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Subject[RFC PATCH 1/6] uprobes/x86: Emulate unconditional rip-relative jmp's
0xeb and 0xe9. Anything else?

TODO: move ->fixup into the union along with rip_rela_target_address.

Reported-by: Jonathan Lebon <jlebon@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
arch/x86/include/asm/uprobes.h | 8 +++++++-
arch/x86/kernel/uprobes.c | 40 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 47 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
index 9f8210b..cca62c5 100644
--- a/arch/x86/include/asm/uprobes.h
+++ b/arch/x86/include/asm/uprobes.h
@@ -44,9 +44,15 @@ struct arch_uprobe {
u16 fixups;
const struct uprobe_xol_ops *ops;

+ union {
#ifdef CONFIG_X86_64
- unsigned long rip_rela_target_address;
+ unsigned long rip_rela_target_address;
#endif
+ struct {
+ s32 disp;
+ u8 ilen;
+ } ttt;
+ };
};

struct arch_uprobe_task {
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 1ea7e1a..32ab147 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -466,6 +466,42 @@ static struct uprobe_xol_ops default_xol_ops = {
.post_xol = default_post_xol_op,
};

+static bool ttt_emulate_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ regs->ip += auprobe->ttt.ilen + auprobe->ttt.disp;
+ return true;
+}
+
+static struct uprobe_xol_ops ttt_xol_ops = {
+ .emulate = ttt_emulate_op,
+};
+
+static int ttt_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
+{
+
+ switch (OPCODE1(insn)) {
+ case 0xeb: /* jmp 8 */
+ case 0xe9: /* jmp 32 */
+ break;
+ default:
+ return -ENOSYS;
+ }
+
+ /* has the side-effect of processing the entire instruction */
+ insn_get_length(insn);
+ if (WARN_ON_ONCE(!insn_complete(insn)))
+ return -ENOEXEC;
+
+ auprobe->ttt.ilen = insn->length;
+ auprobe->ttt.disp = insn->moffset1.value;
+ /* so far we assume that it fits into ->moffset1 */
+ if (WARN_ON_ONCE(insn->moffset2.nbytes))
+ return -ENOEXEC;
+
+ auprobe->ops = &ttt_xol_ops;
+ return 0;
+}
+
/**
* arch_uprobe_analyze_insn - instruction analysis including validity and fixups.
* @mm: the probed address space.
@@ -483,6 +519,10 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
if (ret)
return ret;

+ ret = ttt_setup_xol_ops(auprobe, &insn);
+ if (ret == 0 || ret != ENOSYS)
+ return ret;
+
/*
* Figure out which fixups arch_uprobe_post_xol() will need to perform,
* and annotate arch_uprobe->fixups accordingly. To start with, ->fixups
--
1.5.5.1


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