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change "different" to "difference" in alt text #51

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2 changes: 1 addition & 1 deletion src/content/chapters/1-the-basics.mdx
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Expand Up @@ -78,7 +78,7 @@ In kernel mode, anything goes: the CPU is allowed to execute any supported instr

Processors start in kernel mode. Before executing a program, the kernel initiates the switch to user mode.

<img src='/images/kernel-mode-vs-user-mode.png' loading='lazy' style='max-width: 500px; margin: 0 auto;' alt='Two fake iMessage screenshots demonstrating the different between user and kernel mode protections. The first, labeled Kernel Mode: right side says "Read this protected memory!", left side replies "Here you go, dear :)". The second, labeled User Mode: right side says "Read this protected memory!", left side replies "No! Segmentation fault!"' width='1072' height='433' />
<img src='/images/kernel-mode-vs-user-mode.png' loading='lazy' style='max-width: 500px; margin: 0 auto;' alt='Two fake iMessage screenshots demonstrating the difference between user and kernel mode protections. The first, labeled Kernel Mode: right side says "Read this protected memory!", left side replies "Here you go, dear :)". The second, labeled User Mode: right side says "Read this protected memory!", left side replies "No! Segmentation fault!"' width='1072' height='433' />

An example of how processor modes manifest in a real architecture: on x86-64, the current privilege level (CPL) can be read from a register called `cs` (code segment). Specifically, the CPL is contained in the two [least significant bits](https://en.wikipedia.org/wiki/Bit_numbering) of the `cs` register. Those two bits can store x86-64's four possible rings: ring 0 is kernel mode and ring 3 is user mode. Rings 1 and 2 are designed for running drivers but are only used by a handful of older niche operating systems. If the CPL bits are `11`, for example, the CPU is running in ring 3: user mode.

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