netdev - [PATCH 2/4] net/bpf: refactor freeing of executable allocations

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Date:   Sat, 17 Nov 2018 10:57:13 -0800
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Jessica Yu <jeyu@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        "David S. Miller" <davem@...emloft.net>,
        linux-arm-kernel@...ts.infradead.org, linux-mips@...ux-mips.org,
        linuxppc-dev@...ts.ozlabs.org, sparclinux@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH 2/4] net/bpf: refactor freeing of executable allocations

All arch overrides of the __weak bpf_jit_free() amount to the same
thing: the allocated memory was never mapped read-only, and so
it does not have to be remapped to read-write before being freed.

So in preparation of permitting arches to serve allocations for BPF
JIT programs from other regions than the module region, refactor
the existing bpf_jit_free() implementations to use the shared code
where possible, and only specialize the remap and free operations.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
---
 arch/mips/net/bpf_jit.c           |  7 ++-----
 arch/powerpc/net/bpf_jit_comp.c   |  7 ++-----
 arch/powerpc/net/bpf_jit_comp64.c |  9 +++------
 arch/sparc/net/bpf_jit_comp_32.c  |  7 ++-----
 kernel/bpf/core.c                 | 15 +++++----------
 5 files changed, 14 insertions(+), 31 deletions(-)

diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c
index 1b69897274a1..5696bd7dccc7 100644
--- a/arch/mips/net/bpf_jit.c
+++ b/arch/mips/net/bpf_jit.c
@@ -1261,10 +1261,7 @@ void bpf_jit_compile(struct bpf_prog *fp)
 	kfree(ctx.offsets);
 }
 
-void bpf_jit_free(struct bpf_prog *fp)
+void bpf_jit_binary_free(struct bpf_binary_header *hdr)
 {
-	if (fp->jited)
-		bpf_jit_binary_free(bpf_jit_binary_hdr(fp));
-
-	bpf_prog_unlock_free(fp);
+	module_memfree(hdr);
 }
diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index a1ea1ea6b40d..5b5ce4a1b44b 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -680,10 +680,7 @@ void bpf_jit_compile(struct bpf_prog *fp)
 	return;
 }
 
-void bpf_jit_free(struct bpf_prog *fp)
+void bpf_jit_binary_free(struct bpf_binary_header *hdr)
 {
-	if (fp->jited)
-		bpf_jit_binary_free(bpf_jit_binary_hdr(fp));
-
-	bpf_prog_unlock_free(fp);
+	module_memfree(hdr);
 }
diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index 84c8f013a6c6..f64f1294bd62 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -1021,11 +1021,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
 	return fp;
 }
 
-/* Overriding bpf_jit_free() as we don't set images read-only. */
-void bpf_jit_free(struct bpf_prog *fp)
+/* Overriding bpf_jit_binary_free() as we don't set images read-only. */
+void bpf_jit_binary_free(struct bpf_binary_header *hdr)
 {
-	if (fp->jited)
-		bpf_jit_binary_free(bpf_jit_binary_hdr(fp));
-
-	bpf_prog_unlock_free(fp);
+	module_memfree(hdr);
 }
diff --git a/arch/sparc/net/bpf_jit_comp_32.c b/arch/sparc/net/bpf_jit_comp_32.c
index 01bda6bc9e7f..589950d152cc 100644
--- a/arch/sparc/net/bpf_jit_comp_32.c
+++ b/arch/sparc/net/bpf_jit_comp_32.c
@@ -756,10 +756,7 @@ cond_branch:			f_offset = addrs[i + filter[i].jf];
 	return;
 }
 
-void bpf_jit_free(struct bpf_prog *fp)
+void bpf_jit_binary_free(struct bpf_binary_header *hdr)
 {
-	if (fp->jited)
-		bpf_jit_binary_free(bpf_jit_binary_hdr(fp));
-
-	bpf_prog_unlock_free(fp);
+	module_memfree(hdr);
 }
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 1a796e0799ec..29f766dac203 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -646,25 +646,20 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
 	return hdr;
 }
 
-void bpf_jit_binary_free(struct bpf_binary_header *hdr)
+void __weak bpf_jit_binary_free(struct bpf_binary_header *hdr)
 {
-	u32 pages = hdr->pages;
-
+	bpf_jit_binary_unlock_ro(hdr);
 	module_memfree(hdr);
-	bpf_jit_uncharge_modmem(pages);
 }
 
-/* This symbol is only overridden by archs that have different
- * requirements than the usual eBPF JITs, f.e. when they only
- * implement cBPF JIT, do not set images read-only, etc.
- */
-void __weak bpf_jit_free(struct bpf_prog *fp)
+void bpf_jit_free(struct bpf_prog *fp)
 {
 	if (fp->jited) {
 		struct bpf_binary_header *hdr = bpf_jit_binary_hdr(fp);
+		u32 pages = hdr->pages;
 
-		bpf_jit_binary_unlock_ro(hdr);
 		bpf_jit_binary_free(hdr);
+		bpf_jit_uncharge_modmem(pages);
 
 		WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(fp));
 	}
-- 
2.17.1