[PATCH v6 37/76] x86/head/64: Move early exception dispatch to C code

Joerg Roedel
2020-08-24T08:56:32Z

Move the assembly coded dispatch between page-faults and all other
exceptions to C code to make it easier to maintain and extend.

Also change the return-type of early_make_pgtable() to bool and make it
static.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20200724160336.5435-37-joro@8bytes.org
---
arch/x86/include/asm/pgtable.h | 2 +-
arch/x86/include/asm/setup.h | 4 +++-
arch/x86/kernel/head64.c | 19 +++++++++++++++----
arch/x86/kernel/head_64.S | 11 +----------
4 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 5e0dcc20614d..a02c67291cfc 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -28,7 +28,7 @@
#include <asm-generic/pgtable_uffd.h>

extern pgd_t early_top_pgt[PTRS_PER_PGD];
-int __init __early_make_pgtable(unsigned long address, pmdval_t pmd);
+bool __init __early_make_pgtable(unsigned long address, pmdval_t pmd);

void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm);
void ptdump_walk_pgd_level_debugfs(struct seq_file *m, struct mm_struct *mm,
diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
index 5c09f50ecf1c..cafae86813ae 100644
--- a/arch/x86/include/asm/setup.h
+++ b/arch/x86/include/asm/setup.h
@@ -39,6 +39,8 @@ void vsmp_init(void);
static inline void vsmp_init(void) { }
#endif

+struct pt_regs;
+
void setup_bios_corruption_check(void);
void early_platform_quirks(void);

@@ -49,9 +51,9 @@ extern void i386_reserve_resources(void);
extern unsigned long __startup_64(unsigned long physaddr, struct boot_params *bp);
extern unsigned long __startup_secondary_64(void);
extern void startup_64_setup_env(unsigned long physbase);
-extern int early_make_pgtable(unsigned long address);
extern void early_idt_setup_early_handler(unsigned long physaddr);
extern void early_load_idt(void);
+extern void __init do_early_exception(struct pt_regs *regs, int trapnr);

#ifdef CONFIG_X86_INTEL_MID
extern void x86_intel_mid_early_setup(void);
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 096b09d06d1c..41514ec1e6f0 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -37,6 +37,8 @@
#include <asm/kasan.h>
#include <asm/fixmap.h>
#include <asm/realmode.h>
+#include <asm/extable.h>
+#include <asm/trapnr.h>

/*
* Manage page tables very early on.
@@ -314,7 +316,7 @@ static void __init reset_early_page_tables(void)
}

/* Create a new PMD entry */
-int __init __early_make_pgtable(unsigned long address, pmdval_t pmd)
+bool __init __early_make_pgtable(unsigned long address, pmdval_t pmd)
{
unsigned long physaddr = address - __PAGE_OFFSET;
pgdval_t pgd, *pgd_p;
@@ -324,7 +326,7 @@ int __init __early_make_pgtable(unsigned long address, pmdval_t pmd)

/* Invalid address or early pgt is done ? */
if (physaddr >= MAXMEM || read_cr3_pa() != __pa_nodebug(early_top_pgt))
- return -1;
+ return false;

again:
pgd_p = &early_top_pgt[pgd_index(address)].pgd;
@@ -381,10 +383,10 @@ int __init __early_make_pgtable(unsigned long address, pmdval_t pmd)
}
pmd_p[pmd_index(address)] = pmd;

- return 0;
+ return true;
}

-int __init early_make_pgtable(unsigned long address)
+static bool __init early_make_pgtable(unsigned long address)
{
unsigned long physaddr = address - __PAGE_OFFSET;
pmdval_t pmd;
@@ -394,6 +396,15 @@ int __init early_make_pgtable(unsigned long address)
return __early_make_pgtable(address, pmd);
}

+void __init do_early_exception(struct pt_regs *regs, int trapnr)
+{
+ if (trapnr == X86_TRAP_PF &&
+ early_make_pgtable(native_read_cr2()))
+ return;
+
+ early_fixup_exception(regs, trapnr);
+}
+
/* Don't add a printk in there. printk relies on the PDA which is not initialized
yet. */
static void __init clear_bss(void)
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 28de83fecda3..08412f308de3 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -349,18 +349,9 @@ SYM_CODE_START_LOCAL(early_idt_handler_common)
pushq %r15 /* pt_regs->r15 */
UNWIND_HINT_REGS

- cmpq $14,%rsi /* Page fault? */
- jnz 10f
- GET_CR2_INTO(%rdi) /* can clobber %rax if pv */
- call early_make_pgtable
- andl %eax,%eax
- jz 20f /* All good */
-
-10:
movq %rsp,%rdi /* RDI = pt_regs; RSI is already trapnr */
- call early_fixup_exception
+ call do_early_exception

-20:
decl early_recursion_flag(%rip)
jmp restore_regs_and_return_to_kernel
SYM_CODE_END(early_idt_handler_common)