[PATCH v3 07/39] x86/ibt,paravirt: Use text_gen_insn() for paravirt_patch()

Peter Zijlstra
2022-03-03T11:34:15Z

Less duplication is more better.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/include/asm/text-patching.h | 20 ++++++++++++++------
arch/x86/kernel/paravirt.c | 23 +++--------------------
2 files changed, 17 insertions(+), 26 deletions(-)

--- a/arch/x86/include/asm/text-patching.h
+++ b/arch/x86/include/asm/text-patching.h
@@ -96,32 +96,40 @@ union text_poke_insn {
};

static __always_inline
-void *text_gen_insn(u8 opcode, const void *addr, const void *dest)
+void __text_gen_insn(void *buf, u8 opcode, const void *addr, const void *dest, int size)
{
- static union text_poke_insn insn; /* per instance */
- int size = text_opcode_size(opcode);
+ union text_poke_insn *insn = buf;
+
+ BUG_ON(size < text_opcode_size(opcode));

/*
* Hide the addresses to avoid the compiler folding in constants when
* referencing code, these can mess up annotations like
* ANNOTATE_NOENDBR.
*/
+ OPTIMIZER_HIDE_VAR(insn);
OPTIMIZER_HIDE_VAR(addr);
OPTIMIZER_HIDE_VAR(dest);

- insn.opcode = opcode;
+ insn->opcode = opcode;

if (size > 1) {
- insn.disp = (long)dest - (long)(addr + size);
+ insn->disp = (long)dest - (long)(addr + size);
if (size == 2) {
/*
* Ensure that for JMP8 the displacement
* actually fits the signed byte.
*/
- BUG_ON((insn.disp >> 31) != (insn.disp >> 7));
+ BUG_ON((insn->disp >> 31) != (insn->disp >> 7));
}
}
+}

+static __always_inline
+void *text_gen_insn(u8 opcode, const void *addr, const void *dest)
+{
+ static union text_poke_insn insn; /* per instance */
+ __text_gen_insn(&insn, opcode, addr, dest, text_opcode_size(opcode));
return &insn.text;
}

--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -69,29 +69,12 @@ noinstr void paravirt_BUG(void)
BUG();
}

-struct branch {
- unsigned char opcode;
- u32 delta;
-} __attribute__((packed));
-
static unsigned paravirt_patch_call(void *insn_buff, const void *target,
unsigned long addr, unsigned len)
{
- const int call_len = 5;
- struct branch *b = insn_buff;
- unsigned long delta = (unsigned long)target - (addr+call_len);
-
- if (len < call_len) {
- pr_warn("paravirt: Failed to patch indirect CALL at %ps\n", (void *)addr);
- /* Kernel might not be viable if patching fails, bail out: */
- BUG_ON(1);
- }
-
- b->opcode = 0xe8; /* call */
- b->delta = delta;
- BUILD_BUG_ON(sizeof(*b) != call_len);
-
- return call_len;
+ __text_gen_insn(insn_buff, CALL_INSN_OPCODE,
+ (void *)addr, target, CALL_INSN_SIZE);
+ return CALL_INSN_SIZE;
}

#ifdef CONFIG_PARAVIRT_XXL