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JustOS/linux-6.13/arch/powerpc/net/bpf_jit_comp.c
justuser 02e73b8cd9 up
2025-01-24 17:00:19 +03:00

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// SPDX-License-Identifier: GPL-2.0-only
/*
* eBPF JIT compiler
*
* Copyright 2016 Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
* IBM Corporation
*
* Based on the powerpc classic BPF JIT compiler by Matt Evans
*/
#include <linux/moduleloader.h>
#include <asm/cacheflush.h>
#include <asm/asm-compat.h>
#include <linux/netdevice.h>
#include <linux/filter.h>
#include <linux/if_vlan.h>
#include <linux/kernel.h>
#include <linux/memory.h>
#include <linux/bpf.h>
#include <asm/kprobes.h>
#include <asm/text-patching.h>
#include "bpf_jit.h"
/* These offsets are from bpf prog end and stay the same across progs */
static int bpf_jit_ool_stub, bpf_jit_long_branch_stub;
static void bpf_jit_fill_ill_insns(void *area, unsigned int size)
{
memset32(area, BREAKPOINT_INSTRUCTION, size / 4);
}
void dummy_tramp(void);
asm (
" .pushsection .text, \"ax\", @progbits ;"
" .global dummy_tramp ;"
" .type dummy_tramp, @function ;"
"dummy_tramp: ;"
#ifdef CONFIG_PPC_FTRACE_OUT_OF_LINE
" blr ;"
#else
/* LR is always in r11, so we don't need a 'mflr r11' here */
" mtctr 11 ;"
" mtlr 0 ;"
" bctr ;"
#endif
" .size dummy_tramp, .-dummy_tramp ;"
" .popsection ;"
);
void bpf_jit_build_fentry_stubs(u32 *image, struct codegen_context *ctx)
{
int ool_stub_idx, long_branch_stub_idx;
/*
* Out-of-line stub:
* mflr r0
* [b|bl] tramp
* mtlr r0 // only with CONFIG_PPC_FTRACE_OUT_OF_LINE
* b bpf_func + 4
*/
ool_stub_idx = ctx->idx;
EMIT(PPC_RAW_MFLR(_R0));
EMIT(PPC_RAW_NOP());
if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))
EMIT(PPC_RAW_MTLR(_R0));
WARN_ON_ONCE(!is_offset_in_branch_range(4 - (long)ctx->idx * 4));
EMIT(PPC_RAW_BRANCH(4 - (long)ctx->idx * 4));
/*
* Long branch stub:
* .long <dummy_tramp_addr>
* mflr r11
* bcl 20,31,$+4
* mflr r12
* ld r12, -8-SZL(r12)
* mtctr r12
* mtlr r11 // needed to retain ftrace ABI
* bctr
*/
if (image)
*((unsigned long *)&image[ctx->idx]) = (unsigned long)dummy_tramp;
ctx->idx += SZL / 4;
long_branch_stub_idx = ctx->idx;
EMIT(PPC_RAW_MFLR(_R11));
EMIT(PPC_RAW_BCL4());
EMIT(PPC_RAW_MFLR(_R12));
EMIT(PPC_RAW_LL(_R12, _R12, -8-SZL));
EMIT(PPC_RAW_MTCTR(_R12));
EMIT(PPC_RAW_MTLR(_R11));
EMIT(PPC_RAW_BCTR());
if (!bpf_jit_ool_stub) {
bpf_jit_ool_stub = (ctx->idx - ool_stub_idx) * 4;
bpf_jit_long_branch_stub = (ctx->idx - long_branch_stub_idx) * 4;
}
}
int bpf_jit_emit_exit_insn(u32 *image, struct codegen_context *ctx, int tmp_reg, long exit_addr)
{
if (!exit_addr || is_offset_in_branch_range(exit_addr - (ctx->idx * 4))) {
PPC_JMP(exit_addr);
} else if (ctx->alt_exit_addr) {
if (WARN_ON(!is_offset_in_branch_range((long)ctx->alt_exit_addr - (ctx->idx * 4))))
return -1;
PPC_JMP(ctx->alt_exit_addr);
} else {
ctx->alt_exit_addr = ctx->idx * 4;
bpf_jit_build_epilogue(image, ctx);
}
return 0;
}
struct powerpc_jit_data {
/* address of rw header */
struct bpf_binary_header *hdr;
/* address of ro final header */
struct bpf_binary_header *fhdr;
u32 *addrs;
u8 *fimage;
u32 proglen;
struct codegen_context ctx;
};
bool bpf_jit_needs_zext(void)
{
return true;
}
struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
{
u32 proglen;
u32 alloclen;
u8 *image = NULL;
u32 *code_base;
u32 *addrs;
struct powerpc_jit_data *jit_data;
struct codegen_context cgctx;
int pass;
int flen;
struct bpf_binary_header *fhdr = NULL;
struct bpf_binary_header *hdr = NULL;
struct bpf_prog *org_fp = fp;
struct bpf_prog *tmp_fp;
bool bpf_blinded = false;
bool extra_pass = false;
u8 *fimage = NULL;
u32 *fcode_base;
u32 extable_len;
u32 fixup_len;
if (!fp->jit_requested)
return org_fp;
tmp_fp = bpf_jit_blind_constants(org_fp);
if (IS_ERR(tmp_fp))
return org_fp;
if (tmp_fp != org_fp) {
bpf_blinded = true;
fp = tmp_fp;
}
jit_data = fp->aux->jit_data;
if (!jit_data) {
jit_data = kzalloc(sizeof(*jit_data), GFP_KERNEL);
if (!jit_data) {
fp = org_fp;
goto out;
}
fp->aux->jit_data = jit_data;
}
flen = fp->len;
addrs = jit_data->addrs;
if (addrs) {
cgctx = jit_data->ctx;
/*
* JIT compiled to a writable location (image/code_base) first.
* It is then moved to the readonly final location (fimage/fcode_base)
* using instruction patching.
*/
fimage = jit_data->fimage;
fhdr = jit_data->fhdr;
proglen = jit_data->proglen;
hdr = jit_data->hdr;
image = (void *)hdr + ((void *)fimage - (void *)fhdr);
extra_pass = true;
/* During extra pass, ensure index is reset before repopulating extable entries */
cgctx.exentry_idx = 0;
goto skip_init_ctx;
}
addrs = kcalloc(flen + 1, sizeof(*addrs), GFP_KERNEL);
if (addrs == NULL) {
fp = org_fp;
goto out_addrs;
}
memset(&cgctx, 0, sizeof(struct codegen_context));
bpf_jit_init_reg_mapping(&cgctx);
/* Make sure that the stack is quadword aligned. */
cgctx.stack_size = round_up(fp->aux->stack_depth, 16);
/* Scouting faux-generate pass 0 */
if (bpf_jit_build_body(fp, NULL, NULL, &cgctx, addrs, 0, false)) {
/* We hit something illegal or unsupported. */
fp = org_fp;
goto out_addrs;
}
/*
* If we have seen a tail call, we need a second pass.
* This is because bpf_jit_emit_common_epilogue() is called
* from bpf_jit_emit_tail_call() with a not yet stable ctx->seen.
* We also need a second pass if we ended up with too large
* a program so as to ensure BPF_EXIT branches are in range.
*/
if (cgctx.seen & SEEN_TAILCALL || !is_offset_in_branch_range((long)cgctx.idx * 4)) {
cgctx.idx = 0;
if (bpf_jit_build_body(fp, NULL, NULL, &cgctx, addrs, 0, false)) {
fp = org_fp;
goto out_addrs;
}
}
bpf_jit_realloc_regs(&cgctx);
/*
* Pretend to build prologue, given the features we've seen. This will
* update ctgtx.idx as it pretends to output instructions, then we can
* calculate total size from idx.
*/
bpf_jit_build_prologue(NULL, &cgctx);
addrs[fp->len] = cgctx.idx * 4;
bpf_jit_build_epilogue(NULL, &cgctx);
fixup_len = fp->aux->num_exentries * BPF_FIXUP_LEN * 4;
extable_len = fp->aux->num_exentries * sizeof(struct exception_table_entry);
proglen = cgctx.idx * 4;
alloclen = proglen + FUNCTION_DESCR_SIZE + fixup_len + extable_len;
fhdr = bpf_jit_binary_pack_alloc(alloclen, &fimage, 4, &hdr, &image,
bpf_jit_fill_ill_insns);
if (!fhdr) {
fp = org_fp;
goto out_addrs;
}
if (extable_len)
fp->aux->extable = (void *)fimage + FUNCTION_DESCR_SIZE + proglen + fixup_len;
skip_init_ctx:
code_base = (u32 *)(image + FUNCTION_DESCR_SIZE);
fcode_base = (u32 *)(fimage + FUNCTION_DESCR_SIZE);
/* Code generation passes 1-2 */
for (pass = 1; pass < 3; pass++) {
/* Now build the prologue, body code & epilogue for real. */
cgctx.idx = 0;
cgctx.alt_exit_addr = 0;
bpf_jit_build_prologue(code_base, &cgctx);
if (bpf_jit_build_body(fp, code_base, fcode_base, &cgctx, addrs, pass,
extra_pass)) {
bpf_arch_text_copy(&fhdr->size, &hdr->size, sizeof(hdr->size));
bpf_jit_binary_pack_free(fhdr, hdr);
fp = org_fp;
goto out_addrs;
}
bpf_jit_build_epilogue(code_base, &cgctx);
if (bpf_jit_enable > 1)
pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
proglen - (cgctx.idx * 4), cgctx.seen);
}
if (bpf_jit_enable > 1)
/*
* Note that we output the base address of the code_base
* rather than image, since opcodes are in code_base.
*/
bpf_jit_dump(flen, proglen, pass, code_base);
#ifdef CONFIG_PPC64_ELF_ABI_V1
/* Function descriptor nastiness: Address + TOC */
((u64 *)image)[0] = (u64)fcode_base;
((u64 *)image)[1] = local_paca->kernel_toc;
#endif
fp->bpf_func = (void *)fimage;
fp->jited = 1;
fp->jited_len = cgctx.idx * 4 + FUNCTION_DESCR_SIZE;
if (!fp->is_func || extra_pass) {
if (bpf_jit_binary_pack_finalize(fhdr, hdr)) {
fp = org_fp;
goto out_addrs;
}
bpf_prog_fill_jited_linfo(fp, addrs);
out_addrs:
kfree(addrs);
kfree(jit_data);
fp->aux->jit_data = NULL;
} else {
jit_data->addrs = addrs;
jit_data->ctx = cgctx;
jit_data->proglen = proglen;
jit_data->fimage = fimage;
jit_data->fhdr = fhdr;
jit_data->hdr = hdr;
}
out:
if (bpf_blinded)
bpf_jit_prog_release_other(fp, fp == org_fp ? tmp_fp : org_fp);
return fp;
}
/*
* The caller should check for (BPF_MODE(code) == BPF_PROBE_MEM) before calling
* this function, as this only applies to BPF_PROBE_MEM, for now.
*/
int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, u32 *fimage, int pass,
struct codegen_context *ctx, int insn_idx, int jmp_off,
int dst_reg)
{
off_t offset;
unsigned long pc;
struct exception_table_entry *ex, *ex_entry;
u32 *fixup;
/* Populate extable entries only in the last pass */
if (pass != 2)
return 0;
if (!fp->aux->extable ||
WARN_ON_ONCE(ctx->exentry_idx >= fp->aux->num_exentries))
return -EINVAL;
/*
* Program is first written to image before copying to the
* final location (fimage). Accordingly, update in the image first.
* As all offsets used are relative, copying as is to the
* final location should be alright.
*/
pc = (unsigned long)&image[insn_idx];
ex = (void *)fp->aux->extable - (void *)fimage + (void *)image;
fixup = (void *)ex -
(fp->aux->num_exentries * BPF_FIXUP_LEN * 4) +
(ctx->exentry_idx * BPF_FIXUP_LEN * 4);
fixup[0] = PPC_RAW_LI(dst_reg, 0);
if (IS_ENABLED(CONFIG_PPC32))
fixup[1] = PPC_RAW_LI(dst_reg - 1, 0); /* clear higher 32-bit register too */
fixup[BPF_FIXUP_LEN - 1] =
PPC_RAW_BRANCH((long)(pc + jmp_off) - (long)&fixup[BPF_FIXUP_LEN - 1]);
ex_entry = &ex[ctx->exentry_idx];
offset = pc - (long)&ex_entry->insn;
if (WARN_ON_ONCE(offset >= 0 || offset < INT_MIN))
return -ERANGE;
ex_entry->insn = offset;
offset = (long)fixup - (long)&ex_entry->fixup;
if (WARN_ON_ONCE(offset >= 0 || offset < INT_MIN))
return -ERANGE;
ex_entry->fixup = offset;
ctx->exentry_idx++;
return 0;
}
void *bpf_arch_text_copy(void *dst, void *src, size_t len)
{
int err;
if (WARN_ON_ONCE(core_kernel_text((unsigned long)dst)))
return ERR_PTR(-EINVAL);
mutex_lock(&text_mutex);
err = patch_instructions(dst, src, len, false);
mutex_unlock(&text_mutex);
return err ? ERR_PTR(err) : dst;
}
int bpf_arch_text_invalidate(void *dst, size_t len)
{
u32 insn = BREAKPOINT_INSTRUCTION;
int ret;
if (WARN_ON_ONCE(core_kernel_text((unsigned long)dst)))
return -EINVAL;
mutex_lock(&text_mutex);
ret = patch_instructions(dst, &insn, len, true);
mutex_unlock(&text_mutex);
return ret;
}
void bpf_jit_free(struct bpf_prog *fp)
{
if (fp->jited) {
struct powerpc_jit_data *jit_data = fp->aux->jit_data;
struct bpf_binary_header *hdr;
/*
* If we fail the final pass of JIT (from jit_subprogs),
* the program may not be finalized yet. Call finalize here
* before freeing it.
*/
if (jit_data) {
bpf_jit_binary_pack_finalize(jit_data->fhdr, jit_data->hdr);
kvfree(jit_data->addrs);
kfree(jit_data);
}
hdr = bpf_jit_binary_pack_hdr(fp);
bpf_jit_binary_pack_free(hdr, NULL);
WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(fp));
}
bpf_prog_unlock_free(fp);
}
bool bpf_jit_supports_kfunc_call(void)
{
return true;
}
bool bpf_jit_supports_far_kfunc_call(void)
{
return IS_ENABLED(CONFIG_PPC64);
}
void *arch_alloc_bpf_trampoline(unsigned int size)
{
return bpf_prog_pack_alloc(size, bpf_jit_fill_ill_insns);
}
void arch_free_bpf_trampoline(void *image, unsigned int size)
{
bpf_prog_pack_free(image, size);
}
int arch_protect_bpf_trampoline(void *image, unsigned int size)
{
return 0;
}
static int invoke_bpf_prog(u32 *image, u32 *ro_image, struct codegen_context *ctx,
struct bpf_tramp_link *l, int regs_off, int retval_off,
int run_ctx_off, bool save_ret)
{
struct bpf_prog *p = l->link.prog;
ppc_inst_t branch_insn;
u32 jmp_idx;
int ret = 0;
/* Save cookie */
if (IS_ENABLED(CONFIG_PPC64)) {
PPC_LI64(_R3, l->cookie);
EMIT(PPC_RAW_STD(_R3, _R1, run_ctx_off + offsetof(struct bpf_tramp_run_ctx,
bpf_cookie)));
} else {
PPC_LI32(_R3, l->cookie >> 32);
PPC_LI32(_R4, l->cookie);
EMIT(PPC_RAW_STW(_R3, _R1,
run_ctx_off + offsetof(struct bpf_tramp_run_ctx, bpf_cookie)));
EMIT(PPC_RAW_STW(_R4, _R1,
run_ctx_off + offsetof(struct bpf_tramp_run_ctx, bpf_cookie) + 4));
}
/* __bpf_prog_enter(p, &bpf_tramp_run_ctx) */
PPC_LI_ADDR(_R3, p);
EMIT(PPC_RAW_MR(_R25, _R3));
EMIT(PPC_RAW_ADDI(_R4, _R1, run_ctx_off));
ret = bpf_jit_emit_func_call_rel(image, ro_image, ctx,
(unsigned long)bpf_trampoline_enter(p));
if (ret)
return ret;
/* Remember prog start time returned by __bpf_prog_enter */
EMIT(PPC_RAW_MR(_R26, _R3));
/*
* if (__bpf_prog_enter(p) == 0)
* goto skip_exec_of_prog;
*
* Emit a nop to be later patched with conditional branch, once offset is known
*/
EMIT(PPC_RAW_CMPLI(_R3, 0));
jmp_idx = ctx->idx;
EMIT(PPC_RAW_NOP());
/* p->bpf_func(ctx) */
EMIT(PPC_RAW_ADDI(_R3, _R1, regs_off));
if (!p->jited)
PPC_LI_ADDR(_R4, (unsigned long)p->insnsi);
if (!create_branch(&branch_insn, (u32 *)&ro_image[ctx->idx], (unsigned long)p->bpf_func,
BRANCH_SET_LINK)) {
if (image)
image[ctx->idx] = ppc_inst_val(branch_insn);
ctx->idx++;
} else {
EMIT(PPC_RAW_LL(_R12, _R25, offsetof(struct bpf_prog, bpf_func)));
EMIT(PPC_RAW_MTCTR(_R12));
EMIT(PPC_RAW_BCTRL());
}
if (save_ret)
EMIT(PPC_RAW_STL(_R3, _R1, retval_off));
/* Fix up branch */
if (image) {
if (create_cond_branch(&branch_insn, &image[jmp_idx],
(unsigned long)&image[ctx->idx], COND_EQ << 16))
return -EINVAL;
image[jmp_idx] = ppc_inst_val(branch_insn);
}
/* __bpf_prog_exit(p, start_time, &bpf_tramp_run_ctx) */
EMIT(PPC_RAW_MR(_R3, _R25));
EMIT(PPC_RAW_MR(_R4, _R26));
EMIT(PPC_RAW_ADDI(_R5, _R1, run_ctx_off));
ret = bpf_jit_emit_func_call_rel(image, ro_image, ctx,
(unsigned long)bpf_trampoline_exit(p));
return ret;
}
static int invoke_bpf_mod_ret(u32 *image, u32 *ro_image, struct codegen_context *ctx,
struct bpf_tramp_links *tl, int regs_off, int retval_off,
int run_ctx_off, u32 *branches)
{
int i;
/*
* The first fmod_ret program will receive a garbage return value.
* Set this to 0 to avoid confusing the program.
*/
EMIT(PPC_RAW_LI(_R3, 0));
EMIT(PPC_RAW_STL(_R3, _R1, retval_off));
for (i = 0; i < tl->nr_links; i++) {
if (invoke_bpf_prog(image, ro_image, ctx, tl->links[i], regs_off, retval_off,
run_ctx_off, true))
return -EINVAL;
/*
* mod_ret prog stored return value after prog ctx. Emit:
* if (*(u64 *)(ret_val) != 0)
* goto do_fexit;
*/
EMIT(PPC_RAW_LL(_R3, _R1, retval_off));
EMIT(PPC_RAW_CMPLI(_R3, 0));
/*
* Save the location of the branch and generate a nop, which is
* replaced with a conditional jump once do_fexit (i.e. the
* start of the fexit invocation) is finalized.
*/
branches[i] = ctx->idx;
EMIT(PPC_RAW_NOP());
}
return 0;
}
static void bpf_trampoline_setup_tail_call_cnt(u32 *image, struct codegen_context *ctx,
int func_frame_offset, int r4_off)
{
if (IS_ENABLED(CONFIG_PPC64)) {
/* See bpf_jit_stack_tailcallcnt() */
int tailcallcnt_offset = 6 * 8;
EMIT(PPC_RAW_LL(_R3, _R1, func_frame_offset - tailcallcnt_offset));
EMIT(PPC_RAW_STL(_R3, _R1, -tailcallcnt_offset));
} else {
/* See bpf_jit_stack_offsetof() and BPF_PPC_TC */
EMIT(PPC_RAW_LL(_R4, _R1, r4_off));
}
}
static void bpf_trampoline_restore_tail_call_cnt(u32 *image, struct codegen_context *ctx,
int func_frame_offset, int r4_off)
{
if (IS_ENABLED(CONFIG_PPC64)) {
/* See bpf_jit_stack_tailcallcnt() */
int tailcallcnt_offset = 6 * 8;
EMIT(PPC_RAW_LL(_R3, _R1, -tailcallcnt_offset));
EMIT(PPC_RAW_STL(_R3, _R1, func_frame_offset - tailcallcnt_offset));
} else {
/* See bpf_jit_stack_offsetof() and BPF_PPC_TC */
EMIT(PPC_RAW_STL(_R4, _R1, r4_off));
}
}
static void bpf_trampoline_save_args(u32 *image, struct codegen_context *ctx, int func_frame_offset,
int nr_regs, int regs_off)
{
int param_save_area_offset;
param_save_area_offset = func_frame_offset; /* the two frames we alloted */
param_save_area_offset += STACK_FRAME_MIN_SIZE; /* param save area is past frame header */
for (int i = 0; i < nr_regs; i++) {
if (i < 8) {
EMIT(PPC_RAW_STL(_R3 + i, _R1, regs_off + i * SZL));
} else {
EMIT(PPC_RAW_LL(_R3, _R1, param_save_area_offset + i * SZL));
EMIT(PPC_RAW_STL(_R3, _R1, regs_off + i * SZL));
}
}
}
/* Used when restoring just the register parameters when returning back */
static void bpf_trampoline_restore_args_regs(u32 *image, struct codegen_context *ctx,
int nr_regs, int regs_off)
{
for (int i = 0; i < nr_regs && i < 8; i++)
EMIT(PPC_RAW_LL(_R3 + i, _R1, regs_off + i * SZL));
}
/* Used when we call into the traced function. Replicate parameter save area */
static void bpf_trampoline_restore_args_stack(u32 *image, struct codegen_context *ctx,
int func_frame_offset, int nr_regs, int regs_off)
{
int param_save_area_offset;
param_save_area_offset = func_frame_offset; /* the two frames we alloted */
param_save_area_offset += STACK_FRAME_MIN_SIZE; /* param save area is past frame header */
for (int i = 8; i < nr_regs; i++) {
EMIT(PPC_RAW_LL(_R3, _R1, param_save_area_offset + i * SZL));
EMIT(PPC_RAW_STL(_R3, _R1, STACK_FRAME_MIN_SIZE + i * SZL));
}
bpf_trampoline_restore_args_regs(image, ctx, nr_regs, regs_off);
}
static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_image,
void *rw_image_end, void *ro_image,
const struct btf_func_model *m, u32 flags,
struct bpf_tramp_links *tlinks,
void *func_addr)
{
int regs_off, nregs_off, ip_off, run_ctx_off, retval_off, nvr_off, alt_lr_off, r4_off = 0;
int i, ret, nr_regs, bpf_frame_size = 0, bpf_dummy_frame_size = 0, func_frame_offset;
struct bpf_tramp_links *fmod_ret = &tlinks[BPF_TRAMP_MODIFY_RETURN];
struct bpf_tramp_links *fentry = &tlinks[BPF_TRAMP_FENTRY];
struct bpf_tramp_links *fexit = &tlinks[BPF_TRAMP_FEXIT];
struct codegen_context codegen_ctx, *ctx;
u32 *image = (u32 *)rw_image;
ppc_inst_t branch_insn;
u32 *branches = NULL;
bool save_ret;
if (IS_ENABLED(CONFIG_PPC32))
return -EOPNOTSUPP;
nr_regs = m->nr_args;
/* Extra registers for struct arguments */
for (i = 0; i < m->nr_args; i++)
if (m->arg_size[i] > SZL)
nr_regs += round_up(m->arg_size[i], SZL) / SZL - 1;
if (nr_regs > MAX_BPF_FUNC_ARGS)
return -EOPNOTSUPP;
ctx = &codegen_ctx;
memset(ctx, 0, sizeof(*ctx));
/*
* Generated stack layout:
*
* func prev back chain [ back chain ]
* [ ]
* bpf prog redzone/tailcallcnt [ ... ] 64 bytes (64-bit powerpc)
* [ ] --
* LR save area [ r0 save (64-bit) ] | header
* [ r0 save (32-bit) ] |
* dummy frame for unwind [ back chain 1 ] --
* [ padding ] align stack frame
* r4_off [ r4 (tailcallcnt) ] optional - 32-bit powerpc
* alt_lr_off [ real lr (ool stub)] optional - actual lr
* [ r26 ]
* nvr_off [ r25 ] nvr save area
* retval_off [ return value ]
* [ reg argN ]
* [ ... ]
* regs_off [ reg_arg1 ] prog ctx context
* nregs_off [ args count ]
* ip_off [ traced function ]
* [ ... ]
* run_ctx_off [ bpf_tramp_run_ctx ]
* [ reg argN ]
* [ ... ]
* param_save_area [ reg_arg1 ] min 8 doublewords, per ABI
* [ TOC save (64-bit) ] --
* [ LR save (64-bit) ] | header
* [ LR save (32-bit) ] |
* bpf trampoline frame [ back chain 2 ] --
*
*/
/* Minimum stack frame header */
bpf_frame_size = STACK_FRAME_MIN_SIZE;
/*
* Room for parameter save area.
*
* As per the ABI, this is required if we call into the traced
* function (BPF_TRAMP_F_CALL_ORIG):
* - if the function takes more than 8 arguments for the rest to spill onto the stack
* - or, if the function has variadic arguments
* - or, if this functions's prototype was not available to the caller
*
* Reserve space for at least 8 registers for now. This can be optimized later.
*/
bpf_frame_size += (nr_regs > 8 ? nr_regs : 8) * SZL;
/* Room for struct bpf_tramp_run_ctx */
run_ctx_off = bpf_frame_size;
bpf_frame_size += round_up(sizeof(struct bpf_tramp_run_ctx), SZL);
/* Room for IP address argument */
ip_off = bpf_frame_size;
if (flags & BPF_TRAMP_F_IP_ARG)
bpf_frame_size += SZL;
/* Room for args count */
nregs_off = bpf_frame_size;
bpf_frame_size += SZL;
/* Room for args */
regs_off = bpf_frame_size;
bpf_frame_size += nr_regs * SZL;
/* Room for return value of func_addr or fentry prog */
retval_off = bpf_frame_size;
save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET);
if (save_ret)
bpf_frame_size += SZL;
/* Room for nvr save area */
nvr_off = bpf_frame_size;
bpf_frame_size += 2 * SZL;
/* Optional save area for actual LR in case of ool ftrace */
if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE)) {
alt_lr_off = bpf_frame_size;
bpf_frame_size += SZL;
}
if (IS_ENABLED(CONFIG_PPC32)) {
if (nr_regs < 2) {
r4_off = bpf_frame_size;
bpf_frame_size += SZL;
} else {
r4_off = regs_off + SZL;
}
}
/* Padding to align stack frame, if any */
bpf_frame_size = round_up(bpf_frame_size, SZL * 2);
/* Dummy frame size for proper unwind - includes 64-bytes red zone for 64-bit powerpc */
bpf_dummy_frame_size = STACK_FRAME_MIN_SIZE + 64;
/* Offset to the traced function's stack frame */
func_frame_offset = bpf_dummy_frame_size + bpf_frame_size;
/* Create dummy frame for unwind, store original return value */
EMIT(PPC_RAW_STL(_R0, _R1, PPC_LR_STKOFF));
/* Protect red zone where tail call count goes */
EMIT(PPC_RAW_STLU(_R1, _R1, -bpf_dummy_frame_size));
/* Create our stack frame */
EMIT(PPC_RAW_STLU(_R1, _R1, -bpf_frame_size));
/* 64-bit: Save TOC and load kernel TOC */
if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && !IS_ENABLED(CONFIG_PPC_KERNEL_PCREL)) {
EMIT(PPC_RAW_STD(_R2, _R1, 24));
PPC64_LOAD_PACA();
}
/* 32-bit: save tail call count in r4 */
if (IS_ENABLED(CONFIG_PPC32) && nr_regs < 2)
EMIT(PPC_RAW_STL(_R4, _R1, r4_off));
bpf_trampoline_save_args(image, ctx, func_frame_offset, nr_regs, regs_off);
/* Save our return address */
EMIT(PPC_RAW_MFLR(_R3));
if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))
EMIT(PPC_RAW_STL(_R3, _R1, alt_lr_off));
else
EMIT(PPC_RAW_STL(_R3, _R1, bpf_frame_size + PPC_LR_STKOFF));
/*
* Save ip address of the traced function.
* We could recover this from LR, but we will need to address for OOL trampoline,
* and optional GEP area.
*/
if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE) || flags & BPF_TRAMP_F_IP_ARG) {
EMIT(PPC_RAW_LWZ(_R4, _R3, 4));
EMIT(PPC_RAW_SLWI(_R4, _R4, 6));
EMIT(PPC_RAW_SRAWI(_R4, _R4, 6));
EMIT(PPC_RAW_ADD(_R3, _R3, _R4));
EMIT(PPC_RAW_ADDI(_R3, _R3, 4));
}
if (flags & BPF_TRAMP_F_IP_ARG)
EMIT(PPC_RAW_STL(_R3, _R1, ip_off));
if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))
/* Fake our LR for unwind */
EMIT(PPC_RAW_STL(_R3, _R1, bpf_frame_size + PPC_LR_STKOFF));
/* Save function arg count -- see bpf_get_func_arg_cnt() */
EMIT(PPC_RAW_LI(_R3, nr_regs));
EMIT(PPC_RAW_STL(_R3, _R1, nregs_off));
/* Save nv regs */
EMIT(PPC_RAW_STL(_R25, _R1, nvr_off));
EMIT(PPC_RAW_STL(_R26, _R1, nvr_off + SZL));
if (flags & BPF_TRAMP_F_CALL_ORIG) {
PPC_LI_ADDR(_R3, (unsigned long)im);
ret = bpf_jit_emit_func_call_rel(image, ro_image, ctx,
(unsigned long)__bpf_tramp_enter);
if (ret)
return ret;
}
for (i = 0; i < fentry->nr_links; i++)
if (invoke_bpf_prog(image, ro_image, ctx, fentry->links[i], regs_off, retval_off,
run_ctx_off, flags & BPF_TRAMP_F_RET_FENTRY_RET))
return -EINVAL;
if (fmod_ret->nr_links) {
branches = kcalloc(fmod_ret->nr_links, sizeof(u32), GFP_KERNEL);
if (!branches)
return -ENOMEM;
if (invoke_bpf_mod_ret(image, ro_image, ctx, fmod_ret, regs_off, retval_off,
run_ctx_off, branches)) {
ret = -EINVAL;
goto cleanup;
}
}
/* Call the traced function */
if (flags & BPF_TRAMP_F_CALL_ORIG) {
/*
* The address in LR save area points to the correct point in the original function
* with both PPC_FTRACE_OUT_OF_LINE as well as with traditional ftrace instruction
* sequence
*/
EMIT(PPC_RAW_LL(_R3, _R1, bpf_frame_size + PPC_LR_STKOFF));
EMIT(PPC_RAW_MTCTR(_R3));
/* Replicate tail_call_cnt before calling the original BPF prog */
if (flags & BPF_TRAMP_F_TAIL_CALL_CTX)
bpf_trampoline_setup_tail_call_cnt(image, ctx, func_frame_offset, r4_off);
/* Restore args */
bpf_trampoline_restore_args_stack(image, ctx, func_frame_offset, nr_regs, regs_off);
/* Restore TOC for 64-bit */
if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && !IS_ENABLED(CONFIG_PPC_KERNEL_PCREL))
EMIT(PPC_RAW_LD(_R2, _R1, 24));
EMIT(PPC_RAW_BCTRL());
if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && !IS_ENABLED(CONFIG_PPC_KERNEL_PCREL))
PPC64_LOAD_PACA();
/* Store return value for bpf prog to access */
EMIT(PPC_RAW_STL(_R3, _R1, retval_off));
/* Restore updated tail_call_cnt */
if (flags & BPF_TRAMP_F_TAIL_CALL_CTX)
bpf_trampoline_restore_tail_call_cnt(image, ctx, func_frame_offset, r4_off);
/* Reserve space to patch branch instruction to skip fexit progs */
im->ip_after_call = &((u32 *)ro_image)[ctx->idx];
EMIT(PPC_RAW_NOP());
}
/* Update branches saved in invoke_bpf_mod_ret with address of do_fexit */
for (i = 0; i < fmod_ret->nr_links && image; i++) {
if (create_cond_branch(&branch_insn, &image[branches[i]],
(unsigned long)&image[ctx->idx], COND_NE << 16)) {
ret = -EINVAL;
goto cleanup;
}
image[branches[i]] = ppc_inst_val(branch_insn);
}
for (i = 0; i < fexit->nr_links; i++)
if (invoke_bpf_prog(image, ro_image, ctx, fexit->links[i], regs_off, retval_off,
run_ctx_off, false)) {
ret = -EINVAL;
goto cleanup;
}
if (flags & BPF_TRAMP_F_CALL_ORIG) {
im->ip_epilogue = &((u32 *)ro_image)[ctx->idx];
PPC_LI_ADDR(_R3, im);
ret = bpf_jit_emit_func_call_rel(image, ro_image, ctx,
(unsigned long)__bpf_tramp_exit);
if (ret)
goto cleanup;
}
if (flags & BPF_TRAMP_F_RESTORE_REGS)
bpf_trampoline_restore_args_regs(image, ctx, nr_regs, regs_off);
/* Restore return value of func_addr or fentry prog */
if (save_ret)
EMIT(PPC_RAW_LL(_R3, _R1, retval_off));
/* Restore nv regs */
EMIT(PPC_RAW_LL(_R26, _R1, nvr_off + SZL));
EMIT(PPC_RAW_LL(_R25, _R1, nvr_off));
/* Epilogue */
if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && !IS_ENABLED(CONFIG_PPC_KERNEL_PCREL))
EMIT(PPC_RAW_LD(_R2, _R1, 24));
if (flags & BPF_TRAMP_F_SKIP_FRAME) {
/* Skip the traced function and return to parent */
EMIT(PPC_RAW_ADDI(_R1, _R1, func_frame_offset));
EMIT(PPC_RAW_LL(_R0, _R1, PPC_LR_STKOFF));
EMIT(PPC_RAW_MTLR(_R0));
EMIT(PPC_RAW_BLR());
} else {
if (IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE)) {
EMIT(PPC_RAW_LL(_R0, _R1, alt_lr_off));
EMIT(PPC_RAW_MTLR(_R0));
EMIT(PPC_RAW_ADDI(_R1, _R1, func_frame_offset));
EMIT(PPC_RAW_LL(_R0, _R1, PPC_LR_STKOFF));
EMIT(PPC_RAW_BLR());
} else {
EMIT(PPC_RAW_LL(_R0, _R1, bpf_frame_size + PPC_LR_STKOFF));
EMIT(PPC_RAW_MTCTR(_R0));
EMIT(PPC_RAW_ADDI(_R1, _R1, func_frame_offset));
EMIT(PPC_RAW_LL(_R0, _R1, PPC_LR_STKOFF));
EMIT(PPC_RAW_MTLR(_R0));
EMIT(PPC_RAW_BCTR());
}
}
/* Make sure the trampoline generation logic doesn't overflow */
if (image && WARN_ON_ONCE(&image[ctx->idx] > (u32 *)rw_image_end - BPF_INSN_SAFETY)) {
ret = -EFAULT;
goto cleanup;
}
ret = ctx->idx * 4 + BPF_INSN_SAFETY * 4;
cleanup:
kfree(branches);
return ret;
}
int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
struct bpf_tramp_links *tlinks, void *func_addr)
{
struct bpf_tramp_image im;
void *image;
int ret;
/*
* Allocate a temporary buffer for __arch_prepare_bpf_trampoline().
* This will NOT cause fragmentation in direct map, as we do not
* call set_memory_*() on this buffer.
*
* We cannot use kvmalloc here, because we need image to be in
* module memory range.
*/
image = bpf_jit_alloc_exec(PAGE_SIZE);
if (!image)
return -ENOMEM;
ret = __arch_prepare_bpf_trampoline(&im, image, image + PAGE_SIZE, image,
m, flags, tlinks, func_addr);
bpf_jit_free_exec(image);
return ret;
}
int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *image_end,
const struct btf_func_model *m, u32 flags,
struct bpf_tramp_links *tlinks,
void *func_addr)
{
u32 size = image_end - image;
void *rw_image, *tmp;
int ret;
/*
* rw_image doesn't need to be in module memory range, so we can
* use kvmalloc.
*/
rw_image = kvmalloc(size, GFP_KERNEL);
if (!rw_image)
return -ENOMEM;
ret = __arch_prepare_bpf_trampoline(im, rw_image, rw_image + size, image, m,
flags, tlinks, func_addr);
if (ret < 0)
goto out;
if (bpf_jit_enable > 1)
bpf_jit_dump(1, ret - BPF_INSN_SAFETY * 4, 1, rw_image);
tmp = bpf_arch_text_copy(image, rw_image, size);
if (IS_ERR(tmp))
ret = PTR_ERR(tmp);
out:
kvfree(rw_image);
return ret;
}
static int bpf_modify_inst(void *ip, ppc_inst_t old_inst, ppc_inst_t new_inst)
{
ppc_inst_t org_inst;
if (copy_inst_from_kernel_nofault(&org_inst, ip)) {
pr_err("0x%lx: fetching instruction failed\n", (unsigned long)ip);
return -EFAULT;
}
if (!ppc_inst_equal(org_inst, old_inst)) {
pr_err("0x%lx: expected (%08lx) != found (%08lx)\n",
(unsigned long)ip, ppc_inst_as_ulong(old_inst), ppc_inst_as_ulong(org_inst));
return -EINVAL;
}
if (ppc_inst_equal(old_inst, new_inst))
return 0;
return patch_instruction(ip, new_inst);
}
static void do_isync(void *info __maybe_unused)
{
isync();
}
/*
* A 3-step process for bpf prog entry:
* 1. At bpf prog entry, a single nop/b:
* bpf_func:
* [nop|b] ool_stub
* 2. Out-of-line stub:
* ool_stub:
* mflr r0
* [b|bl] <bpf_prog>/<long_branch_stub>
* mtlr r0 // CONFIG_PPC_FTRACE_OUT_OF_LINE only
* b bpf_func + 4
* 3. Long branch stub:
* long_branch_stub:
* .long <branch_addr>/<dummy_tramp>
* mflr r11
* bcl 20,31,$+4
* mflr r12
* ld r12, -16(r12)
* mtctr r12
* mtlr r11 // needed to retain ftrace ABI
* bctr
*
* dummy_tramp is used to reduce synchronization requirements.
*
* When attaching a bpf trampoline to a bpf prog, we do not need any
* synchronization here since we always have a valid branch target regardless
* of the order in which the above stores are seen. dummy_tramp ensures that
* the long_branch stub goes to a valid destination on other cpus, even when
* the branch to the long_branch stub is seen before the updated trampoline
* address.
*
* However, when detaching a bpf trampoline from a bpf prog, or if changing
* the bpf trampoline address, we need synchronization to ensure that other
* cpus can no longer branch into the older trampoline so that it can be
* safely freed. bpf_tramp_image_put() uses rcu_tasks to ensure all cpus
* make forward progress, but we still need to ensure that other cpus
* execute isync (or some CSI) so that they don't go back into the
* trampoline again.
*/
int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
void *old_addr, void *new_addr)
{
unsigned long bpf_func, bpf_func_end, size, offset;
ppc_inst_t old_inst, new_inst;
int ret = 0, branch_flags;
char name[KSYM_NAME_LEN];
if (IS_ENABLED(CONFIG_PPC32))
return -EOPNOTSUPP;
bpf_func = (unsigned long)ip;
branch_flags = poke_type == BPF_MOD_CALL ? BRANCH_SET_LINK : 0;
/* We currently only support poking bpf programs */
if (!__bpf_address_lookup(bpf_func, &size, &offset, name)) {
pr_err("%s (0x%lx): kernel/modules are not supported\n", __func__, bpf_func);
return -EOPNOTSUPP;
}
/*
* If we are not poking at bpf prog entry, then we are simply patching in/out
* an unconditional branch instruction at im->ip_after_call
*/
if (offset) {
if (poke_type != BPF_MOD_JUMP) {
pr_err("%s (0x%lx): calls are not supported in bpf prog body\n", __func__,
bpf_func);
return -EOPNOTSUPP;
}
old_inst = ppc_inst(PPC_RAW_NOP());
if (old_addr)
if (create_branch(&old_inst, ip, (unsigned long)old_addr, 0))
return -ERANGE;
new_inst = ppc_inst(PPC_RAW_NOP());
if (new_addr)
if (create_branch(&new_inst, ip, (unsigned long)new_addr, 0))
return -ERANGE;
mutex_lock(&text_mutex);
ret = bpf_modify_inst(ip, old_inst, new_inst);
mutex_unlock(&text_mutex);
/* Make sure all cpus see the new instruction */
smp_call_function(do_isync, NULL, 1);
return ret;
}
bpf_func_end = bpf_func + size;
/* Address of the jmp/call instruction in the out-of-line stub */
ip = (void *)(bpf_func_end - bpf_jit_ool_stub + 4);
if (!is_offset_in_branch_range((long)ip - 4 - bpf_func)) {
pr_err("%s (0x%lx): bpf prog too large, ool stub out of branch range\n", __func__,
bpf_func);
return -ERANGE;
}
old_inst = ppc_inst(PPC_RAW_NOP());
if (old_addr) {
if (is_offset_in_branch_range(ip - old_addr))
create_branch(&old_inst, ip, (unsigned long)old_addr, branch_flags);
else
create_branch(&old_inst, ip, bpf_func_end - bpf_jit_long_branch_stub,
branch_flags);
}
new_inst = ppc_inst(PPC_RAW_NOP());
if (new_addr) {
if (is_offset_in_branch_range(ip - new_addr))
create_branch(&new_inst, ip, (unsigned long)new_addr, branch_flags);
else
create_branch(&new_inst, ip, bpf_func_end - bpf_jit_long_branch_stub,
branch_flags);
}
mutex_lock(&text_mutex);
/*
* 1. Update the address in the long branch stub:
* If new_addr is out of range, we will have to use the long branch stub, so patch new_addr
* here. Otherwise, revert to dummy_tramp, but only if we had patched old_addr here.
*/
if ((new_addr && !is_offset_in_branch_range(new_addr - ip)) ||
(old_addr && !is_offset_in_branch_range(old_addr - ip)))
ret = patch_ulong((void *)(bpf_func_end - bpf_jit_long_branch_stub - SZL),
(new_addr && !is_offset_in_branch_range(new_addr - ip)) ?
(unsigned long)new_addr : (unsigned long)dummy_tramp);
if (ret)
goto out;
/* 2. Update the branch/call in the out-of-line stub */
ret = bpf_modify_inst(ip, old_inst, new_inst);
if (ret)
goto out;
/* 3. Update instruction at bpf prog entry */
ip = (void *)bpf_func;
if (!old_addr || !new_addr) {
if (!old_addr) {
old_inst = ppc_inst(PPC_RAW_NOP());
create_branch(&new_inst, ip, bpf_func_end - bpf_jit_ool_stub, 0);
} else {
new_inst = ppc_inst(PPC_RAW_NOP());
create_branch(&old_inst, ip, bpf_func_end - bpf_jit_ool_stub, 0);
}
ret = bpf_modify_inst(ip, old_inst, new_inst);
}
out:
mutex_unlock(&text_mutex);
/*
* Sync only if we are not attaching a trampoline to a bpf prog so the older
* trampoline can be freed safely.
*/
if (old_addr)
smp_call_function(do_isync, NULL, 1);
return ret;
}
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