| Message ID | 1459781544-14310-3-git-send-email-ard.biesheuvel@linaro.org |
|---|---|
| State | New |
| Headers | show |
On 4 April 2016 at 17:13, James Morse <james.morse@arm.com> wrote: > Hi Ard, > > On 04/04/16 15:52, Ard Biesheuvel wrote: >> Since we record the boot_args [x0 .. x3] early at boot anyway, there is >> no need to keep the FDT address in a callee saved register with file scope >> in head.S. So simply refer to boot_args[0] directly in the call to >> setup_machine(), and drop the handling of x21 from head.S entirely. > > Won't this break Big Endian? > (or more accurately: bootloader-endian != kernel-endian) > > The stores in preserve_boot_args happen before the EE/E0E bits have been > set/cleared by el2_setup(), so they happen with boot-loader:endianness. The > loads after el2_setup() happen with kernel:endianness. > That is a very good point. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On 4 April 2016 at 17:19, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote: > On 4 April 2016 at 17:13, James Morse <james.morse@arm.com> wrote: >> Hi Ard, >> >> On 04/04/16 15:52, Ard Biesheuvel wrote: >>> Since we record the boot_args [x0 .. x3] early at boot anyway, there is >>> no need to keep the FDT address in a callee saved register with file scope >>> in head.S. So simply refer to boot_args[0] directly in the call to >>> setup_machine(), and drop the handling of x21 from head.S entirely. >> >> Won't this break Big Endian? >> (or more accurately: bootloader-endian != kernel-endian) >> >> The stores in preserve_boot_args happen before the EE/E0E bits have been >> set/cleared by el2_setup(), so they happen with boot-loader:endianness. The >> loads after el2_setup() happen with kernel:endianness. >> > > That is a very good point. I think it would not be unreasonable to factor out the configuration of the endianness at the current exception level, and invoke it first before recording the boot args, since we now rely on el2_setup() to do that. That would also fix the 'bug' where the boot_args are recorded in the endianness of the bootloader, although I doubt anyone cares deeply about that one. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 69b33535911e..9d8f928c355c 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -234,16 +234,15 @@ ENDPROC(stext) * Preserve the arguments passed by the bootloader in x0 .. x3 */ preserve_boot_args: - mov x21, x0 // x21=FDT - - adr_l x0, boot_args // record the contents of - stp x21, x1, [x0] // x0 .. x3 at kernel entry - stp x2, x3, [x0, #16] + adr_l x4, boot_args // record the contents of + stp x0, x1, [x4] // x0 .. x3 at kernel entry + stp x2, x3, [x4, #16] dmb sy // needed before dc ivac with // MMU off - add x1, x0, #0x20 // 4 x 8 bytes + mov x0, x4 + add x1, x4, #0x20 // 4 x 8 bytes b __inval_cache_range // tail call ENDPROC(preserve_boot_args) @@ -480,7 +479,6 @@ __mmap_switched: mov x4, sp and x4, x4, #~(THREAD_SIZE - 1) msr sp_el0, x4 // Save thread_info - str_l x21, __fdt_pointer, x5 // Save FDT pointer ldr_l x4, kimage_vaddr // Save the offset between sub x4, x4, x24 // the kernel virtual and @@ -492,7 +490,7 @@ __mmap_switched: #endif #ifdef CONFIG_RANDOMIZE_BASE cbnz x23, 0f // already running randomized? - mov x0, x21 // pass FDT address in x0 + ldr_l x0, boot_args // pass FDT address in x0 bl kaslr_early_init // parse FDT for KASLR options cbz x0, 0f // KASLR disabled? just proceed mov x23, x0 // record KASLR offset diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c index 9dc67769b6a4..83a3e484a90a 100644 --- a/arch/arm64/kernel/setup.c +++ b/arch/arm64/kernel/setup.c @@ -64,8 +64,6 @@ #include <asm/xen/hypervisor.h> #include <asm/mmu_context.h> -phys_addr_t __fdt_pointer __initdata; - /* * Standard memory resources */ @@ -304,7 +302,7 @@ void __init setup_arch(char **cmdline_p) early_fixmap_init(); early_ioremap_init(); - setup_machine_fdt(__fdt_pointer); + setup_machine_fdt(boot_args[0]); parse_early_param();
Since we record the boot_args [x0 .. x3] early at boot anyway, there is no need to keep the FDT address in a callee saved register with file scope in head.S. So simply refer to boot_args[0] directly in the call to setup_machine(), and drop the handling of x21 from head.S entirely. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/arm64/kernel/head.S | 14 ++++++-------- arch/arm64/kernel/setup.c | 4 +--- 2 files changed, 7 insertions(+), 11 deletions(-) -- 2.5.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel