From c7a2a3618290594867b4829900b434704ab31dbc Mon Sep 17 00:00:00 2001 From: "Mike Rapoport (Microsoft)" Date: Tue, 18 Aug 2026 16:05:10 +0300 Subject: [PATCH] x86/bpf: Make arch_bpf_trampoline_size allocate from EXECMEM_MODULE_DATA Jiri Olsa reports slowdown of tracing_multi benchmark that allocates huge number of trampolines [1]. The slowdown caused by extra protection changes in execmem_alloc_rw() and execmem_free(). With ROX caches enabled, all execmem allocations except EXECMEM_MODULE_DATA are ROX after the allocation. execmem_alloc_rw() temporarily sets them to W+NX and execmem_free() resets them back to ROX. The only user of bpf_jit_alloc_exec_rw() is x86::arch_bpf_trampoline_size() that only needs a temporary writable buffer in the modules address space. On x86 executable memory and module data are constrained to the same address range, so x86::arch_bpf_trampoline_size() can directly use execmem_alloc(EXECMEM_MODULE_DATA) Replace the call to bpf_jit_alloc_exec_rw() with a call to execmem_alloc(EXECMEM_MODULE_DATA) in x86::arch_bpf_trampoline_size() and drop bpf_jit_alloc_exec_rw() helper. Fixes: 5bf02dbf39fa ("bpf, x86: Make sure allocation in arch_bpf_trampoline_size() is writable") Reported-by: Jiri Olsa Signed-off-by: Mike Rapoport (Microsoft) Signed-off-by: Daniel Borkmann Tested-by: Jiri Olsa Link: https://lore.kernel.org/all/an8r7EODLIL-bZM3@krava Link: https://lore.kernel.org/bpf/20260818130510.3110054-1-rppt@kernel.org --- arch/x86/net/bpf_jit_comp.c | 8 +++++--- include/linux/filter.h | 1 - kernel/bpf/core.c | 5 ----- 3 files changed, 5 insertions(+), 9 deletions(-) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 1a9fb530adc3..2853e87797a7 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include #include @@ -3818,15 +3819,16 @@ int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags, * * We cannot use kvmalloc here, because we need image to be in * module memory range. - * Since it must be writable use bpf_jit_alloc_exec_rw(). + * Since it must be writable use execmem_alloc(EXECMEM_MODULE_DATA) + * that returns writable memory in the module address space. */ - image = bpf_jit_alloc_exec_rw(PAGE_SIZE); + image = execmem_alloc(EXECMEM_MODULE_DATA, PAGE_SIZE); if (!image) return -ENOMEM; ret = __arch_prepare_bpf_trampoline(&im, image, image + PAGE_SIZE, image, m, flags, tnodes, func_addr); - bpf_jit_free_exec(image); + execmem_free(image); return ret; } diff --git a/include/linux/filter.h b/include/linux/filter.h index 4a9bc6a848f2..39decde7fc73 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -1376,7 +1376,6 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr, void bpf_jit_binary_free(struct bpf_binary_header *hdr); u64 bpf_jit_alloc_exec_limit(void); void *bpf_jit_alloc_exec(unsigned long size); -void *bpf_jit_alloc_exec_rw(unsigned long size); void bpf_jit_free_exec(void *addr); void bpf_jit_free(struct bpf_prog *fp); struct bpf_binary_header * diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index d55e737ed75a..8b294dfc1ad4 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -1128,11 +1128,6 @@ void *bpf_jit_alloc_exec(unsigned long size) return execmem_alloc(EXECMEM_BPF, size); } -void *bpf_jit_alloc_exec_rw(unsigned long size) -{ - return execmem_alloc_rw(EXECMEM_BPF, size); -} - void bpf_jit_free_exec(void *addr) { execmem_free(addr);