powerpc/fadump: pass additional parameters when fadump is active

Append the additional parameters passed/set in the dedicated parameter
area (RTAS_FADUMP_PARAM_AREA) to bootargs in fadump capture kernel.
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240509115755.519982-4-hbathini@linux.ibm.com

arch/powerpc/include/asm/fadump.h

@@ -19,12 +19,14 @@ extern int is_fadump_active(void);
 extern int should_fadump_crash(void);
 extern void crash_fadump(struct pt_regs *, const char *);
 extern void fadump_cleanup(void);
+extern void fadump_append_bootargs(void);
 
 #else	/* CONFIG_FA_DUMP */
 static inline int is_fadump_active(void) { return 0; }
 static inline int should_fadump_crash(void) { return 0; }
 static inline void crash_fadump(struct pt_regs *regs, const char *str) { }
 static inline void fadump_cleanup(void) { }
+static inline void fadump_append_bootargs(void) { }
 #endif /* !CONFIG_FA_DUMP */
 
 #if defined(CONFIG_FA_DUMP) || defined(CONFIG_PRESERVE_FA_DUMP)

arch/powerpc/kernel/fadump.c

@@ -131,6 +131,41 @@ static int __init fadump_cma_init(void)
 static int __init fadump_cma_init(void) { return 1; }
 #endif /* CONFIG_CMA */
 
+/*
+ * Additional parameters meant for capture kernel are placed in a dedicated area.
+ * If this is capture kernel boot, append these parameters to bootargs.
+ */
+void __init fadump_append_bootargs(void)
+{
+	char *append_args;
+	size_t len;
+
+	if (!fw_dump.dump_active || !fw_dump.param_area_supported || !fw_dump.param_area)
+		return;
+
+	if (fw_dump.param_area >= fw_dump.boot_mem_top) {
+		if (memblock_reserve(fw_dump.param_area, COMMAND_LINE_SIZE)) {
+			pr_warn("WARNING: Can't use additional parameters area!\n");
+			fw_dump.param_area = 0;
+			return;
+		}
+	}
+
+	append_args = (char *)fw_dump.param_area;
+	len = strlen(boot_command_line);
+
+	/*
+	 * Too late to fail even if cmdline size exceeds. Truncate additional parameters
+	 * to cmdline size and proceed anyway.
+	 */
+	if (len + strlen(append_args) >= COMMAND_LINE_SIZE - 1)
+		pr_warn("WARNING: Appending parameters exceeds cmdline size. Truncating!\n");
+
+	pr_debug("Cmdline: %s\n", boot_command_line);
+	snprintf(boot_command_line + len, COMMAND_LINE_SIZE - len, " %s", append_args);
+	pr_info("Updated cmdline: %s\n", boot_command_line);
+}
+
 /* Scan the Firmware Assisted dump configuration details. */
 int __init early_init_dt_scan_fw_dump(unsigned long node, const char *uname,
 				      int depth, void *data)

arch/powerpc/kernel/prom.c

@@ -813,6 +813,9 @@ void __init early_init_devtree(void *params)
 	 */
 	of_scan_flat_dt(early_init_dt_scan_chosen_ppc, boot_command_line);
 
+	/* Append additional parameters passed for fadump capture kernel */
+	fadump_append_bootargs();
+
 	/* Scan memory nodes and rebuild MEMBLOCKs */
 	early_init_dt_scan_root();
 	early_init_dt_scan_memory_ppc();