[RFC PATCH v3 11/11] powerpc64/bpf: Add support for bpf trampolines

Naveen N Rao
2024-06-20T19:09:47Z

Add support for bpf_arch_text_poke() and arch_prepare_bpf_trampoline()
for 64-bit powerpc.

BPF prog JIT is extended to mimic 64-bit powerpc approach for ftrace
having a single nop at function entry, followed by the function
profiling sequence out-of-line and a separate long branch stub for calls
to trampolines that are out of range. A dummy_tramp is provided to
simplify synchronization similar to arm64.

BPF Trampolines adhere to the existing ftrace ABI utilizing a
two-instruction profiling sequence, as well as the newer ABI utilizing a
three-instruction profiling sequence enabling return with a 'blr'. The
trampoline code itself closely follows x86 implementation.

While the code is generic, BPF trampolines are only enabled on 64-bit
powerpc. 32-bit powerpc will need testing and some updates.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
---
arch/powerpc/include/asm/ppc-opcode.h | 14 +
arch/powerpc/net/bpf_jit.h | 11 +
arch/powerpc/net/bpf_jit_comp.c | 702 +++++++++++++++++++++++++-
arch/powerpc/net/bpf_jit_comp32.c | 7 +-
arch/powerpc/net/bpf_jit_comp64.c | 7 +-
5 files changed, 738 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
index 076ae60b4a55..9eaa2c5d9b73 100644
--- a/arch/powerpc/include/asm/ppc-opcode.h
+++ b/arch/powerpc/include/asm/ppc-opcode.h
@@ -585,12 +585,26 @@
#define PPC_RAW_MTSPR(spr, d) (0x7c0003a6 | ___PPC_RS(d) | __PPC_SPR(spr))
#define PPC_RAW_EIEIO() (0x7c0006ac)

+/* bcl 20,31,$+4 */
+#define PPC_RAW_BCL() (0x429f0005)
#define PPC_RAW_BRANCH(offset) (0x48000000 | PPC_LI(offset))
#define PPC_RAW_BL(offset) (0x48000001 | PPC_LI(offset))
#define PPC_RAW_TW(t0, a, b) (0x7c000008 | ___PPC_RS(t0) | ___PPC_RA(a) | ___PPC_RB(b))
#define PPC_RAW_TRAP() PPC_RAW_TW(31, 0, 0)
#define PPC_RAW_SETB(t, bfa) (0x7c000100 | ___PPC_RT(t) | ___PPC_RA((bfa) << 2))

+#ifdef CONFIG_PPC32
+#define PPC_RAW_STL PPC_RAW_STW
+#define PPC_RAW_STLU PPC_RAW_STWU
+#define PPC_RAW_LL PPC_RAW_LWZ
+#define PPC_RAW_CMPLI PPC_RAW_CMPWI
+#else
+#define PPC_RAW_STL PPC_RAW_STD
+#define PPC_RAW_STLU PPC_RAW_STDU
+#define PPC_RAW_LL PPC_RAW_LD
+#define PPC_RAW_CMPLI PPC_RAW_CMPDI
+#endif
+
/* Deal with instructions that older assemblers aren't aware of */
#define PPC_BCCTR_FLUSH stringify_in_c(.long PPC_INST_BCCTR_FLUSH)
#define PPC_CP_ABORT stringify_in_c(.long PPC_RAW_CP_ABORT)
diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
index cdea5dccaefe..58cdfbfbef94 100644
--- a/arch/powerpc/net/bpf_jit.h
+++ b/arch/powerpc/net/bpf_jit.h
@@ -21,6 +21,9 @@

#define CTX_NIA(ctx) ((unsigned long)ctx->idx * 4)

+#define SZL sizeof(unsigned long)
+#define BPF_INSN_SAFETY 64
+
#define PLANT_INSTR(d, idx, instr) \
do { if (d) { (d)[idx] = instr; } idx++; } while (0)
#define EMIT(instr) PLANT_INSTR(image, ctx->idx, instr)
@@ -81,6 +84,13 @@
EMIT(PPC_RAW_ORI(d, d, (uintptr_t)(i) & \
0xffff)); \
} } while (0)
+#define PPC_LI_ADDR PPC_LI64
+#define PPC64_LOAD_PACA() \
+ EMIT(PPC_RAW_LD(_R2, _R13, offsetof(struct paca_struct, kernel_toc)))
+#else
+#define PPC_LI64 BUILD_BUG
+#define PPC_LI_ADDR PPC_LI32
+#define PPC64_LOAD_PACA() BUILD_BUG()
#endif

/*
@@ -165,6 +175,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
u32 *addrs, int pass, bool extra_pass);
void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx);
void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx);
+void bpf_jit_build_fentry_stubs(u32 *image, struct codegen_context *ctx);
void bpf_jit_realloc_regs(struct codegen_context *ctx);
int bpf_jit_emit_exit_insn(u32 *image, struct codegen_context *ctx, int tmp_reg, long exit_addr);

diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index 984655419da5..54df51ce54c8 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -22,11 +22,81 @@

#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_FTRACE_PFE_OUT_OF_LINE
+" blr ;"
+#else
+" mflr 11 ;"
+" 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_FTRACE_PFE_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_FTRACE_PFE_OUT_OF_LINE))
+ EMIT(PPC_RAW_MTLR(_R0));
+ WARN_ON_ONCE(!is_offset_in_branch_range(4 - (long)ctx->idx * 4)); /* TODO */
+ 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_BCL());
+ 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))) {
@@ -222,7 +292,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)

fp->bpf_func = (void *)fimage;
fp->jited = 1;
- fp->jited_len = proglen + FUNCTION_DESCR_SIZE;
+ fp->jited_len = cgctx.idx * 4 + FUNCTION_DESCR_SIZE;

if (!fp->is_func || extra_pass) {
if (bpf_jit_binary_pack_finalize(fp, fhdr, hdr)) {
@@ -369,3 +439,633 @@ 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_save_args(u32 *image, struct codegen_context *ctx, int nr_regs, int regs_off)
+{
+ for (int i = 0; i < nr_regs; i++)
+ EMIT(PPC_RAW_STL(_R3 + i, _R1, regs_off + i * SZL));
+}
+
+static void bpf_trampoline_restore_args(u32 *image, struct codegen_context *ctx, int nr_regs, int regs_off)
+{
+ for (int i = 0; i < nr_regs; i++)
+ EMIT(PPC_RAW_LL(_R3 + i, _R1, regs_off + i * SZL));
+}
+
+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;
+ struct bpf_tramp_links *fentry = &tlinks[BPF_TRAMP_FENTRY];
+ struct bpf_tramp_links *fexit = &tlinks[BPF_TRAMP_FEXIT];
+ struct bpf_tramp_links *fmod_ret = &tlinks[BPF_TRAMP_MODIFY_RETURN];
+ int i, ret, nr_regs = m->nr_args, stack_size = 0;
+ struct codegen_context codegen_ctx, *ctx;
+ u32 *image = (u32 *)rw_image;
+ ppc_inst_t branch_insn;
+ u32 *branches = NULL;
+ bool save_ret;
+
+ /* TODO: 32-bit enablement */
+ if (IS_ENABLED(CONFIG_PPC32))
+ return -ENOTSUPP;
+
+ /* Extra registers for struct arguments */
+ for (i = 0; i < m->nr_args; i++)
+ if (m->arg_size[i] > sizeof(unsigned long))
+ nr_regs += round_up(m->arg_size[i], sizeof(unsigned long)) / sizeof(unsigned long) - 1;
+
+ /* TODO: We only support functions with in-register arguments - up to 8 per powerpc ABI */
+ if (nr_regs > 8)
+ return -ENOTSUPP;
+
+ ctx = &codegen_ctx;
+ memset(ctx, 0, sizeof(*ctx));
+
+ /*
+ * Generated stack layout:
+ *
+ * func prev back chain [ back chain ]
+ * [ ] --
+ * LR save area [ r0 save (64-bit) ] | header
+ * [ r0 save (32-bit) ] |
+ * dummy frame for unwind [ back chain 1 ] --
+ * [ padding ] align stack frame
+ * alt_lr_off [ real lr (pfe ool) ] 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 ]
+ * [ TOC save (64-bit) ] --
+ * [ LR save (64-bit) ] | header
+ * [ LR save (32-bit) ] |
+ * bpf trampoline frame [ back chain 2 ] --
+ *
+ * TODO: tail call cnt?
+ */
+
+ /* Minimum stack frame header */
+ stack_size = STACK_FRAME_MIN_SIZE;
+
+ /* Room for struct bpf_tramp_run_ctx */
+ run_ctx_off = stack_size;
+ stack_size += round_up(sizeof(struct bpf_tramp_run_ctx), SZL);
+
+ /* Room for IP address argument */
+ ip_off = stack_size;
+ if (flags & BPF_TRAMP_F_IP_ARG)
+ stack_size += SZL;
+
+ /* Room for args count */
+ nregs_off = stack_size;
+ stack_size += SZL;
+
+ /* Room for args */
+ regs_off = stack_size;
+ stack_size += nr_regs * SZL;
+
+ /* Room for return value of func_addr or fentry prog */
+ retval_off = stack_size;
+ save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET);
+ if (save_ret)
+ stack_size += SZL;
+
+ /* Room for nvr save area */
+ nvr_off = stack_size;
+ stack_size += 2 * SZL;
+
+ /* Optional save area for actual LR in case of ool ftrace */
+ if (IS_ENABLED(CONFIG_FTRACE_PFE_OUT_OF_LINE)) {
+ alt_lr_off = stack_size;
+ stack_size += SZL;
+ }
+
+ /* Padding to align stack frame, if any */
+ stack_size = round_up(stack_size, SZL * 2);
+
+
+ /* Create dummy frame for unwind, store original return value */
+ EMIT(PPC_RAW_STL(_R0, _R1, PPC_LR_STKOFF));
+ EMIT(PPC_RAW_STLU(_R1, _R1, -STACK_FRAME_MIN_SIZE));
+
+ /* Create our stack frame */
+ EMIT(PPC_RAW_STLU(_R1, _R1, -stack_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();
+ }
+
+ bpf_trampoline_save_args(image, ctx, nr_regs, regs_off);
+
+ /* Save our return address */
+ EMIT(PPC_RAW_MFLR(_R3));
+ if (IS_ENABLED(CONFIG_FTRACE_PFE_OUT_OF_LINE))
+ EMIT(PPC_RAW_STL(_R3, _R1, alt_lr_off));
+ else
+ EMIT(PPC_RAW_STL(_R3, _R1, stack_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_FTRACE_PFE_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_FTRACE_PFE_OUT_OF_LINE))
+ /* Fake our LR for unwind */
+ EMIT(PPC_RAW_STL(_R3, _R1, stack_size + PPC_LR_STKOFF));
+
+ /* Save function arg count -- see bpf_get_func_arg_cnt() */
+ /* TODO: should this be nr_args? */
+ 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 FTRACE_PFE_OUT_OF_LINE as well as with traditional ftrace instruction
+ * sequence
+ */
+ EMIT(PPC_RAW_LL(_R3, _R1, stack_size + PPC_LR_STKOFF));
+ EMIT(PPC_RAW_MTCTR(_R3));
+
+ /* Restore args */
+ bpf_trampoline_restore_args(image, ctx, 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));
+
+ /* 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(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, stack_size + STACK_FRAME_MIN_SIZE));
+ EMIT(PPC_RAW_LL(_R0, _R1, PPC_LR_STKOFF));
+ EMIT(PPC_RAW_MTLR(_R0));
+ EMIT(PPC_RAW_BLR());
+ } else {
+ if (IS_ENABLED(CONFIG_FTRACE_PFE_OUT_OF_LINE)) {
+ EMIT(PPC_RAW_LL(_R0, _R1, alt_lr_off));
+ EMIT(PPC_RAW_MTLR(_R0));
+ EMIT(PPC_RAW_ADDI(_R1, _R1, stack_size + STACK_FRAME_MIN_SIZE));
+ EMIT(PPC_RAW_LL(_R0, _R1, PPC_LR_STKOFF));
+ EMIT(PPC_RAW_BLR());
+ } else {
+ EMIT(PPC_RAW_LL(_R0, _R1, stack_size + PPC_LR_STKOFF));
+ EMIT(PPC_RAW_MTCTR(_R0));
+ EMIT(PPC_RAW_ADDI(_R1, _R1, stack_size + STACK_FRAME_MIN_SIZE));
+ 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);
+}
+
+/*
+ * 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_FTRACE_PFE_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. Old trampoline is only freed
+ * through bpf_tramp_image_put() which uses rcu_tasks, so we don't need to do the same here.
+ */
+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];
+
+ /* TODO: 32-bit enablement */
+ if (IS_ENABLED(CONFIG_PPC32))
+ return -ENOTSUPP;
+
+ 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 -ENOTSUPP;
+ }
+
+ /*
+ * 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 -ENOTSUPP;
+ }
+ 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);
+ 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);
+ return ret;
+}
diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
index a0c4f1bde83e..c4db278dae36 100644
--- a/arch/powerpc/net/bpf_jit_comp32.c
+++ b/arch/powerpc/net/bpf_jit_comp32.c
@@ -127,13 +127,16 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
{
int i;

+ /* Instruction for trampoline attach */
+ EMIT(PPC_RAW_NOP());
+
/* Initialize tail_call_cnt, to be skipped if we do tail calls. */
if (ctx->seen & SEEN_TAILCALL)
EMIT(PPC_RAW_LI(_R4, 0));
else
EMIT(PPC_RAW_NOP());

-#define BPF_TAILCALL_PROLOGUE_SIZE 4
+#define BPF_TAILCALL_PROLOGUE_SIZE 8

if (bpf_has_stack_frame(ctx))
EMIT(PPC_RAW_STWU(_R1, _R1, -BPF_PPC_STACKFRAME(ctx)));
@@ -198,6 +201,8 @@ void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
bpf_jit_emit_common_epilogue(image, ctx);

EMIT(PPC_RAW_BLR());
+
+ bpf_jit_build_fentry_stubs(image, ctx);
}

/* Relative offset needs to be calculated based on final image location */
diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index 288ff32d676f..b58d1be63ea4 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -126,6 +126,9 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
{
int i;

+ /* Instruction for trampoline attach */
+ EMIT(PPC_RAW_NOP());
+
#ifndef CONFIG_PPC_KERNEL_PCREL
if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2))
EMIT(PPC_RAW_LD(_R2, _R13, offsetof(struct paca_struct, kernel_toc)));
@@ -200,6 +203,8 @@ void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
EMIT(PPC_RAW_MR(_R3, bpf_to_ppc(BPF_REG_0)));

EMIT(PPC_RAW_BLR());
+
+ bpf_jit_build_fentry_stubs(image, ctx);
}

int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func)
@@ -303,7 +308,7 @@ static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 o
*/
int b2p_bpf_array = bpf_to_ppc(BPF_REG_2);
int b2p_index = bpf_to_ppc(BPF_REG_3);
- int bpf_tailcall_prologue_size = 8;
+ int bpf_tailcall_prologue_size = 12;

if (!IS_ENABLED(CONFIG_PPC_KERNEL_PCREL) && IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2))
bpf_tailcall_prologue_size += 4; /* skip past the toc load */
--
2.45.2