[PATCH v5 15/21] arm64: idreg-override: use early FDT mapping in ID map

Ard Biesheuvel
2022-06-24T15:14:00Z

Instead of calling into the kernel to map the FDT into the kernel page
tables before even calling start_kernel(), let's switch to the initial,
temporary mapping of the device tree that has been added to the ID map.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm64/kernel/head.S | 1 +
arch/arm64/kernel/idreg-override.c | 17 ++++++-----------
2 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 8283ff848328..64ebff634b83 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -472,6 +472,7 @@ SYM_FUNC_START_LOCAL(__primary_switched)
#endif
mov x0, x21 // pass FDT address in x0
bl early_fdt_map // Try mapping the FDT early
+ mov x0, x22 // pass FDT address in x0
bl init_feature_override // Parse cpu feature overrides
#ifdef CONFIG_RANDOMIZE_BASE
tst x23, ~(MIN_KIMG_ALIGN - 1) // already running randomized?
diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index 8a2ceb591686..f92836e196e5 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -201,16 +201,11 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
} while (1);
}

-static __init const u8 *get_bootargs_cmdline(void)
+static __init const u8 *get_bootargs_cmdline(const void *fdt)
{
const u8 *prop;
- void *fdt;
int node;

- fdt = get_early_fdt_ptr();
- if (!fdt)
- return NULL;
-
node = fdt_path_offset(fdt, "/chosen");
if (node < 0)
return NULL;
@@ -222,9 +217,9 @@ static __init const u8 *get_bootargs_cmdline(void)
return strlen(prop) ? prop : NULL;
}

-static __init void parse_cmdline(void)
+static __init void parse_cmdline(const void *fdt)
{
- const u8 *prop = get_bootargs_cmdline();
+ const u8 *prop = get_bootargs_cmdline(fdt);

if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
__parse_cmdline(CONFIG_CMDLINE, true);
@@ -234,9 +229,9 @@ static __init void parse_cmdline(void)
}

/* Keep checkers quiet */
-void init_feature_override(void);
+void init_feature_override(const void *fdt);

-asmlinkage void __init init_feature_override(void)
+asmlinkage void __init init_feature_override(const void *fdt)
{
int i;

@@ -247,7 +242,7 @@ asmlinkage void __init init_feature_override(void)
}
}

- parse_cmdline();
+ parse_cmdline(fdt);

for (i = 0; i < ARRAY_SIZE(regs); i++) {
if (regs[i]->override)