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powerpc64/bpf: fix JIT code size calculation of bpf trampoline #8714

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powerpc64/bpf: fix JIT code size calculation of bpf trampoline #8714

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29 changes: 23 additions & 6 deletions arch/powerpc/net/bpf_jit_comp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -833,7 +833,12 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im
EMIT(PPC_RAW_STL(_R26, _R1, nvr_off + SZL));

if (flags & BPF_TRAMP_F_CALL_ORIG) {
PPC_LI_ADDR(_R3, (unsigned long)im);
/*
* Emit maximum possible instructions while getting the size of
* bpf trampoline to ensure trampoline JIT code doesn't overflow.
*/
PPC_LI_ADDR(_R3, im ? (unsigned long)im :
(unsigned long)(~(1UL << (BITS_PER_LONG - 1))));
ret = bpf_jit_emit_func_call_rel(image, ro_image, ctx,
(unsigned long)__bpf_tramp_enter);
if (ret)
Expand Down Expand Up @@ -889,7 +894,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im
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];
if (im)
im->ip_after_call = &((u32 *)ro_image)[ctx->idx];
EMIT(PPC_RAW_NOP());
}

Expand All @@ -912,8 +918,14 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im
}

if (flags & BPF_TRAMP_F_CALL_ORIG) {
im->ip_epilogue = &((u32 *)ro_image)[ctx->idx];
PPC_LI_ADDR(_R3, im);
if (im)
im->ip_epilogue = &((u32 *)ro_image)[ctx->idx];
/*
* Emit maximum possible instructions while getting the size of
* bpf trampoline to ensure trampoline JIT code doesn't overflow.
*/
PPC_LI_ADDR(_R3, im ? (unsigned long)im :
(unsigned long)(~(1UL << (BITS_PER_LONG - 1))));
ret = bpf_jit_emit_func_call_rel(image, ro_image, ctx,
(unsigned long)__bpf_tramp_exit);
if (ret)
Expand Down Expand Up @@ -972,7 +984,6 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im
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;

Expand All @@ -988,7 +999,13 @@ int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
if (!image)
return -ENOMEM;

ret = __arch_prepare_bpf_trampoline(&im, image, image + PAGE_SIZE, image,
/*
* Pass NULL as bpf_tramp_image pointer to differentiate the intent to get the
* buffer size for trampoline here. This differentiation helps in accounting for
* maximum possible instructions if the JIT code size is likely to vary during
* the actual JIT compile of the trampoline.
*/
ret = __arch_prepare_bpf_trampoline(NULL, image, image + PAGE_SIZE, image,
m, flags, tlinks, func_addr);
bpf_jit_free_exec(image);

Expand Down
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