Documentation/arch/x86/exception-tables.rst

File Facts

System

Linux kernel

Corpus path

Documentation/arch/x86/exception-tables.rst

Extension

.rst

Size

14309 bytes

Lines

358

Domain

Support Tooling And Documentation

Bucket

Documentation

Inferred role

Support Tooling And Documentation: documentation

Status

atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

• Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.
• Touches user memory; correctness depends on fault-safe copying and privilege boundary handling.
• Defines or uses C structs; map object ownership, embedded links, reference counts, and lock ownership.

Dependency Surface

• No C-style include directives detected by the generator.

Detected Declarations

• function table

Annotated Snippet

switch ((sizeof(*(buf)))) {
            case 1:
              __asm__ __volatile__(
                "1:      mov" "b" " %2,%" "b" "1\n"
                "2:\n"
                ".section .fixup,\"ax\"\n"
                "3:      movl %3,%0\n"
                "        xor" "b" " %" "b" "1,%" "b" "1\n"
                "        jmp 2b\n"
                ".section __ex_table,\"a\"\n"
                "        .align 4\n"
                "        .long 1b,3b\n"
                ".text"        : "=r"(__gu_err), "=q" (__gu_val): "m"((*(struct __large_struct *)
                              (   __gu_addr   )) ), "i"(- 14 ), "0"(  __gu_err  )) ;
                break;
            case 2:
              __asm__ __volatile__(
                "1:      mov" "w" " %2,%" "w" "1\n"
                "2:\n"
                ".section .fixup,\"ax\"\n"
                "3:      movl %3,%0\n"
                "        xor" "w" " %" "w" "1,%" "w" "1\n"
                "        jmp 2b\n"
                ".section __ex_table,\"a\"\n"
                "        .align 4\n"
                "        .long 1b,3b\n"
                ".text"        : "=r"(__gu_err), "=r" (__gu_val) : "m"((*(struct __large_struct *)
                              (   __gu_addr   )) ), "i"(- 14 ), "0"(  __gu_err  ));
                break;
            case 4:
              __asm__ __volatile__(
                "1:      mov" "l" " %2,%" "" "1\n"
                "2:\n"
                ".section .fixup,\"ax\"\n"
                "3:      movl %3,%0\n"
                "        xor" "l" " %" "" "1,%" "" "1\n"
                "        jmp 2b\n"
                ".section __ex_table,\"a\"\n"
                "        .align 4\n"        "        .long 1b,3b\n"
                ".text"        : "=r"(__gu_err), "=r" (__gu_val) : "m"((*(struct __large_struct *)
                              (   __gu_addr   )) ), "i"(- 14 ), "0"(__gu_err));
                break;
            default:
              (__gu_val) = __get_user_bad();
          }
        } while (0) ;
      ((c)) = (__typeof__(*((buf))))__gu_val;
      __gu_err;
    }
  );

WOW! Black GCC/assembly magic. This is impossible to follow, so let's
see what code gcc generates::

 >         xorl %edx,%edx
 >         movl current_set,%eax
 >         cmpl $24,788(%eax)
 >         je .L1424
 >         cmpl $-1073741825,64(%esp)
 >         ja .L1423
 > .L1424:
 >         movl %edx,%eax
 >         movl 64(%esp),%ebx
 > #APP
 > 1:      movb (%ebx),%dl                /* this is the actual user access */
 > 2:
 > .section .fixup,"ax"
 > 3:      movl $-14,%eax
 >         xorb %dl,%dl
 >         jmp 2b

Annotation

• Detected declarations: `function table`.
• Atlas domain: Support Tooling And Documentation / Documentation.
• Implementation status: atlas-only.
• This snippet crosses the user/kernel memory boundary; validate fault handling and access checks before translating the pattern.

Implementation Notes

• This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
• Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
• Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.