode_t*) __vmalloc(PAGE_SIZE,
- GFP_KERNEL|__GFP_HIGHMEM, __pgprot(__PAGE_KERNEL_EXEC));
+
+ /*
+ * For the %rip-relative displacement fixups to be doable, we
+ * need our instruction copy to be within +/- 2GB of any data it
+ * might access via %rip. That is, within 2GB of where the
+ * kernel image and loaded module images reside. So we allocate
+ * a page in the module loading area.
+ */
+ kip->insns = module_alloc(PAGE_SIZE);
if (!kip->insns) {
kfree(kip);
return NULL;
@@ -481,7 +614,7 @@ static void free_insn_slot(kprobe_opcode
hlist_add_head(&kip->hlist,
&kprobe_insn_pages);
} else {
- vfree(kip->insns);
+ module_free(NULL, kip->insns);
kfree(kip);
}
}
-
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