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Subject[tip: core/kprobes] x86/alternative: Remove text_poke_loc::len
The following commit has been merged into the core/kprobes branch of tip:

Commit-ID: 97e6c977ccf128c3f34d6084ad53fc0021f90e03
Gitweb: https://git.kernel.org/tip/97e6c977ccf128c3f34d6084ad53fc0021f90e03
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Wed, 09 Oct 2019 12:44:20 +02:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 27 Nov 2019 07:44:24 +01:00

x86/alternative: Remove text_poke_loc::len

Per the BUG_ON(len != insn.length) in text_poke_loc_init(), tp->len
must indeed be the same as text_opcode_size(tp->opcode). Use this to
remove this field from the structure.

Sadly, due to 8 byte alignment, this only increases the structure
padding.

Tested-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191111132457.989922744@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/alternative.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index cfcfadf..6e3ee73 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -938,7 +938,6 @@ static void do_sync_core(void *info)

struct text_poke_loc {
void *addr;
- int len;
s32 rel32;
u8 opcode;
const u8 text[POKE_MAX_OPCODE_SIZE];
@@ -965,6 +964,7 @@ int notrace poke_int3_handler(struct pt_regs *regs)
{
struct text_poke_loc *tp;
void *ip;
+ int len;

/*
* Having observed our INT3 instruction, we now must observe
@@ -1004,7 +1004,8 @@ int notrace poke_int3_handler(struct pt_regs *regs)
return 0;
}

- ip += tp->len;
+ len = text_opcode_size(tp->opcode);
+ ip += len;

switch (tp->opcode) {
case INT3_INSN_OPCODE:
@@ -1085,10 +1086,12 @@ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries
* Second step: update all but the first byte of the patched range.
*/
for (do_sync = 0, i = 0; i < nr_entries; i++) {
- if (tp[i].len - sizeof(int3) > 0) {
+ int len = text_opcode_size(tp[i].opcode);
+
+ if (len - sizeof(int3) > 0) {
text_poke((char *)tp[i].addr + sizeof(int3),
(const char *)tp[i].text + sizeof(int3),
- tp[i].len - sizeof(int3));
+ len - sizeof(int3));
do_sync++;
}
}
@@ -1141,7 +1144,6 @@ void text_poke_loc_init(struct text_poke_loc *tp, void *addr,
BUG_ON(len != insn.length);

tp->addr = addr;
- tp->len = len;
tp->opcode = insn.opcode.bytes[0];

switch (tp->opcode) {
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