linux-kernel - Re: [PATCH] x86/boot: Use EFI setup data if provided

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Date:   Mon, 25 Mar 2019 00:27:41 +0000
From:   Junichi Nomura <j-nomura@...jp.nec.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     "fanc.fnst@...fujitsu.com" <fanc.fnst@...fujitsu.com>,
        "bp@...e.de" <bp@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>
Subject: Re: [PATCH] x86/boot: Use EFI setup data if provided

On Fri, Mar 22, 2019 at 04:23:28PM +0100, Borislav Petkov wrote:
> On Fri, Mar 22, 2019 at 11:03:43AM +0000, Junichi Nomura wrote:
> > Commit 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in
> > boot_params") broke kexec boot on EFI systems.  efi_get_rsdp_addr()
> > in the early parsing code tries to search RSDP from EFI table but
> > whose address is virtual.
> > 
> > Since kexec(1) provides physical address of config_table via boot_params,
> > efi_get_rsdp_addr() should look for setup_data in the same way as
> > efi_systab_init() in arch/x86/platform/efi/efi.c does.
> 
> If the kexec kernel should continue to use efi_systab_init() then you
> should make efi_get_rsdp_addr() exit early in the kexec-ed kernel.

I'm not sure which way kexec devel is going. Added kexec list.
Here is the version that exits early in efi_get_rsdp_addr().

[PATCH] x86/boot: Don't try to search RSDP from EFI when kexec-booted

Commit 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in
boot_params") broke kexec boot on EFI systems.  efi_get_rsdp_addr()
in the early parsing code tries to search RSDP from EFI table but
whose address is virtual.

Normally kexec(1) provides physical address of config_table via boot_params
and EFI code uses that during initialization.
For the early boot code, we just exit efi_get_rsdp_addr() early if the kernel
is booted by kexec.

Fixes: 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in boot_params")
Signed-off-by: Jun'ichi Nomura <j-nomura@...jp.nec.com>
Cc: Chao Fan <fanc.fnst@...fujitsu.com>
Cc: Borislav Petkov <bp@...e.de>

diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index 0ef4ad5..1cefc43 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -44,6 +44,24 @@ static acpi_physical_address get_acpi_rsdp(void)
 	return addr;
 }
 
+static bool is_kexec_booted(void)
+{
+	struct setup_data *data;
+
+	/*
+	 * kexec-tools provides EFI setup data so that kexec-ed kernel
+	 * can find proper tables.
+	 */
+	data = (struct setup_data *) boot_params->hdr.setup_data;
+	while (data) {
+		if (data->type == SETUP_EFI)
+			return true;
+		data = (struct setup_data *) data->next;
+	}
+
+	return false;
+}
+
 /* Search EFI system tables for RSDP. */
 static acpi_physical_address efi_get_rsdp_addr(void)
 {
@@ -57,6 +75,10 @@ static acpi_physical_address efi_get_rsdp_addr(void)
 	int size, i;
 	char *sig;
 
+	/* If the system is kexec-booted, poking EFI systab may not work. */
+	if (is_kexec_booted())
+		return 0;
+
 	ei = &boot_params->efi_info;
 	sig = (char *)&ei->efi_loader_signature;