[PATCH v3 1/3] bpf: define bpf_jit_alloc_exec_limit for riscv JIT

[PATCH v3 1/3] bpf: define bpf_jit_alloc_exec_limit for riscv JIT

[Lorenz Bauer]

Expose the maximum amount of useable memory from the riscv JIT.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Acked-by: Luke Nelson <luke.r.nels@gmail.com>
---
 arch/riscv/net/bpf_jit_core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/riscv/net/bpf_jit_core.c b/arch/riscv/net/bpf_jit_core.c
index fed86f42dfbe..0fee2cbaaf53 100644
--- a/arch/riscv/net/bpf_jit_core.c
+++ b/arch/riscv/net/bpf_jit_core.c
@@ -166,6 +166,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 	return prog;
 }
 
+u64 bpf_jit_alloc_exec_limit(void)
+{
+	return BPF_JIT_REGION_SIZE;
+}
+
 void *bpf_jit_alloc_exec(unsigned long size)
 {
 	return __vmalloc_node_range(size, PAGE_SIZE, BPF_JIT_REGION_START,
-- 
2.30.2

Re: [PATCH v3 1/3] bpf: define bpf_jit_alloc_exec_limit for riscv JIT

[Björn Töpel]

On Thu, 14 Oct 2021 at 16:26, Lorenz Bauer <lmb@cloudflare.com> wrote:
>
> Expose the maximum amount of useable memory from the riscv JIT.
>
> Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
> Acked-by: Luke Nelson <luke.r.nels@gmail.com>

Acked-by: Björn Töpel <bjorn@kernel.org>

> ---
>  arch/riscv/net/bpf_jit_core.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/arch/riscv/net/bpf_jit_core.c b/arch/riscv/net/bpf_jit_core.c
> index fed86f42dfbe..0fee2cbaaf53 100644
> --- a/arch/riscv/net/bpf_jit_core.c
> +++ b/arch/riscv/net/bpf_jit_core.c
> @@ -166,6 +166,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
>         return prog;
>  }
>
> +u64 bpf_jit_alloc_exec_limit(void)
> +{
> +       return BPF_JIT_REGION_SIZE;
> +}
> +
>  void *bpf_jit_alloc_exec(unsigned long size)
>  {
>         return __vmalloc_node_range(size, PAGE_SIZE, BPF_JIT_REGION_START,
> --
> 2.30.2
>

[PATCH v3 2/3] bpf: define bpf_jit_alloc_exec_limit for arm64 JIT

[Lorenz Bauer]

Expose the maximum amount of useable memory from the arm64 JIT.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
---
 arch/arm64/net/bpf_jit_comp.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 41c23f474ea6..803e7773fa86 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -1136,6 +1136,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 	return prog;
 }
 
+u64 bpf_jit_alloc_exec_limit(void)
+{
+	return BPF_JIT_REGION_SIZE;
+}
+
 void *bpf_jit_alloc_exec(unsigned long size)
 {
 	return __vmalloc_node_range(size, PAGE_SIZE, BPF_JIT_REGION_START,
-- 
2.30.2

[PATCH v3 3/3] bpf: prevent increasing bpf_jit_limit above max

[Lorenz Bauer]

Restrict bpf_jit_limit to the maximum supported by the arch's JIT.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
---
 include/linux/filter.h     | 1 +
 kernel/bpf/core.c          | 4 +++-
 net/core/sysctl_net_core.c | 2 +-
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 47f80adbe744..8231a6a257f6 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1050,6 +1050,7 @@ extern int bpf_jit_enable;
 extern int bpf_jit_harden;
 extern int bpf_jit_kallsyms;
 extern long bpf_jit_limit;
+extern long bpf_jit_limit_max;
 
 typedef void (*bpf_jit_fill_hole_t)(void *area, unsigned int size);
 
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index b6c72af64d5d..ab84b3816339 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -525,6 +525,7 @@ int bpf_jit_enable   __read_mostly = IS_BUILTIN(CONFIG_BPF_JIT_DEFAULT_ON);
 int bpf_jit_kallsyms __read_mostly = IS_BUILTIN(CONFIG_BPF_JIT_DEFAULT_ON);
 int bpf_jit_harden   __read_mostly;
 long bpf_jit_limit   __read_mostly;
+long bpf_jit_limit_max __read_mostly;
 
 static void
 bpf_prog_ksym_set_addr(struct bpf_prog *prog)
@@ -818,7 +819,8 @@ u64 __weak bpf_jit_alloc_exec_limit(void)
 static int __init bpf_jit_charge_init(void)
 {
 	/* Only used as heuristic here to derive limit. */
-	bpf_jit_limit = min_t(u64, round_up(bpf_jit_alloc_exec_limit() >> 2,
+	bpf_jit_limit_max = bpf_jit_alloc_exec_limit();
+	bpf_jit_limit = min_t(u64, round_up(bpf_jit_limit_max >> 2,
 					    PAGE_SIZE), LONG_MAX);
 	return 0;
 }
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index c8496c1142c9..5f88526ad61c 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -419,7 +419,7 @@ static struct ctl_table net_core_table[] = {
 		.mode		= 0600,
 		.proc_handler	= proc_dolongvec_minmax_bpf_restricted,
 		.extra1		= &long_one,
-		.extra2		= &long_max,
+		.extra2		= &bpf_jit_limit_max,
 	},
 #endif
 	{
-- 
2.30.2