Subject: [PATCH 1/2] x86/boot: Add error_putdec() helper

From: "H. Peter Anvin" <[email protected]>

Add a helper to print decimal numbers to early console.

Suggested-by: Borislav Petkov (AMD) <[email protected]>
Signed-off-by: H. Peter Anvin (Intel) <[email protected]>
Signed-off-by: Jun'ichi Nomura <[email protected]>
Link: https://lore.kernel.org/lkml/20240123112624.GBZa-iYP1l9SSYtr-V@fat_crate.local/

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -164,21 +164,34 @@ void __putstr(const char *s)
outb(0xff & (pos >> 1), vidport+1);
}

-void __puthex(unsigned long value)
+static noinline void __putnum(unsigned long value, unsigned int base,
+ int mindig)
{
- char alpha[2] = "0";
- int bits;
+ char buf[8*sizeof(value)+1];
+ char *p;

- for (bits = sizeof(value) * 8 - 4; bits >= 0; bits -= 4) {
- unsigned long digit = (value >> bits) & 0xf;
+ p = buf + sizeof(buf);
+ *--p = '\0';

- if (digit < 0xA)
- alpha[0] = '0' + digit;
- else
- alpha[0] = 'a' + (digit - 0xA);
+ while (mindig-- > 0 || value) {
+ unsigned char digit = value % base;
+ digit += (digit >= 10) ? ('a'-10) : '0';
+ *--p = digit;

- __putstr(alpha);
+ value /= base;
}
+
+ __putstr(p);
+}
+
+void __puthex(unsigned long value)
+{
+ __putnum(value, 16, sizeof(value)*2);
+}
+
+void __putdec(unsigned long value)
+{
+ __putnum(value, 10, 1);
}

#ifdef CONFIG_X86_NEED_RELOCS
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -63,8 +63,10 @@ void *malloc(int size);
void free(void *where);
void __putstr(const char *s);
void __puthex(unsigned long value);
+void __putdec(unsigned long value);
#define error_putstr(__x) __putstr(__x)
#define error_puthex(__x) __puthex(__x)
+#define error_putdec(__x) __putdec(__x)

#ifdef CONFIG_X86_VERBOSE_BOOTUP


Subject: [PATCH 2/2] x86/boot: Add a message about ignored early NMIs

Commit

78a509fba9c9 ("x86/boot: Ignore NMIs during very early boot")

added an empty handler in early boot stage to avoid boot failure due to
spurious NMIs.

Add a diagnostic message to show when early NMIs have occurred and/or
what happened to them.

[ bp: Touchups. ]

Suggested-by: Borislav Petkov <[email protected]>
Suggested-by: H. Peter Anvin <[email protected]>
Signed-off-by: Jun'ichi Nomura <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Link: https://lore.kernel.org/lkml/20231130103339.GCZWhlA196uRklTMNF@fat_crate.local

--
v2
* Moved variable declaration and definition to the right place
based on comments from Kirill.
No functional changes.
v3
* Removed comment and updated message in the NMI handler.
* Use error_putdec() helper.

diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
--- a/arch/x86/boot/compressed/ident_map_64.c
+++ b/arch/x86/boot/compressed/ident_map_64.c
@@ -389,5 +389,5 @@ void do_boot_page_fault(struct pt_regs *regs, unsigned long error_code)

void do_boot_nmi_trap(struct pt_regs *regs, unsigned long error_code)
{
- /* Empty handler to ignore NMI during early boot */
+ spurious_nmi_count++;
}
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -52,6 +52,7 @@ struct port_io_ops pio_ops;

memptr free_mem_ptr;
memptr free_mem_end_ptr;
+int spurious_nmi_count;

static char *vidmem;
static int vidport;
@@ -493,6 +494,12 @@ asmlinkage __visible void *extract_kernel(void *rmode, unsigned char *output)
/* Disable exception handling before booting the kernel */
cleanup_exception_handling();

+ if (spurious_nmi_count) {
+ error_putstr("Spurious early NMIs ignored: ");
+ error_putdec(spurious_nmi_count);
+ error_putstr("\n");
+ }
+
return output + entry_offset;
}

diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -59,6 +59,7 @@ extern char _head[], _end[];
/* misc.c */
extern memptr free_mem_ptr;
extern memptr free_mem_end_ptr;
+extern int spurious_nmi_count;
void *malloc(int size);
void free(void *where);
void __putstr(const char *s);

Subject: [tip: x86/boot] x86/boot: Add error_putdec() helper

The following commit has been merged into the x86/boot branch of tip:

Commit-ID: 9ba8ec8ee67a00eb5631364e4b716f35559724d4
Gitweb: https://git.kernel.org/tip/9ba8ec8ee67a00eb5631364e4b716f35559724d4
Author: H. Peter Anvin <[email protected]>
AuthorDate: Fri, 02 Feb 2024 03:51:43
Committer: Borislav Petkov (AMD) <[email protected]>
CommitterDate: Tue, 06 Feb 2024 10:50:21 +01:00

x86/boot: Add error_putdec() helper

Add a helper to print decimal numbers to early console.

Suggested-by: Borislav Petkov (AMD) <[email protected]>
Signed-off-by: H. Peter Anvin (Intel) <[email protected]>
Signed-off-by: Jun'ichi Nomura <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Link: https://lore.kernel.org/lkml/20240123112624.GBZa-iYP1l9SSYtr-V@fat_crate.local/
Link: https://lore.kernel.org/r/[email protected]
---
arch/x86/boot/compressed/misc.c | 33 ++++++++++++++++++++++----------
arch/x86/boot/compressed/misc.h | 2 ++-
2 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index b99e08e..bf2aac4 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -164,21 +164,34 @@ void __putstr(const char *s)
outb(0xff & (pos >> 1), vidport+1);
}

-void __puthex(unsigned long value)
+static noinline void __putnum(unsigned long value, unsigned int base,
+ int mindig)
{
- char alpha[2] = "0";
- int bits;
+ char buf[8*sizeof(value)+1];
+ char *p;

- for (bits = sizeof(value) * 8 - 4; bits >= 0; bits -= 4) {
- unsigned long digit = (value >> bits) & 0xf;
+ p = buf + sizeof(buf);
+ *--p = '\0';

- if (digit < 0xA)
- alpha[0] = '0' + digit;
- else
- alpha[0] = 'a' + (digit - 0xA);
+ while (mindig-- > 0 || value) {
+ unsigned char digit = value % base;
+ digit += (digit >= 10) ? ('a'-10) : '0';
+ *--p = digit;

- __putstr(alpha);
+ value /= base;
}
+
+ __putstr(p);
+}
+
+void __puthex(unsigned long value)
+{
+ __putnum(value, 16, sizeof(value)*2);
+}
+
+void __putdec(unsigned long value)
+{
+ __putnum(value, 10, 1);
}

#ifdef CONFIG_X86_NEED_RELOCS
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index bc2f0f1..6502bc6 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -63,8 +63,10 @@ void *malloc(int size);
void free(void *where);
void __putstr(const char *s);
void __puthex(unsigned long value);
+void __putdec(unsigned long value);
#define error_putstr(__x) __putstr(__x)
#define error_puthex(__x) __puthex(__x)
+#define error_putdec(__x) __putdec(__x)

#ifdef CONFIG_X86_VERBOSE_BOOTUP