Instead of returning to the asm calling code to invoke the trampoline,
call it straight from the C code that sets the scene. That way, we don't
need the struct return type for returning two values, and we can make
the call conditional more cleanly in a subsequent patch.
Signed-off-by: Ard Biesheuvel <[email protected]>
---
arch/x86/boot/compressed/head_64.S | 20 +++-----------
arch/x86/boot/compressed/pgtable_64.c | 28 ++++++++------------
2 files changed, 15 insertions(+), 33 deletions(-)
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 3b5fc851737ffc39..94b614ecb7c2fd55 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -441,24 +441,12 @@ SYM_CODE_START(startup_64)
#endif
/*
- * paging_prepare() sets up the trampoline and checks if we need to
- * enable 5-level paging.
- *
- * paging_prepare() returns a two-quadword structure which lands
- * into RDX:RAX:
- * - Address of the trampoline is returned in RAX.
- * - Non zero RDX means trampoline needs to enable 5-level
- * paging.
- *
+ * set_paging_levels() updates the number of paging levels using a
+ * trampoline in 32-bit addressable memory if the current number does
+ * not match the desired number.
*/
movq %r15, %rdi /* pass struct boot_params pointer */
- call paging_prepare
-
- /* Pass the trampoline address and boolean flag as args #1 and #2 */
- movq %rax, %rdi
- movq %rdx, %rsi
- leaq TRAMPOLINE_32BIT_CODE_OFFSET(%rax), %rax
- call *%rax
+ call set_paging_levels
/*
* cleanup_trampoline() would restore trampoline memory.
diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c
index 09fc18180929fab3..b62b6819dcdd01be 100644
--- a/arch/x86/boot/compressed/pgtable_64.c
+++ b/arch/x86/boot/compressed/pgtable_64.c
@@ -16,11 +16,6 @@ unsigned int __section(".data") pgdir_shift = 39;
unsigned int __section(".data") ptrs_per_p4d = 1;
#endif
-struct paging_config {
- unsigned long trampoline_start;
- unsigned long l5_required;
-};
-
/* Buffer to preserve trampoline memory */
static char trampoline_save[TRAMPOLINE_32BIT_SIZE];
@@ -106,10 +101,10 @@ static unsigned long find_trampoline_placement(void)
return bios_start - TRAMPOLINE_32BIT_SIZE;
}
-struct paging_config paging_prepare(void *rmode)
+asmlinkage void set_paging_levels(void *rmode)
{
- struct paging_config paging_config = {};
- void *tramp_code;
+ void (*toggle_la57)(void *trampoline, bool enable_5lvl);
+ bool l5_required = false;
/* Initialize boot_params. Required for cmdline_find_option_bool(). */
boot_params = rmode;
@@ -130,12 +125,10 @@ struct paging_config paging_prepare(void *rmode)
!cmdline_find_option_bool("no5lvl") &&
native_cpuid_eax(0) >= 7 &&
(native_cpuid_ecx(7) & (1 << (X86_FEATURE_LA57 & 31)))) {
- paging_config.l5_required = 1;
+ l5_required = true;
}
- paging_config.trampoline_start = find_trampoline_placement();
-
- trampoline_32bit = (unsigned long *)paging_config.trampoline_start;
+ trampoline_32bit = (unsigned long *)find_trampoline_placement();
/* Preserve trampoline memory */
memcpy(trampoline_save, trampoline_32bit, TRAMPOLINE_32BIT_SIZE);
@@ -144,7 +137,7 @@ struct paging_config paging_prepare(void *rmode)
memset(trampoline_32bit, 0, TRAMPOLINE_32BIT_SIZE);
/* Copy trampoline code in place */
- tramp_code = memcpy(trampoline_32bit +
+ toggle_la57 = memcpy(trampoline_32bit +
TRAMPOLINE_32BIT_CODE_OFFSET / sizeof(unsigned long),
&trampoline_32bit_src, TRAMPOLINE_32BIT_CODE_SIZE);
@@ -154,7 +147,8 @@ struct paging_config paging_prepare(void *rmode)
* immediate absolute address, so we have to adjust that based on the
* placement of the trampoline.
*/
- *(u32 *)(tramp_code + trampoline_ljmp_imm_offset) += (unsigned long)tramp_code;
+ *(u32 *)((u8 *)toggle_la57 + trampoline_ljmp_imm_offset) +=
+ (unsigned long)toggle_la57;
/*
* The code below prepares page table in trampoline memory.
@@ -170,10 +164,10 @@ struct paging_config paging_prepare(void *rmode)
* We are not going to use the page table in trampoline memory if we
* are already in the desired paging mode.
*/
- if (paging_config.l5_required == !!(native_read_cr4() & X86_CR4_LA57))
+ if (l5_required == !!(native_read_cr4() & X86_CR4_LA57))
goto out;
- if (paging_config.l5_required) {
+ if (l5_required) {
/*
* For 4- to 5-level paging transition, set up current CR3 as
* the first and the only entry in a new top-level page table.
@@ -196,7 +190,7 @@ struct paging_config paging_prepare(void *rmode)
}
out:
- return paging_config;
+ toggle_la57(trampoline_32bit, l5_required);
}
void cleanup_trampoline(void *pgtable)
--
2.39.2
On Mon, May 08, 2023 at 09:03:16AM +0200, Ard Biesheuvel wrote:
> Instead of returning to the asm calling code to invoke the trampoline,
> call it straight from the C code that sets the scene. That way, we don't
> need the struct return type for returning two values, and we can make
> the call conditional more cleanly in a subsequent patch.
>
> Signed-off-by: Ard Biesheuvel <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
--
Kiryl Shutsemau / Kirill A. Shutemov