FAILED: patch "[PATCH] bpf: fix bpf_probe_read_kernel prototype mismatch" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y
git checkout FETCH_HEAD
git cherry-pick -x 6a5a148aaf14747570cc634f9cdfcb0393f5617f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023090946-wrath-compacter-d8a5@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

6a5a148aaf14 ("bpf: fix bpf_probe_read_kernel prototype mismatch") 1f9a1ea821ff ("bpf: Support new sign-extension load insns") 06accc8779c1 ("bpf: add support for open-coded iterator loops") 215bf4962f6c ("bpf: add iterator kfuncs registration and validation logic") a461f5adf177 ("bpf: generalize dynptr_get_spi to be usable for iters") d0e1ac227945 ("bpf: move kfunc_call_arg_meta higher in the file") 653ae3a874ac ("bpf: clean up visit_insn()'s instruction processing") 98ddcf389d1b ("bpf: honor env->test_state_freq flag in is_state_visited()") d54e0f6c1adf ("bpf: improve stack slot state printing") 0d80a619c113 ("bpf: allow ctx writes using BPF_ST_MEM instruction") 6fcd486b3a0a ("bpf: Refactor RCU enforcement in the verifier.") 20c09d92faee ("bpf: Introduce kptr_rcu.")
8d093b4e95a2 ("bpf: Mark cgroups and dfl_cgrp fields as trusted.") 66e3a13e7c2c ("bpf: Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr") 05421aecd4ed ("bpf: Add xdp dynptrs")
b5964b968ac6 ("bpf: Add skb dynptrs")
d96d937d7c5c ("bpf: Add __uninit kfunc annotation")
485ec51ef976 ("bpf: Refactor verifier dynptr into get_dynptr_arg_reg") 8357b366cbb0 ("bpf: Define no-ops for externally called bpf dynptr functions") 1d18feb2c915 ("bpf: Allow initializing dynptrs in kfuncs")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 6a5a148aaf14747570cc634f9cdfcb0393f5617f Mon Sep 17 00:00:00 2001
From: Arnd Bergmann <[email protected]>
Date: Tue, 1 Aug 2023 13:13:58 +0200
Subject: [PATCH] bpf: fix bpf_probe_read_kernel prototype mismatch

bpf_probe_read_kernel() has a __weak definition in core.c and another definition with an incompatible prototype in kernel/trace/bpf_trace.c, when CONFIG_BPF_EVENTS is enabled.

Since the two are incompatible, there cannot be a shared declaration in a header file, but the lack of a prototype causes a W=1 warning:

kernel/bpf/core.c:1638:12: error: no previous prototype for 'bpf_probe_read_kernel' [-Werror=missing-prototypes]

On 32-bit architectures, the local prototype

u64 __weak bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr)

passes arguments in other registers as the one in bpf_trace.c

BPF_CALL_3(bpf_probe_read_kernel, void *, dst, u32, size,
const void *, unsafe_ptr)

which uses 64-bit arguments in pairs of registers.

As both versions of the function are fairly simple and only really differ in one line, just move them into a header file as an inline function that does not add any overhead for the bpf_trace.c callers and actually avoids a function call for the other one.

index ceaa8c23287f..abe75063630b 100644
@@ -2661,6 +2661,18 @@ static inline void bpf_dynptr_set_rdonly(struct bpf_dynptr_kern *ptr)
 }
 #endif /* CONFIG_BPF_SYSCALL */
 
+static __always_inline int
+bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr)
+{
+	int ret = -EFAULT;
+
+	if (IS_ENABLED(CONFIG_BPF_EVENTS))
+		ret = copy_from_kernel_nofault(dst, unsafe_ptr, size);
+	if (unlikely(ret < 0))
+		memset(dst, 0, size);
+	return ret;
+}
+
 void __bpf_free_used_btfs(struct bpf_prog_aux *aux,
 			  struct btf_mod_pair *used_btfs, u32 len);
 

index baccdec22f19..0f8f036d8bd1 100644
@@ -1650,12 +1650,6 @@ bool bpf_opcode_in_insntable(u8 code)
 }
 
 #ifndef CONFIG_BPF_JIT_ALWAYS_ON
-u64 __weak bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr)
-{
-	memset(dst, 0, size);
-	return -EFAULT;
-}
-
 /**
  *	___bpf_prog_run - run eBPF program on a given context
  *	@regs: is the array of MAX_BPF_EXT_REG eBPF pseudo-registers

@@ -2066,8 +2060,8 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn)
 		DST = *(SIZE *)(unsigned long) (SRC + insn->off);	\
 		CONT;							\
 	LDX_PROBE_MEM_##SIZEOP:						\
-		bpf_probe_read_kernel(&DST, sizeof(SIZE),		\
-				      (const void *)(long) (SRC + insn->off));	\
+		bpf_probe_read_kernel_common(&DST, sizeof(SIZE),	\
+			      (const void *)(long) (SRC + insn->off));	\
 		DST = *((SIZE *)&DST);					\
 		CONT;
 

@@ -2082,7 +2076,7 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn)
 		DST = *(SIZE *)(unsigned long) (SRC + insn->off);	\
 		CONT;							\
 	LDX_PROBE_MEMSX_##SIZEOP:					\
-		bpf_probe_read_kernel(&DST, sizeof(SIZE),		\
+		bpf_probe_read_kernel_common(&DST, sizeof(SIZE),		\
 				      (const void *)(long) (SRC + insn->off));	\
 		DST = *((SIZE *)&DST);					\
 		CONT;

index c92eb8c6ff08..83bde2475ae5 100644
@@ -223,17 +223,6 @@ const struct bpf_func_proto bpf_probe_read_user_str_proto = {
 	.arg3_type	= ARG_ANYTHING,
 };
 
-static __always_inline int
-bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr)
-{
-	int ret;
-
-	ret = copy_from_kernel_nofault(dst, unsafe_ptr, size);
-	if (unlikely(ret < 0))
-		memset(dst, 0, size);
-	return ret;
-}
-
 BPF_CALL_3(bpf_probe_read_kernel, void *, dst, u32, size,
 	   const void *, unsafe_ptr)
 {