github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-09-22 04:34:03 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

selftests/bpf: Check per-CPU address resolution per register

Browse Source 
An ld_imm64 of a per-CPU map value is followed by a mov_percpu_addr that
reuses the same register, so which register the address lands in decides
how the JIT encodes the add. Getting the REX prefix wrong there is
invisible to a functional test unless the address happens to land in an
extended register, which is why this went unnoticed.

Load a .percpu variable into every register in one program and match the
JITed add against the register each one must resolve into.

Signed-off-by: Vineet Gupta <vineet.gupta@linux.dev>
Link: https://patch.msgid.link/20260814220254.3797467-3-vineet.gupta@linux.dev
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
This commit is contained in:
Vineet Gupta 2026-08-14 15:02:54 -07:00 committed by Eduard Zingerman
parent 5bbbce02e5
commit f61306e8c9
2 changed files with 74 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
tools/testing/selftests/bpf/prog_tests/verifier.c
View File

@ -79,6 +79,7 @@
#include "verifier_netfilter_retcode.skel.h"
#include "verifier_bpf_fastcall.skel.h"
#include "verifier_or_jmp32_k.skel.h"
#include "verifier_percpu_addr.skel.h"
#include "verifier_precision.skel.h"
#include "verifier_prevent_map_lookup.skel.h"
#include "verifier_private_stack.skel.h"
@ -240,6 +241,7 @@ void test_verifier_netfilter_ctx(void) { RUN(verifier_netfilter_ctx); }
void test_verifier_netfilter_retcode(void) { RUN(verifier_netfilter_retcode); }
void test_verifier_bpf_fastcall(void) { RUN(verifier_bpf_fastcall); }
void test_verifier_or_jmp32_k(void) { RUN(verifier_or_jmp32_k); }
void test_verifier_percpu_addr(void) { RUN(verifier_percpu_addr); }
void test_verifier_precision(void) { RUN(verifier_precision); }
void test_verifier_prevent_map_lookup(void) { RUN(verifier_prevent_map_lookup); }
void test_verifier_private_stack(void) { RUN(verifier_private_stack); }

72
tools/testing/selftests/bpf/progs/verifier_percpu_addr.c Normal file
View File

@ -0,0 +1,72 @@
// SPDX-License-Identifier: GPL-2.0
#include <vmlinux.h>
#include <bpf/bpf_helpers.h>
#include "bpf_misc.h"
#if defined(__TARGET_ARCH_x86)
int percpu_data SEC(".percpu");
/*
* An ld_imm64 of a per-CPU map value is followed by a mov_percpu_addr that
* reuses the same register, so check that the add resolves into the register
* the address was loaded into, for every register.
*/
SEC("raw_tp")
__description("per-CPU address resolution")
__success
__arch_x86_64
__jited(" movabsq $0x{{.*}}, %rax")
__jited(" addq %gs:{{.*}}, %rax")
__jited(" movabsq $0x{{.*}}, %rdi")
__jited(" addq %gs:{{.*}}, %rdi")
__jited(" movabsq $0x{{.*}}, %rsi")
__jited(" addq %gs:{{.*}}, %rsi")
__jited(" movabsq $0x{{.*}}, %rdx")
__jited(" addq %gs:{{.*}}, %rdx")
__jited(" movabsq $0x{{.*}}, %rcx")
__jited(" addq %gs:{{.*}}, %rcx")
__jited(" movabsq $0x{{.*}}, %r8")
__jited(" addq %gs:{{.*}}, %r8")
__jited(" movabsq $0x{{.*}}, %rbx")
__jited(" addq %gs:{{.*}}, %rbx")
__jited(" movabsq $0x{{.*}}, %r13")
__jited(" addq %gs:{{.*}}, %r13")
__jited(" movabsq $0x{{.*}}, %r14")
__jited(" addq %gs:{{.*}}, %r14")
__jited(" movabsq $0x{{.*}}, %r15")
__jited(" addq %gs:{{.*}}, %r15")
__naked void percpu_addr(void)
{
asm volatile (" \
r0 = %[percpu_data] ll; \
r1 = %[percpu_data] ll; \
r2 = %[percpu_data] ll; \
r3 = %[percpu_data] ll; \
r4 = %[percpu_data] ll; \
r5 = %[percpu_data] ll; \
r6 = %[percpu_data] ll; \
r7 = %[percpu_data] ll; \
r8 = %[percpu_data] ll; \
r9 = %[percpu_data] ll; \
r0 = 0; \
exit; \
" :
: __imm_addr(percpu_data)
: __clobber_all);
}
#else
SEC("raw_tp")
__description("percpu addr dummy")
__success
int dummy_test(void)
{
return 0;
}
#endif
char _license[] SEC("license") = "GPL";