WIP: bpf, arm: Fix up bpf_user_pt_regs_t

This type by default uses struct pt_regs and embeds 'unsigned long' elems
which don't play nicely between 32-bit kernel and 64-bit BPF space. Try
creating a custom version for arm32.

Also hoping to fix following test error:

tester_init:PASS:tester_log_buf 0 nsec
process_subtest:PASS:obj_open_mem 0 nsec
process_subtest:PASS:specs_alloc 0 nsec
run_subtest:PASS:obj_open_mem 0 nsec
libbpf: prog 'kprobe_resolved_ctx': BPF program load failed: -EINVAL
libbpf: prog 'kprobe_resolved_ctx': failed to load: -EINVAL
libbpf: failed to load object 'test_global_func_ctx_args'
run_subtest:FAIL:unexpected_load_failure unexpected error: -22 (errno 22)
VERIFIER LOG:
=============
arg#0 reference type('UNKNOWN ') size cannot be determined: -22
0: R1=ctx() R10=fp0
; return kprobe_struct_ctx_subprog(ctx); @ test_global_func_ctx_args.c:57
0: (85) call pc+1
invalid bpf_context access off=71 size=1 is_valid_access=kprobe_prog_is_valid_access
Caller passes invalid args into func#1 ('kprobe_struct_ctx_subprog')
processed 1 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
=============
kernel-patches#444/20  test_global_funcs/kprobe_resolved_ctx:FAIL

Signed-off-by: Tony Ambardar <tony.ambardar@gmail.com>

Author: guidosarducci

arch/arm/include/asm/perf_event.h

@@ -8,6 +8,10 @@
 #ifndef __ARM_PERF_EVENT_H__
 #define __ARM_PERF_EVENT_H__
 
+#ifdef CONFIG_PERF_EVENTS
+#define perf_arch_bpf_user_pt_regs(regs) (struct pt_regs___bpf *)regs
+#endif
+
 #define perf_arch_fetch_caller_regs(regs, __ip) { \
 	(regs)->ARM_pc = (__ip); \
 	frame_pointer((regs)) = (unsigned long) __builtin_frame_address(0); \

arch/arm/include/uapi/asm/bpf_perf_event.h

@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI__ASM_BPF_PERF_EVENT_H__
+#define _UAPI__ASM_BPF_PERF_EVENT_H__
+
+struct pt_regs___bpf {
+	unsigned int uregs[18];
+};
+
+typedef struct pt_regs___bpf bpf_user_pt_regs_t;
+
+#endif /* _UAPI__ASM_BPF_PERF_EVENT_H__ */

tools/include/uapi/asm/bpf_perf_event.h

@@ -1,5 +1,7 @@
 #if defined(__aarch64__)
 #include "../../arch/arm64/include/uapi/asm/bpf_perf_event.h"
+#elif defined(__arm__)
+#include "../../arch/arm/include/uapi/asm/bpf_perf_event.h"
 #elif defined(__arc__)
 #include "../../arch/arc/include/uapi/asm/bpf_perf_event.h"
 #elif defined(__s390__)