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uprobes/x86: Simplify riprel_{pre,post}_xol() and make them similar

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Ignoring the "correction" logic riprel_pre_xol() and riprel_post_xol()
are very similar but look quite differently.

1. Add the "UPROBE_FIX_RIP_AX | UPROBE_FIX_RIP_CX" check at the start
   of riprel_pre_xol(), like the same check in riprel_post_xol().

2. Add the trivial scratch_reg() helper which returns the address of
   scratch register pre_xol/post_xol need to change.

3. Change these functions to use the new helper and avoid copy-and-paste
   under if/else branches.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
This commit is contained in:
Oleg Nesterov 2014-04-27 18:13:31 +02:00
parent 7f55e82bac
commit c90a695012
1 changed files with 14 additions and 16 deletions
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30
arch/x86/kernel/uprobes.c
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@ -326,22 +326,24 @@ static void riprel_analyze(struct arch_uprobe *auprobe, struct insn *insn)
}
}
static inline unsigned long *
scratch_reg(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
return (auprobe->def.fixups & UPROBE_FIX_RIP_AX) ? &regs->ax : &regs->cx;
}
/*
* If we're emulating a rip-relative instruction, save the contents
* of the scratch register and store the target address in that register.
*/
static void riprel_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
struct uprobe_task *utask = current->utask;
if (auprobe->def.fixups & (UPROBE_FIX_RIP_AX | UPROBE_FIX_RIP_CX)) {
struct uprobe_task *utask = current->utask;
unsigned long *sr = scratch_reg(auprobe, regs);
if (auprobe->def.fixups & UPROBE_FIX_RIP_AX) {
utask->autask.saved_scratch_register = regs->ax;
regs->ax = utask->vaddr;
regs->ax += auprobe->def.riprel_target;
} else if (auprobe->def.fixups & UPROBE_FIX_RIP_CX) {
utask->autask.saved_scratch_register = regs->cx;
regs->cx = utask->vaddr;
regs->cx += auprobe->def.riprel_target;
utask->autask.saved_scratch_register = *sr;
*sr = utask->vaddr + auprobe->def.riprel_target;
}
}
@ -349,14 +351,10 @@ static void riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs,
long *correction)
{
if (auprobe->def.fixups & (UPROBE_FIX_RIP_AX | UPROBE_FIX_RIP_CX)) {
struct arch_uprobe_task *autask;
autask = &current->utask->autask;
if (auprobe->def.fixups & UPROBE_FIX_RIP_AX)
regs->ax = autask->saved_scratch_register;
else
regs->cx = autask->saved_scratch_register;
struct uprobe_task *utask = current->utask;
unsigned long *sr = scratch_reg(auprobe, regs);
*sr = utask->autask.saved_scratch_register;
/*
* The original instruction includes a displacement, and so
* is 4 bytes longer than what we've just single-stepped.