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Donenfeld" , "Peter Zijlstra (Intel)" , "Theodore Ts'o" , =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= , Xin Li , Andrew Cooper , Andy Lutomirski , Ard Biesheuvel , Borislav Petkov , Brian Gerst , Dave Hansen , Ingo Molnar , James Morse , Jarkko Sakkinen , Josh Poimboeuf , Kees Cook , Nam Cao , Oleg Nesterov , Perry Yuan , Thomas Gleixner , Thomas Huth , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-sgx@vger.kernel.org, x86@kernel.org References: <20251112043730.992152-1-hpa@zytor.com> <20251112043730.992152-8-hpa@zytor.com> Content-Language: en-US, sv-SE From: "H. Peter Anvin" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: B6F301A000B X-Stat-Signature: 8yfkxgexkbsyxqh4tacz4hpo99i6k93i X-Rspam-User: X-HE-Tag: 1762982756-325301 X-HE-Meta: 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 AluHZg5Z NvNnGlwF1ECEaFyPHskcDmNKZGJ7HNVcOl1YGApfZy7RWnPfpHyr7hJBQbg1F2SWC0eB4N4vQpVzOEnki0Hfqoti0gZPjTAwpXkk7TXAdDc9bt1FiaC/iEYOXxyC87MCLajfBFkDfgNicmLotT6s9CQsebPs8qICqBWJ7Fjv/qZmvYT+KAl9Te7qoO0z/7goKEm8cOdWjiEVkg+I/QtKktEab5dLxw7p+e/QV61Aw7RhN+7EELWfFj3/wHb/hacrpSOWRCYRD3BA7iXdTbTQQ3daXEJBmvIbLqvOtCvqOyLDJeJRyDSkS3BibGIsDXFQ87YnBzrK1NrkplBI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2025-11-12 02:31, Uros Bizjak wrote: > > Unfortunately, %ebp is still special with -fno-omit-frame-pointer, so > using "ebp" as _sys_arg6 on 32-bit targets will result in: > > error: bp cannot be used in ‘asm’ here > > Please see how %ebp register is handled in > arch/x86/include/asm/vmware.h, vmware_hypercall_hb_out() and > vmware_hypercall_hb_in(). > #ifdef CONFIG_X86_64 #define VMW_BP_CONSTRAINT "r" #else #define VMW_BP_CONSTRAINT "m" #endif asm_inline volatile ( UNWIND_HINT_SAVE "push %%" _ASM_BP "\n\t" UNWIND_HINT_UNDEFINED "mov %[in6], %%" _ASM_BP "\n\t" "rep outsb\n\t" "pop %%" _ASM_BP "\n\t" UNWIND_HINT_RESTORE : "=a" (out0), "=b" (*out1) : "a" (VMWARE_HYPERVISOR_MAGIC), "b" (cmd), "c" (in2), "d" (in3 | VMWARE_HYPERVISOR_PORT_HB), "S" (in4), "D" (in5), [in6] VMW_BP_CONSTRAINT (in6) : "cc", "memory"); return out0; That code is actually incorrect, in at least two ways: 1. It should be conditioned on frame pointers enabled, not x86-64 vs i386. 2. The compiler is perfectly within its right to emit an %esp-relative reference for the "m"-constrained [in6]. This is particularly likely when *not* compiled with frame pointers, see #1. A better sequence might be: pushl %[in6] push %ebp mov 4(%esp),%ebp pop %ebp pop %[junk] Then %[in6] can even safely be a "g" constraint (hence pushl). -hpa