From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 21 Dec 2023 20:10:22 +0000 (-0500)
Subject: Cleanup: kallsyms wrapper refactoring
X-Git-Url: http://git.liburcu.org/?p=lttng-modules.git;a=commitdiff_plain;h=b4a626cb684d2797df0329dd80c2df95e490c621

Cleanup: kallsyms wrapper refactoring

Move the Christmas tree of #ifdef which was implemented in
do_get_kallsyms() into separate functions:

- kallsyms_pre_arch_adjust(),
- kallsyms_get_arch_call_addr().

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I1bfdb43682e466f446d376ba7a122e295a2f0ea1
---

diff --git a/src/wrapper/kallsyms.c b/src/wrapper/kallsyms.c
index e5b5e310..2535c2a5 100644
--- a/src/wrapper/kallsyms.c
+++ b/src/wrapper/kallsyms.c
@@ -20,25 +20,6 @@
 # error "LTTng-modules requires CONFIG_KPROBES on kernels >= 5.7.0"
 #endif
 
-#ifdef LTTNG_CONFIG_PPC64_ELF_ABI_V1
-#if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,18,0))
-#include <asm/elf.h>
-
-#define LTTNG_FUNC_DESC_TYPE struct func_desc
-#define LTTNG_FUNC_DESC_ADDR_NAME addr
-
-#else
-
-#include <asm/types.h>
-
-#define LTTNG_FUNC_DESC_TYPE func_descr_t
-#define LTTNG_FUNC_DESC_ADDR_NAME entry
-#endif
-
-static
-LTTNG_FUNC_DESC_TYPE kallsyms_lookup_name_func_desc;
-#endif
-
 static
 unsigned long (*kallsyms_lookup_name_sym)(const char *name);
 
@@ -48,17 +29,10 @@ int dummy_kprobe_handler(struct kprobe *p, struct pt_regs *regs)
 	return 0;
 }
 
+#ifdef LTTNG_CONFIG_PPC64_ELF_ABI_V2
 static
-unsigned long do_get_kallsyms(void)
+void kallsyms_pre_arch_adjust(struct kprobe *probe)
 {
-	struct kprobe probe;
-	int ret;
-	unsigned long addr;
-
-	memset(&probe, 0, sizeof(probe));
-	probe.pre_handler = dummy_kprobe_handler;
-	probe.symbol_name = "kallsyms_lookup_name";
-#ifdef LTTNG_CONFIG_PPC64_ELF_ABI_V2
 	/*
 	 * With powerpc64 ABIv2, we need the global entry point of
 	 * kallsyms_lookup_name to call it later, while kprobe_register would
@@ -67,15 +41,40 @@ unsigned long do_get_kallsyms(void)
 	 * which is the length of one instruction to kallsyms_lookup_name to
 	 * avoid the adjustment.
 	 */
-	probe.offset = 4;
+	probe->offset = 4;
+}
+#else
+static
+void kallsyms_pre_arch_adjust(struct kprobe *probe)
+{
+}
 #endif
-	ret = register_kprobe(&probe);
-	if (ret)
-		return 0;
+
 #ifdef LTTNG_CONFIG_PPC64_ELF_ABI_V2
+static
+unsigned long kallsyms_get_arch_call_addr(const struct kprobe *probe)
+{
 	/* Substract 4 bytes to get what we originally want */
-	addr = (unsigned long)(((char *)probe.addr) - 4);
+	return (unsigned long)(((char *)probe->addr) - 4);
+}
+
 #elif defined(LTTNG_CONFIG_PPC64_ELF_ABI_V1)
+# if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,18,0))
+# include <asm/elf.h>
+# define LTTNG_FUNC_DESC_TYPE struct func_desc
+# define LTTNG_FUNC_DESC_ADDR_NAME addr
+# else
+# include <asm/types.h>
+# define LTTNG_FUNC_DESC_TYPE func_descr_t
+# define LTTNG_FUNC_DESC_ADDR_NAME entry
+
+static
+LTTNG_FUNC_DESC_TYPE kallsyms_lookup_name_func_desc;
+# endif
+
+static
+unsigned long kallsyms_get_arch_call_addr(const struct kprobe *probe)
+{
 	/*
 	 * Build a function descriptor from the address of
 	 * 'kallsyms_lookup_name' returned by kprobe and the toc of
@@ -84,16 +83,41 @@ unsigned long do_get_kallsyms(void)
 	 */
 	kallsyms_lookup_name_func_desc.LTTNG_FUNC_DESC_ADDR_NAME = (unsigned long) probe.addr;
 	kallsyms_lookup_name_func_desc.toc = ((LTTNG_FUNC_DESC_TYPE *) &sprint_symbol)->toc;
-	addr = (unsigned long) &kallsyms_lookup_name_func_desc;
-#else
-	addr = (unsigned long)probe.addr;
-#endif
-#ifdef CONFIG_ARM
-#ifdef CONFIG_THUMB2_KERNEL
+	return (unsigned long) &kallsyms_lookup_name_func_desc;
+}
+#elif defined(CONFIG_ARM) && defined(CONFIG_THUMB2_KERNEL)
+static
+unsigned long kallsyms_get_arch_call_addr(const struct kprobe *probe)
+{
+	unsigned long addr = (unsigned long)probe->addr;
+
 	if (addr)
 		addr |= 1; /* set bit 0 in address for thumb mode */
+	return addr;
+}
+#else
+static
+unsigned long kallsyms_get_arch_call_addr(const struct kprobe *probe)
+{
+	return (unsigned long)probe->addr;
+}
 #endif
-#endif
+
+static
+unsigned long do_get_kallsyms(void)
+{
+	struct kprobe probe;
+	int ret;
+	unsigned long addr;
+
+	memset(&probe, 0, sizeof(probe));
+	probe.pre_handler = dummy_kprobe_handler;
+	probe.symbol_name = "kallsyms_lookup_name";
+	kallsyms_pre_arch_adjust(&probe);
+	ret = register_kprobe(&probe);
+	if (ret)
+		return 0;
+	addr = kallsyms_get_arch_call_addr(&probe);
 	unregister_kprobe(&probe);
 	return addr;
 }