From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Johan Almbladh <johan.almbladh@anyfinetworks.com>
Cc: bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 1/9] powerpc/lib: Add helper to check if offset is within conditional branch range
Date: Sun, 3 Oct 2021 09:50:59 +0200 [thread overview]
Message-ID: <6745a836-1991-24d0-f02a-437f06052c63@csgroup.eu> (raw)
In-Reply-To: <f8d581e6a5d9555180c38e009f90d236f310f85e.1633104510.git.naveen.n.rao@linux.vnet.ibm.com>
Le 01/10/2021 à 23:14, Naveen N. Rao a écrit :
> Add a helper to check if a given offset is within the branch range for a
> powerpc conditional branch instruction, and update some sites to use the
> new helper.
>
> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> ---
> arch/powerpc/include/asm/code-patching.h | 1 +
> arch/powerpc/lib/code-patching.c | 7 ++++++-
> arch/powerpc/net/bpf_jit.h | 7 +------
> 3 files changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
> index a95f63788c6b14..4ba834599c4d4c 100644
> --- a/arch/powerpc/include/asm/code-patching.h
> +++ b/arch/powerpc/include/asm/code-patching.h
> @@ -23,6 +23,7 @@
> #define BRANCH_ABSOLUTE 0x2
>
> bool is_offset_in_branch_range(long offset);
> +bool is_offset_in_cond_branch_range(long offset);
> int create_branch(struct ppc_inst *instr, const u32 *addr,
> unsigned long target, int flags);
> int create_cond_branch(struct ppc_inst *instr, const u32 *addr,
> diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
> index f9a3019e37b43c..e2342b9a1ab9c9 100644
> --- a/arch/powerpc/lib/code-patching.c
> +++ b/arch/powerpc/lib/code-patching.c
> @@ -228,6 +228,11 @@ bool is_offset_in_branch_range(long offset)
> return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
> }
>
> +bool is_offset_in_cond_branch_range(long offset)
> +{
> + return offset >= -0x8000 && offset <= 0x7FFF && !(offset & 0x3);
> +}
Would be better without capital letters in numbers, in extenso 0x7fff
instead of 0x7FFF
> +
> /*
> * Helper to check if a given instruction is a conditional branch
> * Derived from the conditional checks in analyse_instr()
> @@ -280,7 +285,7 @@ int create_cond_branch(struct ppc_inst *instr, const u32 *addr,
> offset = offset - (unsigned long)addr;
>
> /* Check we can represent the target in the instruction format */
> - if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
> + if (!is_offset_in_cond_branch_range(offset))
> return 1;
>
> /* Mask out the flags and target, so they don't step on each other. */
> diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
> index 99fad093f43ec1..935ea95b66359e 100644
> --- a/arch/powerpc/net/bpf_jit.h
> +++ b/arch/powerpc/net/bpf_jit.h
> @@ -78,11 +78,6 @@
> #define PPC_FUNC_ADDR(d,i) do { PPC_LI32(d, i); } while(0)
> #endif
>
> -static inline bool is_nearbranch(int offset)
> -{
> - return (offset < 32768) && (offset >= -32768);
> -}
> -
> /*
> * The fly in the ointment of code size changing from pass to pass is
> * avoided by padding the short branch case with a NOP. If code size differs
> @@ -91,7 +86,7 @@ static inline bool is_nearbranch(int offset)
> * state.
> */
> #define PPC_BCC(cond, dest) do { \
> - if (is_nearbranch((dest) - (ctx->idx * 4))) { \
> + if (is_offset_in_cond_branch_range((long)(dest) - (ctx->idx * 4))) { \
> PPC_BCC_SHORT(cond, dest); \
> EMIT(PPC_RAW_NOP()); \
> } else { \
>
next prev parent reply other threads:[~2021-10-03 7:54 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-01 21:14 [PATCH 0/9] powerpc/bpf: Various fixes Naveen N. Rao
2021-10-01 21:14 ` [PATCH 1/9] powerpc/lib: Add helper to check if offset is within conditional branch range Naveen N. Rao
2021-10-01 21:37 ` Song Liu
2021-10-04 18:02 ` Naveen N. Rao
2021-10-03 7:50 ` Christophe Leroy [this message]
2021-10-04 18:03 ` Naveen N. Rao
2021-10-01 21:14 ` [PATCH 2/9] powerpc/bpf: Validate branch ranges Naveen N. Rao
2021-10-01 21:45 ` Song Liu
2021-10-02 17:29 ` Johan Almbladh
2021-10-03 7:54 ` Christophe Leroy
2021-10-04 18:11 ` Naveen N. Rao
2021-10-01 21:14 ` [PATCH 3/9] powerpc/bpf: Remove unused SEEN_STACK Naveen N. Rao
2021-10-01 21:47 ` Song Liu
2021-10-02 17:30 ` Johan Almbladh
2021-10-03 7:55 ` Christophe Leroy
2021-10-04 18:11 ` Naveen N. Rao
2021-10-05 5:50 ` Christophe Leroy
2021-10-05 20:22 ` Naveen N. Rao
2021-10-01 21:14 ` [PATCH 4/9] powerpc/bpf: Handle large branch ranges with BPF_EXIT Naveen N. Rao
2021-10-01 21:53 ` Song Liu
2021-10-02 17:31 ` Johan Almbladh
2021-10-03 7:59 ` Christophe Leroy
2021-10-04 18:24 ` Naveen N. Rao
2021-10-05 5:46 ` Christophe Leroy
2022-01-07 11:46 ` Naveen N. Rao
2021-10-01 21:14 ` [PATCH 5/9] powerpc/bpf: Fix BPF_MOD when imm == 1 Naveen N. Rao
2021-10-01 21:55 ` Song Liu
2021-10-02 17:32 ` Johan Almbladh
2021-10-01 21:14 ` [PATCH 6/9] powerpc/bpf: Fix BPF_SUB when imm == 0x80000000 Naveen N. Rao
2021-10-01 22:01 ` Song Liu
2021-10-02 17:33 ` Johan Almbladh
2021-10-03 8:07 ` Christophe Leroy
2021-10-04 18:18 ` Naveen N. Rao
2021-10-05 5:40 ` Christophe Leroy
2021-10-01 21:14 ` [PATCH 7/9] powerpc/bpf: Limit 'ldbrx' to processors compliant with ISA v2.06 Naveen N. Rao
2021-10-02 17:35 ` Johan Almbladh
2021-10-01 21:14 ` [PATCH 8/9] powerpc/security: Add a helper to query stf_barrier type Naveen N. Rao
2021-10-01 21:14 ` [PATCH 9/9] powerpc/bpf: Emit stf barrier instruction sequences for BPF_NOSPEC Naveen N. Rao
2021-10-02 17:41 ` [PATCH 0/9] powerpc/bpf: Various fixes Johan Almbladh
2021-10-04 18:19 ` Naveen N. Rao
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