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Shutemov" , Linus Torvalds , Joerg Roedel Subject: [PATCH v5 10/20] x86/decompressor: Call trampoline directly from C code Date: Wed, 7 Jun 2023 09:23:32 +0200 Message-Id: <20230607072342.4054036-11-ardb@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230607072342.4054036-1-ardb@kernel.org> References: <20230607072342.4054036-1-ardb@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4967; i=ardb@kernel.org; h=from:subject; bh=RE5W68XPDnGbVeBBhzYfWFU/rF3D5/t2hy2u0mxg2G8=; b=owGbwMvMwCFmkMcZplerG8N4Wi2JIaXBoIDntVbaGYNZF05+sOFs4/9fbFG/J2ci3y7xstQHa wyWvNLqKGVhEONgkBVTZBGY/ffdztMTpWqdZ8nCzGFlAhnCwMUpABPZac/IcHT6wfvuCzqYQtm8 5p/yNOfat+FKT3SVjenlky/bb5Y2WTIyTDWK3W/aMfkuT+YFS/N1CWLtN1b8ZQu9cnz5srAnFZ4 nWQA= X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-Spam-Status: No, score=-7.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1768028607399566687?= X-GMAIL-MSGID: =?utf-8?q?1768028607399566687?= 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, the struct return type is no longer needed for returning two values, and the call can be made conditional more cleanly in a subsequent patch. Acked-by: Kirill A. Shutemov Signed-off-by: Ard Biesheuvel --- 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 cdefafd456c70335..3d4da7e5270c8d4d 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -430,24 +430,12 @@ 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 d66639c961b8eeda..1d28ad95ea839531 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, which needs to be adjusted 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)